Why does Morocco have so much phosphate?

The Earth's crust contains an average of 0.27 percent P2O5. Most of it in the mineral apatite Ca10(PO4)6(OH,F,Cl)2.

  Apatite is slowly soluble in neutral or alkaline waters, and its solubility increases with increasing acidity.

  The PO4 content of most river and lake waters ranges from about 0.01 to 0.5 part per million (ppm), but may be much higher in soft acid waters and highly saline alkaline lakes. About one-sixth of the phosphate carried to the sea by runoff is in dissolved form. The ocean as a whole is nearly saturated with phosphate, but its distribution within the ocean is not uniform; deep cold waters contain nearly 0.3 ppm PO*, but warm surface waters contain only 0.01 ppm or less. Oceanic circulation brings phosphate- rich water to the surface in several environments, and phosphate may be precipitated either inorganically or biochemically, as the pH and temperature increase near the surface.

  Most of the world's phosphate production comes from marine phosphorites, many of which are associated with black shale and chert. Secondary processes including diagenetic phosphatization of calcium carbonate and .interstitial precipitation, reworking by waves and currents, and weathering have often played a prominent part in forming deposits of mineable quality.

  Common igneous rocks, such as granite, diorite, gabbro, and peridotite, contain only from about 0.005 to 0.4 percent P205 ,  but some of the less common alkalic rocks, such as ijolite and turjaite, can contain more than 1  percent. Variations in phosphate content of igneous rocks generally parallel those of ilmenite and magnetite.Apatite is slowly soluble in neutral or alkaline waters, and its solubility increases with increasing acidity, decreasing hardness, and decreasing temperature.

  Most phosphorus is carried to the sea as phosphate minerals or adsorbed on iron or aluminum hydroxides or clay.

  Most of the world's phosphate production comes from marine phosphorites. The richest and largest of these form at low latitudes in areas of upwelling associated with divergence, chiefly along the west coasts of the continents or, in large mediterranean seas, along the equatorial side of the basin. Lesser but significant concentrations form along the west sides of poleward-moving warm currents along the eastern coasts of continents.

In the Moroccan phosphate deposits however,

  The unconsolidated sediments on the continental shelf and uppermost continental slope off Morocco and the Spanish Sahara are sands, silty sands, and silts. Their sand fraction is carbonate-rich and considered to be mainly relict from Pleistocene times when sea level was lower. This relict sand is mixed with, and locally buried by, Holocene detrital silts which are concentrated on the slope and the middle shelf. Phosphate is locally abundant in the form of sand-sized detrital grains. These were derived from Cretaceous and Tertiary phosphatic rocks cropping out on the shelf, by erosion during the Pleistocene. The sand-sized phosphatic detritus is concentrated in relict placer-type deposits near parent-rock outcrops. Longshore transport during the Pleistocene has contributed further concentrations of phosphatic sand along the shelf edge. These deposits are of low grade (< 8% P 2O 5) and are of no economic interest at present. No signs of Recent phosphate mineral formation were noted. Thus, the hypothesis that this phenomenon is linked with the upwelling of nutrient-rich water does not appear to apply, at this time, to the region studied.


Which places on Earth would be affected the least by severe climate change?

The places on Earth that have historically had the most stable climates are typically within the tropics and close to sea level/coastlines.  The tropics are not influenced as much by the rest of the Earth's weather patterns since it is more of a source of weather (e.g. the strong convective atmospheric motion that moves air away from the tropics due to the dominant solar heating).  Staying close to coastlines ensures that any rising global temperatures are moderated by the abundance of water.  Staying close to sea level ensures that you are not influenced much by changes in glacier activity nor snow-melt elevation changes.

There is literature that states that tropical ecosystems are most sensitive to climate change, and that tropical areas will see climate change sooner.  However, my point is that the climate itself will be the least extreme in the tropical regions near the ocean. Furthermore, I would like to point out that climate change per se will not make most of the planet uninhabitable as the question insinuates.  As the climate changes, there will certainly be very large changes to the land-surface and ecosystems... including desertification of some areas.  However, any regions with sustainable ecosystems will be habitable, given that there is a source of fresh water large enough for the human population (which the Tropics often have, due to frequent rain... though areas dependent on snow-melt feeding rivers will suffer).


What is the line crossing the Pacific Ocean that is shown on maps?

It's the international date line and marks the boundary between the time zones that are +12 and -12 hours from UTC / Greenwich. It should follow the +/-180 degree meridian line, but zigs and zags to include territories or islands within a "day" thus the Aleutians islands are in the same time zone as the Hawaiian islands.


I would think this is questionable, though we don't have a definitive answer yet.

We usually think Jupiter has a roughly solar composition, which according to the solar abundance measurments of Asplund et al. 2009 would mean the total carbon mass of Jupiter is about $10^{-3}$ of Jupiter's total mass. So there's roughly $0.3$ Earth masses of carbon floating around in Jupiter.
Next we need an idea of where this stuff is floating around.

We know that Carbon is floating around in Jupiter's atmosphere and is enriched relative to solar values by around a factor of $\sim3$, which corrects our estimate of total carbon in Jupiter to roughly one Earth mass, if Jupiter is well-mixed.

The keyword here is "well-mixed". If carbon atoms stay solved in hydrogen at high pressures in Jupiter's core, then no diamonds can be formed. Only if there is a rain-out similar to helium (see also the phase diagram for hydrogen and helium-mixtures) then droplets or other accumulations of carbon can form, which will be pressed into diamonds.

The research however at the moment does not focus very much on carbon dissolution at high pressure, so I cannot cite anything reliable on what carbon will do. The reason for this is that the above cited helium-rainout and core erosion which are considered important at the moment.

I'll try and find some more sources on this as soon as I can go beyond the paywall to the research articles.

Comment on the high pressure-experiments and Juno: To my knowledge carbon-hydrogen mixtures are not being looked at in the labs, but this knowledge might also be flawed.

Juno will mostly be sensitive to Jupiter's density distribution at pressures up to ~1000 bars. Initial estimates show, that even if Jupiter has a dense, rocky core of 20 Earth masses, this will be barely visible in the data. To then filter out how much is carbon will be nigh-impossible with the current mission.


Where can I find an anisotropic PREM-like model for Earth's interior?

Here's an extensive list of Earth models, many of which are anisotropic. You'll probably want to focus on tomographic models rather than reference models.
http://ds.iris.edu/spud/earthmodel


What geophysical knowledge have we learned by the construction of IceCube?

IceCube was initiated as the Antarctic Muon And Neutrino Detector Array (AMANDA) project. Since the sensor array involved drilling deep holes vertically into the Antarctic ice sheet by melting ice, no ice cores were retrieved. The bore holes have, however, been used to construct temperature profiles through the Antarctic ice sheet published in a paper in PNAS. Gathering information of internal temperature is important to understand, for example, basal geothermal heat fluxes and estimating whether or not the ice sheet base is at the melting point and can support liquid water.

In the glaciological literature, very little has been published but then the projects AMANDA and IceCube have never focussed on such questions.

Price et al. (2002) Temperature profile for glacial ice at the South Pole: Implications for life in a nearby subglacial lake. PNAS, 99, (12), 7844-7847. https://doi.org/10.1073/pnas.082238999


Wind speed data plot contains blank gaps

The answer is actually pretty easy. The WRF model lies on a grid. The vertical component of the grid is unevenly spaced, though you can manually space it. The vertical coordinate of WRF uses a sigma vertical coordinate (even though the namelist calls them eta): $$\sigma=\frac{P-P_{surface}}{P_{top}-P_{surface}}$$. So the values of sigma are specified (or just resorted to the default values). So when you get altitude levels for WRF, there is a space between the levels. You would probably find something similar if you change the y-axis to west-east or south-north.
The default vertical spacing for WRF has higher resolution near the surface, which is useful for convection and PBL modeling.


Riverbed 'stones' - I assume you mean things like pebbles, boulders, etc. are pieces of rock that have weathered out and been deposited in the river. Some come from rock that is very close to where they are located and some have been transported from very far away. In general (and it is a very broad generalization) the rounder the stone, the longer it has been in the river and the more likely it is to have come from far away. Of course that depends on the hardness of the rock, and other factors, too.

Some rocks are newer than others. Some have been formed quite recently and some are billions of years old.


Data sets for historical sea level estimates

There are a number of publicly available proxy records for sea-level/temperature curves, I'd start with Google Scholar if you want refereed articles but a straight Google search can give you good results if you use the right search terms, like "sea-level over time" gave me some useful results; I'd recommend the Wikipedia result as most useful to you.


Here's a take on calculating earth's thermal expansion and shrinking, under certain assumptions mentioned in the text. It seems to me, from a short overview, that the core is assumed to be constant over the time. It focuses on the mantle part of the earth, its mineral phases and convetion. Take it with a grain of salt:

https://www.sciencedirect.com/science/article/pii/S167498711200148X

tl,dr: after consolidation, earth's radius was 120km larger than today. It shrank by 110km in a few million years, then expanded a bit (11km), then contracted by 8km, and subsequently contracted by around 12km to the present day.

If they say so :-)


How would waves (in a fluid) behave without intermolecular attraction?

There are different factors that make water a media for waves. For transversal waves the viscosity and cohesion of molecules are essential. Even if the water is assumed not to evaporate. Try to imagine pushing a boat forward in a liquid with low viscosity. The propeller will just easily skid without generating any wave or traction.
However for P waves a liquid with low or no viscosity would still work as long as it can contract and expand under stress. If you in a crude way look at a differential cube of that liquid omega= (k/m)^1/2. K is the water stiffness index and m is its mass.


Relationship between atmospheric density and atmospheric pressure?

There are two fundamental gas laws that need to be understood:

Boyle's Law which states     ${P_1.V_1 = P_2.V_2}$

From this formula if volume increases pressure decreases and vice versa

The second law is Charles's Law which states ${V_1/V_2 = T_1/T_2}$   or    ${V_1/T_1 = V_2/T_2}$

This law states that if the temperature increases there must be a corresponding increase in volume of the gas and vice versa. Another way of looking at it is if the volume drops so must the temperature and vice versa.

The ideal gas law that you mention in your question can be also be written as:

${PV = mRT}$

Where:

P is pressure,
V is volume
m is mass
R is the universal gas constant
T is temperature

Now, density, ${ρ = m/V}$

Which leads to the equation you used:

${P = ρRT}$

One of the primary ways the atmosphere changes is via changes in temperature. The atmosphere on the side of the Earth facing the Sun warms up, while the atmosphere of the other side of the Earth cools.

According to Charles's Law, for the side facing the Sun, the increase in temperature will cause the volume to increase. An increase in volume will reduce the density, because mass doesn't change. With an increase in temperature and a decrease in density the pressure will remain unchanged.


Britannica says:

  ... because of the significant tectonic activity occurring around the world, it is not clear which of these local changes can be correlated
  to global sea level change. Because there is no evidence of major
  glaciations in the Jurassic, any global sea level change must have
  been due to thermal expansion of seawater or plate tectonic activity
  (such as major activity at seafloor ridges). Some geologists have
  proposed that average sea levels increased from Early to Late Jurassic time.

Notice, that we have no information about the change of the mass of water from Jurassic till now.

Even the articles https://www.sciencedirect.com/science/article/pii/S2095383615000267 that shows, how the sea level changed, touch only relative changes in the sea level. As we don't know the statistics for depths and heights for these times, we can guess, that the ocean/land area ratio was greater than now, but the guess is very wild. Any number of percents could be only a sheer speculation.


Solifluction is not restricted to cold climates. Gelifluction on the other hand is, it requires by definition a permanent/seasonal layer of frozen soil. In periglazial environments the porewater above the frozen ground layer becomes easily saturated. Solifluction encompasses numerous processes, Gelifluction is one of them...

The wikipedia page for Solifluction provides more information.


Simplest formula of a calcium phosphate mineral?

Yes, you are correct in your calculation. However, the most common hydrated calcium phosphate in nature is indeed hydroxyapatite. Note that industrially, there are several other calcium phosphates (see link, note that none of them is your calcium phosphate) The reason that it forms instead of the "simpler" mineral is that it is more stable thermodynamically. I'm not certain about the exact reasons for that.

Apatite is so stable that in nature and rocks, almost whenever you have phosphate, it binds with calcium to form apatite. The only way to not have apatite is to not have calcium, not have phosphate, or have some really exotic system that suppresses its formation.

This is also known experimentally. In experiments that simulated calcium phosphate systems as early as the 60s, it was hard to crystallise anything but apatite.


What causes the 'calm before the storm'?

Quoting from Is there really a "calm before the storm"? at howstuffworks.com this sometimes happens ("Other storms skip the calm and proudly announce their presence by instantly unleashing bad weather").

  As warm, moist air is pulled into a storm system, it leaves a
  low-pressure vacuum in its wake. The air travels up through the storm
  cloud and helps to fuel it. The updrafts in the storm, however,
  quickly carry the air upward, and when it reaches the top of the cloud
  mass, this warm moist air gets spit out at the top. This air is sent
  rolling out over the big, anvil-shaped head of the thunderclouds or
  the roiling arms of hurricanes. From there, the air descends -- drawn
  back toward lower altitudes by the very vacuum its departure created
  in the first place.

That descending air becomes warmer and drier which is relatively stable, and once it blankets a region, it stabilizes that air in turn. This causes the calm before a storm.

Follow the link so see a more extended explanation with graphics.


Nonlinear Stokes equations for glacier modeling

If your viscosity $\mu(u)$ is constant, then there is no difference between the two formulations because
$$
  \text{div} (\mu \nabla u^t) = \mu \nabla (\text{div} u)
$$
and for incompressible materials $\text{div} u=0$. So the two formulations are identical for constant viscosities. For variable viscosities, this is a bit more complicated and may in fact not be correct.

In general, the second form you show (with the addition of the transpose of the gradient) is the physically correct form because it involves the strain rate $\varepsilon  = \frac 12(\nabla u + \nabla u^t)$ which is the physically correct quantity where the gradient $\nabla u$ has no physical reality. (This is because the invariants of $\varepsilon$ are independent of the choice of coordinate system, but the invariants of $\nabla u$ depend on the choice of coordinate system.)

The first form you show is a simplification one can work with if you know that (i) you have an incompressible fluid, and (ii) you have no Neumann type boundary conditions (as the "natural" boundary conditions for the two formulations are different).


Mild climate, low-humidity city all year round

Low humidity means nowhere near the coast or near any large lakes. Warm winter temperatures without being too hot in summer means tropical high elevation or lower latitude inland sub-tropical. Parts of sub-Saharan Africa might suit, although cities like Kampala or Nairobi have relative humidities which reach the high 70s. As Milancuric writes, you need to be more specific about 'low humidity'.


Why does an artesian well dry slower than a normal well?

Well B is a normal water table well, which will have a relatively steep, tight, local, and deep 'cone of depression'. Well A doesn't have a 'cone of depression' - it has a 'cone of depressurization', which has an entirely different physical configuration. That is, wide and shallow. So the drawdown in well B will fall rapidly, whilst there isn't really a drawdown in well A, at all. Rather, the pressure surface in well A decreases until much of the aquifer - typically several square kilometres - is depressurized. Note that the two processes are entirely different. In a water table aquifer pumping actually drains the pores between grains in the upper aquifer, like water draining out of a sponge. In a confined aquifer, the yield is supplied by depressurizing the aquifer - so the saturated surface doesn't actually drain at all.


In winter, is pond water warmer with or without a fountain? I have goldfish

In nature, fish survive in ponds due to a lack of turnabout of water.

(Fresh) Water has its highest density at 4°C, meaning both warmer and colder water float on top of 4°C water. Wind may push surface water to the bottom, slightly lowering the temperature at the bottom of the pond. Still, once the surface starts to freeze, this proccess is discontinued, creating a temperature-gradient with the relatively warm 4°C water at the bottom - until spring. Thus fish don't freeze to death.

Meaning, leaving your fountain running is a rather bad idea.

As to the issue of possible lack of  oxygen - I can't answer that reliably.


What are the affirmations regarding the effects of climate change that have a high degree of consensus amongst climate scientists?

Is there a large, documented consensus on any estimate of sea level
  raise or any other more "direct" effect on the human population?

As Will said in a comment, IPCC has some estimates on that matter, although they vary depending on which emission scenario you choose. From the technical summary of the IPCC Special Report on Ocean and Cryosphere in a Changing Climate, section "Projections":

  Future rise in GMSL [global mean sea level] caused by thermal expansion, melting of glaciers and ice sheets and land water storage changes, is strongly dependent on which Representative Concentration Pathway (RCP) emission scenario is followed. SLR [sea level rise] at the end of the century is projected to be faster under all scenarios, including those compatible with achieving the long-term temperature goal set out in the Paris Agreement. GMSL will rise between 0.43 m (0.29–0.59 m, likely range; RCP2.6) and 0.84 m (0.61–1.10 m, likely range; RCP8.5) by 2100 (medium confidence) relative to 1986–2005.

As for the meaning of this sea level rise on human population, it's better to look at the summary for policymakers of the same report:

  The increasing frequency of high water levels can have severe impacts
  in many locations depending on exposure (high confidence). [...] Extreme sea levels and
  coastal hazards will be exacerbated by projected increases in tropical
  cyclone intensity and precipitation (high confidence). Projected
  changes in waves and tides vary locally in whether they amplify or
  ameliorate these hazards (medium confidence).

On a more "philosophical" note, it is really difficult to predict the effect on humans because of the prophet's dilemma. If we know bad things are going to happen, we will (or at least we should...) take measures to prevent them. Then the predicted things will not happen, making the prediction seem wrong, even if it was right at the time it was made! So we can predict that the sea level will rise (it will, no question about that), but we cannot predict the effect this rise will have on humans, because they will likely adapt to it before the effect happens.


What is the origin of the Montmartre mountain in Paris?

A clue is in the full name of the hill: 'Butte Montmartre'. A butte is an erosional feature in which a block of resistant rock overlies a less resistant layer. Erosion of the soft layer below causes the more resistant rock to erode as well by undercutting. This can lead to an isolated hill in a relatively flat surrounding.

The Montmartre hill itself consists of relatively resistant sedimentary rocks (can't find what exactly, although Deffontaines (2005) and De Wever (2002) hint at sandstones and shales) overlying soft marls and gypsum, which was mined until 1860, also contributing to instability of the butte (Deffontaines, 2005). Evaporite-diapirism, as mentioned by Spießbürger, might therefore have played a role as well.

Deffontaines, B., B. Fruneau, A. Prunier-Leparmentier, A. Arnaud, R. Cojean, E. Pajot, J. Rudant (2005) Urban instability revealed by DINSAR and SPN Interferometry: The Montmartre "Funiculaire" case example (Paris, France). Géoline 2005
De Wever, P., F. Guillocheau, J. Reynaud, E. Vennin, C. Robin, A. Cornée, D. Rouby (2002) Deux siècles de stratigraphie dans le bassin de Paris. Comptes Rendus Palevol


The 1967 International Biological Programme has a handbook of suggestions for various methods to calculate primary productivity of forests. A subset of these measures would be effective for measuring litter production.

Regarding leaves and other falling litter,

  Bags suspended from hoops (Ovington & Murray 1964) about 1 m above the
  soil. The hoops would be at least 0.5 m in diameter. The bag should be
  freely permeable to water (nylon mesh, cheese cloth, sail cloth, etc.)
  to reduce moisture and decomposition inside the bag. Care must be
  taken with this type of litter trap that the hoop does not incline out
  of the horizontal and the bag must be pegged or weighted to prevent it
  blowing inside out.

Further, the handbook suggests no less than 20 leaf traps in one sample area, and checking contents every week especially in moist areas. Also, to account for branch fall, the weekly collection should check for and weigh fallen branches in a 20m X 20m area.

For fine roots:

  An additional estimate of fine roots can be obtained either by
  excavation of soil monoliths, or by taking soil cores (e.g. Bray,
  Lawrence & Pearson 1959) down to a depth of at least 50 cm and washing
  out the fine roots over a sieve. So far as is possible only live roots
  should be included.

For ground cover:

  Where distinct plants of a single or only a few species are present,
  the best procedure will be to collect a number of individual plants of
  each species (preferably including subterranean organs) at monthly
  intervals through the year. The collected plants are separated into
  leaves, flowers, stems and roots, which are dried and weighed. These
  individual plant data can then be combined with density (number of
  individual plants/area) data for conversion to an area basis. The sum
  of (Species A max. biomass - min. biomass) + (Species B max. biomass min.
  biomass) ... gives an estimate of net production.

I believe that should account for the significant components of litter production.


First of all, the rocks do not disappear they dissolve, so they are still there only dissolved into the liquid.

You are using an acid (vinegar), this has a low pH.

The rocks you are using (limestone) they have a high pH (alkaline).

The alkaline rock you add to the acid will dissolve but only until the acid is neutralized. The reaction stops when the pH reaches close to 7,0.

If you had used less limestone or more vinegar the rock will be fully dissolved but the pH of the liquid will stay low. To neutralize the vinegar you must then add more limestone.

So you did nothing wrong except maybe using too little acid.

I will stop my answer here, but if you had taken this reaction one step further you would have made marble (the bubbling you might have seen was carbon dioxide CO2).


I found the paper you initially referred to here:

http://onlinelibrary.wiley.com/doi/10.1029/JB073i006p01889/full

based on the hyperlink by the xkcd webpage you referred

http://www.agu.org/pubs/crossref/1968/JB073i006p01889.shtml

The full reference for this paper is: Oetzel, G. N. (1968), Computation of the diameter of a lightning return stroke, J. Geophys. Res., 73(6), 1889–1896, doi:10.1029/JB073i006p01889.

In the abstract:

  The diameter of a first return stroke is found to lie in the range 1–4 cm. Subsequent return strokes are smaller, with diameters in the range 0.2–0.5 cm. In many cases, strokes to towers have shown evidence of the smaller strokes occurring alone. These are explained as strokes initiated by an upward leader.

This paper is quite old - but is relevant nevertheless.

A more recent paper review the physics of lightning in this review paper, titled 'The Physics of lightning' by Dwyer and Uman (2014). They present the various steps implied when a lightning form, illustrated by this illustration (Figure 1):

Basically, there is several stages when a lightning strike. There is the stepped leader component, that somewhat lead the way for the exchanges that will follow. In the figure, we notice the positive and negative signs (+ / -) and how they change position depending on the discharge.

The stepped leader can be followed by return strikes and so on. In this paper they mention diameters for the stepped leader, which may appear to be much larger than the return stroke, such as in the range of one to ten meter in diameter:

  The luminous diameter of the stepped leader has been measured photographically to be between 1 and 10 m.

But - this is by using photography - yet the core of the lightning at the center (the core) seem to be a few centimeter in diameter:

  It is thought, however, that most of the stepped-leader current flows down a narrow conducting core a few centimeters in diameter at the center of the observed leader.

So in the end both papers tend toward similar centimeter-scale measurements for the lightning core.

The core: aforementioned literature refer to the component of the actual lightning as a 'current carrying core' surrounded by a corona sheath. The sheath is what appear to be 1 to 10 m in diameter, where the actual 'electricity channel' is centimeter wide;

so this core as the centimeter wide channel is the electron pathway.


GIMMS NDVI3g grid cells not entirely square-shaped?

Your understanding is inaccurate. The shifts by $\frac{1^\circ}{24}$ are only relevant for figuring out, where the pixel centers are located and where to start when you are looking to find the right grid index for a certain point. As for the resolution, it is much simpler. We have $4320$ pixels covering $360^\circ$ in longitude direction, i.e. a resolution of $\frac{1^\circ}{12}$ and similarly for the latitudinal resolution.

As for the square-nature of these pixels, they are only squares in lat-lon coordinates, not in terms of length on the ground.


What are the challenges in predicting lithology directly from acoustic impedance?

Yes, lithology interpretation/classification directly from seismic inversion products is something people do.  I've seen it work very well in oil and  gas exploration and development of fields.

I personally think that there are two main challenges involved in predicting lithology from seismic inversion impedances. It would be a bit of a cop out to say that the whole inversion and lithology prediction process is challenging, so I won't, even though it is. So, assuming that you achieve good inversion results, by which I mean that your inversion synthetics match input seismic angle stacks and your inversion products (estimated elastic properties) match calibration points (upscaled well logs), I think that the challenges are the uncertainties associated with the:

ability to discriminate rock types in study area, and
low-frequency model

Below I go into a little more detail regarding these two factors. Just remember that I'm talking about lithology prediction from an absolute inversion. Also, I will talk about "elastic properties" a lot, by which I mean the P-impedance, S-impedance and density, or their derivatives like Lambda, Mu and Poisson's ratio if you're that way inclined.

Discrimination of rock types

Before you attempt to predict lithologies from seismic inversion results, you need to know the expected elastic properties of the rocks in your study area. If the various rock types in your study area have the exact same elastic properties, distinguishing them from inversion products is going to be impossible, no matter how good your inversion is. To make a good lithology prediction you need to know the elastic properties of the measured or predicted rocks in your study area. If the rocks have similar (e.g. overlapping) rock properties you need to account for this uncertainty in your lithology prediction.

For example, say you are targeting gas and the predicted reservoir is sandstone. Does a gas filled sand have different elastic properties to a brine filled sand? What about from the sealing shale? What are the expected range of elastic properties for these rocks? By doing forward modelling experiments (e.g. Gassman fluid substitution and/or lithology mixing) you could answer questions that address risk-cases like: what are the expected elastic properties of a low saturation gas sand or a high porosity brine sand? If high porosity brine sands and gas-sands have similar/overlapping elastic properties and I end up predicting a gas-sand from my inversion, what is the probability that the gas-sand is 'real'?

(source)

The above image shows the elastic properties for three lithologies: sandstone, shale and limestone, in terms of P-wave velocity** (Vp) and the ratio of P- to S- velocity (Vp/Vs). Provided your inversion results are accurate, these lithologies would be distinguishable because their property populations do not overlap.

The mean P-wave velocity (Vp) for the limestone is approximately 5800 m/s. But what if the mean Vp was 4000 m/s? The limestone population would then overlap with the shale, meaning that it would be difficult to discriminate between the two lithologies from your inversion results with great confidence.

A thorough rock physics study is necessary before attempting any seismic inversion project to understand the elastic properties of your rocks and to ensure that your target rocks are distinguishable. If your rocks have sufficiently different elastic properties then lithology prediction from seismic inversion is feasible.  You can use your rock physics study to define how your lithologies can be classified from the inversion results (e.g. depth dependent probability density functions of P-impedance versus Vp/Vs for each lithology/fluid type).

** Vp can only be estimated from seismic inversion if you also get a good density result, which is uncommon. I'd prefer it if this graph showed P-impedance (Vp * density), but beggars can't be choosers.

Low-frequency model

So, you know the elastic properties of the rocks in your study area and you know that they can be theoretically discriminated, and you want to predict lithologies from seismic inversion results? I think that the next challenge in lithology prediction are the uncertainties associated with the low-frequency model, because the low-frequency model:

determines the absolute value of estimated elastic properties

so has a very big influence on the predicted lithology

is built by interpolating/extrapolating sparse data (e.g. well logs or rock physics trends)

i.e. a lot of the spatial variation of the low-frequency model is not measured

A low-frequency model is used to fill in the low-frequency elastic property gap not measured by seismic data, and allow absolute elastic properties to be estimated. For conventional marine seismic with a bandwidth of, say, 10-60Hz, the low-frequency model will provide the inversion with elastic properties of the study area between 0-10Hz (see picture below). What kind of geological information is captured within this low-frequency range? Large scale geological changes, like compaction trends, or the elastic property changes associated with low-order sequence stratigraphy cycles.

(source)

Without a low-frequency model, inversion can only provide the relative impedances of two layers; this is called a relative inversion. Inversion with a low-frequency model is called an absolute inversion, and it seeks to estimate the total elastic property of the layer, independent of impedance of above/below layers. If you get the low-frequency model wrong, your absolute elastic properties will also be wrong and therefore you will predict incorrect lithologies.

A low-frequency model can be built by extrapolating low-pass filtered well logs (P- and S-sonic and density), rock physics trends, etc throughout the study area, creating a 3D distribution of elastic properties. How can you be sure that you have a good low-frequency model?

Blind well testing can give you confidence in your model.
Use a robust method for extrapolating your well logs or rock physics trends.
Even better would be to improve the low-frequencies of your seismic data through deghosting, to reduce the influence of the low-frequency model on your final interpretation.

Final thoughts

You can create different criteria for classifying lithologies, run an absolute inversion and predict lithology fairly easily these days. But if you don't have confidence in your ability to discriminate between different rock types or you're not sure if your estimated absolute elastic properties are correct, you cannot be sure that the lithologies you have predicted are useful. So what to do? Firstly you need to do a really good rock physics study first to understand the elastic properties of the rocks, and rocks you predict to be present, in your study area. Secondly put in a lot of effort to making sure you have a robust low-frequency model.


The table below gives you a nice summary snapshot up to 2015.

Reference:  Kamp, P.J., 2016. Towards an Ultra Sensitive Seismic Accelerometer (Master's thesis, University of Twente).

Sercel accelerometer, the top one in the table, is widely used in Oil and Gas industry, for example, to monitor induced seismicity. Below is an excerpt from the article: "A high-sensitivity MEMS-based accelerometer", by J. Laine and D. Mougenot (2014), The Leading Edge, 33(11).

1 g is about ~10 m/s^2 (9.80665) so 1 ng ~ 10^-8  m/s^2. For the Sercel then 360 ng mentioned in the paper (three times the rms noise level) = 3.6 ^10-6 m/s^2.

Correct me if I am wrong.


Can anyone explain the torque that causes the Earth's axial precession?

Any object with a non-spherical moment of inertia tensor that is subject to a non-uniform gravitational field will experience a torque due to the gradient of the gravitational field. This can result in a benefit or a challenge for artificial satellites.

The Earth has a non-spherical moment of inertia tensor due to its equatorial bulge, and the Moon's and the Sun's gravitational field are non-uniform (gravitational acceleration more or less follows an inverse square law). This means the Earth is subject to instantaneous gravity gradient torques from the Moon and the Sun.

These torques would average out to zero if the Earth's equator was aligned with the Earth's orbital plane about the Sun and the Moon's orbital plane about the Earth and if the orbits were circular. Since this isn't the case, residual torques exist after averaging (better: integrating) the instantaneous gravity gradient torques over time. It is these averaged / integrated torques that result in the axial precession.


Can the forecast N+1 days ahead be more certain than the forecast N days ahead?

Typically, days with conditions which might produce local instabilities would produce a less certain forecast than a day with a stabilize pattern even if the more stable day was further in the future.  For instance, tomorrow may have the potential for localized disturbances some maybe there will be thunderstorms, maybe they will not form.  But two days later, a large high pressure zone will almost certainly clear everything out or a band of rain will definitely reach the area.


Can a voltage difference precede cloud-to-ground lightning, and can it be measured over a short distance?

There is always a background voltage difference from the ground up, of about 100V per vertical meter resulting in a net voltage difference of about 400,000V between the top of the atmosphere and earth ground. However, being a good insulator, makes for lousy conductivity, therefore the current density is extremely low which would make measuring with a common multimeter pretty hard: there's just not enough surface area on those tiny leads over which to contact air and ground. Add to that the very low current density, and your digital multimeter (DMM) is nowhere near sensitive enough to measure that voltage difference.

Although the moments preceding a lightning strike will generate a potential of tens of millions of volts, using a DMM still leaves you with a few big problems:

1) Lighting is an energy transmission that channels through a "pipe" of ionized air molecules. You'd be hard pressed to predict where that pipe is going to set up, getting there in time, and most importantly, surviving the instant supernova of steam that your body would turn into.

2) You're still left with the problem of the tiny surface area of DMMs leads. Sure, there's a big voltage potential, but the current density is still too small to measure with an unmodified DMM. Like Trond Hansen notes above, you'd need to connect your DMM to a large "collector" to actually see the difference, (then calculate the current density observed based on the surface area of your collector.)


Ocean water coming from Mantle vs coming from meteorites

The answer of this post clarifies also this related question:
Water on Mars and Earth

  If water on Earth came from meteorites, why doesn't Mars have
  substantial water?

  First off, that's a conjecture regarding the origin of the Earth's
  water rather than a known fact. A few times a year or so, a new
  journal article will appear that argues that the Earth's water is
  primordial, then another arguing that it came from comets, then yet
  another arguing that it came from asteroids.

  If the Earth's water is mostly primordial, most of it is over 4.5
  billion years old. If it came from asteroids or comets that collided
  with the Earth after the Earth had formed, it's still very, very old.
  Regardless of the source, almost all of the Earth's water has been
  here for at least 3.8 billion years old, since the end of the late
  heavy bombardment.

Mars and Earth are both rocky planets. If the water was there, at Mars or at the Earth on Archaic, then I guess degassing of Mantle was more quick than I thougth and what my hydrology teacher told us had not a lot of sense. "Regardless of the source", so then water came from both sources but probably meteorites are not the main source.


What you are looking for is called a zero-dimensional climate model. The equation without the Greenhouse effect is simple, though with a lot of simplifications, one with a very crude, linearized, Greenhouse effect is possible.


Who are the 3% in the often cited "97% of climate scientists"?

As the abstract makes clear, the finding of Cook et al. (2013) is not really "97% of researchers agree..."; rather, it is "97% of peer-reviewed publications agree". They didn't just go through some directory of climate researchers asking them what they thought. They read the abstracts of all 11,944 publications they found on the topic, and classified them according to what the abstract said. (The classification was blinded and crowdsourced -- read the paper for details.) As a secondary check, they asked the original researchers themselves to evaluate their own abstracts, presumably to control for any bias which Cook et al. might be bringing to the evaluation. The proportions of abstracts endorsing the consensus were 97.1% and 97.2% respectively for the two methodologies.

Note that this isn't asking researchers anything about their own beliefs. Imagine that, for instance, Jane Q. Scientist privately believes that the earth will cool by 5°C in the next century, but that she hasn't found any solid data to back up this belief, so hasn't yet managed to publish anything supporting it. However, in 1998 she published a paper which provided evidence for anthropogenic global warming. Perhaps she now disbelieves the conclusions of that paper, but it remains in the literature because the data and reasoning were strong enough to stand up to peer review, no matter what the original author now thinks. In practice, of course, it's likely that scientists' personal beliefs will be similar to their published results, but I feel it's very important to stress that this study is not an opinion poll -- it's an evaluation of the research itself. (The media can be a little sloppy in their reporting of this distinction.)

Thus, your question is a little misconstrued: we can't answer "Who are the 3%?" because the 3% are research articles rather than people. However, we can ask "Which are the 3% of published research abstracts which do not support the scientific consensus?" And since Cook et al. (2013) is an open access paper with supporting data provided, you can easily answer this question for yourself: simply download the data file from the supplementary data page and look at the papers with an endorsement rating of 5, 6, or 7. (It's in CSV format, so is easy to load into a spreadsheet or text editor.) Further supplementary data is available from the project page at Skeptical Science, and replication of the research is actively encouraged. If you're interested in the actual people behind the 3% of "non-consensus" papers you can look at the author lists for those publications (though of course there's no guarantee that all those authors would still stand by all their conclusions).

I suggest that you start your investigations by reading the paper itself. It's clear and concise, and will give you much more thorough information about the methodology and supporting data than I've been able to fit into this answer.

Cook, J., Nuccitelli, D., Green, S. A., Richardson, M., Winkler, B., Painting, R., ... & Skuce, A. (2013). Quantifying the consensus on anthropogenic global warming in the scientific literature. Environmental Research Letters, 8(2), 024024.


Best sources / methods to find additional cloud information for current weather conditions?

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite provides new insight into the role that clouds and atmospheric aerosols (airborne particles) play in regulating Earth's weather, climate, and air quality.

CALIPSO combines an active lidar instrument with passive infrared and visible imagers to probe the vertical structure and properties of thin clouds and aerosols over the globe.

The data from the satellite can be found here (https://eosweb.larc.nasa.gov/project/calipso/calipso_table), from what I see, the latest dataset is about a week old. While this won't give you the cloud type, it will surely give you the cloud heights, you will have to apply some knowledge though to differentiate between clouds and aerosols.

For the cloud type, I suggest you can look at visible satellite data or infrared satellite data to look at clouds and judge the cloud type.

This is the e-wall from Penn State,
http://mp1.met.psu.edu/~fxg1/ewall.html
If you look at the left panel about mid-page, you see the heading 'Satellite' and you can look at the visible and infrared spectrum and also a water vapor satellite image.

This approach seems very raw, but this is what I could remember off the top of my head. I don't know of a page that provides real time data about cloud height and cloud type.


Why does a subduction zone produce a serpentinization diapir rather than volcanism?

After some brief research, serpentinite diapirism occurs due to deep penetration of seawater at temperature around 100-200$^o$C [1]. To the south of the rift that was forming the ophiolite sequence there was an oceanic plate subducting as African plate moved north. This subducting oceanic plate provided the seawater that serpentinized the harzburgite in the ophiolite sequence. From my understanding this removed the water from the system before it reached depths to form partial melt. The subducting plate also assisted in pushing the diapir to the surface through the detachment faults present from the rifting.[1]:http://earth.huji.ac.il/data/pics/Nuriel%20et%20al%202009.pdf [image]:http://www.moa.gov.cy/moa/gsd/gsd.nsf/dmlTectonic_en/dmlTectonic_en?OpenDocument

tectonic evolution http://www.moa.gov.cy/moa/gsd/gsd.nsf/f6b12283222a96a3c225734000315725/a9e0eeb1c9dc2e5ec225734000329c12/MainText/0.8A?OpenElement&FieldElemFormat=jpg


Why does the colour of Earths oceans vary?

The color of the ocean water does indeed vary depending on the chemical composition of the water. In addition, the color of the ocean in satellite images is affected by the position of the satellite, angel of the sun, and weather.

Color of water in general

Water appears blue because long wavelengths (red or yellow light) are absorbed more efficiently in water than short (blue or green) wavelengths. Therefore, when a water body — in a swimming pool, for example — is illuminated by a white light source (the sun) the light that scatters back from the water tends to be blue rather than red.

The color of the water can further be altered by its chemical composition. In nature, the apparent color of water also depends on the light source, that is, the weather. The same ocean can appear very different in bright sunlight and on a cloudy, stormy day.

Color depends on substances in the water

The color of the ocean water can be greatly altered by substances dissolved or suspended in the water.
Typical substances that affect the color are chlorophyll (from waterborne algae) that make water appear green, or suspended particulate matter, such as silts and clay, that cause yellow or brown color. These are clearly seen in coastal areas, where local plankton blooms can turn water bright green, or river plumes carrying a high concentration of suspended particulate matter can be clearly identified from their brown waters. Other substances can alter the color of water as well. Colored dissolved organic matter (CDOM) related to decaying detritus, can turn water yellowish or green, for example. Water temperature and salinity themselves do not significantly affect the color of the water.

The color of the ocean, therefore, does depend on the location. For example, waters in areas with high primary production tend to be more green.

Color of oceans in satellite images

In satellite images, the color of the ocean can be influenced by the relative angle of the sun and the satellite versus the ocean surface. The ocean can appear darker if the satellite is at an oblique angle with respect to the ocean surface and/or if the sun is shining from an acute angle. In the case of geostationary satellites, the ocean near the equator can therefore appear to be brighter than in the high latitudes.

Moreover, the color of oceans may be affected by the surface roughness. Surface waves affect the way light is reflected and refracted in the surface and may cause the ocean to appear darker.

Consequently, the color of oceans may vary greatly in satellite images due to the track of the satellite and local weather conditions. This is often visible in large composite images, made out of multiple satellite tracks, where the ocean may appear patchy with different colors.


Why do trees break at the same wind speed?

Image source: Wikimedia Commons
Note that in the above image, that almost all of the trees had their tops snapped off. This claim is about tree's being snapped in two and is not about trees falling over or being uprooted.
This claim is approximately valid for many species of trees. Apparently oaks can withstand slightly higher wind speeds than can pines. This claim does not apply to non-woody trees such as palms. It also is not true for species of woody trees that have evolved to live in areas where winds occasionally exceed 42 m/s (the equivalent of a category two hurricane).

I just do not understand what can cause such behavior to be valid for all size and types of trees.

The authors of a recent paper on this subject attribute it to evolution. While winds frequently exceed 30 m/s (126 km/h), they very rarely exceed 50 m/s (180 km/h) in most places. The sweet spot in a tree's ability to sustain winds is between these limits. A tree that is too flimsy will be snapped by a heavy gale, won't live to maturity, and won't spawn offspring. A tree that is too sturdy is wasting precious energy building unneeded structure.
As for why and how, it's a matter of allometry. Trees grow in girth as the age and add to their canopy. Tree allometry investigates the relationship between tree girth at chest height and other features of trees such as height and canopy area. The relationship between girth and canopy area is close to linear.
Another factor is defects, which are places where a tree is most likely to snap in two. The extent of these defects also scales with size. Young trees lose tiny branches; the young tree eventually grows around these, leaving the small defect buried deep inside the tree as it ages. Older trees lose larger branches, leaving behind a potentially larger defect.
References:
Critical wind speed at which trees break.
Trees, regardless of size, all break at the same wind speed. Here’s why.
Urban Tree Database and Allometric Equations.


High resolution DEM for digital soil mapping and modelling

It depends on your area of interest. If you are just testing a method, one of the large coverage free DEMs with high resolution (2m) is ArcticDEM, but as its name say it covers the Arctic only (Alaska, Northern Canada, Northern Europe, Russia, etc.). You can check that one out (ArcticDEM)

This is the coverage of ArcticDEM


What is the mechanism for deep-sea volcanism of the Gakkel Ridge in the Arctic?

There is some considerable uncertainty as the exact mechanisms. However, the recent seismicity and pyroclastic deposits detected around the ridge provide a unique opportunity to observe and model the baheviour of ultraslow spreading ridges.

According to the article Explosive volcanism on the ultraslow-spreading
Gakkel ridge, Arctic Ocean (Sohn et al. 2008), to overcome the pressure of the seawater, it becomes a question of the amount of volatiles (particularly $\ce{CO2}$ available in the magma chamber to cause fragmentation resulting in the glassy pyroclastic deposits observed around the volcanic centres on the Gakkel Ridge.

Sohn et al. hypothesise that the ultraslow spreading nature of the Gakkel Ridge would cause long intervals between volcanic events, which in the article, Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85°E (Pontbriand et al. 2012) suggest to be around 10,000 years.

The long interval times allow for the accumulation of large volumes of volatiles in the upper part of the magma chambers. These would erupt periodically when the pressure in the magma chamber exceeds the deep sea-water pressure.  Models from Sohn et al. suggest that a weight fraction of 14% $\ce{CO2}$ (~75% volume fraction) would be required - a value considerably higher than those measured at most mid ocean ridges.  Pontbriand et al. estimate that $\ce{CO2}$ supersaturation in the magma chambers of the Gakkel Ridge to occur around 1500-2000 year timeframes (i.e. well within the estimated volcanism interval).

Pontbriand et al. go further and suggest that one of the most important implications of the observations (and modelling) of explosive volcanism on deep-sea ultraslow spreading ridges challenge the hypothesis that eruption volume varies inversely with mid ocean ridge spreading rates.


Hurricane eye on landfall and relation to wind speeds

The winds are at a maximum velocity Vmax in they eye wall, a thin annulus immediately around the eye. With increasing distance the winds fall off. If a hurricane was a Rankine vortex, the wind velocity at radius R from the center of the eye would be V(R) = Vmax X (Reye/R), where Reye is the radius of the eye. In reality friction usually prevents a hurricane from being a perfect Rankine vortex. Instead it typically a modified Rankine vortex, with V(R) = Vmax X (Reye/R)^n, where n is typically in the range 1/2 < n < 3/4 (perhaps n = 2/3 is the best overall average value). Of course this is a radially-smoothed-out wind velocity distribution. In the approach of an actual hurricane, wind does not increase monotonically as R decreases. But V(R) = Vmax X (Reye/R)^2/3 typically approximates the secular trend of its increase.


Are airliners sensors used to feed weather prediction models?

Indeed, airlines are equipped to measure atmospheric data and then put into weather models. The WorldMeteorological Organization's program is called AMDAR. Several articles highlight the impact that the lack of flights have had on the initialization of weather models.

https://www.npr.org/sections/coronavirus-live-updates/2020/04/03/826848818/one-more-coronavirus-problem-accurate-weather-forecasts

https://www.boston25news.com/news/local/covid-19-forecast-how-grounded-flights-are-impacting-weather-forecasting-data/RB7HY6G5ONGE3EHROUKSKT4SB4/

There are a few papers that explore the impact that aircraft data has on initialization:
https://journals.ametsoc.org/doi/full/10.1175/MWR-D-17-0380.1
https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-14-00055.1
https://journals.ametsoc.org/doi/pdf/10.1175/2009WAF2222321.1


In a barometer, you have a tube submerged in a fluid, with a vacuum at the top. If air pressure is low, the fluid can drain out of the tube, letting you read how much lower the air pressure is than some reference value. So, the height of the fluid in the tube goes down as air pressure goes down.

The "inverted barometer" is, in my opinion, much easier to understand.  Over the oceans, high pressure systems push down on the water, lowering sea surface heights a bit. Here, sea surface height goes down as air pressure goes up.  So, it's inverted from a barometer.  But it's really just saying "If I push on something, it'll move" :-p


Is there a lake whose sole source of water is rain and has a hole at the bottom draining it?

I think there is some misunderstanding of the water balance of a lake, or to put it differently, why some holes in the ground are dry while some are filled with water (known as lakes). The linked articles contain lists of closed lakes, but I'll also try to explain how lakes are formed.

Fresh water comes from the rainfall (and snow and moisture) that falls on the ground, and if it does not evaporate, it will eventually seep down into the groundwater when it reaches the groundwater table.

The groundwater flows towards lower elevation, known as hydrostatic head, and eventually, it reaches the sea level. If you would dig a number of holes from the sea towards the mountains, you'll see that if the holes are deep enough to reach groundwater (wells), the elevation of the groundwater surface will form a slope. If the geology is such that the water only flows slowly through the ground and the precipitation is high, the slope can be steep, but if you have e.g. a sandy ground and low precipitation, the groundwater table is subhorizontal. Indeed, in areas with high evaporation, the slope can face away from the ocean, towards a local depression as e.g. the Dead Sea or Death Valley.

If the groundwater table crosses the ground so that the elevation of ground is lower than the hydrostatic pressure of the groundwater, the groundwater will be exposed and form a lake or enter a river. The lakes and rivers are manifestations of the groundwater level. Sometimes there is a delayed response time as water flows much quicker in a river than in the ground. This causes flash floods to flow above the ground if there is not enough time for surface water to penetrate the surface. Like a coffee filter overflooding if one pour water in it too fast. Given enough time, the surface water will enter the groundwater and flow towards the ocean or evaporate.

Sometimes there are features that speed up the flow, e.g. karsts or gravel lenses that have a very high hydraulic conductivity so that water can flow rather fast through. Interesting phenomena can occur that control this kind of quick drains if e.g. the drainage gets frozen and clogged in winter or there are some other seasonal variations. This is maybe what you describe as a drain hole, but usually, lakes without outlets just adjust the water back into the groundwater by penetration and by evaporation of the surface.

Dissolved salt is concentrated in lakes without an outlet and they are called closed lakes or endorheic basin. If the climate is changing, an open lake can become a closed lake and vice versa.

A lake is always a temporary feature. They fill up with sediments over time and becomes a part of the river path. As you noticed, there is always a special reason for a lake to form, e.g. rapid post-glacial rebound, rifting or an impact crater.

Ponds and tarns without a visible outlet are rather common, at least in post-glacial areas as Canada or Scandinavia, but if a lake has enough inflow, its level will rise until it gets a visible outlet. Depressions without a visible outlet are called sinks.

How pure the water in the lake is depends on a number of factors. Silt and clay come from fast-flowing inlet rivers or wind. The residual time and current for the water in the lake defines how much of the sediments that have time to settle. The bathymetry is also an important factor as local depocenters can take care of most of the sediments. Fine sediments can take a long time to settle. Finally, the biology of the lake is naturally very important.


Analyzing composition of a mineral using SEM

You would be lucky if you could identify it with only elemental composition. XRD would be the best method to identify material ( the elemental composition is also needed ). Our lab normally used XRD and XRF , and only went to the SEM when special information was needed.


How does metamorphism change talc into soapstone?

Soapstone is a form of talc. It is basically talc plus other minerals, such as micas, chlorite and amphiboles, depending on the initial rocks that were metamorphosed. Soapstone is also called a talc-schist.
Soapstone is formed by the metamorphism of ultramafic protoliths, such as dunite or serpentinite and the metasomatism of siliceous dolomites. The metamorphism occurs in the regions where tectonic plates are present, where the rocks are subjected to heat and pressure, with flowing liquids, but without melting. Soapstone is derived from hydrothemal alteration of peridotite and related ultramafic rocks.


What geophysical events can (temporarily) increase the Earth's rate of rotation?

TL;DR
The Earth's rotational angular momentum is indeed being transferred to the Moon's orbit. However, this is a very slow process that is barely noticeable even over the course of hundreds of years. That long-term trend is invisible in the short thirty year span shown in the graph in the question. The variations seen in the plot result from transfer of angular momentum amongst components of the Earth (solid Earth, the atmosphere, the oceans, and the outer and inner core) and from changes in the Earth's inertia tensor.
About the Graph in the Question
Regarding that graph, what you are seeing are

The cumulative effect of transfer of angular momentum to the Moon since the early 1800s, and
Short-term effects that have nothing to do with that long-term trend.

Regarding the first item, our 86,400 seconds per day is based on the length of day in about 1821. The CGS second was defined in the late 1800s based on data collected over a ~100 year period, centered around 1821. The SI second is now based on atomic clocks, but the definition was intentionally made consistent with that old CGS second. The length of day has increased by about 2 milliseconds since the early 1800s.
Suppose the Earth's rotation rate held steady at one mean solar day per 86,400.002 seconds, the average rotation rate over the last several decades. We would still need to add a leap second every 500 days or so because of that 2 milliseconds increase in the length of day. That's the primary feature you are seeing in the plot shown in the question.
Regarding the second item, the variations during the 30 year span in that plot don't have much to do with the variation over the 200 year span since the early 1800s, and those in turn don't have much to do with the very, very long term variations in length of day due to transfer of angular momentum to the Moon. That very, very long  term trend becomes obvious only over the course of many tens of thousands of years or more. Over the short term (a hundred years is "short term" in this sense), various cyclical effects dominate over this very long term trend. The transfer of angular momentum to the Moon is completely hidden in the 30 year span covered in the plot shown in the question. That's just too short a time span to see that transfer of angular momentum.
So what is that plot showing? The two most notable features are the long stretch between 1900 and 1998 with almost yearly leap second adjustments and the long stretch between 1999 and 2006 with no leap second adjustments.
Short-term Variations in Length of Day
Those leap second adjustments make it a bit hard to see what's going on. Here's a much better portrayal:

Source: https://hpiers.obspm.fr/eop-pc/earthor/ut1lod/UT1.html_nov08
The first thing you should look at in the above plot is the top curve. This is LOD, length of day (better: excess length of day). The length of a day is 86400 seconds and a tiny bit more. LOD is defined to be just that tiny bit more. LOD decreased between 1973 to 1987 and then again between 1993 to 2004. The Earth's rotation rate was very slightly increasing during those intervals.
As mentioned above, angular momentum is being transferred from the Earth to the Moon, but this is a very slow process. What this means is that the Earth's total angular momentum is very nearly constant over the span of years, even decades. Note that it's angular momentum, not angular velocity that is the nearly conserved quantity. Angular velocity can change while angular momentum remains constant. The graph above depicts change in period, and hence change in angular velocity.
The Earth comprises five different rotating systems: The inner core, the outer core, the mantle and crust, the oceans, and the atmosphere. Our terrestrial timescales, UT1 and UTC, are based on the rotation of the mantle and crust only. These five systems do not quite rotate in unison. For example, the inner core is currently rotating slightly faster than one revolution per day while the outer core is rotating slightly slower than one revolution per day. These systems transfer angular momentum amongst themselves.
Some of this transfer is visible in the "Seasonal Variations" plot in the above graph. The mantle and crust transfer angular momentum to and from the oceans and atmosphere on a seasonal basis. What's left after removing those season variations and other high frequency variations (shown as "Irregular Variations" in the above graph) is the white "Trend" line overlaid on top of the blue plot. This white curve shows multi-year variations in the length of day.
Summary
The trend over hundreds of millennia a very gradual increase in length of day due to transfer of angular momentum from the Earth's rotation to the Moon's orbit about the Earth, currently about 2.3 milliseconds per day per century. That's not visible in the plot shown in the question. Over the past several millennia, post-glacial rebound has exchanged less dense ice/water in the polar regions with more dense rock. This reduced the Earth's moment of inertia and thus increased the Earth's rotation rate. Over decades, variations in length of day largely due to interactions between the core and mantle. The inter-annual variations are due to transfers of angular momentum amongst the core, mantle, oceans, and atmosphere. The El Niño–Southern Oscillation and changes in the gravitational field are key drivers in these inter-annual variations.


What is this geological formation in the Santa Cruz mountains that looks like a cave interior?

Well given that travertine springs trail is right next door, in castle rocks state park I am going to guess travertine. Which is a calcium carbonate mineral deposited from geothermal springs, hot ground water brings up the dissolved travertine which is deposited as the hot water evaporates, but can also slowly be dissolved and redeposited by rain. Thy can form very quickly, on the span of years or decades. There are many travertine geothermal springs in the area. If you want more information try this link for a start.
https://en.wikipedia.org/wiki/Travertine_Hot_Springs


its the same way atolls form, sea level changes and tectonic plates move while the corals keep growing up as the land sinks. Any spot high enough for coral to survive can slowly grow in this way. they can end up hundreds of meters above the sea floor by the slow gradual process of growing coral.
I find a simple animation makes it easier to follow.
Cays are just trapped sand in the coral reef, the sand can come from the erosion of nearby  islands, volcanic, or even erosion of the coral itself. This is why most cays occur near other land masses or in volcanically active areas.
Just as land can sink it can also rise, pushing those deposits high above the waterline, note these cays are very rare. Also note the parts far above the water are dead ancient corals not living ones, although there may be leaving coral around the base. there are ancient fossil corals in the Himalayas after all.


How to open old GOES-1 satellite image files downloaded from NOAA CLASS

Unfortunately, the older weather satellite data is, the harder it is to read.
Perhaps NOAA's Weather and Climate Toolkit can open it.

The old stuff usually comes in tightly packed binary formats that may or may not be well documented (these satellites were designed to take pictures of clouds for weather forecasters to use, us future generations were more or less an afterthought).  Just to illustrate the difficulty: I've previously worked with data from the NOAA HIRS instrument from the late 1970s/early 1980s, and found that the headers contained a mixture of ASCII and EBCDIC information, and that some necessary calibration parameters for the thermistors on the on-board internal warm calibration target were simply lost, and that for some satellites, the available header documentation did not match what was actually in there, and I couldn't read most of the headers.  Other information useful for interpretation existed in the NOAA library, but was unavailable to me due to export restrictions (ITAR).

The imager on the first generation GOES satellites is the Visible-Infrared Spin Scan Radiometer (VISSR, flown on GOES-1–3 between 1975 and 1993.  A similar instrument with the same name has flown on several Japanese HIMAWARI GMS satellites between 1977 and 2000.

Pytroll is a series of Python packages to read and process satellite data.  It includes Satpy, which can read a large number of meteorological satellite imager data formats.  I think that anything that can be read by Satpy should be openable by the Satellite Information Familiarization Toolkit (SIFT), under development at the University of Wisconsin-Madison.

Unfortunately, I don't think Satpy has a reader for GOES VISSR (most focus is on current and future instruments), although there are plans for GMS VISSR (I don't know why this issue was closed).  Considering the similarity of the instruments, a reader for one should hopefully be similar to a reader for the other.  At least for GMS VISSR, file format documentation is available.  For GOES VISSR, some information appears retained at CEDA, but unfortunately that appears to be lacking in the detail you would need.

If you plan to develop a reading routine (you'd need to learn Python first if you don't know it already), do hop in to the Pytroll slack for advice.  There are also Pytroll workshops (normally twice a year) that are a great resource if you intend to work on a new satellite reader.

There might exist propriety software that can read this data, but unless you work at an employer that holds a license for such, that is going to be difficult to access.


Why do diamond mines seem to always appear conical? Are the above-ground mines all that way? All at about the same angle?

The main hard rock sources of diamonds are either kimberlites or lamproites.

Many kimberlite and lamproite deposits occur as:

  carrot-shaped, vertical intrusions termed 'pipes'

As the term "carrot-shaped" suggests, the general shape of the pipes is conical and when viewed in horizontal cross-sections they are generally quasi-circular.

When such structures are mined by open cut methods, as with open cut mines of tabular orebodies it is impossible to mine any open pit to any great depth with vertical walls for ground stability reasons. The mine walls are stepped and the parts of the walls between the horizontal steps are sloped. Because of this, open pit mines start out wide at the top, on the surface, and they get narrower with depth.

If the deposit being mined has a quasi-circular horizontal cross-section and is shaped something like a carrot then the open cut mine will also be conical or quasi-conical in shape.


What is the height above ground of NCEP/NCAR Reanalysis 1 variables?

The height coordinate varies and is described for the various variables on the site you link.  For example:

  Levels:

  Surface or near the surface (.995 sigma level), or entire atmosphere (eatm)

and

  Levels:

  17 Pressure levels (mb): 1000,925,850,700,600,500,400,300,250,200,150,100,70,50,30,20,10
  Some variables have less: omega (to 100mb) and Humidities (to 300mb).

For the pressure levels coordinate the height above the ground is variable and dependent on atmospheric conditions.  The sigma levels are terrain following and flatten out with height and will vary with local topography. (see this for more info)

You can estimate height using the hypsometric equation, or use the geopotential field from the data to determine the height at specific grid locations (it will vary horizontally).  For processing, I would recommend using the geopotential data since it is available for each of the vertical coordinate possibilities in this dataset.


Beringia - history of the region, periods of sea level fall/rise - paleogeography of Pleistocene

Ok, I am answering to myself:
here are the papers, everything is in there

https://www.nature.com/nature/journal/v423/n6942/full/nature01690.html

https://www.nature.com/ngeo/journal/v3/n2/full/ngeo729.html


From a review of weather observations, that statement is false.

Below are  the synoptic weather maps for Australia for 11 August 2015 and  12 August 2015. There are no weather fronts, or adverse weather in the western two-thirds of the continent.

Alice Springs (lat:-23.8, long: 133.89) is in the centre of the continent. It's weather observations for 11 August 2015 reveal the temperature ranged between $5.8$ $^oC$ and $26.0$ $^oC$ and the dew point  range was between $-18.8$ $^oC$ and $-2.5$ $^oC$.

Similarly for Darwin (lat: -12.42, long: 130.89), which is located on the coast in the sub tropics, in the central north of the country, the temperature range for 11 August 2015 was $19.7$ $^oC$ to $30.1$ $^oC$, while the dew point range was $15.4$ $^oC$ to $19.8$ $^oC$.

Perth (lat: -31.93, long: 115.98), on the southern western coast has a temperate Mediterranean climate. It's temperature range was $10.2$ $^oC$ to $17.6$ $^oC$ and the dew point range was $5.7$ $^oC$ to $11.7$ $^oC$.

Adelaide (lat: -34.95, long: 138.52), on the southern coast, in the centre region , also has a temperate climate and its temperature ranged from $7.6$ $^oC$ to $15.4$ $^oC$ and the dew point range was $-0.3$ $^oC$ to $8.5$ $^oC$.

Lastly, Brisbane (lat: -27.39, long: 153.13) which is on the east coast  had temperatures between $8.2$ $^oC$ and $21.9$ $^oC$ and the dew point varied between $6.9$ $^oC$ and $15.8$ $^oC$.

All these weather observations show significant variance in the dew point for these locations given the respective temperature ranges and the lack of weather fronts and adverse weather systems.


Yes. It's kept warm by slowly  decaying primordial radioactive elements. They are: Uranium (238) and Thorium (232). The half life of the first is 4.4 billion years, the second around 14 billion years.

They heat the surface even to this date, and it's around 0.2K warmer than if they were absent.

Owing to their continued decay, this temperature differential will decrease .

Extension: On the most popular models (and David Hammen's comment :-) ), Uranium and Thorium are in the crust and   mantle, and not in the core. Despite that, their radioactive decay heats the Earth.


How was the atmospheric/oceanic circulation different prior to the formation of the Isthmus of Panama?

Concerning the thermohaline circulation: the defining part of it, I think, is the formation of bottom water in the polar regions.

The formation of Antarctic Bottom Water (AABW) in the Southern Ocean is strongly linked to the presence of the Antarctic Circumpolar current (ACC). The ACC was possible only after the opening of the Tasmanian Gateway and the Drake Passage (between Antarctica & South America) which both happened in the Late Eocene / earliest Oligocene. The ACC is thought to have been the deep, strong current it is today since the Late Oligocene at the very latest (Lyle et al. 2008), so the AABW is also thought to have existed since the Oligocene.

However as far as the North Atlantic Deep Water (NADW) formation is concerned: it is linked indeed in part to the Gulf Stream and the Northern Hemisphere glaciation. While the latter only occurred ca. 3.6Ma (e. g. Muddelsee & Raymo 2005), the Gulf Stream is a direct consequence of the closure of the isthmus of Panama: the shallowing (and therefore closure to deep current) of the Panama Seaway is thought to have happenned at ca. 4.6Ma (Haug & Tiedemann 1998) with a complete closure at 2.6Ma (Lunt et al. 2008).

So it is rather safe to say that the thermohaline circulation as we know it today settled probably around 3.6Ma (therefore mid-Pliocene).

Back in the Eocene (55 to 33Ma), the formation of bottom water is thought to have occurred in middle to low latitude (e. g. Kennett & Stott 1990) leading to a very completely different kind of global circulation.

The impact on the ENSO (if it existed at the time) is, as far as I know, unknown but since South America was still here to limit it eastward I don't think it ever reached Africa.

References:
Haug, G. H. & R. Tiedemann. 1998. Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation. Nature, 393: 673-676.
Kennett, J. P. & L. D. Stott. 1990. Proteus and Proto-oceanus: ancestral Paleogene oceans as revealed from Antarctic stable isotopic results; ODP Leg 113. In P. F. Barker et al. (Eds), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 113: 865-880.
Lunt, D. J., P. J. Valdes, A. Haywood & I. C. Rutt. 2008. Closure of the Panama Seaway during the Pliocene: implications for climate and Northern Hemisphere glaciation. Climate Dynamics, 30: 1-18.
Lyle, M., Gibbs, S., Moore T. C., Rea, D. K., 2007. Late Oligocene initiation of the Antarctic Circumpolar Current: evidence from the South Pacific. Geology, 35(8): 691-694.
Mudelsee, M. & M. E. Raymo. 2005. Slow dynamics of the Northern Hemisphere glaciation. Paleoceanography, 20: PA4022.


I'm ignorant of all the organic and inorganic chemical reactions that can destroy or create water, and the factors controlling them. But I can give a shot to the part of the question related to volcanoes and the water stored on Earth's interior:

The most abundant gas in volcanic eruptions is water, corresponding to more than the 80% of emitted gases in volume (source).
If we consider on of the largest volcanic eruptions we know about: The toba supervolcano eruption 75,000 years ago. The water volume emitted has been estimated in $540\, \text{km}^3$.

Figure: Comparison of ejected material from notable eruptions (source)

From that perspective, you can see that you would need about 2.5 million Toba eruptions to re-fill the oceans.

In the past, over the history of Earth it could be reasonable to think that the volcanic output could average to the equivalent one Toba eruption every 2000 years, something that would be enough to deliver the volume of water currently in the oceans, but over 4.5 billion years.

However, most volcanic activity on Earth is related to subduction volcanism (including Toba), and such volcanism relies on water input to produce the erupting magmas, and arguably, a large fraction of the erupted water is the same water that was lost in the corresponding subduction zone.

We can then conclude that volcanic water input could eventually help keeping the level on a drying ocean, but at a very slow rate and over very long timescales. But if the oceans ever go dry, volcanism is unlikely to revert the situation.

In the context of the question that motivated this one, the rate at which volcanoes release water dwarf that of water losses to space. However, over long enough times those losses could dry our both the ocean and the Earth interior. But more importantly, I don't know if the net transfer of water from/to the Earth's interior is zero (in balance) or if the mantle is actually sucking water from the oceans, or filling them up. It might be that instead of worrying of planets loosing their water to space, we should worry about them loosing it to their guts.


Why is the warm phase of the Pacific Decadal Oscillation associated with stronger El Niños?

According to the State Climate Office of North Carolina webpage Global Patterns - Pacific Decadal Oscillation (PDO), experts believe

  the PDO can intensify or diminish the impacts of ENSO according to its phase. If both ENSO and the PDO are in the same phase, it is believed that El Niño/La Niña impacts may be magnified. Conversely, if ENSO and the PDO are out of phase, it has been proposed that they may offset one another, preventing "true" ENSO impacts from occurring.

Essentially, almost analogous to constructive and destructive interference in sound.

Another relationship, from the University of Alaska, Fairbanks webpage The Pacific Decadal Oscillation also asserts that

  A positive, or warm phase PDO, produces climate and circulation patterns that are very similar to El Niño. Likewise, a negative, or cool phase PDO, produces climate and circulation patterns similar to La Niña (Gershunov and Barnett, 1998).

As can be seen in the image below:

Image source: Pacific Decadal Oscillation (PDO) Graphics

The consequences for forecasting are summed up by the NASA News web-article A Quirky El Niño as being the case

  If El Niño begins during a cool phase of the PDO, El Niño tends to be milder and less predictable. El Niños that come during a warm PDO are stronger and "better behaved, in the sense that we can predict their consequences

References:

Gershunov, A. and T.P. Barnett. Interdecadal modulation of ENSO teleconnections. Bulletin of the American Meteorological Society, 79(12): 2715-2725.


The relationship between specific discharge and flux

I assume you are talking about the fluid dynamics description of flux, which is the rate of volume flow across a unit area.

1.

  Is flux simply specific discharge × area?

Yes you are correct.

$$Specific~Discharge = \frac{Volumetric~Flux}{Area}$$

therefore

$$Volumetric~Flux = Specific~Discharge~\cdot~Area$$

2.

  And when we speak of flux of an element eg. N-flux, is that specific
  discharge × concentration × area?

When you speak of an element the rationale is the same but will depend on whether the model you are devising contains 1D, 2D or 3D fluid elements. The latter is defined as above.


Is there such a thing as a "basalt dike"?

"Basalt" per definition is a fine grained rock (that is, you can't see the individual crystals with the naked eye, aka aphanitic) with a certain chemical composition. The coarse grained form of this rock is called a "gabbro". A diabase (or dolerite) is something in between, but let's ignore it for the meanwhile for the sake of simplicity.

So quoting from your question:

  I've always understood that basalt is an extrusive rock (formed by
  eruption), and dikes are intrusions (no eruption)

This is not entirely accurate. Assuming that we are talking about rocks of this specific composition, then every extrusive rock is a basalt but not every intrusive rock is a gabbro (or diabase). Fine grained rocks, and basalts in our case, can also form in hypabyssal settings (underground, for example dykes) if conditions are favourable for very quick nucleation. When a magma of 1100 °C intrudes a 20 °C surface or 100 °C rocks several hundred metres deep, the cooling rate is not too different, causing similar fine grained textures in the rock.

The concept of "basaltic" may differ in context. For example, people commonly use basaltic when the rock is similar to the sensu stricto composition of basalt/gabbro, but not quite. It does not necessarily mean that we are talking about a gabbro with a composition similar to basalt. In a wider context, it may refer to "basaltic" vs "granitic" compositions, whereby their coarse and fine grained forms are called "gabbro" and "rhyolite", respectively. No idea why this terminology is rooted like that.

I'll finish with a photograph of a basalt dyke that I took some years ago:


If planting trees is ineffective to tackle climate change, why do people plant them?

Planting trees has a short term benefit in carbon sequestration but will not offset the carbon from fossil fuel burning. However, in some places trees provide a benefit of increasing soil carbon which can have a longer lasting effect. Thus, one benefit is to increase the time needed to implement replacements to fossil fuels. Trees can increase cooling through greater evapotranspiration than grassland, in some climate zones. That, however, may have an impact on water resources. Wood and paper products that are not recycled remove carbon from the natural system, although the effect is small.

Burning wood instead of fossil fuels has a positive impact on the carbon budget where the carbon is recycled back into tree plantations.


Naming convention for sea ice thickness per unit area of ice or ocean

It would appear that you are spot on with the commonly used terms in your question.  A well-referenced post on the Arctic forums (not by me) entitled 'Average sea ice thickness vs effective sea ice thickness', provide information about this very question.  Specifically:

Average Sea Ice Thickness = Volume of Sea Ice/Ice Covered Area

Effective Sea Ice Thickness = Volume of Sea Ice/Grid Cell Area

According to the author of the post, (an Administrator of that site), these terms are imbedded in a lot of the published literature - for example, in the article "Uncertainties in Arctic sea ice thickness and volume: new estimates and implications for trends".


Geode-like rock but it's empty inside. Why does this happen?

Geodes form where there is a gas bubble or some other sort of cavity in volcanic or sedimentary rocks. I once found scores of them eroding out of a sea cliff in Oman, and they looked very similar to yours. I can tell that your geode was formed in sedimentary rock like mine were. What happens is that over millions of years, water seeps in, sometimes bringing in sand and clay particles which line the cavity when it occurs in sedimentary rock. This mineral rich water, sometimes from hydrothermal sources, seeps into the cavity and precipitates various minerals, mostly silicon dioxide, around the sides of the hollow. This usually results in a lining of quartz crystals, but can produce amethyst or opal, both of which are composed of silicon dioxide. Very rarely, opalized fossils are found inside geodes. As for your empty geode, I presume that either the necessary seepage of mineral-laden water never happened, or it never had time to happen. The process takes millions of years.


What geological mechanisms result in the great depth of the Mariana Trench?

As taken from Wikipedia:

There are several factors that control the depth of trenches. The most important control is the supply of sediment, which fills the trench so that there is no bathymetric expression. It is therefore not surprising that the deepest trenches (deeper than 8,000 m (26,000 ft)) are all nonaccretionary. In contrast, all trenches with growing accretionary prisms are shallower than 8,000 m (26,000 ft).
A second order control on trench depth is the age of the lithosphere at the time of subduction. Because oceanic lithosphere cools and thickens as it ages, it subsides. The older the seafloor, the deeper it lies and this determines a minimum depth from which seafloor begins its descent. This obvious correlation can be removed by looking at the relative depth, the difference between regional seafloor depth and maximum trench depth. Relative depth may be controlled by the age of the lithosphere at the trench, the convergence rate, and the dip of the subducted slab at intermediate depths.
Finally, narrow slabs can sink and roll back more rapidly than broad plates, because it is easier for underlying asthenosphere to flow around the edges of the sinking plate. Such slabs may have steep dips at relatively shallow depths and so may be associated with unusually deep trenches, such as the Challenger Deep.

A simple picture for anyone who doesn't understand how these trenches form:

(source: wikispaces.com)
Also, the Mariana Trench isn't the only super deep trench in the ocean... 10 deepest parts of the ocean


The image shown is a lenticular cloud, a type of cloud often observed around significant topographical features such as the mountain peaks shown in the photo. Depending on the local atmospheric moisture, they can occur on their own (as in this case), apart from other cloud features.

All cloud growth depends on the condensation of water resulting from air being cooled as it is lifted vertically by some forcing mechanism. However, these clouds are an exception to more typical cloud growth, which depends on the atmosphere having a tendency (or instability) for air to continue rising - and thereby condensing more liquid water - once forced upward.

Following the initial source cited above, lenticular clouds form in environments that are stable (i.e., not conducive) to these vertical motions, so upward motion is entirely driven by air forced over an obstacle - in this case, mountain terrain. From a horizontal view, the vertical motion forced by this obstacle commonly takes the form of a persistent wave pattern:  image source

This occurs downwind of the terrain feature, with clouds forming over the portion of the wave featuring upwards vertical motion. This becomes extremely evident when viewing time-lapse videos of this phenomenon.


There are various charts but not exactly what you want. This one combines burning, industry and cement but shows land sources and sinks separately:

CarbonBrief,  Le Quéré, C. et al. (2016)


What tectonic structures delineate the split between the Australian and Indian tectonic plates?

The structures are not mature or well defined and deformation was thought to be diffused, i.e., distributed over a large area. Earthquakes such as the M8.6 2012 Indian Ocean earthquake (largest strike-slip earthquake on record) appear to accommodate some, if not all, of the deformation.

Seafloor geodesy is relatively a new field. Most studies are limited to areas near the coast, e.g., US (Cascadia), Japan etc.


Salinity and temperature both affects the density of sea water. When water with a fixed salinity cools down, it becomes heavier and sinks. In the same way, when vapor or ice removes water from sea water, the remains is more saline and heavier.
Thermohaline circulation can work as you describe. Surface water in the tropics is saline, due to evaporation, but warm due to high temperature in the atmosphere and therefor low density. As it reach colder climate (less solar energy per area), it cools down and the high salinity makes it sink. Surface water in polar regions also get heavier as ice is formed of water and leave the salt behind in the sea.

This is very simplified model, you can read more on the topic here and here.


Looks like Cirrus Fibratus (Ci fib) to me.

See e.g. Wolkenatlas or Clouds Online.

Regarding the formation of Ci fib, Name of Clouds says:

  Cirrus fibratus clouds are formed when winds at high altitudes are strong and flow over the cold air from below. The combination of the warm air and the moisture is usually unevenly distributed hence the trail of fine fibers at the ends of such clouds.


What fraction of dry land is below sea level?

This question is intriguing. At the current rate of sea rise (about 3 mm per year), all of the Earth's dry land below sea level would be submerged in just a decade. There are an estimated 49 countries around the global with at least some real estate below -0- metres elevation, but the sum of all the potential volume (around 7,500 km^3) is insignificant compared to the volume of water generated by glacial and ice cap melt:  "A meter of sea level rise is a volume 50 times greater than all of the depressions that are below sea level in the world", according to this link: http://mountainmystery.com/2015/08/17/hiding-rising-seas-in-sunken-deserts/.


First of all, earth doesn't have the same atmosphere it had, back when dinosaurs walked the earth, when most of current carbon-deposits formed. Some atmospheres earth had would even be toxic to humans. So, you're right, changing the atmosphere at the speed we're doing it is the problem, not the change in general.

Second, yes, earth is a rather closed system (with minor leaks, but anyway). Still, the timescale is important.

Let's go with a simple allegory:

Say, your friend had a pickup-truck (sorry, in my mind deniers all drive SUV or pickup^^). He uses it to transport a lot of material, e.g. paving stones. He knows, his truck is able to transport the total amount of stones (because he tried in the past, or because the specifications say so, or because someone told him, doesn't matter - like we know that earth's atmosphere held a lot more CO2 back in the day).

Is he going to just dump the whole load at once from 2 m height into the back of his truck? I doubt so, because that would at least put some dents in the truck, or might even break the springs or an axle.

He'd pack the stones there manually and use enough padding to make sure nothing gets damaged or slips during the transport.

Currently we're dumping the stones all at once - and we'll surely break the vehicle, if we really continue. Earth, like the truck, needs to adapt to changes. And, as we know, geological timescales are a lot longer than we can truly observe - thus the current changes, though stretching over several generations, are way too fast for earth to really adapt.

Third: While earth is a closed system, states within a closed system may change. Say, you have a terrarium with some mice and a lot of wood. Then you burn the wood. The mice might survive the fire, but in the end will suffocate, since there is a lot more CO2 in their atmosphere now.

So, yes, releasing trapped carbon from fossile fuels and whatnot to the atmosphere doesn't change the overall mass of system earth. But it changes the state of the system - and we are depending on the current state of the system.

Also - I know, this is not scientifically - say we are wrong when it comes to greenhouse gasses, and he is right. What if we undertook a lot of effort to not to produce them, to clean our environment, to create less waste? We'd wake up one morning and be "Dang, we made our planet worth living on again, how could we?!" - Or, as one of my professors put it: "Would you get on a plane when there is a 10 % chance, the plane is going to crash?"


What is the ratio of infra-red light absorbed by green house gases?

There is no simple relationship since it all depends on the frequency (IR spectral lines for most species of molecules are a mess). The most direct and precise way of calculation is through line-by-line calculation from a large spectrum database. The atmospheric column will be very different based on angle off normal, weather, and even time of day (water content has diurnal variability, mostly).

Surface temperature and surface properties also influence the distribution of emitted IR.

See also: Atmospheric radiative transfer codes


Are there any photographs of mountains without significant erosion (on Earth or otherwise)

Here's how astronomers of the late 19th century thought the Moon would appear:

Recreations in Astronomy by H. D. Warren D. D., published in 1879, via http://en.wikipedia.org/wiki/Selenography.

Here's what Apollo 15 astronauts saw:

  Apollo 15 Lunar Module Falcon at the Hadley-Apennine landing site. Hadley Delta in the background rises approximately 4,000 meters (about 13,124 feet) above the plain. The base of the mountain is approximately 5 kilometers (about 3 statute miles) away.

Source: NASA, from Four Out of Six Apollos.

Below is a photograph of the even taller Mons Hadley, 1.1 km taller than Hadley Delta shown above:

Source: NASA, photograph as15-86-11603, from Apollo Imagery.

Compare the above with mountains on the Earth. Here's a picture of Mont Blanc, a mountain here on the Earth comparable in size to  the smaller of the two lunar mountains portrayed above:

Photograph by Zoharby, taken from Wikimedia Commons, licensed under Creative Commons Attribution-ShareAlike 3.0 Unported license.

  Alternatively, are there any mountains on Earth where (for whatever reason) erosion hasn't played a big role in shaping them so far, and which therefore look similar to the uneroded mountains one would find on an airless world?

Nathaniel, you have a mistaken view of erosion. Erosion eventually does tear the tallest mountains down to tiny little hills. However, erosion also makes those tall mountains very jagged at first. Erosion is the primary reason why Mont Blanc and other new, tall mountains are so jagged. Liquid water seeps into cracks in the rocks and then freezes into ice. Ice has a lower density than water. This means that liquid water expands upon freezing. That expansion breaks the rock that form mountains into jagged edges.

Another reason our mountains are jagged is plate tectonics. The Earth is the only body in the solar system that exhibits plate tectonics. New continental crust forms largely from older continental crust. Erosion eventually brings particles torn from mountains to a flat area or river delta, where they collect. The material brought to those collection areas changes over time. The end result: Strata (layered rock formations). The different strata in rock have different strengths and weaknesses and thus erode differently. That differential erosion results in jagged mountains.

Bottom line: You don't see jagged mountains on the Moon or Mars because they don't have water in all three phases and because they don't have plate tectonics.


Pectens seem to have evolved from Chlamys in the late Eocene or early Oligocene. The coarseness and rib spacing of Vertipectens has been slowly evolving since the early and Mid-Miocene, so they have been around for at least 16 million years, maybe up to 20 million years. If you want to be precise you will need to read-up on the fine detail. Pectens are a classic case of 'ontogeny recapitulating phylogeny', and their identification is complicated by parallel and convergent evolution of different species. As fossils, they are quite common, and probably more useful as indicators of the palaeo-environment, than as age indicators. Where you find such fossils you will very likely find associated micro-fossils in the same rock, which are more diagnostic of age.