Could Australia's bushfires aerosols actually decrease global temperature?

Well, the amount and intensity of wild fires are a direct outcome of global warming, that's not really news.

According to this article that cites a work i can't find, until the mid of December 2019 the Australian fires emitted ~250million tons of carbon, ~50% of Australia's yearly production. A recovery in the coming decades is unlikely, because the ecosystem is already compromised. It is "too optimistic" to assume that the forests will regrow and they will "never end up accumulating as much carbon as they had before". Instead, large areas of burning forests must more and more be seen as a biospheric component that can turn from a carbon sink to a source.

Here's an example (sorry paywalled, but the abstract has the interesting points and it is peer reviewed) for boreal forest fires, where fires can lead from net accumulation over several fire events to a net loss, leading to a positive feedback. A similar process is expected for the Amazon rain forest fires.

To the question: an exact answer seems to be difficult. It depends on how much aerosols end up where in the atmosphere and stays for how long. The effect can be modelled: Here, a fire aerosol laiden atmosphere's lower 6km can be warmed because they become a heat trap. The trap is caused because aerosols have a stabilizing effect on the upper atmosphere. A forest fire's plume has a different composition than a volcanic eruption !

This paper describes a similar effect, the absorption of solar radiation by carbon can heat the atmosphere.

I am aware that there may be other effects, inclduing atmospheric cooling, but i leave that part to somebody else. All in all, the negative effects of carbon release and the potential loss of regenerative abilities of the biosphere - because of drought, erosion, loss of biodiversity and the ecosystem, soil sterilization, invasive organisms as well as the difficulties to respond in time because of the sheer area affected by fire (all depending on intensity, duration and area) - by far outweigh any cooling effects of wild fires.


What instrumentation and/or measurement is likely being shown in this video of giant Siberian craters/sinkholes?

It looks like a geophysical method. But a wide variety of such methods have been applied to the Yamal crater by Olenchenko et al. (2015):

The complex of geophysical survey techniques included electrical resistivity tomography (ERT), near-field transient electromagnetic sounding (Transient Electro Magnetic (TEM) sounding), magnetic survey, and radioactivity survey.

I'd say it looks like the first one (ERT), but it's just an "educated speculation"! :)


For how long has the Earth been habitable for humans?

One needs breathable air, drinkable water, and food to survive. Food as we know it was nonexistent prior to the Ediacaran, which began about 635 million years ago. Life was exceedingly primitive (single celled) prior to that. Breathable air is a more significant challenge. A breathable atmosphere means sufficient oxygen and not too much carbon dioxide. Oxygen levels rose to above half it's current amount in the atmosphere about 850 million years ago, but carbon dioxide didn't fall below 5000 ppm until about 450 million years ago, when it dropped precipitously and caused an ice age and an extinction event. Extinction events would be something to avoid, so about 440 million years ago.


Sun dogs are bright spots to one or both sides of the sun. They are a form of halo created by ice crystals in the atmosphere.

What you saw was most likely cloud iridescence, which is a phenomenon that occurs closed to either the moon of the sun. The iridescence is caused by diffraction created by water droplets or small ice crystals individually scattering light. Large crystals produce a halo, not iridescence.


Which equations describe complete (or near complete) behaviour of magma moving through rocks?

From McKenzie's original 1984 paper and from Spiegelman & McKenzie (1987) paper the equations that govern the conservation of momentum and mass of a low-viscosity fluid melt (magma) in a deformable matrix (rocks) are:

${\partial\over\partial t} (\rho_f\phi) + \nabla \cdot (\rho_f\phi{\bf v})=\Gamma$

${\partial\over\partial t} [\rho_s(1-\phi)] + \nabla \cdot [\rho_s(1-\phi){\bf V]}=-\Gamma$

${\bf v}-{\bf V}=-{k_\phi\over\rho \mu}\nabla \mathscr{P} $

$\nabla \mathscr{P}=\eta\nabla^2{\bf V}+(\zeta+{\eta\over3})\nabla(\nabla\cdot{\bf V})+(1-\phi)\Delta\rho g\hat k $

$k_\phi \sim \alpha^2{\phi^n\over c} $

where $\rho_f$ is the density of the magma, $\phi$ is the porosity or the volume fraction occupied by the magma, ${\bf v}$ is the magma velocity, $\Gamma$ is the "melting function", which gives the rate of mass transfer from matrix to magma, $\rho_s$ is the density of the solid matrix, ${\bf V}$ is the matrix velocity, $k_\phi$, is the permeability, $\mathscr{P}$ is the piezometric pressure (the pressure in excess of hydrostatic pressure, $\mathscr{P}=P-\rho_fgz$), $\Delta\rho=\rho_s-\rho_f$ and $\hat k$ is the unit vector in the $z$ direction with $z$ increasing downwards. The permeability, $k_\phi$, can be expressed as a non-linear function of the grain size $\alpha$, porosity, and a dimensionless coefficient, $c$.


What is the largest earthquake attributable solely to volcanic activity

Earthquakes associated with volcanism or volcanic rifting are typically small. They are caused by over-pressurized magma as it moves around and intrudes into brittle rocks.

Sometimes, e.g., in Hawaii, you get earthquakes due to the gravitational sliding (e.g., the M6.9 earthquake in 2018 beneath Kilauea) as new eruption causes the volcano to grow in size (adding mass) which in turn cause it to slide over the older volcanic rocks underneath.

I don't think there's an exact upper bound for such an event but it is unlikely to exceed ~7.5. Another thing to keep in mind is that rocks near active volcanoes tend to be relatively hotter which in theory should cause less shaking during the earthquake (due to lower stress drop).


Why did "Glaciologist Princess Elsa" have to leave the glacier because it was too warm?

I'm the scientist in the article; someone just saw this question and emailed me about it! (I'm on as a guest here since I don't have an account, so you'll hopefully trust it's me. Even if you don't believe it's me, I hope the answer will still be useful.)

It's entirely a safety issue. The best way to get around on the surface of the glaciers in this area is to cross-country ski on the snowy surface. If that snow gets thin or melts away completely, it's very risky to be on the glacier because the crevasses in the ice below become exposed. We're all trained in crevasse rescue, but we'd rather no one fall in the first place! My field site normally has ample snow thickness at the time I was there, but an early and extreme heat wave in the area put the whole icefield about a month ahead in the melt season. We did our best getting as much data as possible, but ultimately safety comes first and we had to get out of there.


What are the advantages in looking at an OLR map versus looking at IR satellite imagery?

First OLR map is usually graded in flux units (W/m2) thus it is quantitative data, not just a visual picture.

Clouds themselves are not a very reliable indicator of high convection and thunderstorm activity. They could form elsewhere and get blown into a dry region. Also with an OLR map students would not be distracted with the shapes of the clouds.

AIRS OLR products combine infrared and microwave data. Microwave data helps to distinguish between areas of strong convection and nonprecipitating clouds.

Here is a typical OLR product from GOES satellite (taken from Hai-Tien Lee presentation). Such images can be generated with 15 minute interval so the movement of the MJO pattern can be easily observed.


There are a couple reasons for this.  First, Lake Michigan is still cold this time of year, relative to the land that surrounds it.  Warm air flowing over the lake will exchange heat and cool, reducing its buoyancy, which will alter the heights at which clouds will form and inhibit lift for surface parcels to achieve that height.

That helps explain the cloudlessness over the lake, but this extends a bit inland as well.  I'd have to do a little digging to verify this, but just from that image it looks like that demarcation of cloud/no cloud around the lake is a sea breeze front (or in this case, a lake breeze).  The daytime lake breeze flows inland from the water, rises over land and then flows back to the lake where it descends.  This will promote clouds where the circulation rises and inhibit them where the circulation falls.

There may also be an orographic effect on along the northern portion of western MI shore, as there are large sand dunes and hills in that area.  The upslope flow could be the reason the clouds hug that shore a bit closer than other regions around the lake.

In summary, that looks like a really well defined lake breeze circulation, which explains the shape and location of the clouds.


Converting glacier volume to mass: what ice density to use?

This is a non-trivial issue. When you look at volume change of a glacier, you typically subtract two digital elevation models to obtain the difference between the two. First, you must differentiate between ice sheets where ice berg calving reduces volume and more ordinary glaciers with melt processes. There are of course calving glaciers as well so it is possible to get into great detail for any one specific glacier, so here I will just discuss the most common case which is a smaller glacier with melt-freeze conditions.

The change in elevation differs in magnitude across the glacier surface due to the movement of the glacier and accumulation-melt processes. The surface material can be (1) glacier ice, (2) snow, (3) firn snow that has survived a melt season) or (4) super imposed ice all with more or less differing densities, you need to assess what sort of material has been removed.

Ice can be approximated by a density of 900 kg/m3, firn has a density of about 600 kg/m3 but it must be remembered that the firn is converted to glacier ice by metamorphic processes so that the density changes with depth from 600 to 900 kg/m3. the transition to ice occurs at depths of about 30 m in temperate glaciers although few studies exist on the actual processes that occur. Snow have very differing densities but considering averages, I would say that it would vary between 350 to maybe 500 kg/m3 for winter (cold) conditions and around 550 kg/m3 for a melting snow pack. Super-imposed ice is closer to ice and probably varies in the upper range of 800--900 kg/m3.

To make matters worse, snow superimposes firn which in turn superimposes ice. This means that in the accumulation area, volume change can result from both a reduction in a snow cover and the firn layer. In the zone near the equilibrium line there can be a loss of both firn and ice. this is also where the superimposed ice will play a role.

So there is no simple density to use since the loss you try to estimate will involve varying types of densities spatially as well as vertically. For annual changes, you can largely ignore the vertical distribution, but with volume changes covering larger periods where climate change influences the longer term location of the equilibrium line and the size of the accumulation area, vertical layering also has to be included.

As a first approximation, a surface zonation of ice snow and possibly firn can be used and perhaps lumping snow and firn with a single density of around 600 kg/m3 can be used. I would, however, say that to some extent any choice you make will be wrong, so being aware of complexity and the limitations is the only way forward.

EDIT:

A couple of useful sources relating to the question:

Huss, M., 2013. Density assumptions for converting geodetic glacier volume change to mass change. The Cryosphere [Open Access]

Moholdt, G., (Referee) Interactive comment on “Density assumptions for converting geodetic glacier volume change to mass change” by M. Huss. The Crypshere Discuss. [Open Access]


How accurately can a tsunami be predicted? Have there been any successful evacuations?

The ability to predict depends on the cause of the tsunami. Earthquakes can't be predicted, so a tsunami caused by an earthquake can't be predicted. A meteor can be tracked for a considerable time in space before sticking earth so a tsunami caused by an meteor strike can be predicted.

There is also the possibility of a tsunami early warning system. There are currently sensors in some parts of the ocean which can detect a tsunami before "landfall" and provide an early warning system. Think of it somewhat like tracking a hurricane which generally takes a lot longer to reach land.

In a webpage it was reported that "in 1933 HVO [Hawaiian Volcano Observatory] used seismograms to predict (accurately) the arrival of a tsunami from a distant earthquake, and people in low-lying areas of Hawaii were for the first time successfully warned in advance." The word predict here is somewhat ambiguous. the scientists didn't know the earthquake would happen, but recognized that the earthquake would likely cause a tsunami.

Looking at the map below. Where tectonic plates connect, or where there are underwater volcanoes are prime locations to generate tsunamis.


DC component in Hilbert transform concept for seismic data

The 'DC Component' is a standard term used to describe the mean energy of a signal ( https://en.wikipedia.org/wiki/DC_bias ), which in the frequency domain corresponds to the component of 0 frequency. The DC component does not depend on the time -- while the other frequencies 'wiggle' around it. In seismic signals I think we don't generally have a DC components: the signal moves around a point of 0 pressure/displacement.

The authors then make their statement in a bit of an awkward way in my opinion. What they mean, is that the Hilbert transform applied to any 'DC component' is 0: thrown away!


Under which conditions is this a realistic representation of a storm?

Fury Road storm seems like quite a realistic representation of a huge thunderstorm advancing over a desert. The gust front would lift the sand in the bottom ahead of the storm center. Winds inside the storm would diverge at a higher altitude causing the sand to fall ahead of the actual storm.

In reality thunderstorms do produce dust storms with their gust fronts, but there isn't as visible upper part as in the screenshot of the film. This is because the storm is moving so fast that the dust hasn't had time to get lifted up and blown forwards from above. Such storm should have very slow speed advancing on average and large updrafts lifting dust efficiently upwards. And perhaps the dust is very fine so that it acts like gas and gets easily advected.

The situation is similar to an actual cumulonimbus/thunderstorm where the top and the bottom of the cloud are pronounced. See illustration of a cumulonimbus here.


Short answer: Tsunami models use the shallow-wave mathematical approach, because their wavelength is usually much larger than the relevant water depth determining their propagation.

Long answer:
Tsunamis are often called 'tidal waves' to highlight the idea that their characteristic time response is closer to tydes than to the standard wind waves we are used to see in a beach. The full spectrum of water wave periods is shown in this figure (tsunamis being classified as long-period waves, together with waves caused by meteorological events):
Classification of the spectrum of ocean waves according to wave period. Redrawn from Figure 1 in: Walter H. Munk (1950) "Origin and generation of waves". Proceedings 1st International Conference on Coastal Engineering, Long Beach, California. ASCE, pp. 1–4.

This image shows that the wave frequency depends on the cause behind the perturbation of the water surface.

Oceanographers generally treat ocean waves as free surface waves in an ideal fluid [2].

Mathematically, tsunamis are surface gravity waves approached as shallow-water waves (see chapter 4.1.5 in here), meaning that the wavelength λ > 20H (H being the water depth). The involved shallow-water-wave mathematical approximations oppose to the deep-water waves (λ < H, see section 4.1.4 in the same [ref 3]).

Whereas for shallow waves the wave frequency and the wave speed are (ref. 3):

$ω = \sqrt {g k 2H}$    with $k = 2\pi / \lambda$

$c = \sqrt {g H}$

for deep-water waves, instead:

$ω = \sqrt {g k}$

$c = \sqrt {\frac{g \lambda}{2\pi}}$

As the wave approaches the shore and H decreases, the wave velocity decreases and energy is preserved by increasing the wave amplitude.

Detailed information here: 3.


What is seismic stretch in geophysical method?

I believe you are referring to - as @ye-ti-800 has already pointed out - the apparent stretch that results from the NMO correction applied to CMP gathers. There is a great tutorial supplied by a Leading Edge article that may be accessed here: https://wiki.seg.org/wiki/Step-by-step_NMO_correction. It is important to note, though, that the article does not go into details about stretch mute. The article just goes into the specific details of the "mechanics" occurring during a conventional NMO correction and accompanied stretch that results from it.


Does the elliptical orbit of the Earth have effect on Earth's climate?

Short answer.   When the Earth is closest to the sun in January that softens the seasonal variation in the Northern Hemisphere and it increases the seasonal variation in the Southern Hemisphere, so for now, in the Northern Hemisphere, the Summers are colder than they would be with a circular orbit and the winters are hotter.   The opposite is true in the Southern Hemisphere.

Overall the eccentricity variation doesn't change how much solar energy hits the Earth by much, so it's not the total solar energy.   It's when combined with precession, and the effect on the seasons, that the global effect can be significant.

If we had a perfectly circular obit then the only Milankovich cycle that would matter would be axial tilt.  Ice ages would either be on a 41,000 year cycle - very neat and tidy, or they wouldn't happen at all cause the orbital variation wouldn't be enough to get ice ages started.  Other factors, like solar minimums could play a role and over longer periods of time, continental drift and variations in plant life, so, maybe not that exactly that, but I think it's likely.

Too long answer:   Hotter summers and colder winters (or the opposite) is a form of climate change that accompanies the orbital cycles.  All the orbital cycles change climate at least by seasonally.  But if I'm reading your question right, you're asking about global temperature, not just seasonal variation.

Eccentricity has an effect because the two hemispheres are quite different and because it amplifies the effect of precession.

Oceans tend to be a temperature buffer.  They circulate and they warm up slowly and they cool down slowly so they don't get too hot in summer or too cold in winter.  Land can vary in temperature significantly more.   This buffering can be seen in this average temperature chart of the two hemispheres.

The Northern Hemisphere varies about 13 degrees C and the Southern about 5.5 C.   Those numbers might seem low, but remember that near the equator, seasonal variation is small and there's more land near 0 latitude than up near 90 or -90.   How accurate this chart is, isn't really relevant.   It doesn't need to be perfect.  What's relevant is that seasonal variation is much smaller in the Southern Hemisphere because so much of it is ocean, even with the Sun being closest in January which should make the Southern Hemisphere season variation more extreme.  The ocean is the key factor.

With that in mind we can ignore the smaller variation in the Southern Hemisphere and just look at the Northern Hemisphere variation for any orbataly driven climate effects.   Before we get into eccentricity, it's important to understand Axial Precession.   The Earth, as you noted, is closest to the Sun in early January, January 4th this year.  that 3.4% closer That means Earth gets nearly 7% more sunlight in the first week of January than it gets in the first week of June.   That 7% is too small to move the seasons, but it's enough to affect them a bit.   Earth overall gets more solar energy January (Northern Hemisphere Winter) and less solar energy in June.   The Northern Hemisphere's more exteme seasonal variaiton comes into play when the Earth is closest to the Sun in May-June-July-August - that should happen in about 8,000 years, give or take.  The cycle averages about every 23,000 years, so roughly 11,500 years between highs and lows for each hemisphere.

The most relevant factor is the Northern Hemisphere Summer.   This is what is thought to drive ice ages back and forth.   Snow can last on land a long time in higher Northern latitudes and when the summers are less hot, the snow can last well into May, June, even all year around.   The warmer winters are less of a factor cause you still get snow in warm winters, sometimes, it snows more heavily when the winter is warmer.    It's the cooler Northern Hemisphere Summers that allow snow build-up and make ice ages possible.  Eccentricity (combined with precession) plays a key role on the periodic, colder Northern Hemisphere summer.

Don't worry, we're not entering an ice age in a few thousand years.   We're actually in a cool Northern Hemisphere summer period now, but, It's not quite that automatic.

The eccentricity in effect, determines how significant the axial precession is.   When the orbit is nearly circular, the difference in energy perihelion to aphelion is virtually zero.   Orbital eccentricity is currently dropping, moving towards circular, so we're not in a period of expected significant changes.  (The increased CO2 would prevent an ice age now anyway, but that's another story).  Earth's orbital cycles are in more of a holding pattern than moving towards an ice age.

When eccentricity peaks, the variation in solar energy hitting the Earth, perihelion to aphelion is significant.   It's loosely speaking, about 4 times the eccentricity.  The current eccentricity is 0.017, the current variation, Early January to Early June is about 4 times that or 0.068 or 6.8%.   At peak eccentricity of about .0679 would work out to roughly 27% variation in solar energy hitting the Earth, Perihelion to Aphelion.  (Perhaps nearly 30% with the working out the square).   This 30% variation in solar energy, depending on the perihelion and aphelion fall on the calendar, is sufficient to make ice ages come and go.   ((For very high eccentricity this 4 times rule doesn't work, but it applies pretty close to eccentricity pretty close to 0.))

In laymans terms, think of the eccentricity as turning up or down the effect of axial precession and those two combined, when properly lined up with the hemispheres, have a significant effect.

The 3 cycles together, make a kind of ugly chart of ups and downs.  The orbital effect is rather uneven but Ice ages are often periodic because of feedback mechanisms on Earth.  Once formed, Glaciers are hard to melt and once melted, it takes peak conditions to get them forming again, so many of the smaller ups and downs in the chart don't drive ice ages, only the extremes.

Wikipedia has a nice graph on the Northern Hemisphere solar energy at summer solstice.   When the chart is high, that tends to be a period of glacial melt.  When it's low, that's a period of ice age formation.

Because the eccentricity is currently kind of low and shrinking, we're probably not due for an ice-age for about 50,000 years, at least according to current orbital models, per Wikipedia (same link as just above).


The easiest and larger improvement in accuracy you can implement is switching from the non-differential single frequency GPS measurement to a double frequency and/or differential GPS measurements. That usually takes down the error of single measurements from a few meters to a few tens of centimetres or less.

The GPS systems that are within cell phones, tablets and most ships calculate their position standalone and in real-time using only one of the two civilean frequencies that the GPS satellites broadcast. The greatest source of error of those measurements are the discrepancy between the atmospheric and ionospheric models and the reality.

There are two workarounds to this problem, both often used simultaneously to get even better results.

The first workaround, is two use more sophisticated GPS instruments that can record the two civilian frequencies that the GPS satellites transmit. As each frequency is refracted by the atmosphere in a different way, the GPS can better calculate its effect and correct for it.

The second workaround is to do differential measurements. That is correcting the measurements of your GPS based in the errors recorded at the same time by a nearby GPS station at a fix known position. That is call a base station.

You can install your own base station on the ground near the area you work, or use one from the international network of base stations.

My recommendation, would be that you buy a double frequency GPS. If cost is a constrain, go for an used one on e-bay and you can get an excellent quality GPS for just a few hundred dollars. Then you put that GPS to record while you do your transect and it will generate a file with raw GPS measurements. Then, later, at home you upload that file (maybe after a format conversion) to a free GPS processing service and you will get back a file with the GPS track with MUCH better accuracy than your handheld GPS.
This would be equivalent to use the first workaround I described and the processing I'm suggesting here is called PPP (Precise Point Positioning).

When you record the raw GPS data and do the processing later is called post-processing, and it is the best practice if you don't need the high accuracy measurements in real-time. After a week or so, the DoD issues high accuracy corrections of the positions of the satellites and their internal clocks. So if you wait for this high accuracy corrections you can get better precision than any real-time processing. All this is already embedded in those free online processing systems. So you just need to wait a week, upload your file and wait for the result.

The next step would be to have a second GPS and set up your own base station (or check if you work reasonably close to an existing base station). However, my guess is that the gain in accuracy won't make much sense given the errors in the relative position between your GPS and your bullrake.

A second different approach would be to equip your bullrake with some sort of distance measuring wheel, that rolls over the sea floor and records the distance traveled by the bullrake. But it might be significant technical challenges to make such a device work reliably.


I can't answer part a, but I can help with part b. We first must determine how much kinetic energy, then we can use simple thermodynamics to see how much that could possibly heat up a mass of water.

Kinetic energy calculations are numerically modeled in Dutykh and Dias, 2009. Their largest example uses parameters of a 150km x 50km x 35km fault slipping by 15m at 4 km depth (values in Table 2 of paper). Total energy computed is shown in the graphs below:

Part a. of the table is kinetic energy, and part b. is potential energy. For the earthquake with parameters in Table 2, released kinetic energy is about $3\times10^{14}\text{ J}$, with about the same going into potential energy of the wave. I couldn't find any reliable sources of equating energy release with earthquake magnitude, but according to Wikipedia, $3\times10^{14}\text{ J}$ is equivalent to about a 6.6 earthquake. Take that for what its worth, I was just trying to get a sense of how powerful the earthquake causing the tsunami in question would be.

From here lets see what happens if all that energy (kinetic and potential) is converted to thermal energy. To warm up water noticably, lets say we want a $5\unicode{x2103}$ increase. The specific heat of seawater is $3985 \frac{\text{J}}{\text{kg}\cdot\text{C}}$, and the density is $1025\frac{\text{kg}}{\text{m}^3}$. Therefore the energy released from this tsunami can heat up $$ \frac{6\times10^{14}\text{ J}\cdot 5\unicode{x2103}}{3985 \frac{\text{J}}{\text{kg}\cdot\text{C}}} = 7.5\times10^{11} \text{kg of water} \cdot \frac{1}{1025\frac{\text{kg}}{\text{m}^3}} = 7.3 \times10^{8} \text{m}^3 $$ of water.

The last question is: is this enough? Well, sort of. Since the energy is radiated in all directions, at a distance of 200 km, the tsunami wavefront has a circumference of $2\cdot \pi\cdot200 = 1257 \text{km}$ so each meter of wavefront corresponds to 580 m$^3$ of heated water.

This operates under the assumption that all energy is converted to heat, and that all the tsunami's heat is concentrated in one 580 m$^3$ water slug for ever meter of wavefront at 200 km away. While these assumptions are not perfect, I think a lot depends on the way the wave breaks. If it breaks suddenly (i.e. a suddenly rise from deep water to shallow), you might see a more concentrated conversion of kinetic energy to heat. And 580 m$^3$ is a pretty big mass of water; that would correspond to the heated section of the wavefront being an expanding ring 100m wide and 5.8m deep at 200km distance.

So what I conclude from this thought experiment is that it is plausible that a tsunami from a mid-size earthquake could cause the water hitting the beach to heat up several degrees, given that the wave doesn't travel too far, and that it breaks in the right way (whatever that right way is).

Regarding Samoa, the earthquake at 7.9 put out more energy than we are dealing with here, and Samoa is about 200km from the Tonga trench (though I don't know where in the trench the quake actually took place), so I'll file the hot tsunami theory under plausible.


Why is phase rotation needed to produce the colored inversion operator?

When performing "imaging" we are generally attempting to recover the reflectivity of the earth.  At zero offset the reflectivity is the difference in Acoustic Impedance (AI) normalized by the sum. When performing colored inversion we are seeking to recover a layered representation of the band limited AI and not the reflectivity.  As we go from an AI log to a reflectivity log by differentiating we need to integrate to go the other way.  In the frequency domain integration is a -90 degree phase term and an amplitude weight term.  The amplitude term (1/freq) is taken care of when matching the spectra to that of the well log in the amplitude term.


What would happen if Earth suddenly stopped rotating and revolving at the same time?

Two very different processes! First, if the Earth suddenly stopped rotating then the angular momentum would result in everyone and everything on the Earth's surface being flung sideways at a rate proportional to the distance from the Earth's spin axis. That is, no change at the poles, to 1670 km/hour at the equator. There would also be oceanic tsunami's which would sweep over all but the world's highest mountains. Or would they? The amount of energy required to suddenly halt the Earth's angular momentum is so great that its' dissipation would melt the Earths crust, and vaporize the oceans, so maybe there wouldn't be any oceans to form a tsunami, in which case we would all be caught up in a global cyclone of super-heated steam.
As for Earth ceasing to revolve around the sun, with no centripetal force to balance gravitational attraction we would simply start upon an accelerating drift towards the sun. However, If we assume that our moon stops orbiting the Earth-moon center of gravity, at the same time as Earth (presumably by the same hypothetical process as envisioned by the questioner), then long before we burn up with increasing proximity to the sun, the moon and Earth would collide, also by gravitational attraction.


How could this "aztec temple" mountain (or volcano) have been formed on Antarctica?

Remember that Antarctica is covered in a sheet of ice. Strip away the ice and you get something like this:

(Source:Wikimedia Commons)

This is the Matterhorn in the Alps on the Swiss-Italian border. The word horn is used in glacial geomorphology to refer to a mountain peak that has been ground by glaciers on many sides to create a "pyramidal peak" with sheer, faceted sides.

During the Pleistocene ice ages, the Alps were covered in an ice sheet much like Antarctica is today, and undoubtedly at some point the tip of the Matterhorn poked through the top of the ice, looking very similar to the mountain in your picture.


First to Sail the Jet Stream Around the World

As your diagram shows, the jet stream actually has two circulating components: one is "around the earth" (which is why the transatlantic crossing is so much faster going East than going West), while the second is more like a vortex, with a circulating flow "around" the main direction. This circulating flow is vertical in two places: North of the jet stream it is downwards, and South of the jet stream it is upwards.

That makes for an "almost endless" lift - and you could in principle hover there. It would be very uncomfortable, as the winds in that region are quite strong and turbulent.

It reminds me of something I have seen near the beach: when the wind comes in from the sea, it is lifted up by the dunes; and people with hanggliders can jump off the dune, catch the wind, and literally stay in the air as long as they want (and as long as the wind stays up). If they "miss" the updraft when they first jump off the top of the dune, they are on the beach within five seconds; if they succeed, they fly for an hour or more. Right alongside the sea gulls who discovered the same trick many years ago. Example source:

I don't think you can prevent yourself from traveling around the globe when you do this - in other words, you would have to be content to travel in a mostly Easterly direction. I suspect (but do not know for sure) that the currents are too strong to allow you to traverse in the Westerly direction by ducking in and out of the Jet.


The microseism is ocean waves that couple to the ground to make Rayleigh waves.  The ocean waves are gravity waves which are dispersive (different frequencies travel at different speeds), and 0.2 Hz (not 20 mHz) is the frequency of the waves that travel at the same speed as storm winds to which they couple.

The ground motion doesn't die off, even thousands of kilometers inland, because Rayleigh waves are bound to the surface (so waves from a point source would spread circularly instead of spherically).  The waves are produced all along the coast, which negates the circular spreading.


Lanes of flat ocean surface in coastal waters

There can be many reasons for the lines that you see where the water is not rippled.

1) There is no wind on those specific areas.  Not likely in the photo used as the example but especially when there are cold fronts involved the wind can be very inconsistent over short horizontal distances.

2) You may be seeing the influence of boat wakes that passed over the area recently.

3) You may be seeing variation of the underlying ocean currents.  Especially near the coast with tide changes there can be zones of significant ocean current.  Wind and ocean currents have an influence on wave height and shape.  When the wind blows against the current you get higher steeper waves.  When you get wind blowing with the current you get shorter shallower waves (the smooth sections).  The currents are not just horizontal but have vertical components as well.  The lines identified could be vertical eddies in the current smoothing the surface whereas the smooth / rough line in the foreground is were the major ocean flow is going in opposite directions to each other.

4) If the coast in the foreground is shallow and there are waves coming to shore there then the lines identified to be rip currents caused by water returning from the coast line.

From my personal experience I would say that you are seeing variations in the surface ocean currents, and these currents change how the wind develops waves on the surface.

https://en.wikipedia.org/wiki/Wind_wave


How much does the electric current within the Earth' core depend on the axis of the Earth's orbit?

There's still a lot that isn't understood about the Earth's magnetic field, so there's some uncertainty to any answer to your question.   That said, I touch on some of it.

  isn't the current that causes the magnetic field affected by the
  Earth's axis

I'd say probably not.  We can see this by looking at other objects with magnetic fields relative to their axis.  There are some theories that planets need to rotate to have magnetic fields, but Mercury rotates very slowly and it has a small magnetic field.  Mars rotates with a similar period to Earth and it lost it's magnetic field about 4 billion years ago.

and Neutron Stars.

  Often, the magnetic field is not aligned with the spin axis

The Magnetic Axis and the Axis of Rotation seem to have very little to do with one another.  The Rotation Axis' relation to the plane of the solar system, I suspect that has even less influence, but I have no idea how to go about explaining the why behind that, it just feels improbable to me because the effect seems more internally generated and the inside of the Earth cares which way it spins and stretches, but not how it lines up with the plane of the solar system - (I would guess).

In addition, the Earth's Magnetic North Pole moves around.  Earth's Axis changes very slowly.  It's difficult to see a relation between the two beyond "in the same general area".

  (or perhaps the orbit around the sun)?

It's always good to explore possibilities.  Pretty interesting, short article on Mars' loss of it's Magnetic field here that suggests it's the inner workings of the planets that drive magnetic fields.

When there's enough temperature variation and a liquid medium, spirals (or swirles) can form because circulation is more efficient than convection at heat transfer.  Like the atmosphere, you also have the hotter material wanting to expand and rise and the cooler more condensed material wanting to fall, but you also have increasing pressure as you go down, and, perhaps, not uniform molecular density, so it's a pretty tricky subject requiring lots of math behind when spirals form and when they don't.  The solidifying of the other core into the inner core and heat released from that phase change may play a role too.  (I read that, will post a source if I can find one).

Earth's relatively rapid rotation (and corresponding Coriolis effect) might keep the magnetic field pointing roughly North-South (I would guess) but as noted in the map above, there's a fair bit of wobbling and in addition to that, every few hundred thousand years the field flips.

The Moon may cause the movement of the magnetic poles too.

  (or perhaps the orbit around the sun)?

(yes, I just quoted you twice)

That article just above suggests the stretching and squashing of the Earth, both due to the Moon and the Sun would have an effect, so in a sense, the Orbit around the Sun might affect the magnetic field, but more the tidal effects from the Sun than the actual orbit itself.

Because this field remains unresolved, we should never say never until it's better understood.


The sun rises up at 7:30 in 25°E, What time will the sun rise up in 15°E?

Your maths is not detailed, but you have the correct answer.

The Earth rotates at 15 degrees per hour (360 degrees/24 hours).

The time required to rotate 10 degrees is 10/15 = 0.666 hours, which is 40 minutes.


Does usual city pollution have effects on relative humidity?

By way of reference, "humidity depends on water vaporization and condensation, which, in turn, mainly depends on temperature".

From the information you have supplied in your comments. There are waters in Bucharest and forests in the suburbs, but no waters or forests where the country house is located.

From your information, Bucharest has a number of sources of atmospheric water vapour, the river that flows through it (evaporation of water) and the forests in the suburbs (transpiration of water). Additionally, motor vehicle exhausts will increase the humidity as water vapour is one of the products of the combustion of hydrocarbons.

The warmer the air, the greater its capacity to hold moisture. Cities tend to be warmer than rural areas due to the heat island effect, which is the result of modifying land surfaces and the generation of waste heat.

Humidity in the rural location will arise from evaporation of water in the soil and transpiration from crops or grasses. Such transpiration will produce less water vapour than forests. Additionally, the rural location will have significantly fewer cars producing water vapour in their exhausts. Consequently, the rural location will be less humid than the city.

The reason why Bucharest is more humid that the rural location has more to do with the greater availability and vaporization of water in Bucharest and the temperature of Bucharest than the amount of pollution in Bucharest.


What is the most important source of natural gas? Coal, oil or other?

The most important source of natural gas is natural gas. This is why it is called natural. It is not "made" from oil or coal.

Natural gas forms by decomposition of organic material. Whether the organic material decomposes to coal, oil, or gas depends on the composition of the original material, time, pressure, and temperature. In theory, oil (=long chains of hydrocarbons) can decompose to gas (=mostly methane and small amounts of very short chains of hydrocarbons). I am not certain as to how much of the natural gas in existence went through this oil-like stage.

Coal cannot "become" natural hydrocarbon gas, because it contains no hydrogen. It can be burnt to form carbon dioxide, which is a gas, but this is not what you're talking about.


How to interpret the negative (actual) evapotranspiration values?

Negative values for the ET, both potential and actual, usually refer to condensation.
See also "ERA5 mean evaporation rates data - Why is that negative?"
Regarding the ability of the physically-based hydrological models to handle condensation, I'd say that it's difficult to give you a general answer: it will depend on the specific math behind the model, but my general guess would be that they do.
Even a simple Bucket Model, would integrate condensation in the water balance equation. While a more sophisticate Earth System Model would probably process it in the soil moisture and/or canopy component, in order to better represent these dynamics in the water-energy balance of the specific system. See for instance Longo et al 2019


Why is March colder than September in Northern Hemisphere?

The phenomenon is called seasonal lag.

There's a more extensive answer elsewhere on this site but the basic idea is that temperature lags behind insolation by several weeks, because it takes time to change the mean temperatures of the land, the atmospehere, and especially oceans change their mean temperature. This diagram tries to show the lag, along with various ways of reckoning the seasons:


What causes the different colours of the salt pits in the Saloum Delta in Senegal

Writing about the San Francisco Bay salt ponds, Dr R. J. Rusay notes:

  Due to variable algal concentrations, vivid colors, from pale green to bright red are created. The color indicates the salinity of the ponds.  Micro-organisms change their hues as the salinity of the pond increases.  In low to mid-salinity ponds, green algae are predominant. In middle to high salinity ponds, an algae called Dunaliella salina shifts the color to red. Millions of tiny brine shrimp create an orange cast in mid-salinity ponds. Other bacteria such as Stichococcus also contribute tints.

Rusay says nothing about the Saloum Delta, but the explanation could be similar there.


Does the strength of Earth's magnetic field influence its climate?

There is no significant geomagnetic influence on the cycle of glacials and interglacials. I think the easiest way to determine this is to consider geomagnetic reversals. A reversal obviously involves the largest possible change in the direction of the magnetic field (a full 180°). It also involves some of the largest changes in field intensity, because during a reversal the field intensity drops to a small fraction of its usual value before regrowing to ‘normal’ levels (e.g. Raisbeck et al., 1985). So, if we're expecting geomagnetic field behaviour to have any influence on climate, we'd expect the most obvious effects to appear at reversals.

We can look for this effect by comparing a δ18O record (which gives a proxy for global temperature and ice volume) with a record of magnetic reversals. Here's a figure of the LR04 stack from Lisiecki & Raymo (2005), showing those two records for the past ~5 Myr:

As you can see, nothing spectacular or even noticeable happens at the reversals (the black/white boundaries along the bottom of the plot). They don't seem to correspond to any particular point in the glacial/interglacial cycle.

Of course, it's likely that geomagnetic field strength has some influence on climate, and that these effects are simply swamped by other influences on the spatial and temporal scales we're looking at here. The first possible effect that came to my mind was the geomagnetic field's influence on the amount of incoming cosmic rays, which in turn has an effect on cloud formation. And sure enough, it turns out that Vieira and da Silva (2006) have found such an effect. But I suspect that once you start looking at >10kyr timescales and global signals, such effects get averaged out.

Lisiecki, L. E., & Raymo, M. E. (2005). A Pliocene‐Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography, 20(1).
Raisbeck, G. M., Yiou, F., Bourles, D., & Kent, D. V. (1985). Evidence for an increase in cosmogenic 10Be during a geomagnetic reversal. Nature, 315(6017), 315-317.
Vieira, L. E. A., & da Silva, L. A. (2006). Geomagnetic modulation of clouds effects in the Southern Hemisphere Magnetic Anomaly through lower atmosphere cosmic ray effects. Geophysical research letters, 33(14).


Can an igneous rock have a Vp of less than 1000 m/s and need blasting to excavate?

That seems way too low, even for crustal rocks. Recall: Vp = $\sqrt{[(K + 4G/3)/]}$

If you have a rough idea of the mineralogy of the rock (you do if you know that it's andesite or rhyolite), you can estimate the bulk modulus (K) and shear modulus (G) with a Voigt-Reuss-Hill average and use a reasonable density value (maybe 2500 kg/m3) to get a reasonable number for Vp.

This Wikipedia page has a table of velocities for common rocks that might be helpful.


Where can I find archived night microphysics images from EUMETSAT? I

I think only the Day microphysics RGB composite is a standard EUMETSAT product. However, the night microphysics RGB is available from other data portals like the ePort by Eumetrain.org. There you can access and visualize current or archive night microphysics RGB composites. The Java version works better for me, this is an screenshot of how it looks:


How does the air-circulation in the lower stratosphere look like?

This presentation mentions "Atmospheric Motion Vectors (AMVs)", and specifically mentions a number of AMVs, which separately cover the globe (GOES AMVs ±60N, plus polar AMVs from MODIS/AVHRR/VIIRS, and a combined product from UW CIMSS) but says that are all only 3 layers. That presentation is talking about producing a more global, higher resolution product, but it's only a year old, so I'd guess the data isn't available yet.

However, the UW CIMSS AMV page says that their datasets have 13 layers, so maybe it is suited for what you need. The data is gap-filled with modelled data.


Do the rocks below an active sill go down, or those above go up, or both?

It's both. The rocks above the sill go up, whereas those below it go down. For shallow diking events it's mostly up.

This is all based on theory of linear elasticity. People model deformation using elasticity all the time, especially for studying deformation at volcanoes which one can measure using GPS, leveling, InSAR, etc.


What caused the earth's climate to stabilise ~10 thousand years ago?

You need to examine the assumption that it "stabilized". Rather (and simplistically, of course), the Milankovitch cycle en.wikipedia.org/wiki/Milankovitch_cycles moved from a stable Ice Age regime to an interglacial one.  Absent the current human interference, it would (IIRC, anyway) continue the interglacial for some tens of thousands of years, before entering another ice age.

Nor does the end of the last Ice Age really correlate with the rise of large civilizations, since there was about a 5-6K year gap.  IOW, roughly as long from the end of the Ice Age to the first civilizations, as from them to the present.


Making Sense of Coldwater Ocean Currents

The currents run counterclockwise. That's why the Humboldt Current cools the Pacific coast of South America, because the water is coming from the "six o'clock" position in the Antarctica. But in the Northern Hemisphere, the "six o'clock" position is warm water near the equator, which warms Oregon and Washington.

In the northern hemisphere, the cold Labrador current cools land to its west. That's because the water is coming from the "12 o'clock position near the Arctic. On the other hand, the west coast benefits from warm water currents running in a counterclockwise direction. That's because the "6 'oclock" position in the northern hemisphere is near the tropics, which brings warm water to Washington and Oregon at the "2-3 o'clock" position.

All other things being equal, colder air carries less moisture than warm air, and land near cold water currents is dryer than land near warm water currents.


How and when people first realized that Antarctica is a continent?

The idea of a southern continent is older than the actual discovery of the Antarctica. There was an expectation of the possible existence of a Terra Australis balance the global landmasses and the theory went far back. However, those models were not based on true evidence but rather aesthetic arguments that later just happened to come true. In contradiction, landmasses were also expected to surround the North Pole in the Arctic, and that turned out to be wrong.

Mercator (1595) map of the North Pole and surrounding continent. Some practical canals are suggested to facilitate the short cut from Atlantic to Pacific

There have never been any human population on Antarctica prior to western explorers but Maori navigators, had experienced the cold waters for centuries.

From the 18th century, famous explorers as James Cook and Bellingshausen came close and made sightings that pushed the limits of whaling and hunting, but there was little interest or possibility to actually land and map the area. Cook's circumnavigation rather limited the expected extent of a much larger Terra Australis.

Landings and activities were focused on the sub-antarctic islands and to a minor extent, the peninsula. There was little reason for anyone to cross the dangerous roaring fourties, furious fifties and screaming sixties to get to icy waters with little prospect of economic profit or even survival. Stories about early explorers have been questioned and proved wrong multiple times.

Map from 1770 before the continent was descovered

The first concepts of an Antarctic continent based on actual sights probably originate from The United States Exploring Expedition (1839-42). Wilkes described the findings as a

  vast Antarctic continent [protected by] an impenetrable barrier of
  ice

It's not easy to access the coast and the landing opportunities are few, especially in East Antarctica. USEE's findings have been questioned later and there seems to have been little substance in the claims. The sighted coast might as well have been just clouds. Ross even accused him for cartographical deceit.

Even as exploration continued and increased from the 1890s, the nature of the continent continued to puzzle explorers and adventurers. There was e.g. no consensus whether East and West Antarctica belonged to the same continent or if an icy sea, similar to the Arctic, separated the isolated visited outcrops.

Taylor (1914) http://www.jstor.org/stable/1778593

Griffith Taylor, Geologist to Captain Scott's expedition writes in his very entertaining report from 1914:

  Undoubtedly one of the most fascinating geographical problems, if
  not the most attractive now that both poles are discovered, is to determine if there are one or two continents at the South Pole.
  At an animated discussion in the hut, I pointed out that the South Georgia loop carried the "Pacific" type of coast into West Antarctica, whereas Victoria Land (and apparently Prince Leopold Land) belong to that type characterized by block faults and known as the Atlantic type.

Even as the geologists of the time had a developed vocabulary for rock types and correlations, they still couldn't be sure that Antarctica was indeed one continent or two. As a side note, it should be mentioned that they are indeed right in the doubts. Today we know that East and West Antarctica have very different history and properties. See e.g. Boger (2011).

Large areas of Antarctica is ice-free, eg. this valley in Vestfold Hills, East Antarctica. The area was first explored in the mid to late 1900's but sightings of outcrop would assure explorers that they actually saw the continent they were expecting and not floating ice.

Geologists could also early correlate the rare findings from Antarctica with surrounding continents and started to reconstruct the Gondwana assembly, a work that is still ongoing and due to the lack of outcrops in Antarctica is to a large extent based on geophysical data. Still, geologists and geophysicists are looking for similarities in Africa, India and Australia to understand the nature of the Antarctic geology under the ice cover.

With aviation, it was finally possible to map the hinterland of the continent, and great discoveries were made as late as 1946–47 during Operation Highjump and during the Soviet's expeditions in the 50's.
 (Don't miss this short footage of the discovery of Bunger Hills:
Youtube)

As far as I know, it was not until the International Geophysical Year (IPY) 1957-58 an international effort deploy scientists and collect data firmly defined the physical shape of the continent, that we are still refining today. International collaboration appears to be the key to successful research in Antarctica.

Seismic data is indeed very important to understand the Antarctic lithosphere, but the resolution is low due to the low seismicity and especially the limited number of deployed seismometers. This is, however, improving during recent years and a number of new studies are using seismic tomography and receiver functions to measure the continental shape of Antarctica. See e.g. An et al (2015a) and An et al (2015b). Seismic data is also used to understand the ice sheets and to derive the heat flux that causes basal melting.

Also very important is satellite potential field data. Gravity data e.g. GOCE from ESA is and important constraints, but the resolution is low.
Magnetic data especially from airplanes but also satellites as the flight lines are still sparse is used to map and understand geological terranes covered by ice. The ICECAP project is collecting high-resolution data from flights to improve our understanding of the ice sheets, glaciers and also the bedrock under.

A good start to look for data and information about the physical nature of Antarctica is to download the datasets in the Quantarctica package. It includes gravity and magnetic data (that should be updated soon). The bedrock elevation data can show you that actually large parts of the Antarctic continent are submerged under sea level due to the weight of the ice sheets, subglacial erosion and lack of major endogenic processes that can cause rapid uplifts. For a geologist, it's however not the elevation that the chemical composition and thickness of the crust that define it as one continuous continent.

Rather inaccessible.

Finally, it's worth notice that the Internet is flooded by ridiculous conspiration theories about the lack of information about Antarctica. Whiles being entertaining to watch (with a couple of beers or so), there is not any truth in them, but the phenomina gives in insight in how myths and lies are created and blooming on the internet and how important it is to stay critical about unreliable sources. The reality is that Antarctica is very difficult and expensive to access and, thankfully, its sensitive nature is well protected by international agreements.


How much warming there was over time for a specific month?

It is hard  to help unless you clarify what methods have you tried. However, I would suggest to explore reanalysis weather models, as they are the most accurate source of estimated weather conditions worldwide in the past.

A recommended reanalysis is ERA-interim, starting in 1979 so it gives you  39 years, if you really need 40 you can use JRA-55 that starts on 1955.

The KNMI Climate Explorer is a great way to retrieve and plot data from those models.

If you get in there you can set it to plot monthly mean temperatures for a given location. Here is an example of somewhere in SW Canada:

That will produce a plot like this:

Were you can click the "raw data" to get the raw values, and that will produce an output like this:

Where each row is a year and each column is a month. So you can pick the column of the month of your interest and compute the trend from that.

Does it makes sense?


What's the story of the shear face in the new Mac OS Catalina wallpaper?

This is a bedding plane, once horizontal, but geological forces have tilted it to the diagonal. The strata above have been eroded and washed into the sea, perhaps by a storm, leaving the ancient bedding plane exposed. Tilted strata are not unusual in very ancient rock formations.


Is the theory of hot spots compatible with lengthy volcanism?

Tectonic plates are not single blocks of geology. The Africa Plate, like other tectonic plates, consist of cratons  which are "stable blocks of old crust with deep roots in the subcontinental lithospheric mantle, and less stable terranes, which came together to form plates".

The Africa Plates contains the "Kalahari craton, Congo craton, Tanzania craton and West African craton".

The island and volcano of St Helena, though on the edge of the Africa Plate, is more associated with the Mid Atlantic Ridge than it is with the Africa Plate.

The cratons and other land masses that form the Africa Plate may be mobile, but St Helena and the Mid Atlantic Ridge are not.


Intuitive explanation of precipitation amount

It literally means that the water depth will be 0.5mm. For example, if you place a container under the rain and it fills up to 0.5mm, then the precipitation is 0.5mm.

Despite the fact that a wide container requires more rain to fill up than a narrow container, the larger surface area allows it to collect the right amount of rain water to fill up to the same amount as the narrow container in the same amount of time (as long as the walls are vertical). Therefore, if the rainfall is 1 mm, every square meter receives 1 liter of rain water.

Addendum:

By the way, tuna cans can be distributed along your lawn to serve as a very primitive, but very cheap measurement tool that you can use to create a spatial map of what your irrigation system is doing. You can use that for troubleshooting your efficiency, 1 full can is 1 inch irrigation/rainfall.


Why does aragonite form in one case and an acetate in another?

Common Ca carbonates on Earth's crust have different concentrations of Mg. There is High Magnesium Calcite and Low Magnesium Calcite.
Aragonite has in comparison to calcite high levels of Mg.

If you mixed trusted dolomite with an acid and you took aragonite, a carbonate similar to dolomite but with lower levels of Mg, I suposse aragonite is an intermediate carbonate product in the reaction instead of the complet decomposition of the dolomite. Dolomite is decomposed with HCl at high temperatures and not as quick as calcite. So the high concentration of Mg of the dolomite should alter the thermodynamical equilibrium.

The sequence of the reaction is:

Destruction of dolomite crystals.
Formation of aragonite. --> excess of Mg.

The Mg liberated from dolomite structure follows two ways. Aragonite accepts a low concentration of it. Then surplus Mg could be considered chemical waste while acetic acid is a chemical reactant.
In the case you get calcium acetate, acetic acid accepts Ca and it is transformed, but in this case is just a chemical reactant and his structure is not modified. Note the main difference is there is not excess of Ca.


Difference between sulfuric clouds and sulfuric haze (on Venus)?

According to Wikipedia, haze is an atmospheric phenomenon in which dry particulates obscure the clarity of the sky.

Whereas haze is thought of as a phenomenon of dry air, mist formation is a phenomenon of humid air.

However, haze particles may act as condensation nuclei for the subsequent formation of mist droplets; such forms of haze are known as "wet haze".

In meteorological literature, the word haze is generally used to denote visibility-reducing aerosols of the wet type.

According to Wikipedia,  a cloud is an aerosol with a visible mass of liquid droplets, frozen crystals or particals suspended in the atmosphere, and the droplets don't have to be made of water.

This article states that standard cloud models for Venus consider that all clouds and hazes are composed of liquid droplets of sulfuric acid mixed with water, with sulfuric acid making accounting for 75% to 96% by weight of the cloud composition.
However, other minor constituents may make up the cloud particles.

Clearly regarding the mixture of water and sulfuric acid there is no distinction between clouds and hazes on Venus.

In another article it can be seen on images that the altitude from 30-48 km of the atmosphere of Venus is named "the thin haze region ", whereas
the altitude from 48-50 km is called "lower cloud region ".

The figure on page 14 of the dissertation of Yeon Joo Lee also shows that below the cloud layers there is this "thin haze region" which has almost a thousandfold less extinction coëfficiënt than the clouds above it.

Apparently this huge difference in absorbing the light explains the difference and appearance between sulfuric clouds and sulfuric haze on Venus.

Figure 4 of Bullock and Grinspoon 2001 (paywalled) The Recent Evolution of Climate on Venus (Icarus 150, 1, Mar. 2001, pp 19-37) shows the abundances of H$_2$SO$_4$ and H$_2$O in the cloud region of the atmosphere of Venus. A non-paywalled version can be found with an internet search, but since it does not use https I won't include the link explicitly here.

Explicitely it shows H$_2$SO$_4$ as a gas in the thin haze region and only in the cloud region there is a mixture of water and sulfuric acid liquid.


Satellite image displaying as panchromatic

An RGB image can not be rendered if you only supply information for one color channel. This is because three channels are needed: Red, Green and Blue. Different software will deal with this invalid input in different ways: Some might set the remaining channels as black (i.e. filling with zero values). In that case the resulting image will be monocromatic. In shades of green in your example.

Other software might fill the missing channels with the same information supplied for the available one. In that case the result is a gray scale version of the band supplied.

In a general case, the rendered image will only display varying colors if two or more channels contain different information (i.e. different bands).

As mentioned in the comments, it is important to note that the difference between monocromatic and pancromatic. The former is a general term used to describe images formed by shades of a single color. While the latter is a specific term used in multispectral sensors to denote a band with a wider spectral response, and that usually have also higher spatial resolution.


Hydrophone/geophone sensor sensitivity - noise versus signal

Sound-generating wave action takes place only on the surface, and is usually less noisy than seismic events. I'm not sure what you mean by streamers, but I take it you mean ships. These man made sounds are loudest on the surface and much quieter in the depths, whereas  with seismic noises it is the other way around, so the way to preferentially hear seismic sounds is to send your hydrophones deep. In any case, man made sounds are usually very transient and would not cause much interference. Shipping tends to stick to recognised routes, so you would place your hydrophones away from heavily used shipping lanes.


Effects of global warming on drought in India

Since you asked for an intuitive explanation, my thoughts would be that due to predicted increasing sea and global temperatures, the models used might be predicting a corresponding increase in monsoonal moisture or duration.

From Climate of India :

  In India a tropical wet and dry climate is more common. Noticeably
  drier than areas with a tropical monsoon climate, it prevails over
  most of inland peninsular India except for a semi arid rain shadow
  east of the Western Ghats.

An article on
 the National Geographic site discusses the relationship between the ocean air temperature and the monsoons in India:

  The summer monsoon is associated with heavy rainfall. It usually
  happens between April and September. As winter ends, warm, moist air
  from the southwest Indian Ocean blows toward countries like India, Sri
  Lanka, Bangladesh, and Myanmar. The summer monsoon brings a humid
  climate and torrential rainfall to these areas.

So in a region which is warmer, both air and ocean temperature, this monsoon effect is apparently predicted to be altered accordingly, resulting in either a higher precipitation, or longer duration to the wet cycle, to effectively make this region wetter than it is today. Without knowing more about how the models were derived, this is just speculation however.


Is there a risk with putting out smouldering underground coal reserves?

There isn't a risk to putting it out other than the attempt failing, it is just impractical to do so once a large coal vein catches fire.  You can read more about the Centralia, PA coal fire on wikipedia which sits on top of anthracite coal veins that have been burning for a little over 50 years and are likely to continue to do so for a few hundred years.

Your proposed idea of "inventing weather modification" is not practical. While we have the technology to seed clouds and produce localized rainfall this still depends on the amount of water vapor in the air.  You can bypass evaporating water into the atmosphere, seeding clouds and raining and instead just pump water into the mines and flood them.  That will be much more efficient at getting water into the mines.

So why don't they flood the mines?  That too is not practical, and if memory serves me right, they did try that in Centralia.  The problems are

Mines open into cave systems
Water can flow through very small openings
Coal needs only be hot and in the presence of oxygen to burn.

This means you'll need to keep the coal underwater, isolated from oxygen until you can dissipate all of the geothermal heat mass that has built up in the surrounding rocks from the burning coal.  You'll also have to make the mine water tight in order to flood it.  You'll also need a way to deal with your flood water evaporating and steam build up.

Faced with the realization that extinguishing these fires is impractical the decisions were made to abandon the towns.  There was no real risk in putting the fire out, it just isn't practically possible to do so.  The risk in letting the fire continue to burn was abated by evacuating the town permanently.  Burning coal does not effect the production of new coal (that takes a long time on geological time scales) -- burning coal is a net reduction in coal mass, not a gain.

As an aside, the other problem with cloud seeding, specifically with the Centralia, PA case, is legal.  Pennsylvania farmers were so concerned about the possibility of cloud seeding elswehere in the state depriving them of needed rainfall that in 1968 the PA state legislature passed "WEATHER MODIFICATION - REGULATING RAIN MAKING. Act of Jan. 19, (1968) 1967, P.L. 1024, No. 449" which means you'll need to convince the state to issue a license for your activities, which is not likely to be granted.


About the actual radiative impact of greenhouse gas emission over time

There is no doubt that the sooner the mitigation effort happens, the greater will be its impact.

In other words, the impact on year 2100 climate of the sequestration of 20 billion tons $\ce{CO2}$-eq right now, is much bigger than the impact that the same action will have in 30 years from now. Therefore, a mitigation action today is much cheaper than one done in the future but with equal impact on year 2100 climate (assuming no dramatic changes in the sequestration technology).

This is due to the long lifetime of $\ce{CO2}$ in the atmosphere, that is usually estimated to be longer than a few centuries. Although, some sources place the lower limit at around 30 years, its lifetime is most likely longer than 50 years.

This means that any $\ce{CO2}$ that is not captured today (or emitted), will remain in the atmosphere trapping heat and rising Earth's temperature until year 2100 and beyond.


Is it true that a butterfly flapping its wings can result in a tornado in a distant location?

The butterfly is a colourful illustration of Chaos Theory, and the word butterfly came from the diagram of the state space (see below).

A system that is chaotic is extremely sensitive on its initial value.  In principle, if you know exactly how the state of the universe is now, you could calculate how it develops (but due to other reasons, it is theoretically impossible to know the state exactly — but that's not the main point here).  The issue with a chaotic system is that a very small change in the initial state can cause a completely different outcome in the system (given enough time).

So, suppose that we take the entire atmosphere and calculate the weather happening for the next 20 days; suppose for the moment that we actually do know every bit.  Now, we repeat the calculation, but with one tiny tiny bit that is different; such as a butterfly flapping its wings.  As the nature of a chaotic system is such that a very small change in the initial value can cause a very large change in the final state, the difference between these two initial systems may be that one gets a tornado, and the other doesn't.

Is this to say that the butterfly flapping its wings results in a tornado?  No, not really.  It's just a matter of saying, but not really accurate.

Many systems are chaotic:

Try to drop a leave from a tree; it will never fall the same way twice.
Hang a pendulum below another pendulum and track its motion:

(Figure from Wikipedia)

Or try to help your boyfriend in what must be one of the loveliest illustrations of Chaos Theory ever.  Suppose you are running to catch the bus.  You keep sight of a butterfly, which delays you by a split second.  This split second causes you to miss the bus, which later crashes into a ravine, killing everyone on board.  Later in life, you go on to be a major political dictator starting World War III (Note: this is not the plot of the linked movie, but my own morbid reinterpretation).

Tell me, did this butterfly cause World War III?

Not really.

(Figure from Wikipedia)


Can climate models reliably predict meteorological extremes?

Here's one idea to account for meteorological extremes in our climate models, though I'm not sure if it answers your question and am less certain if it qualifies as reliable (open for feedback on that too):

Take a regional climate model which has simulated into the past and the future. We also have a few decades of observed data to compare the same time period of simulated past. The observed data is going to capture the extreme events much better in every way of course. So, in projecting into the future, if we want to maintain those extremes, we can use the change factor (based on averages, e.g. monthly means) from past-simulation==>future-simulation in order to project past-observed==>future-predicted. Those future-predictions will have the extreme events as they came in the past but with the changed magnitude based on the climate model's past versus future simulations.

This could be applied to meteorological data such as precipitation and other weather variables in order to inform us about the driving weather forces we'll face in future scenarios. In this way our climate models account for meteorological extremes we've observed recently and in the past, which the models may otherwise fall short on.

Otherwise, as folks have explained in comments on the OP, we simply don't have extensive enough observed data that we can rely upon to calibrate these rarer frequency events. I think your last two bullet points sum up our predicament fairly well:

  The available measurements are from a 100-200 year observation period (at best);
  We do not have too much data from different climatic conditions (there might be some phenomena which are not (or not adequately) taken into account in current models, we are somehow biased by the observed, prior 100 year conditions.

However, here are a few studies and leads you could explore which try to overcome these challenges in modeling extreme event return intervals and Probable Maximum Precipitation. These seem like they might be addressing your last question but hopefully it helps clarify the potential out there.

This one using extreme-value theory: Van Den Brink et al, 2004. Estimating return periods of extreme events from ECMWF seasonal forecast ensembles.

  ...applications to meteorological and hydrological situations are
  always  hampered  by  the  brevity  of  the  available  datasets,
  as  the  required  return  levels  exceed  the  record  lengths  by  a
  factor of 10 to 100. In order to overcome this problem, we u
  se archived data from all past seasonal forecast ensemble
  runs  of  the  European  Centre  for  Medium-Range  Weather  F
  orecasts  (ECMWF)  since  1987  as  input  for  extreme-value
  statistics analysis. We make use of the fact that the seasonal forecast has little seasonal skill for the Netherlands, which
  implies that the ensembles can be regarded as i
  ndependent sets that cumulate to over 1500 years.
  We investigate the hydraulic response in the Netherlands
  to extreme synoptic-scale weather systems by studying the
  extreme-value  distributions  of  sea  storm  surge  levels,  wa
  ves  and  river  discharges.  The  application  is  detailed  in  four
  practical examples originating from coastal protection, ri
  ver flooding protection, and water management problems. The
  long record length of the ECMWF data reduces the uncertainty in the 10
  3
  -year and the 10
  4
  -year return values considerably
  with respect to the results based on observational time ser
  ies. The ECMWF dataset gives the opportunity to explore the
  distribution of events that depend on several kinds of extreme (Van Den Brink et al, 2004).

This one using the growth factor method, or "NERC M5 method", as explained on page 10: Skaugen and Førland, 2011. Future change in extreme precipitation estimated in Norwegian catchments.

And here is a study which sums the methods up pretty well and proposes a new one for further research, which sounds good to me and relatively like what I described in pretty broad, simple terms in the first part of my answer: Dyrrdal, 2012. Estimation of extreme precipitation in Norway and a summary of the state-of-the-art. There's many quote-worthy passages in this one so I think I'll leave it to you to explore. Sections 3, 4, and 5 are what I imagine you're most interested in because they cover, respectively, the state-of-the-art guidelines/methods from the World Meteorological Organization and various nations; a proposed new-and-improved method; and a conclusion summarize the above.


How much does sea level rise due to sediment deposition?

In a 1983 Journal of Geology paper by Milliman and Meade, "World-Wide Delivery of River Sediment to the Oceans" (link) it is estimated that the world's rivers carry about $13.5\times 10^9$ tonnes of sediment per year. If we assume an average density of $2.5~\rm{g/cm^3}$, this corresponds to a volume of 8.8 cubic kilometers. The total surface area of the world's oceans is 360 million square kilometers. This means that the sediment of the rivers contributes to a rise in sea level of 15 µm per year, or 1.5 mm per century.

The IPCC estimated in its fifth report that the average rate of sea level rise is about 3.2 mm per year. That means that about 0.5 % of that rise could be attributed to sediment. It is certainly not a major factor, but is non-zero all the same.


how large would the leaks have to be to counteract the positive effects?

Trying a ballpark estimate ... biogas replaces natural gas. For simplicity let's assume the replacement is 1:1, one mole of methane from biogas* replaces one mole of natural gas. This also means that one mole of biomethane "saves" one mole of CO2.

Methane is about 25 times more intensive in terms of cliamte change than CO2. So if 100/25 = 4% leaks, the positive effect would be offset.

The factors influencing gas leakage, from biggest to smallest influence (this is mostly from memory):

Retention time of substrate in gas tight system - depending on retention time in the digesters, the digestate could still have 10% or so of it's total biogas potential, when the digestate storage is open and the HRT is short. One of the later iterations of the German rennewable energy laws specifies 150 days retention time in the gas tight system for this reason & I think this is reasonable for many substrates.
Leaking foil roofs - foil roofs are common on large tanks, especially the connection foil roof/digester is a common point for leakage. This study found leakage rates from plants between 0 and 20 Nm³/h (median 5-10 Nm³/h), size of plants was not given but probably around 500 Nm³/h biogas production.
Methane slip - I don't have numbers to go by, but I think 0.5-1% of gas slip (unburnt gas in the exhaust) in IC motors is common. This regardless of wether you burn natural gas or biogas, AFAIK.
Manure storage - some wastes will ferment on their own, esp. manure.
Everything else - IMO the art of building gas pipes etc. is pretty well developed, if proper procedures are followed and proper materials used leakages from pipes should be neglible.

In summary, the methane loss of biogas plants may well be above the 4% cutoff point I mentioned above, or well below, depending on plant design and quality of building.

However, as you pointed out in comments to your question, you need to also look at what would happen to the feedstock without biogasification. Manure would ferment (but not as completely) in an open pit and emit gasses. Municipal wastes would be either incinerated (likely with additional fuel because of the high moisture content), composted or landfilled (landfilled wastes also ferment and produce biogas, if this goes to the atmosphere, is flared or used productivly depends on the site). I have worked in landfill supervision and design of biogas plants.

At this point, I lack good numbers to really compare biogasification to other disposal paths. Having worked in landfill supervision and design of biogas plants, I have more trust in a properly designed biogas plant to keep methane out of the atmosphere than in a typically, well maintained landfill. But I'm sure you can find shoddy biogas plants that leak, for the same amount of input, worse than some landfills!

Likewise, I'm still looking for hard numbers of fuel usage for incineration of biowastes, so I can't offer a good comparison here.

So IMO, while biogas from energy crops is highly questionable, biogasification of wastes is a net benefit if done properly.

*biogas is anything between 50 and 70% methane, the rest CO2 and traces.


Do lava lakes exist in all volcanoes initially?

No, they do not.

Lava lakes require the lava to have low viscosity (that is, be very fluid or water like). If you look at the Wikipedia article for Lava lake, you will see that "basalt" or "phonolite" are mentioned. Those are indeed types of lavas (actually rock) that are very fluid. These are the kind of lava that end up forming lava flows.

On the other hand, there are other types of lavas that do not flow, because their viscosity is too high: rhyolite is one example. Explosive volcanoes (think Mt St Helens) are explosive (mostly) because of the high viscosity of the lava. Therefore, volcanoes erupting explosively (almost) never have lava lakes, because the lava itself is not fluid enough to make a lake.


Term for the Process of the Early Earth's Crust's Changing Mineral Composition

The term you are searching for is differentiation. In Early Earth the Crust was mafic. Remelting cycles created an enrichment in silica and alkali elements, forming basalts and granites.
As it happens on Continental Crust it is commonly referred as Differentiation of the Continental Crust.
Hacker, B.R. et al (2011): "Differentiation of the continental crust by relamination",
Earth and Planetary Science Letters, Volume 307, Issues 3â€“4, Pages 501-516, ISSN 0012-821X, https://doi.org/10.1016/j.epsl.2011.05.024.


Why was the initial theory of plate tectonics so controversial?

One of the key aspects of plate tectonics is continental drift.

The person who came up up with the theory of continental drift was Alfred Wegener. He published his theory in 1912.

One of the issues with the theory that geologists at the time had, was that Wegener was not a geologist, but a meteorologist. He was publishing a theory that wasn't associated with his field of science. The other issue the geologists had was based on the commonly held opinion:

that the oceanic crust was too firm for the continents to "simply plough through".

When he published his theory, Wegener did not propose a means by which the different land masses could break away from each other.

Initially, some geologists could only conceive the idea that ocean waves might be responsible for breaking up land masses, but they couldn't reconcile the fact that the lack of sediments and the clean breaks in land masses would not support Wegener's theory. Without knowing about plate tectonics the theory of continental drift was difficult to support.

Another reason why Wegener's idea was not initially accepted was because of the way he proposed that continents used to fit together. This was because of the assumption most people had was that the continents split along the lines of coast lines and not the 200 m isobath proposed by Wegener.

Wegener came up with the idea of continental drift by noticing that all the major land masses appeared to fit together like a jigsaw puzzle.

It wasn't until the early 1950s when data from paleomagnetic studies of India showed that India had once been in the southern hemisphere that data started to support Wegener's theory. Also, it wasn't until the 1960s that sea floor spreading data was available to support the theory.


Recent studies have recognised what could be the most massive volcano in the world, a geological feature already known, but was not recognised until recently as being a single volcano.

It is the Tamu Massif in the north-west Pacific (location map shown below), what was thought to be one of the vents of the Shatsky Rise - but recent seismic studies, reported in the article An immense shield volcano within the Shatsky Rise oceanic plateau, northwest Pacific Ocean (Sager et al. 2013) have revealed that it is one single shield volcano. The Geology.com article states that it covers an area of approximately 310,800 square kilometers (120,000 square miles), about "the size of New Mexico" - and, according to Sager et al., making it comparable with the size of Olympus Mons.

Location of the Tamu Massif

Map source: Daily Mail

According to the article Underwater volcano is Earth's biggest (Witze, 2013), that although the 140 million year old Tamu Massif is not as tall as Olympus Mons (nor even Mauna Kea) - in fact, it is still an impressive 4km above the sea floor, its 'footprint rivals that of Olmpus Mons', a comparison is shown below (the source is the linked article):

The authors hint that seismic studies could well find more shield volcanoes on a par or even more massive than Olympus Mons. Of course, as they state, the identification of Tamu Massif as a Olympus Mons sized megavolcano suggests that there have been more such megavolcanoes in Earth's early history, most of course would be eroded, lost to tectonic processes etc.


Gases that are nearly transparent to solar AND thermal radiation?

Google Radiative (or radiation) absorbtion coefficients for gases (or enter specific gas of interest). Most of this data relates to applications in combustion and refrigeration so that is the area to look at. To avoid "contamination" from all the global warming stuff try looking at older things like papers from the 1950's. I have some detailed refrigeration books from the 50's which I think had this data but not to hand right now. Or see if you can get hold of some books like that from your library or a bookstore.

Many gases were studied in great detail with proper experimental measurements to verify well before global warming was a thing. You can find graphs of lots of useful things which can help you with an understanding of how the various gases might work in the atmosphere. For example using the emissivity of CO2 to calculate radiative heat transfer in the atmosphere with the standard Stefan-Boltzmann equation when you know the concentration of CO2 is, say, 400ppmV. Emissivity of CO2 can be surprisingly low at atmospheric concentrations, temperatures and pressures, less than 0.002 typically.


A rough picture about the ground-level ammonia (NH3)

It seems difficult to find a reasonable proxy species for $\mathrm{NH}_3$, since its sources (primarily agriculture) are quite distinct from the sources of more commonly observed pollutants. Some observations of aerosol-bound $\mathrm{NH}_4^+$ might (or might not) be available, but due to the reasons you explain, it is non-trivial to infer the gas-phase $\mathrm{NH}_3$ concentration from the $\mathrm{NH}_4^+$ in aerosols.
There are papers about estimating atmospheric $\mathrm{NH}_3$ from satellite data, see for example here or here. These are for column-integrated and not surface $\mathrm{NH}_3$, however.


If there is enough water underground, in a sealed reservoir (like under the concrete in the picture), as that water freezes, it will expand, putting pressure on what ever water is left unfrozen. That water will be squeezed out through what ever cracks it can find - in this case, upwards. Because the water is already near-freezing (perhaps even slightly below, if it's super cooled), it will freeze very quickly when it hits the air (which will be much colder than the ground, late at night). But if there is still water being pushed up from below, that ice will have to move out of the way (it's weaker than concrete). The friction of the flow of cool upwards might warm it just enough to keep it liquid, and the "stalagmite" will end up with a hollow core that the water is being pumped through, and that structure can just keep building on itself, until it is toppled by wind or gravity.

The picture is a bit grainy, but it looks like that's what's happened there. It also looks like the side of the hollow "stalagmite" has fallen off up the top, and released a bit of the remaining water (or maybe it just melted in the sun).

Edit: Hah, I knew I'd seen this somewhere before - in my freezer! This page describes how Ice spikes form - I basically got it right. It seems that they're more likely to form with de-mineralised water, and the temperature has to be within certain narrow limits.


Global warming - why doesn´t mankind collect heat (thermal energy) and turn it into electricity or send it to space?

Your middle school physics perhaps hasn't gotten to thermodynamics yet. The three laws of which can be summarized as 1) You can't win; 2) You can't even break even; 3) You can't leave the game.

The crucial point here is that heat engines don't actually work on heat, they work on temperature differences.  So you can't really "collect" heat and turn it into other forms of energy, because you need a colder place to transfer the heat to in order to convert the heat to say electricity.  Which is why power plants are usually situated by oceans, lakes, or rivers, in order to use the water as the cold side of the generator.  (And ones that aren't have large cooling towers, in order to use the air.)

When you do move heat around, say with the heat pumps used for home heating and cooling, you're always using some extra energy to "pump" the heat from one place or another.  If you're heating, you move some heat from the ground outside to your house, but the net result is that the system of ground+house gets a bit warmer, because the electricity used for the pump becomes heat.

WRT sending the heat back into space, that's actually the cause of global warming.  Atmospheric CO2 acts as an insulating blanket, preventing some of the sun's heat from being radiated back out into space.  By increasing the amount of CO2 in the atmosphere, we've increased the thickness of the blanket, so the Earth gets warmer.


How to find/calculate the yearly evaporation of a given area?

What you are asking is one of the most difficult issues in hydrology. The evaporation from open water is a function of air temperature, water temperature, humidity, wind speed and fetch, water depth, water salinity,  degree of thermal stratification, and boundary effects (as you correctly point out). It is certainly not a trivial calculation!
As a first approximation you can apply an empirical coefficient to class-A pan evaporation data, but don't expect any great accuracy.

But then you progress towards a further aim of calculating a potential irrigation need. For this purpose I would say that calculating open water evaporation is completely the wrong approach. Rather, calculate the potential evapotranspiration ('ET0'), and then apply appropriate crop factors, as explained in the FAO documentation:
http://www.fao.org/docrep/s2022e/s2022e07.htm
Calculating ET0 is best done using the Penmann-Monteith equation, which is horribly complicated, but there are web sites where you can do the calculations on line. You will need monthly or dekad climate data for the crop(s) you envisage growing. This will be max and min temperature, humidity, average wind speed and average daily hours of bright sunshine. You will also need latitude, longitude and altitude to estimate the solar radiation. Even with all this data, it is a fairly lengthy calculation, but it is your best bet at realistic crop water requirements.


Can we predict the earthquake before it occurs a while? What is the maximum period?What are the signs of an earthquake soon?

Short answer is no.  Earthquakes often occur in clusters but the problem is there is no way of knowing when the largest quake has occurred until the series of quakes is completed.  Studies in fault areas measuring changes in magnetic fields, changes in the local water table, radon gas and radio wave emissions have shown to not be reliable indicators of an impending earthquake.

The United States Geological Survey (USGS) has a publication discussing the possibility that animals feel earthquakes before people.  The basic premise is that animals can feel the P waves, the fastest waves coming from an earthquake, that few humans can feel.  However, a baseline behavior for each animal would need to be measured and the stimuli that an animal would react to would have to be present before the earthquake.  So again, animals are not a reliable precursor to an earthquake.

Given no reliable indicator of an impending earthquake, the most important development in saving lives is the use of early warning systems.  There are several countries that have been implementing these for years including Japan, Mexico, and China.  Many seismologists believe that a warning of up to a minute could be given.  Three of the many factors that determine the effectiveness of an early warning are:

Distance between the earthquake source and the closest seismic
network seismometer (station)
Transfer of information to the regional networks
Detection and characterization of an earthquake

This graph presents estimated warning times from distance of epicenter.

Estimated warning times for locations at different distances from the earthquake epicenter. Locations within 20 miles of the fault will likely not receive any warning as, on average, it will take 10 seconds to detect and locate the earthquake.

Source:https://earthquake.usgs.gov/research/earlywarning/background.php


Why (actually) is the night sky so bright in the city? How far up is that happening?

What's actually happening is scattering of light, both off of aerosol particles and nitrogen and oxygen molecules.

For a review of quantitative models of light pollution as a function of distance from cities see Light Pollution Modeling . Some consider height as well as distance.

To get a rough estimate of what size of lights-out event would be needed to obtain a particular improvement in sky darkness, I would suggest looking at the light pollution map at Dark Site Finder or The night sky in the World.

  Colours correspond to ratios between the artificial sky brightness and the natural sky brightness of: <0.01 (black), 0.01-0.11 (dark-gray), 0.11-0.33 (blue), 0.33-1 (green), 1-3 (yellow), 3-9 (orange), 9-27 (red), >27 (white)

Look at a coastal city such as Miami (which is extremely light-polluted) and see how the degree of light pollution drops off with distance from the city. Or look at a very isolated city such as Bismark, North Dakota.  I would estimate 20 to 40 kilometers away from a source you see a factor of 10 reduction in artificial brightness.


Why is calcium so much more abundant in/on Earth's crust (and oceans) than it is elsewhere? (relatively speaking...)

Two factors need to be considered here.  Magnesium ions are smaller, thus forming more compact formula units, and they are also often mixed with iron ions which make the formula unit weight heavier than you expect.  Magnesium-rich mafic rock, being also iron-bearing and with compact ions, literally packs on the pounds and tends to sink deeper into the crust and the mantle compared with rock (even mafic rock) containing more calcium.
A false bargain
Magnesium may form lighter atoms than calcium, but it also forms smaller atoms--especially when the metal forms cations as in the most common minerals where the metal is bonded to oxygen.  So the magnesium compounds have less formula weight but pack that mass into less volume.  If we compare densities of corresponding calcium and magnesium compounds we see that these effects almost cancel out.  Data for these examples are taken from Wikipedia:
$\text{CaO}$:  3.34 g/cm³
$\text{MgO}$:  3.6 g/cm³
$\text{Ca}_2\text{SiO}_4$:  3.28-3.33 g/cm³ (larnite)
$\text{Mg}_2\text{SiO}_4$:  3.21-3.33 g/cm³ (forsterite)
So there is only a little density difference overall -- in a world where mafic rocks do not contain iron.  Ah, but they do.
Going green, but packing heavy
Why is jade usually green?  The most common jade mineral is nephrite, which is mainly a slightly hydrated calcium-magnesium silicate -- with a little iron mixed in to get that green color, at least at low levels of iron.  The formula for this mineral is a mouthful:  $\text{Ca}_2\color{green}{\text{(Mg,Fe)}}_5\text{Si}_8\text{O}_{22}\text{(OH)}_2$.  As indicated by the text in that suitable green color, the iron is intermixed with the magnesium, not with the calcium.  The same holds true with the simpler, and also green-colored, olivine, $\text{(Mg,Fe)}_2\text{SiO}_{4}$, except that olivine can contain more iron than is usually found in nephrite.
Magnesium and calcium both lie in Group 2 and both form ions with +2 charges.  But that alone does not mean they are intermixed in mineral structures.  To fit nicely into the precise, tightly packed solid phase ions must not only have consistent charges at a lattice site, they must also have consistent sizes.  Calcium ions, with an ionic radius of 114 pm (ionic radius data from Wikipedia), are simply too big to fit where there should be magnesium ions with a radius of 86 pm.  Iron with +2 charge in its high-spin state (oxides of transition metals usually have high-spin ions) comes in at 92 pm, not perfect but a much more acceptable charge/size doppelganger for magnesium.  While nephrite in green jade has only a little iron, olivine can have a full range of iron/magnesium ratio from forsterite ($\text{Mg}_2\text{SiO}_4$) to the dark fayalite $\text{Fe}_2\text{SiO}_4$, with a wide range of densities to match -- all the way from 3.2 to 4.5 g/cm³.  This range overwhelms the small difference we saw earlier between calcium and magnesium compounds without iron noted earlier.
So the combination of a common, small ionic size for iron and magnesium with a relatively heavy atomic weight for iron makes magnesium-rich rocks sufficiently iron-rich and closely-packed to weigh them down.  Calcium adds extra bulk from its own ions and remains iron free in its lattice sites of mineral lattices, so calcium-bearing minerals are less dense and tend to float into the crust (and even continental crust).
Earth's Cream of the Crop
This answer may be compared with the one here regarding the Martian crust.  There, we find more magnesium relative to calcium.  While the calcium vs magnesium/iron differentiation described above occurs there, lack of a specific continental crust means the differentiation is less.  Accordingly, the composition of the Martian crust is closer to that of the magnesium- and iron-rich mantle than that of the terrestrial crust.