Are ice-ages dependent on an un-equal distribution of land-masses? Having read this answer about the precession of the equinoxes and how it affects Earth's climate, my understanding was that only because of the differing affect of continental and maritime insolation that precession of the equinoxes was a factor in ice-sheet growth.

So if all the continents magically switched to be reflected in the equator (i.e. now we have a Southern Hemisphere dominated by continents), would we now have ice-ages at the 'opposite' time (i.e. short SOUTHERN hemisphere summers)?

And if all the continents moved to be equally spread out about the globe, precession of the equinoxes would play no factor in the ice-ages at all?

In addition:

What is the mechanism that causes this effect? i.e. Why do continents determine the ice growth, and not the oceans? The response in the previous question that: "Continents show more seasonal variability" is a little vague.

The Earth's climate switches between "hothouse Earth", where ice is nearly absent worldwide, and "icehouse Earth" where the Earth intermittently has ice that stretches far from the poles. Periods when the Earth is in the icehouse Earth phase are called ice ages. The most recent ice age began about 2.6 million years ago and has not yet ended. We are still in an ice age, as evidenced by the fact that Antarctica and Greenland are still covered by ice. Ice ages last many tens to a few hundred of millions of years.

Ice ages are characterized by glacial periods where ice reaches far from the poles separated by interglacial periods where the climate is a bit more moderate. The glacial and interglacial periods within an ice age last tens to hundreds of thousands of years. The current interglacial period began about 12,000 years ago.  It's the Milankovitch cycles that are responsible for the short duration glacial and interglacial periods within an ice age.

These cycles are still present when the Earth is in a hothouse Earth phase. The Earth was in the hothouse phase for about 250-260 million years before the current ice age. That's 2000 or so multiples of the very longest Milankovitch cycle. The Milankovitch cycles are not responsible for the hothouse Earth / icehouse Earth phases. It's plate tectonics that dictates whether Earth is in a hothouse Earth or icehouse Earth phase.

So what aspects of plate tectonics govern whether the Earth is in a hothouse phase or icehouse phase? Below are a series of images depicting how the Earth looked over recent times.

http://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Blakey_35moll.jpg/640px-Blakey_35moll.jpg
35 million years ago, hardly any ice anywhere.

http://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Blakey_20moll.jpg/640px-Blakey_20moll.jpg
20 million years ago, just a tiny bit of ice in the very far north and very far south.

http://upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Blakey_Pleistmoll.jpg/640px-Blakey_Pleistmoll.jpg
Current ice age, (~2.6 million years ago to present), with ice sometimes reaching as far as 45° latitude.

Source: Ron Blakey, via wikimedia.org. (Blakey's maps are 1200x600, which is a bit wide. I used the 640x320 previews at wikimedia.org.)

There are two key differences at the boundaries of the Pacific Ocean between the pre-ice age Earth and our current ice age Earth. One is the Indonesian seaway. That closed up 3 to 4 million years ago thanks to New Guinea, Indonesia, and the Malay Peninsula. The other is the Panama seaway. That closed up about 3 million years ago thanks to the formation of the Isthmus of Panama. The closing off of the Pacific near the equator drastically changed the global ocean conveyor belt, which in turn drastically changed the climate of the Earth.

So which of these two seaway closures, if any, is the cause of the most recent switch from hothouse Earth to icehouse Earth? A number of researchers put the blame on the formation of the Isthmus of Panama (Bartoli 2005, Nie 2014). Others claim the closure of the Indonesian seaway was responsible (Cane and Molner 2001, Molner 2008). Yet others say "none of the above" (Lunt 2008). The jury is still out, but note that Smith and Pickering 2003 claim that plate tectonics are responsible for each of the four major icehouses in the last 620 million years.

Bartoli, G., et al. (2005). "Final closure of Panama and the onset of northern hemisphere glaciation." Earth and Planetary Science Letters, 237.1: 33-44.

Blakey, Ron. cpgeosystems.com/paleomaps.html (website)

Cane, Mark A., and Peter Molnar (2001). "Closing of the Indonesian seaway as a precursor to east African aridification around 3–4 million years ago." Nature 411.6834: 157-162.

Lunt, Daniel J., et al. (2008). "Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels." Nature 454.7208: 1102-1105.

Molnar, Peter (2008). "Closing of the Central American Seaway and the Ice Age: A critical review." Paleoceanography 23.2.

Nie, Junsheng, et al. (2014). "Pacific freshening drives Pliocene cooling and Asian monsoon intensification." Scientific Reports 4.

Smith, Alan G., and Kevin T. Pickering (2003). "Oceanic gateways as a critical factor to initiate icehouse Earth." Journal of the Geological Society 160.3: 337-340.


What caused a fall in atmospheric oxygen about 1.9 billion years ago? Using chromium isotopes geochemistry, Frei et al. 2009, describe in the article Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes that after the Great Oxidation Event (2.2-2.45 billion years ago), there was a precipitous decline in atmospheric oxygen at about 1.88 billion years ago, to have "all but disappeared" as described by Lyons and Reinhard 2009 in the article Early Earth: Oxygen for heavy-metal fans.

What evidence is there for a the drop in atmospheric oxygen approximately 1.9 billion years ago?

The answer might lie in aerobic respiration. This is of course only one of the many possible explanations but mitochondria (and therefore $\ce{O2}$-breathing eukaryotes) are thought to have evolved circa 2.3 to 1.8 Ga (see for instance Hedges et al., 2001; 2004; 2006). This loose age bracket however is based primarily on molecular data with very few fossil evidence (as I mentioned in an earlier answer of mine, the Proterozoic fossil record of eukaryotes is almost inexistant).
An earlier apparition of aerobic respiration is unlikely (e. g. Knoll & Holland, 1995) as a certain level of $p_{\ce{O2}}$ needed to be reached for this metabolism to be possible.
If aerobic eukaryotes expanded rapidly they might have constituted a strong enough sink of oxygen, which could be responsible for the drop observed by Frei et al., 2009.


Why are $\small\sf{CH_4}$ and $\small\sf{CO_2}$ levels coupled during the Pleistocene? CH4 and CO2 levels show correlation throughout the Pleistocene:

Source: trustyetverify.wordpress.com

What are the reasons of this coupling?

This question is addressed in a Nature paper on "Understanding the glacial methane cycle" (Hopcroft et al. 2017).

There conclusion is that changes in methane concentrations are driven by changes in the biosphere associated with the global temperature changes. The dominant factor is the reduction in methane emissions from wetlands in a colder climate. There is also a reduction in emissions associated with forest fires in the cold phases (colder climate means less forest fires; warmer climate means more forest fires).

Note that the model used by Hopcroft et al. has the CO2 levels prescribed. In this situation the temperature changes in response to the CO2, and then the methane changes in response to the temperature.


Glaciology: odd pattern of smooth and ribbed chunks of ice in Antartica At -69.184611, -68.124276 (just east of the Bugge Islands) there is a triangular ice shelf. On satellite images (as seen on Google/Bing maps) you can see it is riddled with --for lack of a clearer description-- chunks of ice that are either ribbed or smooth.

What are these chunks? And how are they formed?

I think both types of chunks might be created by the glaciers flowing toward the coast; as seen at -69.214204, -67.055682 (mostly ribbed):

and at -69.315307, -67.625613 (mostly smooth):

But how is there a difference between the two?

What you see are ice bergs frozen into a sheet of sea ice. The "chunks" are the ice bergs. Ice shelves are fed by two sources, ice from the interior of the ice sheet and ice formed by compaction of snow accumulating on the shelf itself. This means that a shelf can have very different dynamic regimes. Parts of shelves where ice is mostly formed locally will tend to be smooth whereas shelves feed by ice discharging from the interior can exhibit crevassing. It is very common to have ice streams or more rapidly flowing sectors carrying ice from the interior to the shelf and the position and width of these are often determined by subglacial topography (valleys and ridges where larger flow occurs in the valleys). At the margins of such more rapid sectors velocities drop from maybe hundreds of meters per year to a few or tens of meters per year. This cases severe shearing resulting in formation of cracks/crevasses.

When the ice eventually calves into the ocean as ice bergs, the ice will exhibit different patterns depending from what sectors it originates. The crevassed parts will result in the "ridged" features you see. Essentially, the ridges and furrows are traces of crevasse patterns. In your mid-picture you also see the calving front on the right hand side and it is evident that the ice there is heavily crevassed. It also exhibits flow striping (stripes in the direction of flow, usually perpendicular to the ice front) which indicates rapid flow.


Plotting stereonets in R Is there a package for R to plot Schmidt nets, like it is done in geology?

So far, I only know software like Stereonet. However I think it would make a lot of sense to handle these data in R, to have so much more possibilities in calculations and statistics.

You might try the RockFab package. I am not a structural geologist but I use other R packages for geological endevours.

Documentation.


How does wind cause large waves? I was just wondering about the large waves associated with storms. It seems a little counter-intuitive that large masses of water can be put into motion by moving air (which is much lighter than water). It must take a lot less energy to set a wave oscillating than I am expecting. I'd appreciate an explanation from first principles, though.

This is going to be brief as on a phone : I welcome somebody posting a more complete answer. But the basic principle of large waves appearing from wind is:
 from a smooth water surface, the wind can produce only small ripples. But those ripples mean that the surface is no longer smooth. The higher the ripples get, the more surface there is for the wind to act upon, thus enlarging them more. Thus are local wind waves formed. For these wind waves to build into the large swell that is found in the oceans, this process needs to continue for a number of days, and some hundreds or thousands of miles. Large swell waves hitting the coast may have been formed in a storm the other side of an ocean.


How does the lapse rate in clouds compare with the lapse rate of air? So moisture decreases the temperature lapse rate (relative to the dry adiabat). My question is this: does a cloud decrease the lapse rate at the same rate as 100% humidity would decrease it? Or would it depend on cloud type (e.g. stratus vs cumulus)?

The lapse rate of temperature is ignorant of clouds, it only cares that either $e/e_s < 1$ (dry) or $e/e_s >= 1$ (moist), where $e$ is vapor pressure and $e_s$ is saturation vapor pressure.  A cloud is saturated (and in places supersaturated) and so the lapse rate will be the same as saturated air outside of a cloud.

The theoretical parcel at 100% humidity when subsequently lifted (in the presence of cloud condensation nuclei (CCN)) will itself experience nucleation and condensation and become a cloud.  In this respect there can be no difference between the saturated parcel outside of a cloud and a saturated parcel within a cloud, both will experience the same lapse rates.

With that said, some types of clouds will cause a difference.  Consider a parcel at its level of free convection (LFC) within a deep convective cloud and a parcel far from the cloud, saturated in clear air at the same height.

The parcel in clear air when lifted will cool at the moist lapse rate but entrain the surrounding dry air and the result will be less than moist adiabatic.  The entrainment will also limit the vertical extent of the parcels buoyancy.
The parcel in the deep cloud will be saturated in a moist environment and will rise and cool at the moist adiabatic rate.  As it is inside the cloud, we'll say entrainment is not important.  This parcel will also rise high enough for ice processes to become important and will experience additional warming due to the enthalpies of sublimation and fusion (latent heat released from vapor->solid and liquid->solid transitions).

In this perspective, the parcel in the cloud to have a different temperature profile than the out of cloud parcel.  This isn't because of any difference in the moist lapse rate between the parcels or even how the thermodynamics work out, but rather because of the dynamic effect of entrainment.

Another factor to consider are the radiative properties of clouds vs clear air.  Clouds will absorb terrestrial longwave radiation and warm, and the water vapor in humid air will do the same thing.  Also on the periphery of the cloud where entertainment and evaporation is taking place, there will be some cooling from the phase change.  I don't have back of the envelope estimates for either of these effects, and I feel they are probably tangential to the question asked if we limit consideration of the cloud parcel to a parcel well inside of a deep cloud.


Does earth's size affect the temperature of the poles? What effect does Earth's size have on the temperature of the north and south poles? If the Earth were larger, or smaller, would this affect those temperatures?

The primary factor determining the temperature of a planet is the radiation it receives from its sun.  If this were the only factor, it would be possible to estimate its temperature using the black body radiation law, as described e.g. on Wikipedia.  Based on this calculation, the size of the planet has no effect on its temperature.

However, there are other factors contributing to the temperature of the planet, such as its atmosphere (greenhouse effect), internal heating due to radioactive decay, and the surface reflectivity, affected by such things as plant or snow cover, etc.  All these can and have changed in the past.

The black-body approximation gives a temperature of about -18 C, thus the other factors have a smaller but still significant contribution.

So the question is how are the other factors affected by the size of the planet?

Effect of the atmosphere: I cannot comment.
Internal heating: the heat generated by radioactive decay is proportional to the amount of radioactive material, i.e. the volume of the Earth (proportional to its radius $R$ cubed, $\sim R^3$), assuming a fixed density and composition.  The heat loss is proportional to the surface area ($\sim R^2$).  So the larger the planet, the higher the temperature increase coming from internal heating.


How do we convert the seismic trace wavelet to zero phase which is in mixed phase? As we know the mixed phase data would not give the "real TWTT" through the medium. We need a zero-phase wavelet that can directly correspond to the time taken to travel in a given media. So my question is how do we convert the seismic trace wavelet to zero phase which is in mixed phase? There must be an important processing procedure to do so.

My preferred way of doing this (I've been working in seismic data processing and analysis for over 20 years now) is:

Start with theoretical (or notional) source wavelet.
Shape the source wavelet to zero phase (or minimum phase, depending on your
application).
Design a cross-equalization filter that takes the input
from step 1 as the source and step 2 as the target. This can then be
globally applied to your data.

There are other ways to do this (like with Wiener deconvolution) that make a statistical estimate of what the wavelet should look like, and this was considered acceptable in the industry for many years. However, such statistical processes are not acceptable for all applications, such as 4D (time lapse seismic) analyses, so I prefer processes that are deterministic rather than processes that rely on a stochastic assumption.


Time for water vapor to generate more greenhouse effect than latent heat? I have an argument with a climate change denier.
He says the rise of water vapor in the atmosphere causes a "much larger" cooling effect by taking vaporisation heat from the ground than the heat generated by the additional greenhouse effet.
I say the additional greenhouse effect integrates with time, so after a certain time T (which I suspect "small"), this heat will compensate the latent heat taken from the ground.
Does anyone have a reference establishing the order of magnitude of T ?
Note the question is NOT about the "normal" water cycle where latent heat is taken at vaporisation and released at condensation, it is about the (undisputed) global augmentation of water vapor in the troposphere.

I am doing some calculations on this question myself. The atmospheric lapse rate is about 6.5K/1.000m. The adiabatic lapse rate is 9.8K/1.000 and the dry lapse rate of the naturally unstable atmosphere of Earth should even be 10.8K. So arguably the constant transport of latent heat by vapor from the surface into the atmosphere is reducing the lapse rate by some 4.3K/1.000m. Without a doubt the GHE would be much larger if it was not for the latent heat provided by vapor.
The GHE itself is a function of the emission temperature, which again is a function of the emission altitude. Vapor increases this emission altitude, which is why it is considered a GHG, the most significant one actually.
We need to ask what size GHE has (not 33K, but less), what bigger size it counterfactually had without latent heat and a lapse rate of 10.8K, determine the share of vapor in this case, and compare it to the (negative) effect of latent heat. Depending on what is bigger, vapor is either a GHG or an anti-GHG. From all the modelling so far I get definitely the latter result.


Peak phosphorus - what are the sinks? The minable phosphorus reserves are limited. Where is the mined phosphoprus landing, what are the global phosphorus sinks?

I would assume that most phosphorus is used for fertilizer and ultimately ends up in the water (via consumption by plants, than animals or humans and then wastewater or faeces). The most likely candidate in water would be phosphate ($PO_4^{-3}$). I would assume that phosphate is fixed in microorganisms and that those ultimatly form sediment and get mineralized. But this is a wild guess.

How does the phosphorus cycle actually work after phosphorus is used by humans and emitted into the environment? What are major processes, and in what forms is phosphorus mineralized?

The phosphorous sinks are the ocean and ocean sediments.

The ocean holds $3 \times 10^{15}$ moles of phosphorous.

The annual amount of phosphorous input into the ocean, as well as the amount of burial of phosphorous as sediment is on the order of $10^{10}$ moles.

The sediment is of three categories:

Phosphorous associated with calcium carbonate
Organic phosphorous (associated with organic carbon)
Apatite

See Phosphorous Accumulation in Marine Sediments and the Oceanic Phosphorous Cycle for a detailed analysis.


Why does gold and other metals conglomerate When gold, or some other metals, such as copper, are found, they are often found in large nuggets. But, from what I understand, gold is produced in quite stochastic stellar processes. As such, shouldn't the distribution of gold and other elements be rather uniform, or at least conglomerated according to the stellar process by which they were created? Why do we see large gold nuggets? Shouldn't we find gold mixed uniformly with all the other elements created along side it in its stellar process?

Some things to consider. Even if elements are formed randomly in stars that does not necessarily imply that the elements will be distributed evenly and randomly when the star explodes. Following the explosion of a star there will be a gravitational attraction between the elements created within the star which will cause clumping/agglomeration of the elements.

The other thing to consider is chemical attraction due to ionic charges and the lack or excess of electrons in the outer shells of atoms which causes atoms to chemically combine with other atoms to form molecules.

Many elements and molecules are soluble in water. When conditions change, such as temperature, pressure or chemical attraction, metals can precipitate out of solution and collect en-mass, sometimes forming nuggets.


Centrifugal Force in the Navier Stokes Equations The Navier-Stokes equations are a set of nonlinear differential equations that diagnose wind speed and direction. They are (approximately) expressed as $$\frac{d\vec{u}}{dt}=-\frac{1}{\rho}\nabla P+f\hat{k}\times\vec{u}-g\hat{k}+\nu \nabla^2\vec{u}$$Where $\frac{d}{dt}=\frac{\partial}{\partial t}+u\frac{\partial}{\partial x}+v\frac{\partial}{\partial y}+w\frac{\partial}{\partial z}$, $f$ is the coriolis parameter, $\rho$ is density, $P$ is pressure, $g$ is gravity, $\nu$ is the kinematic viscosity, and $\vec{u}$ is the wind vector.

In synoptic meteorology, it is taught that in jet streaks, the curvature of the jet streak influences the acceleration by the centrifugal force. However, in the equation above, I see no centrifugal component.

Is curvature-based centrifugal motion simply missing, or is it hidden? If it is missing, how would it be expressed (in Cartesian coordinates)? If it is hidden, in which term is it hiding? Could we decompose it into centrifugal and non-centrifugal acceleration? A derivation of cyclostrophic would be sufficient, since it will explicitly say from what part of the equation is curvature.

Based on the state of the discussion in the comments I was not sure whether this has an answer now, but I stumbled over it, and I think I can give a short answer from which one can learn a lot.

I'll base my discussion on polar $(\rho,\phi)$ coordinates, for the sake of clarity. In classical mechanics we use for the position vector $$\vec r= r \vec{e}_r = r \; (\cos\phi, \sin\phi),$$ because $\dot{\vec{e}}_r = \dot{\phi} \; (-\sin\phi, \cos\phi) = \dot{\phi} \; \vec{e}_{\phi}$. In 3D spherical coordinates, we need a few more of those identities, but the algebra remains the same. From this follows $$\dot{\vec r}=\dot{r}\vec{e}_r + r\dot{\phi}\vec{e}_{\phi} $$ and finally
$$\ddot{\vec r}=(\ddot{r}-r \dot{\phi}^2)\vec{e}_r + (r\ddot{\phi} + 2\dot{r} \dot{\phi})\vec{e}_{\phi} $$
where we have already taken into account the change of coordinates, as well as unit vectors.
The next step would decompose $\dot\phi$ as $\dot\phi = \Omega + u/r$, whereas $$r\dot\phi^2 = r\Omega^2 + 2\Omega u + u^2/r$$
where we identify (in order of the terms) 1.) the centrifugal term, 2.) the coriolis term and 3.) the "curvature/metric" term. This procedure works wonderfully also in spherical coordinates and one recovers perfectly the terms that i.e. Holton or Vallis get in their books via lengthy and opaque 'proof-by-picture' methods.

I'm saying the latter because now I draw conclusions for the complete equations, from my derivations which was done from the incomplete ones:
Conclusions:

Centrifugal terms are not what meteorologists call 'curvature/metric' terms. They can seem the same, if one is sloppy and writes $\Omega=vr$. Or what is often done is in order to calculate the orbit of a satellite to set centrifugal force and gravity equal, whereas one uses $u^2/r$, which is in fact the 'curvature' not the centrifugal term. Also the physically metric term is already $r\dot{\phi}^2$, as this one arises from having a curved coordinate system.
As pointed out in the comments, the centrifugal term $r\Omega^2$ is customarily hidden in meteorology with the gravity. We would suspect this happens also in your set, because the Coriolis term appears, which hints that the above computation has been carried out to first order and thus the centrifugal term must float around somewhere.
The curvature terms are nowhere to be found in your set of equations. This is probably due to the terms simply being neglected. Also when viewn in their full form in spherical coordinates, they seem quite messy and I didn't find any convenient way of expressing them through a nice vector-or matrix operation. Therefore I strongly suspect, that people when giving the vectorial form of the NS equations usually neglect them, and only add them when presenting the NS equations in component form.
The above minimalistic derivation makes it clear that the curvature, centrifugal and Coriolis terms originate from having a curved coordinate system. Any curved coordinate system is necessarily non-inertial. Thus in Cartesian coordinates, which are inertial, those terms must necessarily vanish.


Why does the rising of high clouds due to climate change impart positive radiative feedback on radiative forcing? As seen in the figure below.

The larger the temperature difference between surface and cloud, the more positive the radiative forcing is from the cloud.

So as the cloud moves up, it supposedly should move into a colder altitude. But doesn't climate change also increase the temperatures at any given altitude too? If so, why does the cloud move up into a colder altitude due to climate change? (even after accounting for heating at the given altitude?)

The primary mechanism at work here is the type of clouds that exist at different altitudes.

Low clouds of the cumulus or strato-cumulus variety are optically thick and reflective.  These types of clouds will scatter more light than they transmit or absorb, and the energy scattered upward and back into space will not contribute to warming.

High clouds outside of convection tend to be cirrus clouds, which are icy and not optically thick.  These clouds let light pass through freely (you can see the sun through these clouds).  This lets solar energy through but they will absorb longwave (terrestrial) radiation, and this is what will contribute to warming.

This is where a lot of the uncertainty in cloud feedbacks in a warming climate comes from.  If we get more clouds -- low, bright clouds, then this could contribute to cooling, wheras high, transparent (to shortwave) clouds would contribute to warming.  Again, it is not so much the high vs low that matters here, it is the properties of typical clouds at these heights.


If the Kola Superdeep Borehole were opened today, what would come out of it? The BBC News article The Deepest Hole we have Ever dug says:

  This is the Kola Superdeep Borehole, the deepest manmade hole on Earth and deepest artificial point on Earth. The 40,230ft-deep (12.2km) construction is so deep that locals swear you can hear the screams of souls tortured in hell. It took the Soviets almost 20 years to drill this far, but the drill bit was still only about one-third of the way through the crust to the Earth’s mantle when the project came grinding to a halt in the chaos of post-Soviet Russia.

The first image below shows the top of the Kola Superdeep Borehole, and the caption says that it is welded shut.

Is there any way to form a reasonable hypothesis what would happen if it were opened today? Would the 12 km deep well have filled with water, or helium, or natural gas, or is it likely to be filled with air? Would it be under tremendous pressure on the other side of the bolted-down cap?

above: The borehole still exists - but the entrance has been welded shut (Credit: Rakot13/CC BY-SA 3.0), below: The borehole is located in the wilds of Russia's northern Kola Peninsula (Credit: Getty Images)

The only reasonable hypothesis is that it is filled with whatever it was filled with when the well was sealed.

A 12km long pipe with a sealed end is not going to have its contents replaced with something else easily. You could theorise that an intrusion of gas at the bottom opening of the pipe could expel liquid by replacement - possible, but slow.


Is it typically colder after a storm? I've heard that it's colder after a storm. I think this is an interesting question, not least because of the implicit comparison: colder than what? A few different comparisons come to mind, and still others may occur to you.

I have in mind that after a storm means the day after the storm.

I'd love to hear responses to any or all of these. Is it colder after a storm relative to:

how it was right before the storm?
how it is the day after the day after the storm?
how it would've been without the storm?

I'm interested in statistical answers as well as theory-based answers.

@JeopardyTempest rightly points out that I haven't specified what I mean by storm. I'm not too picky here, I'm thinking of events that are between hours and days.

The major factors in temperature change from precipitation...

First, fundamentally rain is falling to the ground from higher in the sky.

Precipitation typically comes from a location where it is colder compared to us on the ground (the troposphere generally is cooler with height, on average around 6.5 Celsius\km.).
Basically, the rain itself usually at least feels colder than the air beforehand, right??

Well, if you do bring something colder to a warmer environment, their temperatures will tend to move towards a balance between the two.
[++ see Second Law of Thermodynamics ++]

So with significant rainfalls, there's a lot of cold water being spread down into our warmer air, and due the dispersed nature of rain (a bunch of small drops rather than one giant stream) it ensures that rain is quite quick and effective in spreading it's cold temperatures into the air.

Second, falling rain also encourages downward air movement, due to friction.
[++ see downdrafts ++]

So not only is rain (that is almost always colder) coming down, but air (that is almost always colder) is coming down too.

Furthermore, rain is cooling the air it is falling through, colder air sinks, so the downdraft is further enhanced.
[++ Actually the air must be quite a bit cooler to sink on its own... see adiabatic warming ++]

So this is a second fairly quick cooling process, as downdrafts occur within the lifecycle of a thunderstorm cell/complex.

And third, some of the rain/snow/sleet/hail/etc water will begin to evaporate (or sublimate!) as it is falling and once it reaches the ground, unless the air is totally saturated.  When water evaporates, it needs to gain energy.  To do so, it takes energy from the environment, namely the air.

This evaporative cooling just exacerbates the first two influences above.  And furthermore can continue to have impacts days after the rainfall compared to drier places, stunting high temperature ascension during the afternoon.

[There are also other factors important in the longer term, such as snow reflecting sunlight (cooling the area), moister air being favored for cloud formation (which cools during the day, warms at night), and the fact moister air changes temperature at a slower rate due to its heat capacity (cooling during the day, warming at night).]

But, the result is, scientifically, when precipitation falls, it is fundamentally a cooling process.
The stronger the precipitation is, the much more significant the cooling.  And certain atmospheric setups enhance the cooling effect even more (steep lapse rates, dry air nearer the ground)

Now, even after saying all that, it actually can still be warmer soon after rainfall.

How in the world is that possible!?!
Because wind can still blow in large amounts of air from other areas... sometimes from environments that haven't yet themselves experienced significant precipitation.
This often happens as warm fronts pass.

[++ Heaviest rainfalls do more often come with cold fronts, which bring in more cold air.  However most (nontropical) lows start with a balance of areas of advancing warm air followed by surging cold air.  So you may well see both... or you may not: in more mature storm systems - as you'll often see in winter - most warm air is completely undercut by cold air... and so many large areas never experience any notable warmup as a storm system works through ++]

Other unbalanced factors can overwhelm the cooling effect as well... like when it's cloud all day, then rains a bit, but finally the sun comes out.  The hot sun can quickly turn the battle back towards the warmer side.

[++ There is indeed at least one other very very rare way, where if the atmosphere is setup perfectly, a strong downdraft can actually begin to warm due to adiabatic compression, but still have enough oomph to reach the ground... and you wind up with a heat burst. ++]

So air after rainfall is cooled in the extreme majority of cases... it's just that your cooled air may instead end up being relocated to other locations.

Check out the topic of outflow boundaries

So, to your questions:

⇒ Will it be colder right after a storm compared to how it was
   right before the storm?
   Most likely

⇒ Will it be colder the day after a storm compared to how it was right before the storm?
   Depends what the weather pattern and air mass movement is like.  If a cold front moves in, yes.  If a warm front moves in, no.  In the tropics or during the height of summer, it will often be about the same the next day as the atmosphere mixes the cool air from yesterday's rain around until it's spread out and minimized, and the air heats back up again the next day when the sun comes out.

⇒ Will it be colder after a storm than it otherwise would have been without the storm?
  Basically yes.  A nearby site that doesn't get the storm's effects will almost certainly be warmer.


Hydro-meteorological hazards vs climate extremes I always saw the definitions of "hydro-meteorological hazards" and "climate extremes" as almost interchangeable in the climate change and natural hazards literature. The other day I was discussing with a colleague claiming that "climate extremes" would be a sort of subset of the natural hazards.

Although, I can find reasonable that, somehow, not all the hazards are climate extremes, I still find formally acceptable to define the most common ones (floods, droughts, heat waves, storms ...) both as climate extremes and hydro-meteorological hazards. Articles in literature (as this, for instance), and also the IPCC Glossary do not seem to make a clear distinction.

Any specialist here that can help me to shed light on this?

The UN International Strategy for Disaster Reduction gives a good definition of a "hydrometeorological hazard": Natural processes or phenomena of atmospheric, hydrological or oceanographic nature, which may cause the loss of life or injury, property damage, social and economic disruption or environmental degradation..

The IPCC define and "Extreme weather event" as follows: "An extreme weather event is an event that is rare at a particular place and time of year".

The debate around extremes is strongly focused on extremes which are of interest to society because of their harmful effect (extreme wind, extreme heat, extreme cold, etc), but the term itself could be interpreted as having a broader meaning. We might, for instance, experience extremes of the surface pressure difference between the Azores and Iceland (a statistic which is studied by climatologist because changes in this statistic have interesting links to weather patterns in Europe) -- but this pressure difference is not usually considered as a hazard.

An earlier answer by haresfur has given several examples of hydro-meteorological hazards which are not climate extremes. To these I would like to add:

Coastal erosion: this is a continuous process caused by tides and storms. It is hazardous for anyone living in a coastal region;
Lightning strikes: thunderstorms always pose a hazard. You could, of course, call every thunderstorm "extreme", but this is not the common usage. Thunderstorms can be common in a given region, but still be a hazard.

Hence, though the bulk of public and scientific debate occurs at the intersection of extremes and hazards, there can be hazards which are not extreme and extremes which are not hazardous.


What kind of rock is this being eaten by a rock-eating worm? The New York Times article This Creature Eats Stone. Sand Comes Out the Other End. describes the shipworm Lithoredo abatanica, an organism that appears to "eat solid rock".

It links to the item in Science This rock-eating ‘worm’ could change the course of rivers which then links to the YouTube video Snippet: Shipworms that eat rocks.

The video shows how easily this rock can be split apart.

The rock was taken from the bottom of the Abatan River on Bohol Island, in the Philippines.

Question: Is it possible from the images, descriptions, and video to say something about this rock? Is it a kind of sandstone? It looks fairly loosely held-together and porous.

Images from NYTimes:

above: Lithoredo abatanica, from inside a piece of rock. CreditM arvin A. Altamia and Reuben Shipway (click for full size)

below: Two large burrows in rock made by shipworms. Credit Marvin A. Altamia and Reuben Shipway (click for full size)

thank you for your interest in the article. I'm the lead author on this paper (Shipway) and I happened to come across your post when looking through all the media stories on this animal.

To answer your question; yes, you're right, the rock is a calcareous sandstone. It was easy to split, partly because it is a naturally soft rock and partly because the shipworms had weakened the structure.

Hope that answered your question.


Do flights affect tides? Can artificial satellite positions affect tides? on Space Exploration.SE asks if artificial satellites can affect tides, because they are a lot closer than our natural satellite, even though they are much smaller in mass.  The top answer to that question is basically "no."

A commenter estimates that Pluto might have a larger effect, but Pluto is such a distant object I didn't think most people could easily relate to that, so I tried running the numbers with something people might be more familiar with, closer to our surface: airplanes.

Let's start by considering a big plane in relatively common use.  The Boeing 747 is well known as a popular aircraft type, and it seems that the version of it they're producing now is the Boeing 747-8.  This page says it has a maximum takeoff weight of 4.48*105 kg and a maximum landing weight of 3.12*105 kg, with a service ceiling of 1.3*104 m.  I'll round that to a weight of 3.5*105 kg mass and 1*104 m height above the surface of the ocean.

Now, the moon.  Wikipedia says the moon has a mass of around 7*1022 kg and a distance from the center of the earth on the order of 4*106 km, which is 4*109 m.  Earth's radius, about 6.3*103 km, is about a tenth of a percent of that distance and lost in the rounding/simplification of the Moon's orbit to be circular instead of its actual eccentricity.

This means that the moon's mass is (7*1022 kg / 3.5*105 kg =) 2*1017 times that of the 747.
The moon's distance from the surface of the ocean is (4*109 m / 1*104m =) 4*105 times that of the 747.

Comments on this answer note that "the amplitude of tides is proportional not to the strength of the gravity force, which is proportional to r2, but to its gradient, which is proportional to r3...a factor of 103 in distance means a factor of 109 in tidal effect."  Therefore, the effect that the distance has on the amplitude would be ((4*105)3 =) 6.4*1016.

Thus the overall effect of the 747 on tides should be (6.4*1016 / 2*1017 =) about a third of the effect of the moon.  It's a back-of-the-envelope order-of-magnitude calculation, but a much larger result than I expected.

Did I mess up somewhere in the math or facts above?  (If not, I'm willing to cut & paste that content into an Answer, but for now it's just showing the work I've done in arriving at this question and attempting to solve it myself.)

Now, there are many flights in the sky at any given moment, all around the world, and to a certain extent any tidal effects of one flight would be cancelled out by the effects of one or more others.   However, the flight map is not completely balanced or evenly distributed north-south or east-west.

Do flights affect tides?

Both airborne planes and the Moon affect the tides, but the effect of airborne planes is so small as to be negligible.

From your sources the mass of a Boeing 747 ($m_{747}$) is $447.696$
$(10)^3$ $kg$.
Likewise, from your sources, the mass of the Moon ($m_{Moon}$ is
$7.347$ $(10)^{22}$ $kg$.
Typically a 747 would fly at an altitude ($r_{747}$) of around $30$
$000$ $ft$. This is close to $10$ $000$ $m$ ($10^4$ $m$).
The distance the Moon is from the Earth ($r_{Moon}$) is $384$
$400$  $km$, which is $384.4$ $(10)^6$ $m$.

Now, Newton's Law of Universal Gravitation states, $F$ $=$ ${G.m_1.m_2}/{r^2}$

Where:
$G$ is the gravitational constant, being $6.6743$ $10^{-11}$ $m^3.kg^{-1}.s^{-2}$,
$m_1$ and $m_2$ are the masses of the two objects being considered & $r$ is the distance between them.

Because tides are being considered only the mass of water is to be considered, not the mass of the Earth. To simplify things I am assuming the area of water affect by each is the same and hence the mass of water will be the same in each case.

For the Earth and Moon system, the force of gravity will be:

$F_{E-M}$ $=$ $6.6743(10)^{-11}$ $.$ $7.347(10)^{22}$ $.$ $m_{ocean}$ $/$ $[{384.4(10)^6}]^2$ $=$ $3.3186(10)^{-5}$ $.$ $m_{ocean}$

For the Earth Boeing 747 system, the force of gravity will be:

$F_{E-747}$ $=$ $6.6743(10)^{-11}$ $.$ $447.696(10)^{3}$ $.$ $m_{ocean}$ $/$ $[{(10)^4}]^2$ $=$ $2.9881(10)^{-13}$ $.$ $m_{ocean}$

Dividing $F_{E-M}$ by $F_{E-747}$ the gravitational force of the Moon is $111$ $060$ greater than that of the plane.

If the tides produced by the Moon are up to $10$ $m$, then the maximum height of a tide produced by a 747 would be around $0.099$ $mm$.


How do long, thin, island chains such as North Carolina's outer banks, form? I can't think of a possible explanation, there's no volcanic activity in the area, and it gets destroyed every time a hurricane passes through. How did it get there?

The outer banks are, literally, a textbook example of what are known as Barrier Islands. They are thought to be formed through interactions between sediment undergoing longshore drift, coastal currents and seabed irregularities, but to spite a number of theories being put forward since the 19th Century we really don't understand their formation.
We do know that their ongoing behaviour makes them analogous to underwater sand dune systems in that:

the material in them is constantly on the move.
their form is controlled by the prevailing conditions.
they offer a degree of protection to the landscape on their inland side.
and
they are vulnerable to drastic alteration during extreme events such as storms or tsunamis.


Estimating the residence time of atmospheric CO2 from bomb 14C This (rather dodgy) graph shows a number of estimates of the residence time of atmospheric CO2:

My question concerns why there is so much variation (Machta, 1974 about 3 years, Seuss and Druffe, 1983 about 12 years) in the estimates based on the decay of bomb 14C, given that it seems reasonably easy to estimate from the decay after the nuclear test ban treaty in 1963:

Is there some complicating factor?

I've been doing some thinking and research about this and some issues that might be relevant are:

small 14C generated from nuclear power reactors ,
the carbon cycle is not at equilibrium, but a naive analysis might
assume that.

Judging by the general quality of the first graph, I don't think that it is the most reliable source. However as I don't feel like reading trough all papers, I will accept the numbers as they are stated. However once you include uncertainties of the observed residence time, I would assume most of the studies are not significantly different from each other.

The variability in the calculated residence time can be due various reasons; the measurement location, the number of observations used and the length of  the observational record.

The measurement location is probably the most important source of variation as results may vary a lot depending on where you measure. Multiple observation locations measuring what is called background air masses would be needed to get a good indication of the global average residence time of $CO_2$ in the atmosphere.

I would say you are spot on with the complicating factors.
Local influences are important as $CO_2$ emissions have different radiocarbon signatures depending on their origin. $CO_2$ from fossil fuel burning contains no radiocarbon while the nuclear industry emits low amounts of pure $^{14}C$ (not necessarily in the form of $^{14}CO_2$ though). The natural sources and sinks of $CO_2$ (biosphere and ocean) are also not in equilibrium with the atmosphere since the atomic bomb tests in 1950s and 1960s. Immediately after the bomb tests, the large amount of $^{14}C$ produced in the atmosphere meant that it was enhanced in  $^{14}CO_2$ compared to the biosphere and the ocean. Since then, $^{14}CO_2$ has decreased in the atmosphere, as it was taken up by the biosphere ant the oceans. This lead to an such a large increase in  $^{14}C$  in the biosphere and the surface ocean, that they are now enhanced compared to the atmosphere.

This graph including the oceans should explain what I mean.


Why won't Yellowstone explode? From my understanding Yellowstone is a massive super-volcano, so why isn't it active? Where has its (correct me if I'm using the wrong term) hot-spot gone? Can it still erupt?

This is a complex question, and I cannot give you a complete answer I'd like to point out that there is a very important article published in February of this year on the subject: volcanoes are in an eruptable state very very short periods of time in the geologic timescale; the mobilization of magma is very rapid but its storage is kept near, but under the solidus (where rock melts). Surely there will be more studies on this.

Since the reservoir of Yellowstone is very large, the chances of having enough eruptable magma to cause Yellowstone to detonate is low, hence why its eruptions are on the time scale of hundreds of thousands of years (very small in terms of geologic time).

The second thing I would like to address is "Hot Spot". The Yellowstone super volcano is supplied by the bifurcation of the Farallon slab as it subducts underneath the North American plate. This bifurcation causes the separated plate to sink displacing hot mantle upwards to the surface causing volcanism (Yellowstone). There isn't a clear definition of what scientists want to call it, often suggested to be a Plume or Hot Spot. It is not migrating. Yellowstone will eventually erupt. It is still Active.

Sorry I could not give you a better answer, but hopefully this illustrates some ideas that might explain why Yellowstone has a long eruption cycle compared to smaller volcanoes.


Is sea erosion the opposite of sea level rising (or rather, an adjacent phenomenon)? Because I understand the mechanism of sea erosion as to take earth away from shorelines (and scatter it deep into the sea floor) and also to derive from climate crisis, I ask the following question:

Is sea erosion the opposite of sea level rising (or rather, an adjacent phenomenon)?

A paper about this was published yesterday in Nature Climate Change: Sandy coastlines under threat of erosion (Vousdoukas et al. 2020).

  While shoreline change can be the combined result of a wide range of potentially erosive or accretive factors, there is a clear cause and effect relationship between increasing sea levels and shoreline retreat, pointing to increased coastal erosion issues. Climate change will also affect waves and storm surges, which are important drivers of coastal morphology.

The study computes projections of shoreline retreat. They computed four projections: two for 2050, and two for 2100, depending on climate change scenarios (RCP 4.5 and RCP 8.5). Here are the results:

  Assuming that there are no physical limits in potential coastal retreat, by mid-century we project a probable (5th–95th percentile) global average long-term shoreline change, ranging from –78.1 to –1.1 m and –98.1 to 0.3 m, under RCP 4.5 and RCP 8.5, respectively (negative values express erosion). By the end of the century the erosive trend becomes even more dominant and we project a probable range from –164.2 to –14.8 m and –240 to –35.3 m under RCP 4.5 and RCP 8.5, respectively.

And here is how it looks on a map (their figure 1):

The caption reads:

  Projected long-term shoreline changes. a–d, Projected shoreline
  changes by the years 2050 (a,c) and 2100 (b,d) under RCP 4.5 (a,b) and
  RCP 8.5 (c,d). Values represent the median change and
  positive/negative values, respectively, express accretion/erosion in
  metres, relative to 2010. The global average median change is shown in
  the inset text for each case, along with the 5th–95th percentile
  range.

Note that this projected retreat is a combination of two factors: the ambient shoreline change (AC) driven by geological, anthropogenic and other physical factors, and the shoreline retreat due to sea level rise (R). But R is the dominant factor, with a worldwide contribution of 82 % to the total retreat (with regional variations, see their figure 2).

In summary, climate change leads to sea level rise, which in turns leads to coastline erosion. Sea erosion is not the opposite of sea level rising, it is a direct consequence of it.


Self-sustaining aquarium in a jar? I've seen some videos of people scooping up some water from a natural body of it, adding some sand and a few plants, and soon enough, they have a (near) self-sustaining aquarium. I've always wanted to do this, but I'm not exactly sure how. There's a river in a small ravine (about 20 ft. deep) behind my house, and a nearby pond, so I think I might be able to manage this, but before I do, is there anything I need to know, or any suggestions on how to pull this off? Thanks in advance!
P.S. I don't want to take any animals (such as frogs), and trap them is a confined space. All I really want is some organisms that are just large enough to see, and I think I'd be good. If I do take anything from the wild, though, I want to return it, and I want to make it a pretty darn good habitat, so it doesn't feel trapped.

It is called an aquarium, put what ever you want in it. With natural waters you have a good chance of collecting dragonfly larva , which will eat about anything else you catch including small fish. Chances of mosquito larva are low in my experience. I don't know why you would not want frog or toad tadpoles ; I have a couple very small feral ponds in my yard and various frogs and toads  deposit uncountable numbers of eggs > tadpoles. Some years I have taken thousands of tadpoles to nearby lakes and dumped them . When I don't do that most get eaten by siblings. You are unlikely to find suitable native plants other than duckweed, so I suggest buying Hornwort at a pet shop -pretty bullet proof.


Is it possible to forecast ocean salinity 100 years into the future? Paleosalinity is measured by chloricity of pore fluids (Adkins 2002).

Current data are provided by the CORA dataset.

In addition to answers to the main question, there are a few more points I'd like to know:

How can one forecast ocean salinity?
What is the relationship between forecast errors and forecast horizon?
Are there any existing global salinity forecasts?
What are the sources of uncertainty in forecasting salinity 100 years ahead?

The answer to the main question is that we are capable of forecasting salinity 100 years into the future. The more relevant question might be how well are we currently forecasting salinity. First, lets look at what we know about how salinity is currently changing.

Global salinity is the result of the balance between surface freshwater flux (evaporation minus precipitation), terrestrial runoff and mixing and advective processes in the ocean. The changes in salinity are intrinsically connected to alterations in the global hydrological cycle and are expected to be a consequence of climate change (Held and Soden, 2006). A general change has been identified with surface subtropical areas becoming saltier and high-latitude regions becoming fresher (Antonov et al., 2002; Boyer et al., 2005). Durack and Wijffels (2010) found salinity increases in regions dominated by evaporation while freshening occurred in precipitation-dominated regions. They suggested the change was a consequence of an intensification of the global hydrological cycle. These results are the basis for the conclusions in the IPCC 2013 report (TFE.1 Figure 1).

The global climate models that are used to evaluate future climate scenarios are calibrated to reproduce the past ocean and atmospheric conditions, which includes trying to match the described salinity trend. They likely constitute the best source of future global salinity estimates. Their ocean salinity forecast is based on the estimation of the global hydrological cycle evolution, especially evaporation, precipitation, river discharge and ocean mixing.

With regard to the quality of the salinity estimates, there is probably a large uncertainty associated with those fields. There is going to be substantial improvement in the quality of the salinity forecast because of the recent availability of better global salinity products. The remote data obtained from satellites (SMOS and Aquarius) have been providing a much better global view of salinity changes. Also, the ARGO profilers are expanding our understanding of the ocean interior.

In terms of evaluating uncertainty, I like the approach of Meier et al., 2006 looking at multi-model ensemble estimates. They combined down-scaled regional models with global simulations under several scenarios and provided several metrics for salinity uncertainties. The relationship between forecast errors and forecast horizons is quite complex and in fact represents an entire field of study. There is a lot of information in the IPCC 2013 report dealing with prediction quality, ensemble generation and size, and forecast quality assessment (for instance Chapter 11).

 Source: Aretxabaleta et al. (2017)

Using a little bit of self-promotion, I can also say that estimating what the current salinity trend from observations is a tough problem. In this recently  published article, we show that the changes in trend are spatially complex and changing in time. We argue that, as mentioned before, the changes in salinity field give a good representation of the long-term changes in the global hydrological cycle.


Was rural visibility (air transparency) longer in pre-industrial times? I mean meteorological visibility (as per Wikipedia, "a measure of the distance at which an object or light can be clearly discerned.")

I want to know if, before modern industry (say pre-1800 A.D.), visibility in rural areas was longer than it is today (in clear weather conditions, of course). If so, by how much?

(Of course in smog-filled cities visibility is obviously limited by pollution. I'm asking about rural areas.)

Pre-industrial would mean that a lot of energy use would be the in-efficient use of wood burning.  I recall that part of J. S. Bach's payment at one of his posts was firewood provided by his employer -- something like "8 cords of birch wood, 2 cords of Alder, split for kitchen use....  I think the list was about 15 cords of wood for a year.  Bach had a big household, but even so.

Flip side:

Certainly the use of coal at the start of the industrial age clouded up the air substantially.  See records of London 'pea soup' fogs.  Coal was used on farms too, but the spread out nature of farms would dilute it somewhat.

I live in a rural area where many people heat with wood in winter, and some with coal.  At this point with an average of one household per square mile it makes little impact.  6 miles away is a coal fired power station.  On a really bad day I can just barely see it's plume.  The dust collection is pretty good.

In pre-industrial times, farms averaged about 5 acres per family unit, about 100 times the current Alberta farm density, and 1000 times Saskatchewan's farm density.

Ok:  What are the contributors to visibility reduction:

Plant transpiration -- water vapour is a big one, but plants also put significant amounts of complex organics into the air.  Most of the 'Blue Ridge" mountain haze is the result of plant activity.  This will change depending on ground cover.  Deciduous trees are more prone to this than grasses and forbs.
Dust from natural activities.  Only occurs in climates dry enough that ground cover is incomplete.
Man made dust.  Tillage in agriculture is the main cause of this, but watch any gravel road too.
Smoke from combustion.  Much depends on how stuff is burned.  Large particulates (e.g. diesel soot) fall out of the air column fairly quickly.

My wild ass guess is that average visibility hit a minimum somewhere between 1930 and 1970 when tillage and coal use was at it's peak, but has since increased due to both less coal being burned, and better combustion design, along with increasing use of zero or minimal tillage in agriculture.

You could get one check on this by looking at particulate measures in glacial ice.


Is the colour of soil determined by the 'proteins' present in soil? According to wikipedia, the colour of soli is determined by proteins present in the soil!

  Soil color is influenced by the amount of proteins present in the soil. Yellow or red soil indicates the presence of iron oxides. Dark brown or black color in soil indicates that the soil has a high organic matter content. Wet soil will appear darker than dry soil.However, the presence of water also affects soil color by affecting the oxidation rate. Soil that has a high water content will have less air in the soil, specifically less oxygen. In well drained (and therefore oxygen rich soils) red and brown colors caused by oxidation are more common, as opposed to in wet (low oxygen) soils where the soil usually appears grey.

The presence of specific minerals can also affect soil color. Manganese oxide causes a black color, glauconite makes the soil green, and calcite can make soil in arid regions appear white.

It sounds a bit strange to me. Pigments proteins do impart colour to the substances they are in (e.g. Haemoglobin in blood) but I wonder if there are any such proteins that could impart the variable colours to soil. Besides the following sentences in the mentioned paragraph do not mention of any protein.

It is possible that the word protein is there by mistake?

Edit:

P.S. The book from where the sentence is quoted is unfortunately not available online.

Soil is a collection of minerals and the color of soil is largely determined by the composition of its minerals.

Protein is derived from biological sources. The only way proteins could affect the color of soil is if the soil also contained large quantities of biological material.


When was the first not-icy desert formed? For how long have deserts existed and which one would be the first to be created? I'm talking about arid, dry deserts, not the Antarctic or Arctic or any other icy deserts.

Deserts have existed since at least the Permian period (299-251 million years ago) when the world's continents had combined into the Pangaea supercontinent. Stretching from pole to pole, this land mass was large enough that portions of its interior received little or no precipitation, according the University of California Museum of Paleontology.

Pangaea broke into smaller land masses which were moved across the surface by tectonic forces, a process that both changed global climate patterns and the climate those continents were exposed to. As a result, current desert regimes date back to no more than 65.5 million years, according to this Encyclopedia Britannica article:

  The desert environments of the present are, in geologic terms,
  relatively recent in origin. They represent the most extreme result of
  the progressive cooling and consequent aridification of global
  climates during the Cenozoic Era (65.5 million years ago to the
  present), which also led to the development of savannas and scrublands
  in the less arid regions near the tropical and temperate margins of
  the developing deserts. It has been suggested that many typical modern
  desert plant families, particularly those with an Asian centre of
  diversity such as the chenopod and tamarisk families, first appeared
  in the Miocene (23 to 5.3 million years ago), evolving in the salty,
  drying environment of the disappearing Tethys Sea along what is now
  the Mediterranean–Central Asian axis.

Which would put the oldest of "modern" desert somewhere in the region of what later became North Africa or South Asia.


What are the ranges of natural (or pre-industrial era) levels of CO2 in the atmosphere in ppm and tons? Are the levels of natural (before the industrial revolution) levels of CO2 and ppm known? Also as a related question, should the "natural" levels be considered before the industrial revolution or before the start of the deforestation 8000 years ago?

There is no such thing as a single "natural" level of $CO_2$: In Earth's history, there have been levels much higher and much lower than currently, and they are all natural.

What we should consider instead is what levels of $CO_2$ are compatible with the mild and stable climate that humanity has enjoyed for the last few millennia, or conversely, which levels will upset the climatic equilibrium and send Earth into a completely new climatic regime.

The means to measure atmospheric $CO_2$ concentrations were invented during the industrial revolution, so we don't have direct records before that. However, we can reconstruct past $CO_2$ concentrations using proxies such as the analysis of air bubbles trapped deep within the ice in Antarctica.

Ice cores were drilled up to ~600 meters deep between 1987 to 1993 at Law Dome (Antarctica), allowing the reconstruction of $CO_2$ concentrations from the last millennium, and it looks like this:

Where the darker blue at the end corresponds to the direct instrumental record (source).

Later, another ice core from Vostok station in Antarctica was drilled to a depth of more than 3.6 km, allowing the reconstruction of atmospheric $CO_2$ concentration during the last 400,000 years, and it looks like this:

(Figure source)

The data from Law Dome and that of modern records at Mauna Loa, Hawaii are also displayed on the end for comparison.

More ice cores have been drilled after Vostok, and all of them tell more or less the same story.

So we know that atmospheric $CO_2$ concentrations now are much higher than at any other time since we invented agriculture. And the people that think they know how the atmosphere works run models and say that current levels will significantly upset the climate as we know it. On the other hand, the people who don't know how the atmosphere works (like me), should just stop producing so much $CO_2$, because we don't ourselves know what the effects could be, and at the same time, we rely on the climate to stay nice and stable to keep your flourishing society alive.

To address the last bit of the question, to transform 1 PPM by volume of atmospheric $CO_2$ into a GigaTon of Carbon you just have to multiply by  2.13. So the pre-industrial base level during the last millennia of 280 PPM is equivalent to ~596 GtC or 2,187 Gt of $CO_2$ (multiply again by 44/12, the ratio of $CO_2$ mass to C mass).


Why does the so called "tornado alley" exist? 75% of the world's tornadoes occur in the USA, and within the USA these tornadoes are most likely to occur in particular regions of the country, such as the well known "tornado alley".  The diagram below shows tornado activity in various parts of the USA, from 1950 to 1998.  It can be seen from the diagram below that most tornadoes occur on the Eastern half of the country.  Within this half of the country, there are regions with much greater tornado activity than others, highlighted in dark red in the diagram below, and includes the so called "tornado alley".  Why is there a higher frequency of tornadoes in these regions compared to other regions of the USA and around the world?

The kind of tornadoes "tornado alley" refers to are associated with supercell thunderstorms.  To first figure out why this region exists, we need to explore why this is a hotspot for supercells.

Thunderstorms require energy and this energy comes in the form of convective available potential energy (CAPE).  This is simply the vertically integrated buoyancy of a parcel from its level of free convection (LFC) to its equilibrium level (EL).  Thunderstorms need CAPE but CAPE is not a great predictor of what kind of storm we get, that falls to vertical windshear.  Supercells form in environments with a 0-6 km shear (this measure if just a vector difference of the winds at these levels) greater than 20 m/s.

CAPE is going to be maximized where you have warm, moist air at the surface and cold air aloft.  The Gulf of Mexico has plenty of water and it is common to find strong southerlies advecting this moisture into the US.  With a particularly strong low level jet, this moisture can be advected as far north as the Dakotas. As warm air is typically found toward the equator, this is also advecting warm air northward.  This results in a tongue of warm, moist air extending northward out of the gulf.

The cool air aloft is provided by the Rockies and high plains.  In the boundary layer, mixing drives the temperature lapse rate toward dry adiabatic, while in the free troposphere the lapse rate is typically less than dry adiabatic.  The high elevations of the mountains mean that there are boundary layers and some layer of atmosphere with a dry adiabatic temperature profile.  These cool, dry adiabatic layers get advected by the westerlies aloft and end up on top of the warm moist air provided by southerlies out of the gulf.

This setup provides CAPE and the necessary shear (southerlies at low levels and westerlies aloft) for supercell thunderstorms.  However, not all supercells form tornadoes, and why is an area of active research.  Tornadoes will be favored with low LCL heights (lifting condensation level) and large low-level shear.  The occurrence of these environments combined with empirical data result in the area termed "tornado alley".

The US isn't the only home to such a place.  There is a similar setup in Bangladesh where warm moist southerlies come off the ocean and cool adiabatic layers come from the high terrain in the region.

Because the atmosphere is giving a nice case study, here is an example of a sounding that demonstrates the above concepts.  This is from a radiosonde launched at Jackson, MS this morning at 12Z.

Key features:

Boundary layer is well mixed (dry adiabatic temperature profile and constant water vapor mixing ratio)
A cap (and a rather large one at that)
An elevated mixed layer extended up to nearly 500 mb (nearly dry adiabatic temperature profile)
Dry midlevels
Southerlies at the surface
Westerlies aloft

Of note, the hodograph has a lot of low-level shear with almost all of the 0-6 km shear contained within the lowest 1 km.  The LCL is also somewhat low.  These are both favorable for tornado formation.  The big question is whether a storm will actually fire, as this sounding has considerable convective inhibition (CIN) from the large temperature inversion capping the boundary layer.  This is a morning sounding though and so there is plenty of time for the temperature to evolve.  The cap can be broken through pure solar heating, though requiring a temperature of 94 F to do so.  Throughout the day the boundary layer will be mixing with the cap, which will reduce its strength.  Moistening the boundary layer can also help decrease the CIN.  Aside from the large cap in the morning, this is a setup favorable for supercells and severe weather.

And the result?  As of 2218Z, here is a view of the Jackson, MS radar:

This is a supercell (well, a line of them and a bit messy looking) with a possible tornado due west of Jackson and moving to the east.

For a broader picture, lets also take a look at the 18Z NAM.

Surface moisture:

This shows a tongue of moisture being advected by the southerlies out of the gulf.

Surface temperature (F):

It is also warm.

Surface based CAPE:

Put this together with midlevel lapse rates and we have lots of CAPE.  But do we have adequate shear?  Here is the 500 mb flow:

500 mb height and relative vorticity:

Flow somewhat westerly, but direction is not as important as the magnitude.

Surface to 500 mb shear:

And as this shows, we have plenty of shear.

This is a classic setup for severe weather and the frequency that this setup occurs and the resulting weather is how tornado alley earned its name.


How high is too high for hydrogen to rise? If hydrogen is the lightest gas known, would it rise making the outermost part of the atmosphere mostly hydrogen?

Images to associate with your answer would be much appreciated.

Thanks

I had a similar question, and then I learned that at the molecular level it is diffusion what dominates, that means that despite Hydrogen is lighter, it won't rise to the top of the atmosphere. Flotation as we visualize it doesn't really work at the molecular level (because it is overcome by chemical diffusion).
Therefore, the Hydrogen in the atmosphere is evenly distributed trough it.

To clarify it further, a parcel of hydrogen would indeed rise, but as soon as it gets diluted in the surrounding air, the buoyancy of individual molecules/atoms would become negligible in comparison to the chemical diffusion that will take the atoms in any direction, not just upwards, leading to further dilution of the original molecules within the parcel throughout the atmosphere.

As for why that's the case, let's me explain how I visualize it: Imagine you put two a thousand million ping-pong balls in the middle of the Pacific ocean. Half of them with a piece of Iron inside. If you put a magnet in the coast of Mexico, you would expect all the balls with the piece of iron to end up in Mexico. However, the forces of the wind and waves hitting the balls in random ways is so much more powerful than the magnetic attraction in this case, that most likely the balls will end up all over the Pacific. In the same way, all molecules in the air are bouncing against each other with such a strength, that the fact that one is lighter than the other doesn't really play a role in the trajectory a molecule will follow on its journey trough the atmosphere.

In any case there is not much Hydrogen in the atmosphere, that only contains a 0.00005 % of molecular Hydrogen (H2).


Why is it still day in Mumbai at 6:47 PM? I captured this news channel picture on Sept 11 2018 from India.

We can clear see It is live telecast from Mumbai, but it is still day time.

This image from https://www.timeanddate.com/sun/india/mumbai shows that daylight ended at 6:44, so 6:47 was three minutes into civil twilight and pretty much close to daylight.

Notice the orange light in the back - I'm assuming that this is a street lamp, which are only turned on at twilight.

Most likely the image appears relatively bright because of camera settings, not because it is full daylight outside.


How does multiple layer seismic reflection work? How do we distinguish arrivals from different layers and their velocities? Whenever we are investigating multiple layer interfaces in a seismic reflection survey the root-mean-squared velocity is often employed to deduce travel time to a certain n-th layer and also to deduce velocity of any given interval. This is done because it is a way to account for refraction that is also occurring between layers which alters the reflection of a shot made through multiple layers.

What I don't understand is how do we know the travel times in any layer beforehand? How are we distinguishing between different travel times and assigning them to different layers we've distinguished? We need travel times of successive layers in order to compute the root-mean-square, but this is puzzling to me because how could you already know them?  Who is to say it is multiple and not just 1? or 3, or 5 or some arbitrary number? What about the arrivals to the geophones tell us this?

I don't get how we know there are extra layers in the first place to which we must assign travel times, and when they do exist, from where do these travel times come?  I have included a graphic to help show what I mean. The more I think about this, the more I start to think I don't understand multiple layer seismic reflection in general.

Source: UC Berkeley Dept. Earth & Planetary Science’s Richard Allen’s  Applied Geophysics GEO594/GLE594  notes for Lecture 15: Seismic reflection - II

It is impossible to to convert one recorded time-series into structural information. As you correctly note, the equation
$$ v_i = \frac{z_i}{t_i}, \tag{1a}$$
or
$$ t_i(z,v) = \frac{z_i}{v_i}, \tag{1b}$$
is difficult to solve when you only a know one time $t_i$. That is, choosing $z_i$ to twice its value would provide twice $v_i$! If you only record time $t$, but try to turn it into two values $(z_i,v_i)$, you have an underdetermined problem.

However, if you have multiple traces, you know from the theory that a flat reflector produces a hyperbolic move-out (I believe it's the following equation, but I'm not 100% certain. Don't quote me on it!):
$$ t_i(x,z,v) = t_0 + \frac{x^2}{v_\text{stacking}}. \tag{3}$$
As you know the location $x$, knowledge of two (rather than one) traces would perfectly constrain $t_0$ and $v_\text{stacking}$! Just like the slides you provide in the link, the velocity $v_\text{stacking}$ is usually simply found by trying many values for the move-out correction velocity, and seeing which velocity value flattens the reflector best! From that knowledge, suddenly you can constrain also the depth, etc.

Reflection seismics deals with the situation that is described in the 5 slides preceding the slide you post. We have a lot of traces, and based on the assumption of hyperbolic moveouts we can perfectly obtain the stacking velocities. The slide you post approaches the problem from the other way around: what are the stacking velocities $v_\text{rms}$ you would find if you know the depth and velocity structure already? This is not necessarily the method used to get structural information from your data! I think that is the cause of the confusion..!


sub soil data finding I am going to search  and finding some subsoil data, (vanGenuchten Parameters, specific storage, Hydraulic conductivity, porosity, Manning coefficient and humidity of root zone) I have no idea about it and want to know if there any sites about this data that one can downloaded them? is there any other way or guide? maybe someone have same problem like me and know about tips that are helping.
Thanks a lot

The United States Geological survey might have some data on soil
As should the US Dept of Agriculture.
More to it, Universities with Agriculture departments


Does depletion of Planck radiation intensity in the upper atmosphere mean that "CO2 has no impact on climate change"? In his recent book, Rex J. Fleming asserts that "CO2 has no impact on climate change", or, as he summarizes on his website:

  There are now over a dozen books available on Amazon.com that point out the various fallacies of the CO2 climate theory – but none of these have zeroed in on the heart of the issue – the failure of the Schwarzschild radiation integrations to maintain the CO2 longwave radiation intensity achieved in the surface warming by H2O and CO2. The resultant Planck radiation intensity is severely depleted in the upper atmosphere. The result is the CO2 molecules merely pass their remaining small residual heat to space un-impeded. CO2 has no impact on climate change.

This claim seems to contradict some basic physics.

Is Fleming correct that the "failure of the Schwarzschild radiation integrations to maintain the CO2 longwave radiation intensity" means that "CO2 has no impact on climate change"?

Talk of Schwarzschild radiation integrations negating the effect of CO2 in atmospheric warming is just mumbo jumbo on a par with creationism, but there is a danger of going too far in the other direction. Carbon dioxide forms 0.0325 percent of the atmosphere, and although a slight increase has been recorded in the past 100 years and attributed to human activity, this increase is infinitesimally small. Whenever I say that climate warming began 12,000 years ago it is always very unpopular, but it nevertheless happens to be a fact. There is unanimous agreement among scientists that the small amount of CO2 in the atmosphere helps to warm the Earth, but where there is less agreement is on the question of whether the minute increase since the industrial revolution has measurably accelerated the climate warming which had already been underway for 12,000 years. Another unpopular idea which also happens to be a fact is that increased atmospheric CO2 causes plants to grow more vigorously, so to some extent increased CO2 content is self-correcting, but only up to a point. It could easily be overwhelmed if the CO2 increase is too rapid.


Why don't they give hurricanes uncommon names? So people with common names don't have to share names with a destructive hurricane.

It's just the system that is used.

The first person to give names to cyclones/typhoons/hurricanes was Clement Wragge, an Australian weather forecaster in the 19 century.

  He first designated tropical cyclones by the letters of the Greek alphabet, then started using South Sea Island girls' names. When the new constituted Australian national government failed to create a federal weather bureau and appoint him director, he began naming cyclones "after political figures whom he disliked. By properly naming a hurricane, the weatherman could publicly describe a politician (who perhaps was not too generous with weather-bureau appropriations) as 'causing great distress' or 'wandering aimlessly about the Pacific.'

During World War 2, US army & navy meteorologists name tropical cyclones after their wives, after having been introduced to a novel, Storm, in which a junior meteorologist named extra-tropical storms after girl friends.

In 1947 the US Air Force Hurricane Office in Miami started using the then new international phonetic alphabet (Able, Baker, Charlie, ...) when naming hurricanes in the North Atlantic Ocean.

When the international phonetic alphabet changed in 1952 (to Alpha, Beta, Charlie ,..) The US Weather Bureau initially started using the armed services practice of using women's names.

In 1975 the Australian Bureau of Meteorology started using a system alternating womens and mens names. After political pressure, in 1979 by the

  US National Hurricane Center (NHC) requested that the WMO's Region IV Hurricane Committee switch to a hurricane name list that alternated men's and women's names following the practice adopted by Australia's Bureau of Meteorology in 1975.

IN the North West Pacific, womens names were first used in 1945. Mens names started being used in 1979. Now they use a series of Asian names, contributed by nations and territories that are members of the WMO Typhoon Committee.


Has anyone driven under, or received camera footage from, the Great Artesian Basin in Australia? I can find information about the basin as a water-source, along with photos of the ground over its 1,700,000 square km surface. But have divers ever entered this space, or tunnels been dug for cameras, have photos ever been taken of it from under its waters?

Groundwater is stored in the porosity of rocks, that is space between clasts or cracks. Larger cavities, e.g. karsts, is usually only a minor contribution to ground water reservoirs and are only common in limestone.

The Great Artesian Basin aquifer is made up of Mesozoic sandstone. It is covered by impermeable rocks that allow pressure to build up within the aquifer so that as rainwater enters at high elevation it will keep the hydrostatic pressure, even when the topography is lower.

The only way to see the rocks at great depths is by drilling and, if the budget allows, also keep core sample to be able to analyze it. Important information also comes from borehole logging when geophysical instruments are lowered into the borehole to measure e.g. porosity and density of the rocks. One can also see the continuation of the formation on the surface and study the rocks to understand how they look at great depths.

This informative document explains some of the features of The Great Artesian Basin rather well, but don't be mislead to think about the aquifers as caves, it is only water soaked rocks.


Volcanoes in the Alps and Himalayas and the subduction of Tethys Sea Geologist have theorized that the Tethys Sea subducted under Eurasian plates. But where are the volcanoes that would have resulted due to this? Where are the volcanoes in the Alps and the Himalayas?

The end of the Tethys Sea and the initiation of the continent-continent collision that formed the Himalayas is thought to have happened about 65 Ma ago (recent studies suggest maybe only 35 Ma). And since then, that colossal collision have produced an estimated 2,500 km of crustal shortening.  That means that 2,500 km of continental surface is gone. A fraction of it was maybe subducted, other fraction squeezed under the other continent and perhaps the larger fraction shortened by thrust and folding. This massive transformation would have been enough to erase a preexisting volcanic arc, that could easily end up under kilometers of rock that came from sediments in the Tethys sea or the sourthern edge of the Eurasian plate (for example mount Everest summit is mostly composed of sedimentary rocks with fragments of trilobites from the Tethys sea).

Nevertheless, part of that volcanic arc indeed is visible now in the surface. No volcanic edifice have survived the cataclysm that give rise to the Himalayas, but the rocks that formed the arc are now known as the Dras Volcanics, a band of volcanic basalts and dacites outcrops that are part of the Indus suture zone. And that are though to originate in the Mesozoic (from about 252 to 66 Ma ago) volcanic arc that existed in the Eurasia plate as a consequence of the subduction of the oceanic crust under the Tethys sea.

This geological map of the Himalayas shows in geen the outcrops of the Indus suture zone.

Taken from The Tethyan Himalayan detrital record shows that India–Asia terminal collision occurred by 54 Ma in the Western Himalaya


What is the tectonic setting for the formation of the Great Dividing Range in Australia? Australia's Great Dividing Range is the largest mountain range on the continent, running down the length of the eastern part of the continent, as shown in the Geoscience Australia map as a dark line, below:

The tallest peak in the range is Mt. Kosciuszko at 2228 m asl.  The Wikipedia entry is rather vague about the formation, with

  The Great Dividing Range was formed during the Carboniferous period—some 300 million years ago—when Australia collided with what is now parts of South America and New Zealand. The range has experienced significant erosion since.

it is particularly vague regarding the question - What is the tectonic setting for the formation of the Great Dividing Range in Australia?

The tectonic history of Australia's Great Dividing Range is very complex, extending back into the Neoproterozoic era (1), and is far more complex than the Wikipedia quote. Additionally, evidence (shown in this answer) demonstrated that the eastern third of the Australian landmass is comprised of accreted arc systems that developed along the continental-oceanic Eastern Gondwana boundary following the initiation of subduction in the late Neoproterozoic (1) forming in a series orogenies (as shown on the map below (2) - not due to a single continental collision. These orogenies are incorporated in the 'Terra Australis' Orogen that ceased approximately 230 million years ago (3).

As can be seen by the diagram below (2), the youngest accreted orogen occurs in the eastern most margins of the Australian landmass, where the Great Dividing Range is.

Also, the cessation of arc accretion, did not end the tectonic story affecting the Great Dividing Range.  Large Igneous Province volcanics occurred in north Queensland in the early Cretaceous, then epeirogenic uplift, exhumation and continental rupturing culminating in the opening of the Tasman Basin occurred in the mid Cretaceous, leading to the separation of Zealandia (New Zealand + submerged continental shelf) and giving shape to the eastern Australian coastline (and eastern boundary of much of the Great Dividing Range) (4).  The rifting process is illustrated below

Image source: Formation of The Australian Alps

References

(1) Cawood et al. 2009 Accretionary orogens through Earth history, The Geological Society

(2) Foster and Goscombe, 2013 Continental Growth and Recycling in Convergent Orogens with Large Turbidite Fans on Oceanic Crust, Geosciences

(3) Cawood, 2005, Terra Australis Orogen: Rodinia breakup and development of the Pacific and Iapetus margins of Gondwana during the Neoproterozoic and Paleozoic, Earth-Science Reviews

(4) Bryan et al. 2012, Early-mid Cretaceous tectonic evolution of eastern
Gondwana: From silicic LIP magmatism to continental rupture, Episodes


Mars maar craters explosive style formation gravitational effect "Maars usually form when magma rises within a fissure and interacts with groundwater. If groundwater ceases to interact with magma at times during the eruption, continued magma ascent to the surface gives rise to a wide range of volcanic forms and products associated closely with maar-diatreme volcanoes."

Currently I am trying to compare maars on Earth to maars of Mars.

How would the gravity of Mars affect the crater formation from the explosion that formed the crater on Mars?

Database of maars crater on Earth show that maars are typically not circular some are very eccentric. Current hypothesis says is because rather than one explosion forming the crater a multitude of continuous explosions formed the crater also needed to form the bigger craters such as the devil mountain lake in Alaska the largest in the world.

My guess is less gravity means that we need less energy to create a crater as big as the ones on Earth. There is evidence of water on mars. There are millions of crater on mars. There is some evidence for volcanic activity.

To put it simply, the explosion is essentially caused by a quick transfer of heat between magma and water. Analogous to throwing water droplets to a pot with hot oil in the stove, it starts splattering all around. (Don't try this at home)

A human tries this experiment on Mars. Same quantity of oil, same heat source and temperature. The only difference is gravity. if on Earth it generated X amount of joules of energy. Will Human on mars get X + some other amount or X - some other amount simply because of Gravitational Difference

I recently saw a video lecture given that went through a calculation of how the size of volcanoes is related to the mass of a planet.  I don't remember the details or the math but the conclusion was that the smaller the planet the bigger the volcano.  This explains why Olympus Mons on Mars is so much bigger than anything on earth.  I can find a link to the lecture if that will help.  The equations are given in the lecture.


Q: Is the crust getting thinner or is the mantle getting smaller Volcanoes spit out magma onto the surface of the crust or crevices on the surface, but the magma comes (in effect) from the mantle right? If that's the case, isn't the mantle turning into the crust by the mantle hardening into mountains and volcanoes? Or maybe the mantle doesn't change size, it just melts more of the crust to suit its size needs. If that was the case, the areas of Earth that aren't constantly spitting magma onto the surface would eventually be thinned out to the point that a hole or giant crack would appear leading straight to the mantle and that would be bad.

The crust is actually getting thicker very gradually as the Earth cools down. This process is well seen on Mars, where due to its smaller size and greater distance from the sun, Mars is cooling faster than the Earth. No one knows exactly how thick the Martian crust is, but what we do know is that magma can no longer find its way to the surface. All the Martian volcanoes are extinct.

On Earth, the magma ejected from volcanoes is mostly recycled oceanic crust. Sea floor spreading from the mid-ocean ridge pushes the oceanic crust on the Pacific Plate toward the continental crust on,for example, the North American plate, where it is forced to dive  beneath the continental crust and driven down into the mantle. For a number of reasons (friction, water content etc) this causes it to melt, and being lighter and more fluid than the mantle it rises to the surface, where it escapes through volcanism.

This is not the whole story, because if oceanic crust is disappearing as it is pushed below the continental crust of another plate, it must somehow be replaced. This happens at the mid ocean ridge, where a deep chasm plunges through the comparatively thin oceanic crust, enabling fresh magma from the mantle to rise up and create new ocean floor. This is constantly spreading out in opposite directions from the mid ocean ridge, hence the term 'sea floor spreading'.


Will the oceans swallow all of the land? I am wondering why, since the oceans could feasibly hold all of the dry land, they in fact do not.  For example, the Mariana Trench drops to -10.9km, while Mount Everest only reaches to +8.8km.  Further, the oceans cover 71% of the surface.  This causes me to suspect that the negative elevation parts of the Earth could easily hold the positive.  Due to erosion, will the oceans eventually consume the mountains?  What is the timescale involved with such a process, and what forces counteract it?

If no new mountains were built, yes. Ultimately the processes of erosion would render the continents flat, and the seas would be left shallow and filled with sediments. The reason that this doesn't occur is that tectonic processes cause 'orogenesis', the formation of new mountains. The subduction of oceanic crust at plate margins is also responsible for trenches such as the Mariana, and ultimately recycles sediments into the mantle; thereby preventing the ocean floor from filling up.


Dynamic cone penetrometer (DCP) results and correlation I have been reading about DCP and watched a video of how it is done (the video is not in English). But there are something things that are still unclear and I would greatly appreciate some help and clarification. I have these questions:

Is there a standard number of times that the hammer must be dropped?
What is recorded after an $x$ number of hammer drops?

Lat/long coordinates of where test occurred?
How far the metal head penetrated the ground (in cm)?

What happens to that data? What does it correlate with to give us the strength of the ground? What is that strength measured in?

The underlying principle of the DCP is that the rate of penetration of the cone, when driven by a standard force, is inversely related to the strength of the material as measured by, for example, the California Bearing Ratio (CBR) test. Where the pavement layers have different strengths, the boundaries between the layers can be identified and the thickness of the layers determined. A typical result is shown.

It is recommended that a reading should be taken at increments of penetration of about 10 mm. However, it is usually easier to take readings after a set number of blows. it is therefore necessary to change the number of blows between readings according to the strength of the layer being penetrated. For good quality granular subbases readings every 5 or 10 blows are normally satisfactory but for weaker sub-base layers and subgrade readings every 1 or 2 blows may be appropriate. Little difficulty is normally experienced with the penetration of most types of granular of weakly stabilised materials. It is more difficult to penetrate strongly stabilised layers, granular materials with large particles and very dense, high quality crushed stone.
The instrument has been designed for strong materials and therefore the operator should persevere with the test. Penetration rates as low as 0.5 mm/blow are acceptable but if there is no measurable penetration after 20 consecutive blows it can be assumed that the DCP will not penetrate the material. Under these circumstances a hole can be drilled through the layer using either an electric or pneumatic drill or by coring. The lower layers of the pavement can then be tested in the normal way.


What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.

When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away.

The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.

It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.


Why is the elevation of the Iberian Peninsula so high? The Iberian peninsula lies more than 600 m above sea level, on average, far above similar geological regions in western Europe. Even tectonically undeformed areas in the inner basins present a topography and a sedimentary infill sometimes higher than 1000 m. Why?

The elevation of continents is generally thought to be the result of the isostatic equilibrium (Archimedes balance) of the crust floating on a fluid mantle (Pratt and Airy models, late XIX century). The thicker the crust (which is less dense than the mantle), the higher topography. The denser the crust, the lower the topography.

Cartoon explaining the concept of isostatic equilibrium, according to which topography (h1) is sustained by a crustal root (b1) in the same way that the elevation of an iceberg reflects the size of its submerged part.

However, the crust of the Iberian Peninsula is about 30-33 km thick on average, similar to most of the western european platform, and nothing suggests that the Iberian crust has a lower density than other regions. Why then is the topography of Iberia higher than 600 m, in contrast with the near sea-level western Europe?

So, the underlying question is: why Iberia is 600m higher than the W European Platform, having its Moho (base of the crust) shallower?

Topographic map of Europe

Depth to the base of the crust in Europe (in km; from Tesauro et al., 2008)

I don't know for sure, but my guess is that at least a part of the high Iberian elevation is due to NNE-SSW compression in northeast Spain, caused by rotation of the Iberian block. That is,the same rotation that opened up the Bay of Biscay deep basin, whilst compressing the Pyrennean mountains. The gentle dip of most of Iberia towards the southwest would fit well with such an explanation.
But then you may ask: 'Why is there a low elevation sedimentary basin just southwest of the Pyrenees?' Check the age of sediments in this trough. I would bet they are pretty recent, and I suspect that there may well be some late-stage counter-rotation caused by the  relative east-west displacement along the Rif-Betic arc.


The different types of plagioclase The fractions of albite $\ce{NaAlSi_3O_8}$ and anorthite $\ce{CaAl_2Si_2O_8}$, which I call $\ce{Ab}$ and $\ce{An}$ in the following list, present in a plagioclase are often used to define it in the following way:

Anorthite: $\ce{An}=90\%-100\%$, $\ce{Ab}=0\%-10\%$;
Bytownite: $\ce{An}=70\%-90\%$, $\ce{Ab}=10\%-30\%$;
Labradorite: $\ce{An}=50\%-70\%$, $\ce{Ab}=30\%-50\%$;
Andesine: $\ce{An}=30\%-50\%$, $\ce{Ab}=50\%-30\%$;
Oligoclase: $\ce{An}=10\%-30\%$, $\ce{Ab}=70\%-90\%$;
Albite: $\ce{An}=0\%-10\%$, $\ce{Ab}=90\%-100\%$.

What I am not sure of is whether these fractions are intended as applying to mass, molarity, volume.

According to the pages Plagioclase composition (from the textbook: Introduction to Mineralogy Nesse, 2000), the percentage definitions are due to the mole percent of $\ce{Ca^{2+}}$ (from anorthite) and the presumed subsequent $\ce{Na+}$ (from albite) ions present in the sample.

This is done under the assumption that the anorthite% + albite% = 100% in a plagioclase sample.

The mole percent are usually represented by percentage proportions of the plagioclase end member anorthite, often in the form of Anx, where 'x' is the mole percent of $\ce{Ca^{2+}}$ present in the plagioclase sample.

Consider the following diagram below - the relevent part for your question is across the base of the triangle:

Image source.

For example, oligoclase is An10%-30% means that it would possess a $\ce{Ca^{2+}}$ mole percent of between 10% to 30%, and a corresponding $\ce{Na+}$ mole percent of between 70% to 90%.


What is this red glassy rock I found rocks looking like this in my backyard but cant get to know what they are or how to find out. Below are pictures

I don’t know if there’s more info I should mention. If there’s anything please advise

See here for some ideas.  You may want to do some testing, at least for Mohs hardness.  But comparing your samples to the typical pictures shown in the referenced site I would guess an alkali feldspar (hardness = 6)  or perhaps rose quartz (hardness =7).  Note the hardnesses, a steel file falls in between at 6.5.