Does the climate have any effect on plate tectonics?

According to the article Cenozoic climate change as a possible cause for the rise of the Andes, the climate could affect mountain building by altering the amount of erosion, and therefore sediment deposits, which could act as a lubricant in subduction zones. In the example given, the lack of sediment increased friction, causing "crumpling" and the building of the Andes.

Given that the climate impacts erosion, that erosion may then affect the stress loading of thrust faults, affecting the earthquake frequency and magnitude, the same as post-glacial rebound.

Isostatic rebound resulting from melting glaciers may also impact volcanics, by changing the pressures, and so lowering the melting point if the rocks. "The average melting rate is increased by about 30 times its steady state value when a 2-km-thick ice sheet melts in 1000 years." In Iceland, the melting of the glaciers at the end of the last ice age correlates with a 30-fold increase in eruption rate. (Source)in


How were smaller reptiles/mammals more successful at surviving the KT event than larger dinosaurs?

It mostly has to do with three factors, numbers, fecundity, and behavior. Let's start with the last, certain behaviors that increase your chances of surviving are far more likely in smaller animals things like burrowing, and hibernation. They are also more likely to be generalists able to eat almost anything, specialization is a death sentence during a major environmental change. They also require less total amounts of food as individuals, it is far easier for a rat to find enough food to survive in a wasteland than an elephant, This is also true in comparing cold-blooded vs warm-blooded animals.

Second you have numbers, there are several billion rats in NYC alone, even with the total destruction of the city it is very easy for a some rats to happen to be lucky enough to survive, small animals will die in larger numbers but there are so many of them they are more likely to have some survive. They literally have the law of large numbers in their favor.

Last is reproduction, size is connected to reproduction, an elephant reproduces once every two years under ideal conditions, while a rat can breed every 24 days, so even if a few elephants do survive they repopulate so slowly they may never recover and some other minor event may finish them off.

So if you combine these not only are small animals more likely to survive they can recover far faster than most large animals, so all things being equal you should expect small animals to be better at surviving and diversifying after a event.


How to define the force at the base of an oceanic crust

Your approach of adding all the forces together is correct. You have a mistake in in the solution of the $F_{oc}$ integral, though.
You forgot to integrate the terms $\rho_{w}gh_{w}$ and $-\rho_{oc}gh_{w}$

It should read:

$F_{oc} = ... = \rho_{w}gh_{w}(h_{w}+h_{oc}) - \rho_{w}gh_{w}h_{w} + 0.5\rho_{oc}g(h_{w}+h_{oc})^{2} - 0.5\rho_{oc}gh_{w}^{2} - \rho_{oc}gh_{w}(h_{w}+h_{oc}) + \rho_{oc}gh_{w}h_{w} $

You have to keep this in mind for $F_{M}$ as well.


Why is the core of Earth in a reduced state? ($\text{Fe}$ and $\text{Ni}$)

Because there wasn't enough oxygen to oxidise all of it. There is only so much oxygen on Earth. Most of it went to oxidise the elements that have higher affinities to oxygen: silicon, magnesium, calcium, aluminium, etc. Iron and nickel have lesser affinity to oxygen, so you start by oxidising some of it, until there is no oxygen left.

But there is still unoxidised iron and nickel left! So this just sinks to the core.

Further reading.


Why is not snow melting in Ladakh at a rapid pace

The albedo of the snow would be the primary reason the snow is not melting.  Using a simplified model there are two main sources of heat energy that the snow can absorb, the heat from the ground below, and the heat from the sun and atmosphere above.  The ground and the atmosphere are going to be colder at high elevation because of the lapse rate that gansub mentioned in his comment, which effectively leaves radiant heat from the sun to warm the snow.  Snow is a good reflector of near infrared to UV, the linked document on the top of page 206 shows the albedo for wavelengths from 400nm (blue/UV) to 900nm (near IR).  On the table you will find that the minimum albedo for snow (assuming fresh snow) is above 0.8 or 80% or better is reflected.

One aspect that might be confusing is that I don't believe you are getting a sunstroke, a body heat issue, but instead a sunburn.  Sunburns are damage to the skin from UV radiation.  At high elevations the UV from the sun is not filtered as much as it is at lower elevations, in addition what does make it through gets reflected back by the snow, effectively doubling the UV exposure when you are in a snow field.  See this site from the World Health Organization,


What would it be like to live in an ice age?

It depends where, the continental landmasses at higher latitudes would be covered by massive ice sheets. Therefore the life in the sections of the US and Europe that are close to the Ice sheets would have conditions similar to what is life in Greenland today. The map would look like this:

(Image taken from planetaryvisions.com)

And the summers would be more mellow than what you are used to. Mean global temperatures would be much lower but at tropical latitudes there would still be warm weather. That means that the temperature gradient between the equator and the poles would be larger, leading to quicker climatic transitions as you travel North or South, and also leading to stronger winds and probably more powerful storms.

Also the sea level would be about 120 meters lower than today, exposing many areas that are now underwater, some of them massive, like the Sunda land bridge (see map in the Indonesia area), many islands would be connected to the continents, like Tasmania to Australia and Sirilanka to India.
England would be connected to Europe and the Persian gulf would be dry, as well as the Yellow sea. New Zealand would be just one big island, and hundreds of islands that are now underwater would poke the oceans.
Using ETOPO1 I've put together a fairly high resolution image of the world showing all the land that would be exposed if the sea level today drops 120m (as it did on the last ice age). You can see it here.

Furthermore, the Pacific and the Atlantic would be completely isolated from each other for navigation proposes, as the Magellan strait and Drake passage would be blocked by ice and the Panama canal would be a nearly impossible feat, with the sea level ~120 m lower than today. So probably, train transport would be much more important to carry goods across the Americas.

The Suez canal would not exist either, and navigation around the Good hope cape at the southern tip of Africa would be constantly threatened and perhaps blocked by icebergs, so most transport between the Indian and Atlantic ocean would be by land too.

The sea ice would be in contact with the tropical gyros, meaning that massive floating ice islands would be seen even at the Ecuador, and icebergs would be all around the oceans.

All that would mean that all the empires that rose from naval power (England, Portugal, Spain) would might not existed, then, maybe Asian powers would rule the world undisputed, and the colonization/invasion of many territories would have never happen or at least would have been delayed, leading to a completely different world distribution and organization.

Another interesting change, would be the scarcity of shallow seas compared to today. The drop in total surface area for a given elevation below current sea level becomes stepper once the sea level drops more than 60 m. Therefore, the sea depth would increase quicker as you go seaward from an "ice age seashore". This would lead also to a drop in coastal water productivity (opposite to what is believed to have happened in the Cretaceous, with high sea level and abundant shallow seas).

Also the day would be about one and a half minutes longer, meaning that the year would have only 364 days.

The change in day length would lead to calendar changes. Currently, a year have 365.2422 days, that is approximated in our calendar to 365.2425, with the fraction part divided as

0.2425 = 0.25-0.01+0.0025

The +0.25 is compensated by adding one day every four years, that is a leap year
The -0.01 is compensated by skipping one leap year every 100 years
And the +0.0025 is compensated by not skipping one leap year every 400 years.

That's how our calendar works today.

Now, if we assume that the figure of a day 1.5 minutes longer is precise, one year would have 364.8621 days, and the fractional part would probably be approximated to 0.8620, and perhaps divided as

0.8620 = 0.80 + 0.05 +0.02 -0.0080

So the calendar rule would perhaps be like

+0.80 compensated by adding one day every year except every 5 years
+0.05 compensated by skipping the above rule exception every 20 years and add a day anyways
+0.02 compensated by skipping the exception to the first rule once more every 50 years.
-0.0080 compensated by not adding an extra day every 125 years

Or something like that, many other arrangements could be imagined. But at the end, a typical year would still have 365 days, but the leap years would have one day less instead of one extra day.


Publicly-available real-time world-wide seismographic information?


When does an island with isthmus become a peninsula?

I think the naming difference is largely qualitative and even arbitrary in some cases. There are lots of 'islands' that are technically connected to a larger landmass by an isthmus of some sort, which would make them peninsulas technically, and not islands.

If you take the definition of a peninsula to be a body of land surrounded by water on three sides, then yes, the island in question could technically be called a peninsula.

Local names of landforms are often linked to cultural or historic influences, just as much as they are to their technical description. There's no 'threshold' of isthmus-width (as far as I'm aware), where once crossed, a peninsula-like island becomes an island-like peninsula . If there was it would be entirely arbitrary.

As an interesting aside, the Isle of Harris in Scotland is not only not an island (there's an isthmus connecting part of it to a larger landmass) but even the isthmus part is not used to define the limit of the island, which occurs at some seemingly arbitrary point on the larger landmass! (see the map in the link to see what I mean)

https://en.wikipedia.org/wiki/Harris,_Scotland


Why do most seismic inversion methods ignore high frequencies?

Because those frequencies are not present in the seismic data.

Here's an example with some typical numbers:

Seismic sample interval: 4 ms
Therefore Nyquist is 0.5 $\times$ 1/0.004 = 125 Hz
Usually there is a filter on the recorder at 0.8 $\times$ Nyquist = 100 Hz
So the seismic does not contain frequencies beyond 100 Hz

The maximum frequency $f_\text{max}$ of the data determines its resolving power. There are various ways to think about and calculate this; here's one formula (Kallweit & Wood, 1982):

$$\tau_\text{min} = \frac{1}{1.4\,f_\text{max}}$$

So in our example, the thinnest resolvable bed is about 1 / (1.4 $\times$ 100) = 7.1 ms, and it will be thicker than that if there is a lot of noise or the bandwidth is not optimal (the earth attenuates high frequencies more than low ones, so this is an absolute minimum).

If we assume a P-wave velocity of 2500 m/s, then 7.1 ms two-way time is about 2500 * (7.1/2) = 8.9 m (55 ft). Ordinary wireline logs have a resolution of 0.15 m or 6 in, so there's a substantial discrepancy. I call this 'the integration gap'.

Because the seismic contains no information about geology thinner than this 8.9 m (in this example), not only is it pointless trying to invert for it, but it would be dangerous: anything we thought we'd resolved would be erroneous. This is why it's necessary to filter the logs back to the resolution of the seismic.

Reference

Kallweit, R & L Wood (1982). The limits of resolution of zero-phase wavelets. Geophysics 47 (7), p 1035–1046, DOI:10.1190/1.1441367.


What will be the depth that water can sink to the ground?

One quick and dirty solution may be to lower the virus-pond level and raise the new-pond level ... so the flow should be from the new-pond to the virus-pond.

Soil being clay may mean the flow is happening below the soil ... if the virus-pond is in contact with the unit below the clay you may already have widespread contamination.


Is VLF-EM scanning for fractures a valid way to find groundwater for a well?

VLF-EM is a perfectly valid technique for helping an expert decide where best to locate wells in geological environments where water is largely flowing in fractures. Typically it is a useful technique in fractured bedrock where a successful water well needs to intercept connected fractures or fissures. In other geologies, for instance porous sandstones, it would be much less useful. Drilling for water in fractured terrains is always a slightly risky proposition; geophysical techniques help site wells to intercept fractures but they can't guarantee yields, which will depend on how large the fractures are and how interconnected they are. A reputable contractor should be prepared to provide references from satisfied clients and that is a good starting point.


Why are alpine river water green - blue?

According to the website Putting the Emerald in Emerald Lake – Where do the colours come from?, the reason for the colour is the same that occurs in lakes, it is due to what is known as or similar material to 'rock flour' - consisting of

  of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock

and relevant to a river environment

  When the sediments enter a river, they turn the river's colour grey, light brown, iridescent blue-green, or milky white.

The colour is due to:

  the suspended material distorts the wavelengths of light, reflecting back more of the green and blue end of the spectrum

These usually originate from glacial melt, even though there are no glaciers in the Julian Alps presently, but there used to be, resulting in according to the WP6 Hydro-geological upgrade and improvement of the GIS of the sources of drinking water webpage as having

  The intergranular aquifer in the alluvium of the Soča/Isonzo River, which is composed of fluvial and fluvioglacial gravel and sand sediments with individual lenses of conglomerates

further explained in the article Bovec basin (Upper Soča valley, Slovenia), as having

  Quaternary
  sediments are represented from bottom to top by partly lithified glaciofluvial sediments, overlain by lacustrine
  chalk. During the Holocene, the chalk was partly eroded (in some areas totally) and covered by glaciofluvial
  sand and gravel which are weakly cemented in some parts into conglomerate and by unconsolidated moraine
  (till).

Potentially, plenty of source material. The particles are small enough to be suspended in the water of the Soča River.


Where do the electric charge carriers for the current for earth's magnetic field come from?

Although Temperature boundary conditions at the mantle do affect the dynamo that sustains itself in the earth's core, it is unlikely that the dynamo's genesis came out of polarized regions in the earth's mantle.

Regardless of the manner of genesis of the core, it is now a self-sustaining dynamo where electric current creates a magnetic field which in turn generates electric current owing to rotation of the earth much as in an electric generator. If you want to read more about it in detail, I would recommend an excellent review paper by Prof. Binod Sreenivasan available at http://ceas.iisc.ernet.in/~bsreeni/currsci10.pdf


Stratosphere height vs. Temperature based on ozone concentration

There are two main points to make here.
The first point is that UV radiation is entering the stratosphere from above (ignoring angular dependencies and scattering), so is preferentially absorbed by ozone higher in the stratosphere.  This is a form of the Beer-Lambert law, which leads to greater absorption higher in the stratosphere.
The second point is that the Dobson Units used in your plot standardize for (partial) pressure and temperature differences between different heights in the stratosphere, so that you can compare the mass or number density of ozone at different levels.  But it doesn't tell you how much ozone there is relative to all the other gases making up the air at a particular height.  A common way to look at this is the mole mixing ratio:

A height–latitude cross section of annual average ozone mixing ratio (ppmv) from the climatology.
Source: McPeters et al (2005), Ozone climatological profiles for satellite retrieval algorithms, GRL.

While the ozone concentration peaks around 20 km, the mixing ratio peaks around 30 to 40 km and doesn’t decline so abruptly with height.  Where the mixing ratio is greater, absorption of a particular amount of UV radiation can have a greater effect on the overall air temperature at that height.
The net effect of these two properties is that heating of the stratosphere by UV absorption (see plot below) peaks in the upper stratosphere around 50 km.  This is why the greatest temperatures are found in the upper stratosphere.

Heating from absorption of UV radiation (K/day)
Source: Haigh (1984) Radiative heating in the lower stratosphere and the distribution of ozone in a two‐dimensional model, QJRMS.


Is there a "submerged object" in Australia that causes a magnetic deviation of 20 degrees?

I'll disagree with Camilo Rada's answer, and show that there is definitely a magnetic anomaly.

We start with the interactive geophysics map of Geoscience Australia, Australia's federal geoscience agency. Our region is this:

Here's the same area with magnetic intensity layer turned on:

You can see a clear magnetic anomaly in this area, and it's actually much more widespread than noted on your map.

  If so, is there a naturally occurring phenomenon…that causes it?

In general, answers to questions like these are yes. But let's explore it further with the geological map of the area:

Overall, the rock type around is "OSn" and "Os". According to the legend, these are high grade metamorphic Ordovician and Silurian rocks, and neighbouring rocks are siliclastic which tells me they shouldn't be too magnetic (confirmed by the magnetic map). The area of Mt Jim has "Dg" (= Devonian granites) which might be slightly magnetic. But here's the thing you were looking for: "Czb", which is short for Cenozoic basalt. And basalts are magnetic.

So to answer your question, the source for the magnetic anomaly isn't a "submerged" (buried would more appropriate here btw), but a basalt fully exposed on the surface.

EDIT

Interestingly, the blog post mentions the presence of basalt, so it's not entirely clear why they claim that there's a "massive, yet unknown, submerged object". Most probably there's simply more basalt, or its intrusive analogue: dolerite or gabbro. These targets are attractive for the mining industries. I would be surprised if it hasn't been drilled at some point by an exploration company, and then the underground cause of the anomaly would be very well known (but probably not publicly).


For lightning to form there has to be a rising current of air within the cloud, carrying ice crystals and water droplets upwards. The droplets become hail, and start to fall as the air becomes thinner, rubbing some electrons off the minute ice crystals, which continue to rise, now positively charged. The soft hail falls to lower levels and is now negatively charged. Positive and negative charges have a great attraction for each other, as the electromagnetic force is almost unbelievably powerful.

Air is a bad conductor, so although the separated charges gradually build up they won't recombine until the build-up of charge is sufficiently strong to overcome the resistance of the air. Leaders from the oppositely charged regions are constantly probing for a viable passage where a lightning flash can get through to recombine their positive and negative charges.

Sometimes a way is found where the build-up of charge is sufficiently strong to overcome air resistance and a lightning stroke occurs, but if the charge build up is not sufficiently strong no spectacular flash will occur. Instead, the separated charges gradually leak away until charge equilibrium is established. So although it may seem to you that conditions are right for lightning to occur, that may not actually be the case.

More unusually, separation of charge can also happen in dry conditions like dust storms and forest fires, where rising dust particles take the place of water. A vaguely similar process of charge separation takes place in a Van der Graaf generator, which can produce artificial miniature lightning discharges.


What exactly are you trying to measure? some of the great North American and Andean batholiths have cooling histories of at least 20 million years, and maybe more than 50 million years. It is perhaps inappropriate to think of the crystallization process as having a single date. Phenocrysts near the top of the pluton are cooler, but may sink to deeper levels where they are partially resorbed or mantled in multiple cycles, giving rise to zoned phenocrysts. It can be a very long process. Generally, late stage pegmatites, which have been enriched in volatiles that depress the melting temperature, will indicate the youngest age of crystallization. Deeper levels of the magma chamber will be older, but really one needs to study the specific field relations, including extent of metamorphic aureole to decide upon the most appropriate younger or older samples. The middle will most probably give a reasonable average date. Remember, what you are measuring is the time of that the mineral cools through its 'closure temperature', which will be slightly to significantly younger than its time of crystallization.

As to the method of isotopic dating, K-Ar is generally OK but the relative error bounds get worryingly large for dates < a million years. Ar-Ar is more precise but more expensive. It's also an excellent method, as is Rb-Sr, especially for really old precambrian plutons - provided the sample is fresh. Any weathering or diagenesis messes up the method.


The rock you have is most likely not platinum ore.  It appears to be sulfide ore most likely composed of galena, pyrite, and maybe copper sulfides such as bornite.

It is more likely that your specimen is silver ore rather than platinum ore.
Mexico has a long history of silver mining.

There is a platinum deposit in southern mexico and it appears to similar to the Bushveld igneous complex deposit.  Ref: Mindat.

Layered chromtite ore looks significantly different.  Reference.

USGS report on Platiunum
Article on current silver mining in Mexico.


This answer assumes 280 PPM CO2, at least until the ice age and oceans begin to draw CO2 from the atmosphere.

If we look at the Pleistocene and we measure how long glacial periods last and how long inter-glacial periods are, You could say, observing the Earth for the last 2.5 million years that being in an ice age is Earth's natural state, with only brief periods between ice ages.

Ice ages have also followed pretty regular patterns that makes them, in theory, somewhat predictable.   Ice ages mostly followed a 40,000 year cycle, between about 2.5 million years ago to about 1 million years ago, then switched to roughly a 100,000 year cycle over the last million years.

It's not precisely known why the cycle switched from 40,000 to 100,000 years.  That's known as the 100,000 year problem.  But if we use the current 100,000 year cycle as a ballpark measuring stick or if we measure the length of interglacial periods (which are generally pretty short, 10,000 - 30,000 years), then the next ice age can be estimated at not too far off.  Maybe 10,000 years.

But if we look closer at what actually triggers ice ages, which is (simplified version), colder summers in the Northern Hemisphere, driven by orbital variations.    We can get a better estimate when ice ages should come by looking for when the Northern Hemisphere summers will get colder.

Milankovich cycles don't always neatly line up and the right conditions for the next ice age, based on orbital changes is a bit unclear.  When the red line in this chart below is low ice ages are more likely to happen, and we're in a dip now, but coming out of a warmer summer period and relativly soon entering another one.   There's a slightly bigger dip that peaks in about 60,000 years from now, another one 100,000 years from now and a bigger one, about 130,000 years from now.

Using this chart as a guideline, the next glaciation is more tricky to predict.   Perhaps in 60,000 years.   These predictions are hard to make though because ice ages are self sustaining.

So, short answer, perhaps the best answer.   Nobody knows.   The Milankovich cycles aren't lining up in the right way to make this prediction easy.  We may be set for an unusually long inter-glacial period.

As for how catastrophic would it be.   Well, for one, we'd see it coming and stopping an ice age would probably be easier than stopping ice from melting.  Releasing CO2 and CH4 into the air for example.  For a longer answer, how catastrophic would it be is a world-building question.


What is the maximum grain size of a sediment that can be point counted using a standard thin section?

you might have guessed: There is no such an easy answer as a precise, always valid maximum grain size.

Point counting is an upscaling technique. It works when the sample area you inspect is >= to the so-called representative elementary area (REA) of the rock facies. The larger your grains, the larger needs the REA to be. Same holds true for increasing heterogeniety and increasing number of mineral phases.
So check if your point count analysis is changing when you increase the inspection area. Once the analysis comes to a stable ratio of analysed items, you found the REA of the rock facies. This REA is a material property and not depending on the step size you choosed (as long as you make sure to obey the law of large numbers for each area).

-> look for "REA"

Best,
Ben


What did tunnel digging teach us about the formation of chains of mountains?

Tunnels have provided nothing more than what was learned from conventional geological drilling and surface mapping. Tunnels provide supplemental information. Very rarely do they provide "make or break" information that is pivotal to geological understanding on a large scale.

A tunnel is a lateral large diameter hole. Geological drilling produces small diameter holes, whose orientation can be lateral, vertical or anything in between. A sample of rock is take by both.

By using in-hole surveys and noting from where, within a hole, a sample was taken from it is possible to know where the rock sample came from. This is useful for creating geological maps of the region. It is even possible to place ground stress measuring devices in both drill holes and tunnels.

The mass of material taken from a hole, whether it be a geological drill hole or a tunnel is not particularly significant in expanding knowledge. More knowledge can be gained from multiple small samples taken over a large area.

Tunnels do give geologists the advantage of walking through a rock mass and seeing some structures like faults. But if the tunnel hasn't intersected a structure then the geologists may not know about it.

Your question is a bit like asking "what can be learn about a country by just walking along its roads". Additional information can be gained by walking off track, navigating rivers, flying over the country and talking to the inhabitants.

Tunnels provide some information. It is useful information, but multiple sources of information given us a better understanding.


What does it mean for waves to "feel" the bottom?

In water wave physics, when we say that the wave "feels" the bottom, we mean that the water depth affects the properties of the wave.

The dispersion relationship for water waves is:

$$
\omega^2 = gk \tanh{(kd)}
$$

where $\omega$ is the wave frequency, $k$ is the wavenumber, $d$ is the mean water depth, and $g$ is gravitational acceleration. We distinguish "shallow" and "deep" water waves by the value of $kd$, which includes both the wavenumber and the water depth:

Shallow water waves when $kd < 0.3$;
Intermediate water waves when $0.3 < kd < 3$;
Deep water waves when $kd > 3$.

Thus, a long swell wave may act as a shallow water wave in depths of 10 m, but also a very short wave may act as a deep water wave in depths of 1 m.

How are these limits for $kd$ obtained? The tangent hyperbolic function has some convenient properties for the limiting values of its argument:

For deep water waves, $kd$ is very large, so $\tanh{(kd)} \rightarrow 1$. The dispersion relationship then reduces to:

$$
\omega^2 = gk
$$

Phase and group speeds are then:

$$
C_p = \dfrac{\omega}{k} = \sqrt{\dfrac{g}{k}}
$$

$$
C_g = \dfrac{\partial \omega}{\partial k} = \dfrac{1}{2}\sqrt{\dfrac{g}{k}}
$$

Notice that $C_p$ and $C_g$ are not a function of water depth, thus it is said that deep water waves don't "feel" the bottom.

On the other hand, for shallow water waves, $kd$ is small (approximately 0.3 or less), and $\tanh{(kd)} \rightarrow kd$. The dispersion relationship is now:

$$
\omega^2 = gk^2d
$$

and phase and group speeds are functions of water depth:

$$
C_p = \dfrac{\omega}{k} = \sqrt{gd}
$$

$$
C_g = \dfrac{\partial \omega}{\partial k} = \sqrt{gd}
$$

So, why is it said that the waves "feel" the bottom at the water depth of half wavelength?

$$
kd = k  \dfrac{\lambda}{2} = k \dfrac{2\pi}{2k} = \pi
$$

and this is approximately the value below which the regime transitions from deep water to intermediate water, i.e. $\tanh{(kd)} \approx 1$ does not hold anymore.


Is there a method to determine the point rainfall intensity for small catchments?

The rational method is especially usefull for small areas. For larger catchments it is less accurate. Then you should use a rainfall-runoff model but that is only possible when you have sufficient data. A more simple method is the use of runoff coefficients. Maybe something like the SCS method.


Iron-nickel phase in pallasite meteorites

First, a correction. A solid solution is between different compositions in the same phase. For example, olivine is a solid solution of forsterite (Mg2SiO4) and fayalite (Fe2SiO4).
There are two common iron–nickel alloys found in meteorites (pallasites and others): kamacite and taenite. They are commonly intergrown into lamallae called "Widmanstätten pattern". It looks like this:

Kamacite has up to about 10% nickel, whereas taenite can get up to ~60% nickel, but commonly found up to 30%.
Kamacite has the space group Im3m, making it hexoctahedral body-centered. Taenite has the space group Fm3m, making it hexoctahedral face-centered.


How do current pollution levels in Los Angeles compare to the 1970s?

The air quality in Los Angeles does not meet federal air quality standards.  That being said, the air quality has improved immensely since the 1970s.

From the California Air Resource Board, in 1965 the maximum one-hour ozone concentration was 0.58 ppm.  Since then, that number has come down to about 0.12 ppm.  You can obtain the latest ozone data from EPA.  See a  30 year ozone trend image below from the South Coast Air Quality Management District:

Particulate matter is a bit tougher to quantify.  PM10 (coarse and fine particles together) has been tracked since the late 80s, but PM2.5 (fine particles) has only been tracked since 1999.  You can read a bit about it here.

The reduction in particulate matter has not been as dramatic as ozone.  This makes sense, though, since ozone is a secondary pollutant whose precursors (NOx and VOCs) largely come from vehicle tailpipes.  NOx and VOC emissions from vehicles has decreased significantly in recent years, especially with fleet turnover.  In contrast, coarse and fine particulate matter come from many different sources, e.g. road dust, agriculture, cooking, etc. which is difficult to control since rain is the major control method.


Glacial extent variability during last glacial period?

This map should address at least part of your question

The here documented GIS map and dataset contains a collection of Last
Glacial Maximum (LGM, ~21k yBP) paleoenvironmental data. It is the
first result of a project that aims to acquire, produce and publish
GIS datasets from non-GIS based sources such as analogous maps,
textual informations or figures of scientific publications for
prehistoric time slices. In combination with modelling results and
already available GIS-datasets related to the mentioned time frame, it
should enable other researchers and members from other projects to use
the maps in their work, properly cited and referenced. The map shows
LGM land ice sheets, paleo-stream networks and inland water in Europe,
a sea-level adapted (-120m) land mass and a Köppen-Geiger climate
classification derived from climate model data.

I know this is more broadly a field of active study and there is a relatively new method of analyzing cosmogenic nuclides to determine for what duration a surface has been exposed to cosmic radiation.
Broadly how this works is that surfaces exposed to cosmic radiation start to develop an isotopic signature, to the degree that you can tell how long a boulder has been exposed to the open sky (within a margin of error).
Joerg M. Schaefer of Lamont-Doherty Earth Observatory explains in Glacial Landscape (Cosmogenic Nuclide) in the Encyclopedia of Scientific Dating Methods:

High-sensitivity cosmogenic nuclide techniques applied to the moraine
record now afford for precise reconstruction of past glacier
fluctuations with centennial resolution and on a time scale ranging
from decades to beyond 100,000 years. It has been a long-standing
dream of geologists and climate scientists alike to precisely map land
ice change during the last ice age through the deglaciation period and
into the current interglacial, referred to as the Holocene.


Yes, if one takes the common meaning of the term "eye of the storm" to be the area of relatively low wind speed near the center of the vortex, most tornadoes can be said to have eyes. Cyclostrophic balance describes a steady-state, inviscid flow with neglected Coriolis force:

$$
\dfrac{v^2}{r} = -\dfrac{1}{\rho}\dfrac{\partial p}{\partial n}
$$

where centripetal force balances radial pressure gradient. Here, $v$ is tangential wind speed, $r$ distance from vortex center, $\rho$ is air density, $p$ is atmospheric pressure and $n$ is the radial direction pointing inward. From here, tangential wind speed is simply:

$$
v = \sqrt{-\dfrac{r}{\rho}\dfrac{\partial p}{\partial n}}
$$

suggesting that $v\to0$ when $r\to0$. While the flow in tornadoes is highly non-stationary and subject to friction, this idealized model shows why there must exist an "eye" inside a vortex or an area of closed circulation. This "eye" may or may not be easily recognized by a hypothetical human observer inside a tornado.


Were there times during human inhabitated Earth were Earth average temperature was hotter than today?

Answers would be "no" and "no."

That graphic isn't sourced, but it appears to refer to the Mid-Holocene Warm Period, roughly 7,000 to 5,000 years ago.

According to NOAA and other sources, the warming of the Mid-Holocene Warm Period was limited to part of the Northern Hemisphere; some regions would have been warmer than today, but not the globe:

  It appears clear that changes in Earth's orbit have operated slowly
  over thousands and millions of years to change the amount of solar
  radiation reaching each latitudinal band of Earth during each month.
  These orbital changes can be easily calculated and predict that the
  Northern Hemisphere should have been warmer than today during the
  mid-Holocene in the summer and colder in the winter.

This graphic from the NOAA page cited above shows the estimated mid-Holocene temperature anomalies (variation from mean).
 Though humans had migrated widely the period, relatively few would have been living outside that cooler blue band.

Were there earlier warmer periods for modern-ish humanity before that? No, since earth was emerging from a glacial period starting about 11,500 years ago, and global average temperatures were gradually rebounding from about 6 degree Celsius cooler than today.

The next previous warm era would have been the Eemian interglacial period about 130,000 years ago, which again was associated with orbital variations.

You could quibble about the era of "human-inhabited" earth; homo sapiens arose about 300,000 years ago, but remained limited to Africa until about 70,000-50,000 years ago.


Why is coal classified as a sedimentary rock?

I'm not sure why you are including shale in your question, unless you are referring to carbonaceous shale, which in not coal, but shale with carbon throughout the matrix of the shale.

Shale is an argillaceous rock, and argillaceous rocks are "detrital sedimentary rocks" [1]. They are composed of clays and the bedding plane within the shales is "due to the orientation of the clay minerals" [1]. Clearly a sedimentary rock.

Coal however, as you state in your question is derived from organic material - vegetation. The deposition of the vegetation material is analogous to the deposition of minerals that formed sedimentary rocks.

Both materials, vegetation and minerals, were transported to a location. In the case of minerals the transportation may have been a long or short distance and carried out by wind, water or gravity (mudslides). Vegetation tends to travel shorter distances than minerals but like the minerals it has traveled and it accumulates.

Over time the vegetation compacts, is heated, undergoes chemical reactions and experiences a very slow form of metamorphosis and petrification.

Being composed of carbon, coal forms a carbonaceous deposit. Having been transported and accumulated in a single deposit it is sedimentary. Having undergone metamorphosis and petrification it is a rock. Consequently it is reasonable to classify coal as a carbonaceous sedimentary rock.

[1] D. G. A Whitten with J. R. V. Brooks, Penguin Dictionary of Geology, 1979


Is it true that distance between earth and sun is closer in winter season (January) and farther in summer season in the Northern Hemisphere?

Yes, it's true (in the northern hemisphere). The small eccentricity of the Earth's orbit is not anywhere close to a key driver in the seasons. The key driver of the seasons is the Earth's obliquity. In the northern hemisphere, the axial tilt of Earth's rotation axis has the northern half of the Earth facing a bit toward the Sun in June/July/August and away from the Sun in December/January/February. The opposite is true in the southern hemisphere.

Eccentricity would be a driver of the seasons if the Earth's rotation and orbital axes were much closer in line with one another than they are. If that were the case, summer and winter would be world-wide phenomena. As it stands, when its summertime in the northern hemisphere its wintertime in the southern hemisphere, and vice versa.

Somewhat paradoxically, even though the Earth is closest to the Sun in early January and furthest from the Sun in early July, the Earth as a whole is cooler during December/January/February than it is during June/July/August. The reason is the uneven distribution of land and ocean between the northern and southern hemispheres.

In 13000 years, northern hemisphere summers will occur near perihelion passage and winters near aphelion passage. Those will be brutal times! Fortunately, I won't be around to see them.


Your concept of weathering is erroneous. It is not uncovering or stripping off material. Weathering is a very slow process of breaking down rocks, soil & minerals, in-situ, via contact with the Earth's atmosphere, water & biological organisms. This can also involve heat & pressure.

Erosion, as you state, involves the moving of material. This can happen due to the action of running water, the impact of water via waves on coastal environments, wind or glaciers dislodging grains of geological material irrespective of whether it is weathered or not. Landslides are another form of erosion.


Relative UVB reflectance of white cloth vs aluminum

I understand that polished aluminum surface reflects more that white. However , the white surface re-emits more energy  so the net affect is that the white retains less energy.


How to tell if fog is made out of water droplets or ice crystals?

This doesn't aim to be a complete answer, but after putting a juicy bounty at Aviation SE on the question "Can pilots tell if a cloud or fog is made out of water droplets or ice crystals when flying through it?", the answer seem to be: No, they can't. And all the things to look at to detect ice clouds doesn't seem to be useful if you don't have a plane at hand. There is nothing like "there is a special refraction pattern around the lights on the wings", or such.

So far it seem like ice and water clouds are indistinguishable.


Transferring water using underground channel

This is already used in some cases. The one I'm familiar with is California's Coachella Valley, best known as the home to Palm Springs.

Farms, golf courses, other businesses, and homes pump far more water out of the region's aquifer than is restored by normal rainfall, so the Coachella Valley Water District pipes in water from the Colorado River and, basically, pours it into the sand at the high end of the 15-mile-long valley.

This water then percolates through the sandy soil down the valley; it's retrieved through local wells. One advantage to delivering the water through the aquifer is that it avoids loss through evaporation.

  The Coachella Valley’s groundwater basin can be imagined as a tilted
  bathtub filled with sand and gravel and topped with a layer of clay;
  water fills the spaces under the clay and in between the sand and
  gravel. --Coachella Valley Water District

This system works because:

There is a (relatively) plentiful external source of water.
The local geology allows water to flow.
The replenishment is largely powered and directed by gravity, which makes it cheap and avoids having to pump water into a system that already has liquid in it and having to worry about whether the water is going where you want.

This Stanford University project talks about the opportunities and challenges for aquifer recharge projects.


How do we apply CO2 sensitivity (3C ± 1.5C for every doubling) to current CO2 levels

You have done multiple things wrong here. One is that you have used a linear interpolation when you should have used a logarithmic interpolation. But that's a different question, one that you have already asked. I'll address that there. That said, a logarithmic interpolation would indicate that the warming due to a 73% increase would be 2.37 °C rather than 2.2 °C.

But that math is incorrect. We have not seen a 73% increase in $\text{CO}_2$ levels over preindustrial times. We have seen a 46.4% increase. The second thing you have done wrong is to incorrectly apply a linear interpolation. The correct value, assuming a linear interpolation is correct, is $\left(\frac{410-280}{560-280}\right)3^{\circ}$, or 1.39 °C.

We have seen more than a 1.39 °C increase from preindustrial times due to the 46.4% increase in $\text{CO}_2$ levels over preindustrial times. The correct math is a logarithmic interpolation: $\log_2\left(1+\frac{410-280}{560-280}\right)3^{\circ}$, or 1.65 °C.

We have not quite seen a 1.65 °C increase. So what's going on? Another thing you have done wrong is to implicitly assume that the current climate represents the steady-state response to the current $\text{CO}_2$ level. It does not.

Climate instead changes rather slowly. Suppose we stopped adding ever more $\text{CO}_2$ to the atmosphere but instead maintained $\text{CO}_2$ at the current level of 410 ppm. Temperatures will continue to rise for quite some time because the climate has not yet reached its steady-state response to the rather sudden rise from 280 ppm $\text{CO}_2$ to the current level of 410 ppm.


Hypothetically, what would happen to the earth if a large hole was drilled through the center?

The best place to ask this question is going to be at xkcd: http://what-if.xkcd.com/ but I will give it a shot.

I'm not a geophysicist, but I'll try to give you a reasonable enough answer.
As you said, making such a hole is not possible.

However, let's try to think what if some magical force made a hole 1 km wide and then suddenly released it. This is what the Earth is made of:

(taken from here: http://www.nature.com/nature/journal/v479/n7374/fig_tab/479480a_F1.html)

The easiest part to explain will be to see what happens in the core. Both the inner and outer core are basically made out of impure iron. The liquid iron will just flow into itself and close the hole rather quickly (think about a similar hole in water). The solid iron is also ductile as there high pressures and temperatures, so it will also flow and close the hole. Think chocolate close to the melting temperature. It's still solid, but it moves. Probably some of the liquid iron will manage to flow into the hole of the solid iron, but it will then solidify because it will have to endure higher pressures.

Now, what happens at the mantle? The lower mantle is also ductile and it will also flow under the pressure. You have to remember the the walls of the hole are under huge pressures - 24 to 136 GPa according to the figure. Some things may "fall inside", but remember that it has to fall over hundreds of kilometers while the hole is only 1 km wide.

The upper mantle is where it becomes interesting. This is just thinking out loud though. The upper mantle is where magmas are being formed, and one of the reasons magma is formed is decompression. Usually this happens because of mid ocean spreading or mantle plumes, but removing one side of let's say a cube of rock is also going to decompress it somewhat. This may cause generation of magma. No worries though - I don't see any reason why it should rise to the surface. If anything at all, it's going to fall down through the hole (but not much, see above). Also, decompression may cause release of volatiles or gas, the most common being CO2 and H2O I guess, also H2S or SO2 depends exactly what is down there. Also, the movement of rocks in an area of the Earth that's not ductile anymore but rather brittle (lithosphere) is sure to cause some earthquakes. Are there earthquakes going to be dangerous for anyone? I don't know.

What would this hole look like if you peeked down? My guess that it will be filled with water. If this hole starts at the ocean, then the ocean will just flow inside and fill it. It is possible that some mega waves or tsunamis will accompany it. It will pour down until it either meets the closed rock, or just evaporates. Remember - it's pretty hot down there. It will evaporate and rise, then cool and starts raining down again and you will have a nice convective cell in the upper few kilometers of this hole.

In contrast, if this was not in the ocean but rather on land, groundwater will fill it in. I guess most of the earth has groundwater (maybe except the large deserts, but even there some water exists) that will just flow inside and create a similar convective cell.


What causes this striped rock formation?

Frost heaving of the striped variety

As soil freezes it expands, this slowly pushes coarser material outwards, (since no ice forms in the stones just between them). This forms in bands of coarse and fine material like you see in your image.

The effect only becomes more exaggerated as the soil gets more and more sorted, since the finer material holds more water and thus expands more. This also means that even the smallest variation in particle size can get the process started.

A variety of patterns can form; sloped ground is especially prone to this sort of striped frost sorting.

B and C in this image are examples from this paper.

Additional source


Is spectrum of sunlight the same in the summer as in the winter?

As you suggest, longer the path, larger the proportion of scattered radiation. Since the shorter wavelengths are more strongly affected by the Rayleigh scattering, sunlight appears more red when the sun is low.

Lower solar elevation angle will also result in longer path through the ozone layer, and hence stronger absorption at the UV-B wavelength range. Together with the Rayleigh scattering, this will result in somewhat less UV-B compared to UV-A, all other things being equal.

The online version of NCAR's TUV radiative transfer model can evaluate the clear sky radiation for a given location and time. At noon, 45° north, I get UV-B/UV-A ratio of about 0.03 for 30th June and 0.01 for 30th January.

In addition to the sun elevation, the radiative fluxes will be affected by a number of factors like clouds, surface albedo (snow!), aerosol extinction, and variations in the ozone layer.


Cross cutting relationships.

Here's a very rough sketch. You had the black stuff, which was then cross-cut by the red intrusion (grey in the original photo), and finally intruded by the blue intrusion (pink the in the original photo).

This is the law of superposition. For more fun follow #SuperpositionPuzzle on Twitter!


Omega, ω is closely related to w in meteorology.
It can be moved towards w using the chain (this reminder from Watkins at SJSU helped)...

ω = dp/dt = (dp/dz)(dz/dt) = (dp/dz)w

[where p is pressure, t is time, z is height, and w is vertical motion in height coordinates]

Often in general meteorology you can estimate dp/dz using the hydrostatic approximation, which assumes gravity and buoyancy approximately balance.  This allows the equations:

dp/dz = −ρg

[where ρ is air density and g is gravitational acceleration]

And so would mean you can continue

ω = (dp/dz)w = −ρgw

which results in w = −ω/ρg.

Note that this is not always valid.  As Holton's An Introduction to Dynamic Meteorology, Volume 1 suggests on page 20:

  This condition of hydrostatic balance provides an excellent
  approximation for the vertical dependence of the pressure field in the
  real atmosphere.  Only for intense small-scale systems such as squall
  lines and tornadoes is it necessary to consider departures from
  hydrostatic balance.

That's a loose idea.  It's been a while, but basically as I remember it, hydrostatic is strongly valid when vertical acceleration (and thus vertical motion when looking near the surface) is much smaller in scale compared to the horizontal motions/accelerations.  So indeed, this is not true in tornadoes and in convection.  So you get very correct values for strong thunderstorms.  But it will help you diagnose regions of rising motion.

You can look a bit more towards breaking it down into more advanced detail and the mathematics of hydrostatic and how it fails in Doswell and Markowski's paper on buoyancy.

But, with such limited model output, not sure that you're looking to get into all of that detail, as I don't believe you'll find any extra help going those avenues with the variables you have.

With just slightly more information, most importantly temperature, you could use the ideal gas law:

 p = ρRT

[where R is the ideal gas constant of the gas under consideration and T is temperature in Kelvin]

This would allow you replace the unknown density, and you'd then end up with:

w = −ωRT/pg

Which you could then either further approximate R to be that for dry air = Rd = 287 J/Kkg, or even work up the adjustment your moisture content variable causes (though don't think doing so would offer much useful improvement as you've already got greater errors due to the failings of the hydrostatic approximation).

Since you don't have temperature, it seems your only remaining option would be to plug in the density approximation for the level of interest from the approximated "Standard Atmosphere" here (use the table where ρ is in units of kg/m^3).

It has been a long while since I've done this stuff, but I don't see any better options.  Unless somehow there's a way to work from the geopotential, maybe apply something like mass continuity in pressure coordinates, and get to something more complex to return something more correct for w.  But if there is, it outpaces me!

So, long story short, it appears that your best hope is w = −ωRT/pg, but it won't be 100% reliable, particularly in strong convection.


In the picture above we see an internal wave propagating in the direction of the wavenumber vector
$$\mathbf{K} = k \mathbf{e_x} + m \mathbf{e_z}$$
which (in 2D) is given by the vector sum of its components. $\mathbf{e_x}$ and $\mathbf{e_z}$ are unit vectors in the horizontal and vertical directions, respectively.

The continuity condition implies that $\mathbf{K} \cdot
\mathbf{u}=0$. Hence, the direction of
energy propagation (group velocity) is perpendicular to the direction of
propagation of wave crests and troughs (phase velocity). Internal gravity waves are transverse waves so the fluid motion is parallel to lines of
constant phase as indicated by the Eulerian velocity vector, $\mathbf{u}$.

The vertical wave number $m$ is the vertical component of the wavenumber vector because in a continuously stratified fluid internal waves can propagate in all directions. In fact, in the real ocean there is a third component, denoted by $l$ which is in the transverse direction so that the full wavenumber vector is

$$\mathbf{K} = k \mathbf{e_x} +  l \mathbf{e_y} + m \mathbf{e_z}$$


Why do heat waves affect Australia unevenly?

It primarily has to do with the pattern on high and low pressure systems as they present themselves over the continent.

In the southern hemisphere, high pressure systems rotate anticlockwise and low pressure systems rotate clockwise.

Because the north of Australia is close to the equator, generally the north of Australia has a low pressure trough over it. High pressure system tend to centered from the mid latitudes of Australia southwards.

If there is a high pressure system just to the south west of Australia, and particularly if there is a low pressure system just to the south, in the Great Australian Bight, cold air from the south will affect Perth and the south west of Australia.

As the high pressure system moves eastwards a low pressure trough can develop over the west coast of Australia. With or without the trough, the high pressure system moves hot air from the central and northern parts of Australia and Perth and the south west experience hot conditions. If the high pressure system is slow moving this can mean prolonged periods of hot weather - heat wave. A low pressure trough along the west coast reinforces the movement of hot air from the central and northern parts of Australia.

With the same high pressure system over the central region of Australia, as hot is drawn from the central and northern parts of Australia over the western parts of the continent, cooler air from the Southern Ocean is drawn over the eastern part of Australia, particularly the south eastern region where Hobart, Melbourne, Canberra and Sydney are located.

When the high pressure system moves to the east of Australia, particularly to the Tasman Sea, between Australia and New Zealand, hot air from the northern and central parts of Australia will be drawn over the south eastern parts of the country and the regions between Adelaide and Sydney will experience hot conditions.

In the synoptic chart below, for 29 December 2019, there is high pressure systems to the west and east of Australia and low pressure system to the south. The effect of these systems is to draw cold air from the south over Perth and the south west of Australia and hot air from the central and northern parts of Australia to the south east of the country.

This is why one part of the Australia with fry, while the other doesn't.


What causes a rainbow, its colours and its shape?

Short answer: A rainbow is formed when light enters a drop of water or an ice crystal and gets refracted and reflected back into an observer's eye.

Longer Answer: Light travels at different velocities depending on the media involved; it travels slower through water than it does through air, for instance. As light enters a raindrop or ice crystal, it first gets refracted. However, not all the frequencies of light get refracted at the same angle. The colors with the shorter wavelengths (e.g. blue, indigo, and violet) get refracted less than the longer wavelengths (red). This spreads the colors out just like passing through a prism. The light then gets reflected off of the back of the raindrop, gets refracted again as it passes out of the raindrop, and travels to the observer's eye.

The reason it is circular is because the light that got refracted and reflected back to the observer, does so at a specific range of angles, 40 to 42 degrees.

In order to see a rainbow, the sun (or other light source) must be directly behind the observer. A straight line is formed from the light source, the observers eyes, and the center of the rainbow. All rainbows are actually circles. We usually see it as an arc because the earth intercepts the circle. (BTW, because of this, no two people, even standing shoulder to shoulder, can see the same exact rainbow. Each rainbow is being created by different raindrops.) If you're ever in an airplane passing over a cloud with the sun above you (as opposed to near the horizon), you may see a complete rainbow. It's pretty awesome.  Here's an illustration:


Does erosion make mountains become higher?

This actually does happen, a feedback loop between the Himalayas and the Indian monsoon.

The Indian Plate is actively shoving itself under the Eurasian Plate, creating the Himalayas.

At the same time, monsoon storms come up against the southern side of the Himalayas. The high mountains enhance the storms' rainfall, and the mountains erode much more on the southern side than the northern side.

Material is transported from the Eurasian Plate down onto the Indian Plate, and the weight removed from the mountains causes isostatic rebound of the Eurasian Plate, allowing the Indian plate to slide underneath, enhancing the uplift of the Himalayas., keeping the monsoon rainfall on their south side, etc.

There's a more detailed explanation and some nice images here.


If a specific mass of air is polluted, will the pollution stick with it?

Air is a fluid, as such it tends to mix and concentrations, of anything, tend to disperse into the wider volume. Erik's cup of tea metaphor is pretty accurate, currents of air will pull apart your exemplar 1m3 and disperse the pollutants therein, the heavier particulate, which is mainly soot, water droplets from combustion, and unburned fuel, will full to the ground fairly quickly. Finer particulate and reactive gases like nitrogen and sulfur oxides will react with water to form acids and fall back to earth with the next rain storm. The exception to this general rule of mixing occurs when there is an inversion layer that puts a "lid" on vertical circulation in a particular area causing a build up of pollutants which often results in smog formation.


What forms do groundwater flow equations have when Dupuit supposition is not considered?

If the pumping well is partially penetrating in the aquifer or the source above the aquifer (e.g., unconfined aquifer, leaky aquifer, under the stream), the vertical flow should be accounted.

The groundwater equation like Thies' solution is not considering the vertical flow. Incorporating the vertical flow would change the governing equation (P.D.E.) form including the vertical hydraulic conductivity. Lots of papers have shown the solution form for considering that.


Where can I find the original scientific articles on Heat index (published by either Larry P. Rothfusz or Steadman)?

After having a look at the references of a few papers about heat index (like this one). It looks like the original publications you are looking for are

The Heat Index "Equation" (or, More Than You Ever Wanted to Know About Heat Index) by Lans P. Rothfusz available here, and
The Assessment of Sultriness. Part I: A Temperature-Humidity Index Based on Human Physiology and Clothing Science, by R. G. Steadman available here.

As a general suggestion, looking at the references in related papers is always a great way to find the original research articles on any topic.


How do we determine subsurface composition?

How do we use the information in g(t) to determine the composition of the medium that the wave is traveling through? Moreover, knowing that the earth is heterogeneous, how can we isolate any one single substance or rock type? How accurate is this kind of measurement?

In short: we can't, and it's not.

Taking the example of oceanic lithosphere, we can take a pretty good stab: we know (approximately) what a cross-section through the oceanic crust and mantle looks like because of the existence of ophiolites. They're pretty consistent in terms of thicknesses of units represented (see the cross-section at that link), so when in oceanic lithosphere we see 2km at a certain velocity underlain by 4km at a different velocity, with a sharp transition between the two, it's a fair bet that the former corresponds to sheeted dykes and the latter to layered gabbros, and so on down.

Some laboratory measurements of the speed of sound waves in various lithologies can be made (including measurements of both synthetic substances and of mantle xenoliths that have, for whatever reason, been brought up to the surface), but they aren't definitive. Seismic anisotropy - different "speeds" to different components of wave phases (e.g. P versus S waves) depending on the angle the wave being measured took through the rock in question - can be linked to e.g. alignment of olivine crystals. As another example we know that the core is of a different composition to the mantle because of the difference in the speed of sound and through mass-balance arguments, but seismic velocity through the core doesn't tell us anything about what it's made of.

To add further complications, variations in seismic speed can always be explained by a trade-off between compositional and thermal variations, as with LLSVPs.

Mostly what we're working with here is a bunch of best guesses. That's not to say they're useless - in a field where you get to run a single experiment that lasts 4.5Ga and you've no control over any of the parameters, best guesses are often the best we have to work with - but they're also very definitely not definitive.


Why is colder seawater more compressible?

First, let's explain what compressibility is. Compressibility is defined as a measure of the relative volume change of a parcel of fluid as a response to a pressure change.

When I calculate the compressibility of seawater using Matlab and the seawater package (equivalent to Fofonoff & Millard, 1983), I obtained that the compressibility increases at cold temperatures for salty, brackish, and fresh water. In fact, water has a minimum compressibility at 46.5°C (Fine & Millero, 1973). As pressure increases the compressibility decreases for any of the salinities considered.

As can be seen in the figure the compressibility is maximum at low temperatures for any salinity (not just seawater) and pressure. So in general, the compressibility of water is maximum at low temperatures due to the internal structure of water. The inverse relationship with temperature seems well accepted (Fine & Millero, 1973) and has a direct relation with other properties like the speed of sound.

In a typical liquid, the compressibility at low temperatures is reduced as the structure becomes more compact. In water, there is a change at low temperatures toward more open-structure clusters (expanded icosahedral water cluster) versus denser clusters (collapsed icosahedral water cluster). As the water structure at lower temperatures is more open, the capacity for it to be compressed increases.

As cold liquid water is heated it shrinks, it becomes less easy to compress, the speed of sound within it increases, gases become less soluble and it is easier to heat.

The compressibility above is calculated using the formula in the figure (same as in the wiki article) and I have included the code to reproduce the results:

T=-2:1:30;
P=0:10:1000;
S=35;
for i=1:length(T)
    for j=1:length(P)
        dens(i,j)=sw_dens(S,T(i),P(j));
        dens15(i,j)=sw_dens(15,T(i),P(j));
        dens0(i,j)=sw_dens(0,T(i),P(j));
    end
end
spvo=1./dens;
spvo15=1./dens15;
spvo0=1./dens0;
for i=1:length(T)
    for j=1:length(P)-1
%        Ev2(i,j)=-(1./spvo(i,j))*(spvo(i,j+1)-spvo(i,j))./(P(j+1)-P(j));
        Ev35(i,j)=(1-spvo(i,j+1)/spvo(i,j))/(P(j+1)-P(j));
        Ev15(i,j)=(1-spvo15(i,j+1)/spvo15(i,j))/(P(j+1)-P(j));
        Ev0(i,j)=(1-spvo0(i,j+1)/spvo0(i,j))/(P(j+1)-P(j));
    end
end
figure(1);clf
for j=[1,20,100]
    line(T,Ev35(:,j),'Color','k','LineWidth',2);
    line(T,Ev15(:,j),'Color','b','LineWidth',2);
    line(T,Ev0(:,j),'Color','r','LineWidth',2);axtt
end
text(T(20),Ev35(20,1),['P=',num2str(P(2)),'dbar'])
text(T(20),Ev35(20,20)*.99,['P=',num2str(P(21)),'dbar'])
text(T(20),Ev35(20,100)*.98,['P=',num2str(P(101)),'dbar'])
text(T(15),Ev0(15,1),['P=',num2str(P(2)),'dbar'],'Color','r')
text(T(15),Ev0(15,20)*.99,['P=',num2str(P(21)),'dbar'],'Color','r')
text(T(15),Ev0(15,100)*.99,['P=',num2str(P(101)),'dbar'],'Color','r')
xlabel('Temperature (degC) ')
ylabel('Compressibility (1/dbar) ')
legend('35 PSU','15 PSU','0 PSU')
text(7,5e-6,'$c_w=-{1\over V}({dV\over dp})$','Interpreter','latex','FontSize',20,'FontWeight','bold')


Did the Haber-Bosch process enable the population explosion?

There are a number of factors that went/are going into the population explosion, food is only one vaccination and antibiotics are a big factor as well.  within food fertilizer is again only one of many factors. Better crop strains, mechanized and better farming techniques, soil science, pesticides, refrigeration, and a dozen other factors contributed.  Keep in mind artificial fertilizers get less important as you go back in time as well so calling it the detonator is incorrect and misleading.

Now when considering crop rotation, crop rotation has pros and cons, there are several nutrients plants need and rotation only helps with some of them, and it relies on having compatible crops to rotate which not every crop or environment has.

Keep in mind the piece wikipedia is quoting is not a peer reviewed paper but an essay in nature, which explains it is referring to several modern countries that fertilize almost exclusively with artificial fertilizers. It is not claiming they cannot use other fertilizers.


How would a world entirely covered in oceans get the nutrients to support life?

If the planet is geologically/volcanically active hydrothermal vents are a way by which nutrients, in the way of minerals and chemicals, can enter the ocean.

Certain types of bacteria can consume the minerals and such bacteria form the base of a food chain. Also, the heat from the hot water can provide energy to life forms.


IF there has been a steady wind direction over that 24 hrs, then yes, this will give you the average wind speed.

If the wind has changed direction, then there may have been higher speeds that have partially cancelled each other out.


Will Venus eventually overheat? When it happens, what will happen to it exactly?

Venus does radiate away heat, but not enough to prevent the surface and lower atmosphere heating to 460C. Too late to prevent overheating, it has already overheated. In the long term, its atmosphere will gradually leak away into space, reducing the present pressure of 90 Earth atmospheres. Exactly how far this process will have gone in 5 billion years' time when the sun swells up to become a red giant is impossible to say. When the sun becomes a red giant, Venus will be inside its tenuous outer layers and therefore scorched by much higher temperatures than it has now, probably reduced to a ball of molten rock spiralling inwards towards the sun's interior.


What are the fields in Petrel's IESX seismic horizon file?

X-coordinate
Y-coordinate
Segment number
Symbol code
Two-way time (ms)
Shot-point number
CDP number
Trace number
Line type (2=2D, I=inline, X=crossline)
2D line name or 3D survey name

The format allows for a column between 8 and 9, for amplitude value — not present in this example.

This is a formatted layout to specific columns. So there is the potential for fields to butt against each other with no spaces between.

The top 2 lines define the horizon name (after PROFILE) and various picking parameters you shouldn't need.

This answer comes from Tom Cox (geoscientist at Schlumberger).


Which type of plant absorbs the most net carbon dioxide per year per square km?

I have no personal expertise in this matter, but performed a quick search of recent literature. From what I can tell, the interest in fast-growing plants is motivated primarily by the desire to maximize bioenergy production, not as a means of carbon sequestration. The typical goal is therefore multiple harvests per year in favorable conditions, meaning any carbon removed from the atmosphere by these plants is returned back to the atmosphere in a matter of months. Two plants commonly mentioned are eucalyptus trees and elephant grass.
Humbertode Jesus Eufrade Junior, et al., "Sustainable use of eucalypt biomass grown on short rotation coppice for bioenergy", Biomass and Bioenergy, Vol. 90, July 2016, pp. 15-21

According to the results obtained, the density planting and fertilization levels have a greater influence on the dry matter yield, energy yield, and nutrient exports. The higher density planting reaches mean values of 30.9 tonnes of dry matter per hectare

Rafael Fiusa de Morais, et al., "Elephant grass genotypes for bioenergy production by direct biomass combustion", Pesq. agropec. bras., Vol. 44, No.2, Feb. 2009

The objective of this work was to evaluate elephant grass (Pennisetum purpureum Schum.) genotypes for bioenergy production by direct biomass combustion. Five elephant grass genotypes grown in two different soil types, both of low fertility, were evaluated. [...] The dry matter yields ranged from 45 to 67 Mg ha-1

There are 100 hectares in a square kilometer, and one Mg is one metric ton, so the reported annual yields correspond to 3090 tons per square kilometer for eucalyptus, and up to 6700 tons per square kilometer for elephant grass. Obviously the dry mass of plants is not just composed of carbon. The FAO provides this helpful data:

The carbon content of vegetation is surprisingly constant across a wide variety of tissue types and species. Schlesinger (1991) noted that C content of biomass is almost always found to be between 45 and 50% (by oven-dry mass).

Assuming 45% carbon content, this means eucalyptus trees can bind 1390 tons of carbon / km2 / year and elephant grass can bind 3015 tons of carbon / km2 / year. A CO2 molecule has atomic weight 44 while carbon has atomic weight 12, so the CO2 tonnage is the 3.66-fold of these numbers, that is ~5100 tons and ~11000 tons, respectively.


There is a limit to how much of a given salt can be dissolved into water, this is known as it's solubility and it's dynamic based upon how much of any particular ion is already present. Once concentrations exceed the local solubility of a given compound precipitation occurs, this can be seen in the modern Mediterranean basin with the precipitation of calcium carbonate onto the seabed. There are also older examples of this response such as chemically precipitated chert in New Zealand.

That's one way in which dissolved chemicals can be re-integrated into the rock cycle, biological processes can also play an important role. Plankton take up many elements from sea water during their life cycle, notably silica and calcite for forming rigid structures these are then deposited in the deep ocean when they and the creatures that predate them die and form the basis for many sedimentary rocks.

So while there is a steady input of mineral salts into the ocean there's only so much of it that can accumulate and in fact a lot of them are removed at far lower concentrations due to biological use and subsequent deposition.

A measure of any deposited material may eventually be subducted with the oceanic crust on which it has settled, at which point it will be integrated into any subductive-melt sourced minerals. There is a trend towards the chemical depletion  of the mantle when it comes to certain elements which appears to be a one way street but the ocean does eventually give back a large percentage of what is dissolved into it.


How much fossil fuel came from the Carboniferous?

The process you're describing in the question is the one at the origin of coal. Although coal deposits are known from the Devonian to the Quaternary, they have been 3 major periods of depositions (see Thomas 2013): the Carboniferous-Early Permian, the Jurassic-Cretaceous and during the Cenozoic. So, indeed the Carboniferous is one of the main period of coal deposit but I couldn't find any numerical evidence in the literature that this is the "main" period of deposit. The idea that it is is most likely due to the fact that the western Europe and eastern USA coal mines (hence historically the most noteworthy) all happen to be Carboniferous.
But as far as oil (petroleum) is concerned, according to Klemme & Ulmishek 1991 (straight from the abstract):

  Six stratigraphic intervals, representing one-third of Phanerozoic
  time, contain petroleum source rocks that have provided more than 90%
  of the world's discovered original reserves of oil and gas (in barrels
  of oil equivalent). The six intervals are (1) Silurian (generated 9%
  of the world's reserves), (2) Upper Devonian-Tournaisian (8% of
  reserves), (3) Pennsylvanian-Lower Permian (8% of reserves), (4) Upper
  Jurassic (25% of reserves), (5) middle Cretaceous (29% of reserves),
  and (6) Oligocene-Miocene (12.5% of reserves)

See Klemme 1994 for a detailed explanation on the origins of the Jurassic source rocks (i. e. 25% of the world's reserve at the time): most of them are marine, but some are fluvial or from lagoonal inland seas (table 3.2).

References:
Klemme, 1994. Petroleum systems of the world involving Upper Jurassic source rocks. In Maggon & Dow (Eds), The petroleum system - from source to trap, AAPG Memoir, 60: 51-72.
Klemme & Ulmishek, 1991. Effective petroleum source rocks of the world; stratigraphic distribution and controlling depositional factors
AAPG Bulletin, 75: 1809-1851.
Thomas, 2013. Coal Geology, 2nd Edition. Wiley-Blackwell, 444pp.


Solubilities (taken from Wikipedia):

MgSO4: 35.1 g/100 mL (20 °C)
Na2SO4: 13.9 g/100 mL (20 °C)

It does seem that the solubilities should be  an order of magnitude higher than  is quoted in the paper you are reading.

Several ideas:

The paper is wrong.
You did not understand the paper correctly.
The solubilities mentioned above are of the pure compound in pure water. If it's in an evaporite basin the the chemistry of the water might differ and the solubilities might also differ.
As an example, the presence of a more soluble salt will cause the less soluble salt to be come even more soluble (a process called "salting-out"). For instance, if you have an almost saturared solution of NaCl, and you add CaCl2, a more soluble salt, you will start preciptating NaCl once enough CaCl2 is added to the system.
There could be other anions in the system which make Na and Mg less soluble. Borates? Phosphates? Carbonates? Fluorides? The solubility is determined by the least soluble component of the system. Adding sulfate to magnesium silicate isn't going to do much to it in terms of solubility (unless it is sulfuric acid of course).


What evidence is there that plant evolutionary history "dances to a different beat" than that of animals?

I'm not going to give an extensive account on "mass extinction" epistomology here but I think the first thing one has to consider is the difficulty of studying numerically paleobiodiversity (mostly because of a gappy fossil record but also an historically unbalanced sampling effort and the rock availability for some of the time periods); although, along the years, we designed better tools to compensate for those biases (see the whole bibliography of John Alroy for instance), this is still a major issue.

Furthermore, the recognition of the "Big Five" (i. e. the five bigger mass extinctions of the Phanerozoic: End Ordovician, Late Devonian, Permian/Triassic boundary, Triassic/Jurassic boundary and Cretaceous/Paleogene boundary) basically derive from the work of Sepkoski (1978, 1979; Raup & Sepkoski 1981, etc...) who studied the diversity of marine biota and more specifically (judging by Sepkoski 1981) marine metazoans. As a consequence everything terrestrial and every non-metazoan (plants, protists, bacteria) are not included in the classic recognition of those events. It so happens that at least the P-T and the K-Pg events have been also recognized in some marine protists (namely foraminifera) and in terrestrial vertebrates (dinosaurs for the K-PG and many groups of 'pelycosaurs' for the P-T to name the more famous); but conceptually this is a significant bias as it may happen that the geological event driving one of those mass extinctions can only affect marine organisms (oceanic anoxia being the most obvious example).

That's for the epistemology part. Now the plants themselves: as you noticed with your quote of Traverse (1988) it is thought that the Embryophyta (i. e. land plants) have not been affected by the Big Five. This idea have since then been somewhat challenged (e. g. McElwain & Punyasena 2007) with evidences that plants indeed were affected by some of those extinctions but maybe not as drastically as what we think happened for marine faunas or terrestrial vertebrates.
It needs to be considered however that the earliest evidences for the existence of land plants date from the Silurian (see Kenrick & Crane 1997 for a short review). Their fossil record remains extremely gappy until the Carboniferous, basically, meaning that the first two of the "Big Five", if they happened to have affected land plants, can not be observed.
Additionally Angiosperms appeared in the early Cretaceous and diversified significantly toward the end of the Cretaceous, meaning that if the K-Pg event had an effect on the other land plants, the number of extinctions in those groups would be drowned by the number of originations in Angiosperms (I don't have any reference for that, it is just food for thought).

Finally, land plants are not the only group that doesn't dance to the beat imposed by the Big Five. For instance there is evidence that radiolarians (a group of marine heterotrophic planktonic protists with an extensive, continuous fossil record) were not affected by the K-Pg crisis (Hollis et al. 1995) nor by the T-J event (Kießling & Danelian 2011). There are still thought to have been, to some extent, affected by the P-T but there is no clear evidence (to my knowledge) for them being affected by the two previous crisis either.
And of course there is the multitude of groups with no (or minimal) fossil record (because they have no fossilizable parts for instance and thus are only recorded in extremely rare occasions) for which we have literally no idea of what happened to them.

References:
Hollis C., Rodgers K.A. & Parker R.J. 1995. Siliceous plankton bloom in the earliest Tertiary of Marlborough, New Zealand. Geology, 23: 835-838.
Kenrick P. & Crane P.R., 1997. The origin and early evolution of plants on land. Nature, 389: 33-39.
Kießling W. & Danelian T., 2011. Trajectories of Late Permian – Jurassic radiolarian extinction rates: no evidence for an end-Triassic mass extinction. Fossil Record, 14: 95-101.
McElwain J. C. & Punyasena S. W., 2007. Mass extinction events and the plant fossil record. Trends in Ecology & Evolution, 22: 548-557.
Raup D. M. & Sepkoski J. J. Jr, 1982. Mass Extinctions in the Marine Fossil Record. Science, 215: 1501-1503.
Sepkoski J. J. Jr, 1978. A kinetic model of Phanerozoic taxonomic diversity I. Analysis of marine orders. Paleobiology, 4: 223-251.
Sepkoski J. J. Jr, 1979. A kinetic model of Phanerozoic taxonomic diversity II. Early Phanerozoic families and multiple equilibria. Paleobiology, 5: 223-251.
Sepkoski J. J. Jr, 1981. A factor analytic description of the Phanerozoic marine fossil record. Paleobiology, 7: 36-53.
Traverse A., 1988. Plant evolution dances to a different beat. Historical Biology, 1: 277-301.


Can we call the Precambrian eons (i.e. Archaic and Proterozoic) eras?

It is and is not an an error depending on how it is used. They are Eons but in older literature they were also, sort of, eras as the Eons were not subdivided as they are now. Especially in literature dealing with the transitions they might refer to them indirectly as eras, such as "In the previous Proterozoic era", proterozoic being possessive. At the time this was technically sloppy but not a big issue, but now that they are subdivided this would be incorrect to do now.

You also have the issue of plurality in older literature. Spelling can vary from country to country and Paleontology is very much a international discipline. Occasionally in older literature Era can sometimes be used as the plural for Era (like sheep and sheep), so a reference to the Proterozoic era may be referring to the multiple eras in the Proterozoic. Again technically sloppy but in the time before electronic word processing a spelling error that might be ignored.

in a time scale they be grouped with era, as eons were often not included, and again they had no named eras in them. If the diagram included eons however this would be incorrect, but was sometimes done to conserve space since otherwise you would have a large blank section in all the smaller subdivisions to make room for fitting them in the eons, technically wromg but often ignored.

Without knowing the context of usage it is hard to say whether it is an error.


Are mantle plumes distributed around the core randomly or in a known pattern?

First of all, the idea of a fixed "hotspot" reference frame is (albeit reluctantly) falling out of favour on a geological timescale; see e.g. http://onlinelibrary.wiley.com/doi/10.1029/GM121p0339/summary ("As studies of plate motions have advanced, however, it has become clear that the global hotspots do not stay fixed relative to each other...") and http://adsabs.harvard.edu/abs/2010AGUFM.U51A0010S ("Hotspot reference frames can only be confidently tied back to about 130 Ma and there is evidence that mantle plumes have moved relative to each other.") Global Moving Hotspot Reference Frames are in the process of being built, see e.g. http://adsabs.harvard.edu/abs/2010AGUFMGP24A..03D

Secondly, identifiable patterns in the distribution of mantle plumes are an area of active research: this year's EGU medal for outstanding young scientist was awarded to Rhodri Davies for his work in this area. Key to most arguments are the presence of Large Low Shear Velocity Provinces (LLSVPs) in the lower mantle, historically assumed to be "slab graveyards" (thermochemical piles created when subducting slabs pool in the lower mantle). The suggestion that these areas were both chemically and thermally distinct from surrounding mantle focussed attention on their margins as a highly probable location for the formation of mantle plumes. However, recent findings (by and cited extensively by Rhodri Davies) increasingly support the idea that these piles are thermal features only, with no chemical difference to surrounding mantle.

Rhodri Davies' research revisits past studies that found hotspots were concentrated along the edges of LLSVPs, and has thoroughly demonstrated that these conclusions are not robust, e.g. to choice of hotspot catalogue, prescribed angular search tolerance (between surface expression and imaged margin), (arbitrary) depth of analysis, and (arbitrary) shear-wave velocity contour. Via Monte Carlo simulations he rules out hotspots being drawn from the margins of the Pacific LLSVP, but cannot rule out the possibility that hotspots are preferentially drawn from the entire areal extent of LLSVPs in both the Pacific and the Atlantic.

RD & his team conclude that present-day hotspot locations are controlled by ancient subduction, rather than the current margins of LLSVPs - which are demonstrated via dynamical simulations to be mobile, even in the presence of dense chemical heterogeneity.

(As a side note, both "hotspots" and "mantle plume" are contested terminology, it's true - but the vast majority of geoscientists believe that mantle plumes do exist. There is complexity to that view, in that the consensus does not require all intraplate volcanism to be the result of atypically hot mantle -- but the idea that mantle plumes simply do not exist, as espoused by mantleplumes.org, does not have wide acceptance.)


According to the paper The lunar moho and the internal structure of the Moon: A geophysical perspective (Khan et al. 2013), suggest 2 causes for the less frequent, yet more energetic shallow moonquakes:

Similar tectonic movements to intraplate quakes on Earth, also mentioned in the NASA paper Interior of the Moon  (Weber, 2013), but this seems unlikely due to the lack of plate tectonics on the Moon, but in an earlier paper, cited by Khan et al. (2013), Shallow moonquakes - How they compare with earthquakes (Nakamura, 1980), suggests that slippage in near surface fracture zones are a possible mechanism.
An alternative explanation suggested is the

  possibility that shallow moonquakes may
  instead be triggered by objects emanating from outside the solar system,
  such as nuggets of strange quark matter.

However, as there have only been 28 recorded since we've been to the moon, it is hard to exactly say.


National Weather Service "average daily/yearly" (temp, rainfall) life cycle?

Climate normals are computed over 30 years.  Not sure why that number of years was chosen specifically.  Perhaps a recent incentive is to identify climate changes (though it actually would make warming appear less significant when looking at anomalies).  But, given that those trends have only gotten interest in the past few decades, the only historical reason I can fathom is to sooner allow more sites to be used.  30 years is a fair number of data points statistically, but for daily normals, it should still have a significant error range.  It would seem a 50 or mean year normals length might be more useful at this point, though indeed climate changing might be comparable to the confidence interval.

But regardless of why they chose that value, that should be the period they are reporting.

If you wanted to verify these values, I was able to find pages to get the 1961-1990 normals (use the find command within this file to determine station id), 1971-2000 normals, and of course 1981-2000 normals.
Or a more robust option would be to use NWS' great ClimateNow data portal (select your local NWS office).  There you can look at annual data for the entire record length, search for specific values, or compute normals for any period you wish (select your station, then Monthly summarized data, and then the mean at the bottom is your normal over the time period you selected) (can also change to avg temp).

I know these portals can be a bit complex to some, so if you wish to mention the area, I can pull the values and edit the answer.  And then you can see just how much the normals have changed :-)


What is the name of this feature on the Red Sea coast of Saudi Arabia?

The area you describe looks like the following (from Google Maps):

According to the World Atlas of Coral Reefs, a picture of this very reef appears on page 240.  The caption for it describes the feature as being the Al Wadj Bank and consisting of fringe and barrier reefs.

There has been a relatively recent study of coral reefs along the Saudi Arabian Red Sea coast, of particular emphasis on reefs between the cities of Haql and Yanbu, published in the paper The Present Status of the Red Sea Coral Reefs between Haql and Yanbu, Saudi Arabia (Hariri, 2012).
In the article, they describe that in terms of Red Sea reefs:

Island fringing reefs exist between the Al Wajh Bank to Umluj
Reticulate patch reefs, composed of interconnected networks of reef matrix separated by sand also are documented to occur in the area.

The literature seems to use both Al Wajh and Al Wadj for the spelling.


Why do wind speeds often jump from 20 knots to 40 knots

This is an (annoying) artefact of BBC weather forecasts, and not an actual feature of the weather.

At low wind speeds, the speed shown is the expected average speed.

At higher wind speeds, the speed shown is the maximum expected gust.

It changes over when the maximum expected gust is 40 mph (not knots). You can tell the difference because average wind speeds have a white background, and gusts have a black background. I tried to post example screenshots, but I couldn't find any location with a >40mph forecast today ;-)

There is a little bit of explanation about half way down this page: https://www.bbc.com/weather/about/17185651


From my correspondence with Dr. Hamilton, who is one of the leading researchers on forest rings (emphasis mine):

They can be irregular (see figure below) but it is not very common. You
are right, the circularity is why we notice them and there are
probably lots that we don’t notice because they are not round.
However, the mechanism of formation that we have postulated ought to
produce circular shapes. All point-source force fields in an isotropic
medium will produce a circle if the area of influence is large enough.
We argue that the source of energy is the electrochemical potential
(redox) difference between the inside and outside of the ring; and the
force is an electrical field. The groundwater and glacial overburden
have fairly isotropic electrical conductivity (the inverse of
resistance) and therefore circularity is a requirement if the current
density is sufficient.

This photo was taken near from northeastern Ontario north of Kapuskasing. The circular ring is  ~150m across.


Is this classification of mineral formation environments correct?

A genetic classification.

Endogenic: Magmatic, Metamorphic, Hydrothermal
Exogenic: Supergene, Sedimentary

For more on this please see Wenk, H. R., & Bulakh, A. (2016). Minerals: their constitution and origin. Cambridge University Press (second edition)
or the first edition of this book(2004).


Area reduction factor reference for precipitation

The answer depends on whether your data is from a single gauge or a network of gauges, and whether you have storm tracking data or not. Sounds to me like you have daily precip at a single gauge without much more information. If you know the annual average precipitation in the basin then a simple area reduction factor (ARF) calculation is basically the ratio of the annual average gauge precipitation over the basin average.

I am not too familiar with the literature on this, but this report seems like a good starting point for background info.


What is this fossil found in flint in Kent?

That is a sea urchin (echinoid) or at least part of one. the pattern of plates is fairly distinctive. 2 rows of small plates alternating with 2 rows of large plates. I am not familiar enough with urchin phylogeny to give you species but you might be able ot get it from the biology stack.


Do man-made machines take natural Nitrogen out of the atmosphere and in turn cause global warming?

The short answer is that using atmospheric nitrogen as a feedstock for industrial processes doesn't really affect the climate per se. It does mess with the environment (primarily through deposition of nitrogen fertiliser) but this is a separate issue.

The problem from a climate point of view, is that the process is virtually certain to emit a lot of greenhouse gasses (primarily CO2 from fossil fuel powered machinery)


Why does San Francisco see so much more fog than Seattle?

As njuffa alludes to there is a current just offshore from the California coast. This is a deep, cold ocean current. As it hits the continental shelf off the coast it is deflected upwards towards the ocean's surface. But here's where it gets different: a thermal low that forms in the Central Valley of California during the summer draws in the air from the Pacific through the delta and bay waters. As that air meets the cold upwelling water that was deflected upward by the continental shelf, it draws moisture from it. That cold water also cools the air which then forms fog and gets drawn into San Francisco. As that moist air gets drawn further inland, it warms sufficiently for the fog to return to vapor. This actually cools the Central Valley to where this onshore breeze (we call it the delta breeze) gets shut off, the valley warms again, and the whole cycle repeats. Of course, other weather factors (position of the Eastern Pacific High, for instance) can override this process, but it is pretty much the standard summertime pattern. If you need citations, I'm not sure I can provide them, as this is something I learned in a physical geography class in college many years ago. I've also seen some other explanations that are just plain wrong.


How to split climate modes of variability into positive, negative and neutral phases?

I think thats a lot of information on the link you pasted. and the indexes shown there are mostly in time (time-series).
Please note two important steps.
FIRST: the index you want to use is already produced in scientific way and published so how is the index produce please read the relevant paper for that which can help. Apart from that these indexes are mostly (Not all of them) are usually developed to capture/shows standardized/normalized/Anomalous  behaviors of the system. So these indexes are representation of the systems with mean of zero and standard deviation of usually one in case of standardized index, and so does varies for each one of them. The anomaly is different story and i won't go there.

SECOND: Now the deviation of the index from mean (which is zero) shows the deviation from mean conditions (that means from neutral conditions). So positive and negative will show the modes of system based on intended interpretation. like for strength positive deviation will be termed as strong and vice versa.

Finally you can select the positive and negative years as modes of climate with positive and negative deviation from mean. Further to dig deep you can look for mechanism and principals that led to these deviations.

If you want to use your data and look for modes of climate, then i will suggest PCA, SVD and EOF analysis which may not be applicable in this case.
I hope that will help


How can I implement a visualization of archived convective data from numerical weather models?

The best model archive I know of offhand is Iowa State Meteorology's Gempak model data in their MTArchive.  Looks like model-wise, they have at least 10 years of GFS (and the predecessor, the AVN).  No idea if the models are complete files (include CAPE) or not, though.

Gempak software is free, though you won't get graphics nearly as polished as WxBell; they've spent a lot of time fine tuning their setup, and likely use newer more flexible tools (probably GrADS or OpenGrADS, both also free).  You could probably get GrADS to use the .gem files, perhaps by converting them?


Geometrical differences of subduction zones

Differences in subduction geometry depend mostly on what type crust takes part in the collision (oceanic to oceanic, continent to continent, oceanic to continent), the speed of the two (or three) colliding parts and the relative movement of the two plates.
Many subduction zones share similar characteristics (like back arc compression and volcanic arc) but there are many differences too. The general geometry of a subduction zone is, in general, well understood, but there are still many questions about how, why and when, mostly because most of our measurements are indirect and the interpretation is still problematic. You can read http://www.platetectonics.com/book/index.asp for a very good and simplified explanation of tectonic plate movement.


Is Bowen ratio an absolute indicator of land surface type based on the amount of heat transfer from the surface?

A very simple answer is that it is related to the demands of the vegetation types and their ability to maximize the net radiation. A "perfect" plant that covered the entire surface would theoretically result in a BR of 0 as 100% of Rn is used for photosynthesis and released as ET, such that H=0 and LE=RN and B=H/L. It obviously doesn't work that way though.

Since $B=y\frac{\partial T}{\partial e}$ where y is the psych constant (~0.4 and really not a constant) it can be seen that the gradients of temperature and moisture, not the actual values, are the only two factors that matter in determining the Bowen ratio. Each plant essentially has a "specific Bowen Ratio" range where they are able to maximize their use of RN for the environment they are in. If the climate changes in that area the plant would not be able to survive.

That is a very very basic and highly simplified explanation, but hopefully it helps