Is volume of air increasing as CO2 levels increase? CO2 levels are increasing, they have crossed 400 ppm, which means that of every million gas molecules in the air, 400 are of CO2.

It has been increasing. Does that mean the total volume of air in the atmosphere is increasing or that some other gas is decreasing as CO2 increases?

Thank you.

[Major edits below]

In short the answer is NO.

Before we get into volume changes, I have to say that volume is a tricky measure to apply to the atmosphere as a whole, because there is no clear limit between the atmosphere and outer space.
Also, the thickness of the atmosphere is quite insensitive to changes in atmospheric mass. For example, the atmosphere of Venus is much more massive than Earth's (93 times more massive). Leading to surface pressures 92 times those of Earth. However, the thickness of the atmosphere is quite similar, with the mesosphere extending to 120 km, only 41% higher than on the Earth, despite having 9300% the mass.

This planetary comparison suggests that more CO$_2$ will lead to a more massive atmosphere and higher atmospheric pressures, but little change in its actual volume (if you somehow manage to define how to measure the volume of the atmosphere).

As an analogy, imagine you have one meter of snow cover, and there is one meter of snowfall. You won't end up with two meters of snow cover. Thise is because the new snow will compact the snow below, leading to something like 1.7 meters of snow cover.

Therefore, more gases in the atmosphere will lead to a denser atmosphere, but have little impact on its thickness.

Now we have to make a very important distinction: It is not the same to add CO$_2$ from a CO$_2$ source (like a volcanic eruption) than add it due to combustion of fossil fuels. This is because the latter do not add molecules to the atmosphere, just turn O$_2$ molecules into CO$_2$. Now, if you look into what this transformation means in terms of volume, you will get a surprise (at least it was a surprise to me):

Given standard conditions (20°C and 1 atm). One cubic meter of O$_2$ weights 1.331 kg. When you use that oxygen to burn fossil fuels all the molecules in it will go from a molecular weight of 32 (O$_2$) to 44.01 (CO$_2$), meaning you end up with 1.831 kg of CO$_2$. Now comes the interesting part: under the same conditions, one cubic meter of CO$_2$ weights 1.842 kg, consequently, our initial cubic meter of O$_2$ turned into 0.994 m$^3$ of CO$_2$, equivalent to a volume reduction of 0.6%. Therefore, burning fossil fuels reduces the volume of the atmosphere.

I was surprised at first by this result, but it nicely explain the classic experiment where a boiled egg get sucked into a bottle:

This is an screenshot of this video where you can see the trick in action (skip to minute 1:10)

Now, despite that burning stuff decrease the volume of the atmosphere. It is important to note that if you add greenhouse gases like CO$_2$ or methane, you are not only increasing the amount of those gases in the atmosphere, because the increase in temperature will lead to an increase in water vapor too. So the atmospheric mass increase will be larger than the mass of CO$_2$ or methane added. And that extra mass is related to additional molecules, so it will lead to extra volume (contrary to the combustion case where the amount of molecules is constant).

Thus, as we burn fossil fuels the mass of the atmosphere increases (as well as the atmospheric pressure), but the volume decreases, and due to the fact that CO$_2$ is the product of combustion, that increase will be at the expense of reducing the amount of molecular oxygen (O$_2$).

Although, this decrease is very small: the atmosphere have ~21% of Oxygen and 0.04% of CO$_2$, so an increase in CO$_2$ of a 30% (similar to going from 300 to 400 ppm), means a reduction of O$_2$ of 0.01%, a relatively small change (using Wikipedia numbers it would go from 20.946% Oxygen to 20.934%). Also, that's strictly true only if you make an instantaneous combustion. Because over time there could be negative feedback working against this imbalance. For instance, plants will increase the rate of photosynthesis (CO$_2$ fertilization effect)

That said, the mass increase (and volume decrease) associated to the CO$_2$ jumping from 300 ppm (pre-industrial levels) to 400 ppm is negligible, and probably dwarfed by day to day changes in particulate material or water vapor.

As a side note, the book "Red Mars", makes a fairly scientifically sound description of how to "terraform" Mars, and how adding CO$_2$, or water vapor increase the atmospheric pressure and surface temperature.


What forms do groundwater flow equations have when Dupuit supposition is not considered? Near pumping wells or near/beneath a stream, the groundwater flow is not totally horizontal and the vertical component of groundwater movement at these points cannot be ignored in reality. Often, groundwater flow equations are derived while assuming that the flow in largely horizontal which is called Duipuit-Forscheimer assumption.

I want to know if we consider the vertical flow near pumping wells and streams, what form will the groundwater flow equations have?

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

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


Is the Arctic sea ice disappearing in a linear or non-linear way? I'd like help to understand these charts. They are charts of Sea Ice Volume. One is drawn with linear decline, the other has all sorts of curves fitted onto it.

Why do we have these different line fits and which is true ?

The box in the lower left of the bottom chart is key to understanding what is presented. Five attempts of a line of best fit have been presented. From the chart, the linear fit (yellow line) is the least best fit, so the loss of Arctic ice not a linear relationship. The other lines are different modeling scenarios the author has attempted.

When testing for lines of best fit, one is trying to find a mathematical equation that will neatly describe something - in this case Arctic ice loss over time.

The other four lines of best fit that were considered were: the exponential curve, Gompertz fit, logarithmic fit and a second order polynomial fit. Visual examination of these curves shows they are very close in describing the data and are close to each other.

The important thing to consider in such curve fits is the value of R2, sometime denoted as r2. A value of 1 means a perfect fit and a value of zero means absolutely not fit.

All four curved lines have a fit greater or equal to 0.902. That is a good result.

The Gompertz fit has an R2 of 0.917 which is the highest value of the options presented. It means that for the data analyzed and evaluated in this study the Gompertz fit is the one that best describes the data. However, given the closeness of R2 values, the other options also give good results, but not as good as the Gompertz fit.


How significant is human influence on seismic activity? Here's a graph from johnstonsarchive.net showing energy released by earthquakes and, however reliable this graph is, it shows huge differences in earthquake activity. About how big percent is the energy of quakes caused by humans?

You have an interesting graph there. In response to your question, I would say that if we actually use the Mw (moment magnitude) measure of seismic activity (which is related to energy release via slip on a fault), we would see that most of the Earthquakes 'caused' by humans (and note that there are still only a few examples of this, (such as the 5.7 Prague, Oklahoma Earthquake), are limited to intraplate earthquakes which only exceed 4 in rare instances such as the above.

The exact 'percent' of energy release due to induced (human-caused) seismicity would probably not even approach single digits, but possibly reside in values approaching zero, when you consider that the vast majority of earthquakes take place at plate boundaries and outnumber induced earthquakes by a large amount.


Why is March colder than September in Northern Hemisphere? Forgive my ignorance of the subject but I was always wondered about the exact reason of this phenomenon.

Vernal equinox happens around March 20, whereas autumnal equinox happens around September 22, so wherever you are in Northern Hemisphere, the length of the day, and consequently the amount of solar energy that reaches the place should be almost the same.

However the average temperatures differ widely, for example Toronto has average temperatures of 2°C to 6°C on March 20th, and 14°C to 19°C on September 22nd. So around 12°C difference [link].

So obviously there is some sort of temperature inertia, as temperatures seem to experience a delay in responding to changes in day length.

What is the main reason for it? Is it effect of sea ice or snow-covered land albedo? Energy stored in oceans? Energy absorbed by melting snow and ice?

The phenomenon is called seasonal lag.

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


How to calculate relative humidity? I am involved in developing a weather based application which needs to calculate relative humidity and display it. I grab other weather variables like temperature, precipitation, wind speed and direction from the weather site. Is it possible to calculate relative humidity using this data?

No, this is not enough.

Relative humidity is defined as the water vapour partial pressure relative relative to the saturation water vapour pressure:

$$
\phi  =  {{e_w} \over {{e^*}_w}}
$$

where ${e^*}_w$ is the equilibrium vapour pressure (which may be relative to either liquid water, or to ice), and $e_w$ is the partial pressure of water.

${e^*}_w$ can be calculated using the Clausius-Clapeyron relation, but to get $e_w$ you need some information on the water content.  This information may come in many forms:

Water vapour mixing ratio (the number of water molecules per unit volume)
Specific humidity (the mass of water per unit volume)
Partial pressure of water vapour ($e_w$)
Dew point, which is the temperature at which $e_w = e^*_w$.

The one you are most likely to find on meteorology websites is the dew point temperature.  Basically, if you have two of temperature, dew point temperature, and relative humidity, you can calculate the third.  For example, see this University of Miami calculator.


When did/will peak conventional oil happen? Global oil reserves are, for practical purposes, limited. We're using them at a rate far exceeding the rate of deposition. At some point, we will have to spend more energy to extract remaining reserves than we get back from burning them (extraction might still be worth it, because plastics and other oil products are really useful).

When is the point at which conventional oil production peaked/will peak?

For the purposes of this question, please only consider conventional oil resources: that is, excluding shale oil, synthetic hydrocarbons, biofuels, oil sands, coal to liquids, and gas to liquids.

The answer depends a lot on what you mean by "excluding shale oil".  Tight oil production, commonly referred to as "shale oil" is about 4 million barrels per day currently (2014), compare to almost none in 2005.

Canadian oil sands production is at 2 millon barrels per day, compare to about 700,000 per day in 2005.

So compare to 2005, tight oil (shale oil) and oil sands production is up about 5 million barrels per day.

Now look at total world oil production:

From the graph it can been seen that subtracting out the 5 million barrels/day of unconventional production, world production is somewhat below the 2005 level. (Quantitative values were 73.9 M bbl/day in 2005; 76.9 M bbl/day in first 8 months of 2014)

With the expectation that tight oil and oil sands production will increase in share of the production, it is entirely possible that the peak in conventional production has already occurred.


What could cause a turn from global warming to global cooling? Except a hypothesized orbital forcing! Ice cores shows that there are several irregular sharp temperature peaks in between of the big 100,000 years glaciations. What could cause those peaks?

Almost all energy excess is stored in the oceans and common sense says that there have to be a threshold for how much energy the oceans can take up without drastically changing the climate. There are two possibilities: either there is a turn to cooling down the oceans or there isn't.

Could the energy from the oceans take over the climate system totally for a time long enough to be cooled down? Could the energy from the oceans, if big enough cause global storms independent of the insolation? Convective clouds transport warm vapor high up in troposphere where condensation release an enormous amount of energy - mostly as heat energy that spreads from there. Could a global cover of convective clouds be maintained entirely by the ocean heat content, if big enough?

In the diagram, there is a well defined peek about 50,000 years ago, for example. Sudden up and sudden down. Increased insolation (or something else) caused a sudden warming, that "immediately" turned back. Could it have been caused by a long time of storms and convection?

Pleistocene's climate variations are well correlated with Milhankovitch Cycles.

  "Variations in eccentricity, axial tilt, and precession of the Earth's
  orbit resulted in cyclical variation in the solar radiation reaching
  the Earth, and that this orbital forcing strongly influenced climatic
  patterns on Earth."

  Source: Milhankovitch Cycles, Wikipedia

At this graph you can see eccentricity explains major Oxygen $δ18$ variations at Pleistocene oceans. $δ18$ is a known proxy for temperature.

  Source: euanmearns.com

The minor peaks are Earth's internal forces reaction to changes on solar radiation. Earth has subsystems that store and interchange the energy received from the Sun, resulting oscillatory climate tendencies.

Aswell as the atmospere and the hydrosphere, cryosphere has internal forces as a subsystem; and oscillatory events (development of ice-break of ice). One example of punctual changes due to cryosphere internal forces dynamics are Heinrich Events, that can influence climate at minor scale than eccentricity does and be correlated with some of the peaks your graph shows.


Recent high seismic activity in Europe It seems that Europe and the Mediterranean Sea have had high seismic activity in last six months. Major events which I remember are:

2020 Aegean Sea earthquake, magnitude of 7.0  Mww
29 December 2020:  Petrinja, Croatia, magnitude 6.4 earthquake
Many Etna volcano eruptions
3 March 2021: Týrnavos, Greece  6.3  Mww
Many earthquakes in recent weeks in Iceland and an alert for volcanic eruption
Today (18 March 2021): 6.0 Mww earthquake in souther Mediterranean Sea, near Béjaïa, Algeria

What could this high seismic activity across Europe tell us?

There is a nice tracker for global earthquake activity at https://www.volcanodiscovery.com/earthquakes/global-seismic-activity-level.html, although it doesn't conveniently allow you to look at regional statistics, as opposed to global or national records.
At a global level there doesn't seem to be any particular increase in events , although in a quasi random series clustering in time and space isn't unexpected.
The perception that there might be an increase is probably a reflection of human and media behaviour; when one event occurs it heightens our interest and the likelihood of noticing other events. The media are far more likely to report a small earthquake occurring in the immediate aftermath of a large earthquake elsewhere in the world, than they would have if it had occurred in isolation.


Would more or less land be usable if global temperatures rose? I think a large portion of the earth's land is unusable from being too cold and land that is too hot does not have enough water and dries out which could be fixed by diverging water to those areas.

Then there is the sea levels rising so some land will be underwater but that will be an insignificant amount compared to the amount of new usable land, not to mention we could reshape land in those areas to prevent it from being underwater.

Yes. current climate change will most likely increase the amount of cultivable lands on Earth. However, it will at a high social cost and at the expense of biodiversity, and I can't emphasize enough the paramount importance of biodiversity for the heath of ecosystems and human food safety.

Consider also that similarly to mining, where the value of a deposit is related not only to the total amount of mineral but also to its concentration, we have to consider also how intensive is the food production allowed by a piece of land. In this regard, climate change can lead to the loss of highly productive areas, compensated only by the gain of large expanses of nutrient poor soils in the tundra.

You should also consider the social impacts of the degradation of current cultivation lands and the economic costs of moving food production pole-wards.

To answer this question with some degree of certainty is extraordinarily complex, because we don't know how exactly climate will change, but several studies have addressed this problem. A good example is The global distribution of cultivable lands: current patterns and sensitivity to possible climate change. There they point that:

  We estimate that climate change, as simulated by global climate
  models, will expand cropland suitability by an additional 16%, mainly
  in the Northern Hemisphere high latitudes. However, the tropics
  (mainly Africa, northern South America, Mexico and Central America and
  Oceania) will experience a small decrease in suitability due to
  climate change.

Figure 4 of the paper shows the current "land suitability index" worldwide.

You can see how the north of America and Eurasia show large expanses (although quite exaggerated by the map projection) of land not suitable for cultivation due to the cold temperatures.
This data can be downloaded here, and I've used it to plot the following figure that shows the mean cultivation suitability index as a function of latitude. It is also plotted the land area as a function of latitude as derived from ETOPO:

As you can see, pole-wards of 56° there is a significant amount of land of which none is suitable for cultivation. However, it is clear that temperature is not the whole picture, and aridity around 25° of latitude can significantly drop cultivation suitability.

I found interesting to see that the left (equator-wards) side of the main peak in cultivation suitability currently at 37° lies at a latitude with a lot of land, so if that end is lost to aridity, the gain of land on its (right) pole-wards end will be smaller due to the downwards trends of land area towards the pole. Nevertheless, as I mentioned, models suggest climate change will increase the overall land surface suitable for agriculture.

Another study: Northward shift of the agricultural climate zone under 21st-century global climate change. Focus on temperature and shows in Fig. 1 how the line that divides temperature regime suitable from cultivation of cereals will migrate northwards under the projected climate change:

However, they highlight the challenges for cultivation in high latitudes, which present a much more dramatic seasonal contrast that traditional crop lands:

  By 2099, roughly 76% of the boreal region might reach
  crop feasible conditions, compared to the current 32%. The leading
  edge of the feasible conditions will shift northwards. However, most of the
  newly gained areas are associated with highly seasonal and monthly
  variations in climatic water balances, a critical component of any
  future land-use and management decisions.

[the cite above was edited for simplification and context]


What Happens When India Stops Hitting Asia For the past 50 million years, India has been colliding with mainland Asia, creating the Himalayan mountain range.

It's not an issue of if the Himalayas would stop rising, but when.  Articles of the past months have said that the range would stop rising in the best guess of 20 million years, not because of gravity, but because of how the mantle influences the movements of the landmasses.

But what the articles never say is what would happen when the Himalayas stop rising in the distant future.  How would the topography of Asia be affected?  How would Tibet react?

You are correct in that, sooner or later (and nobody can say just when) the Indian plate will stop crashing into the Eurasian plate, and the the two plates will effectively fuse into a single plate. The underlying mantle convection is likely to continue for a few million years, tending to displace the combined plate further northward, probably with a component of anti-clockwise rotation, which might result in a few micro-continental fragments breaking off. The Yakutsk peninsular is one such possible candidate.

Probably the single most important result will be the fate of the Himalayan chain. Again, the underlying mantle is likely to take a few million years to gain litho-static equilibrium, so seismic rumblings will continue, but probably with much less intense earthquakes than we have seen recently. Fluvial erosion is probably faster than you think. Within 20 million years, and possibly even in 10 million years, all of the great mountains will be worn down to a pale shadow of their former state. More and more rivers will break through from Tibet, and drain southwards. The Himalayas will become much less of a climatic barrier than they are now, such that the monsoonal air flow, and much of the moisture than it carries, will spill over into Central Asia. The main rivers that feed into the Ganges will carry less water. The climate of Central Asia will change dramatically, but it's difficult to predict exactly how. Currently the air flow from southern Europe is deflected southeasterly across Iran and the Gulf, being effectively blocked by the Central Asian mountains. As these mountains are eroded this airflow will become progressively less hindered, making west central Asia wetter, and the Arabian Gulf even drier than it is already.

Glaciers and snow topped mountains are already in rapid decline because of global warming. The ice will certainly be long-gone by the time the tectonic conveyor belt grinds to a halt.

The eroded debris will drain into the Bay of Bengal. The current effects of rising sea level will flood most of Bangladesh in the short term, but it will ultimately be reformed as erosion overtakes rising sea level.

As for Tibet, one would expect a long period of erosion, mainly by deeply incised rivers dissecting the plateau, much as the Colorado River is cutting away at the Colorado plateau in North America; a process greatly aided by much increased rainfall.


Do we know what the rigid mantle looks like? The rigid mantle, which is hard and lies above the asthenosphere, is separated from the "crust" that we can see and touch by the Mohorovičić discontinuity. Wikipedia provides an image of what may once have been part of the discontinuity, but I haven't been able to find a good source on what the actual rigid mantle looks like.

Do we know what the rigid mantle itself looks like or how it would look to the naked eye? That is, if I could somehow use my Unobtainium 9000 SuperDrill to drill down to the mantle and excavate a 1 meter squared cube of rigid mantle, what would it actually look like once I got it up to the surface? Would it just look like a slab of random silicates like as could be found in some mine today? Would it look distinctly "alien"?

Above the asthenosphere is the lithosphere. The main constituent of the lower lithosphere is peridotite, a coarse-grained igneous rock containing the minerals olivine and pyroxene. Samples of peridotite can be found in the surface. Sections of ocean crust can be uplifted onto continental margins, forming ophiolites (perhaps the best-known example being the Troodos Ophiolite). They are also found as fragments in basalts and kimberlites, the vertical intrusions that often contain diamonds. So there are lots of places on the surface where you can go and see what the upper mantle looks like! But in the meantime, a closeup of a peridotite is shown below.


What's it like inside a natural gas cavern on Earth? I suppose natural gas underground caverns on Earth have substantial volume and gas is in gaseous form there.

As such I wonder how it would look like inside such cavern (with artificial light of course). Will one see a rocky sky at big distance?

What is the actual volume of such caverns? It is correct to talk about methane oceans or seas?

Are they empty or the gas is mixed up with solid substance?

A cavern filled with natural gas would look like an ordinary cavern. However, natural gas is rarely abundant in caverns.

Most natural gas reservoirs occur in the pore spaces of sandstones. These pore spaces are generally up to about 1 mm in diameter. Here's a photomicrograph of a sandstone — the green-blue colour is the pore space; Q, F, L, and M are quartz, feldspar, lithic fragments and mica respectively:

The pores of reservoir rocks also contain 'formation' water in various proportions. The relationship between the water and the hydrocarbons can be quite complex, depending on the fluid composition, the reservoir temperature and pressure, and the mineralogy of the rock.

So what about caverns? Trace amounts of methane probably occur in many, if not most, caverns — we're talking here about abundant methane. This is much less common, but it happens. In certain limestones pore spaces can be quite large — up to several metres in diameter. This is called vuggy porosity. If the limestone is charged with natural gas, the vugs will fill with gas, just like the other pores. The space would look like any other limestone cavity. Very large ones are rare, based on a typical power law size distribution. There are (copyright and unlicensed) images of such super-pores here and here. Recently Mattey et al. (2013; EPSL 374) wrote about methane in a karst in Gibraltar. I'd estimate that less than 1% of the world's gas is held in vuggy reservoirs.

There's another kind of cavern in which you can find natural gas: man-made ones. Natural gas is often stored underground, usually in porous rocks, but sometimes in caverns dissolved out of salt. Around a quarter of natural gas stock is stored this way in the US. Here's a video from such a salt cavern.

Last thing: methane seas can only occur at low temperature. As far as I know, liquefied natural gas or LNG is only stored above ground or on ships in tanks. Lots of natural gas reservoirs have very light hydrocarbon liquids in them — but again the liquid would be in tiny pore spaces, not caverns.


How does salting roads help prevent ice? What kind of salt is used to keep roads from getting icy and how does it work?
Why does ice get thick in some places and other nearby places there is no ice?

Sodium chloride rock salt, NaCl, is usually used for de-icing roads. As mentioned in another answer, the dissolved ions lower the freezing point of water.

Other kinds of salt are also used. Calcium chloride, CaCl2, is more efficient at melting ice. NaCl can not melt ice at temperatures lower than -18C (0 F). A saturated calcium chloride solution won't freeze until ~ -46 C. Calcium chloride is often applied as a solution because the solid becomes sticky as it absorbs water from the air.

Edit: per the link to the Colorado road dept from a comment on another answer, magnesium chloride is used in the liquid deicers. Here is a link to information on different deicers


Which greenhouse gas does the most damage to crops? While there have been lots of studies looking at the effect of greenhouse gasses on increasing temperatures around the planet, my question is what are the effects of emissions on food production.

Tropospheric ozone is a significant greenhouse gas (see e.g. IPCC AR4) and has well established negative effects on crop yields. For example, Van Dingen et al (2009) evaluated yield losses of up to about 15% globally, depending on the crop.


Why does every tsunami travel differently? Tsunamis are quite interesting, as they only happen after a large displacement of water.

Usually, the waves travel quite weirdly. Sometimes there are waves which bounce off of land and go back to sea. Sometimes they go straight to land and don't bother any other pieces of land around them.

So why does this happen?

Why do some tsunamis go straight to land while others are spread out?

And why others take various pathways toward land or the open sea?

The answer to some parts of your question lie mainly in basic physics, there are a number of factors that will affect how a Tsunami will travel after the initial water displacement.

For example, is the initial displacement a point event (such as Tsunami caused by landslides), or an event occurring along a long line, such as the massive fault movement that caused the "Boxing Day" Tsunami of 2004.

A point event allows the water to spread out in all directions from that point, similar to ripples in a pond after a raindrop or pebble falls in, the energy is dissipated equally in all directions and therefore the water displacement - and thus the height of the breaking Tsunami wave - decreases rapidly.

Conversely, a linear event such as the "Boxing Day" tsunami doesn't allow the energy to dissipate equally in all directions, because at any given point along the wave-front, there is more "wave" to the 'left' and 'right' that prevent that dissipation. This allows the energy to be transferred over much greater distances, and allowing the water displacement to be preserved.

As for why some land gets passed by, this is usually an effect of the local topography, going back to the Boxing Day Tsunami example, the Maldives were less effected than they could have been because there was no continental shelf for the waves to encounter and build up on. Bangladesh and other countries north of the fault-line also suffered less than they could have done because the northern and southern ends of the fault acted like point-events, and the waves to the north and south dissipated much more rapidly than those to the east and west.


The climatological variance of albedo, soil moisture in weather models Looking at WRF currently but I am sure this applies to most weather models there is a file (specifically LANDUSE.TBL) that specifies USGS derived albedo, soil moisture and other parameters on a biannual basis - one for summer and one for winter.

Why would not these parameters vary on a more seasonal basis and/or on a annual basis? Why are these these variables assumed to be constant? Would not changing vegetation or land cover modifications affect these values on a regional basis as well as their impact on regional climate?

Also would it make sense to model these values on a regional basis after deriving them from remote sensing as indicated in the below mentioned article http://web.maths.unsw.edu.au/~jasone/publications/evansetal2012a.pdf

WRF model development is done in such a way that users can run the model independently before you start adding more complex options to ingest observations.  There is even an "ideal" mode that new users can take advantage of to learn how the system works (not for simulating real Earth situations).  In "real" mode, there are typically two types of simulations done: a forecast or a retrospective (historical) simulation.  It's important to have real observations ingested into a retrospective simulation, since the intent is to model the event as best you can.  However, this is not possible in forecast mode, since the observations do not yet exist.  So, it is important to have default lookup tables that characterize your unknowns.

Regarding the values in the LANDUSE.tbl, there are many groups that use the monthly MODIS-derived values to ingest into their simulations that replace some of these values.  A "summer" and "winter" lookup table is provided for users in WRF, but those defaults are not appropriate for the best retrospective weather simulations. Forecasting, on the other hand, can use old satellite data (MODIS land-surface data is several days if not weeks old by the time it is processed) but that has error just as a seasonal average would.  The values in the LANDUSE.tbl (except surface roughness) will get overwritten with the VEGPARM.TBL values if you use Noah or the RUC Land Surface Model (LSM). Noah uses monthly values as far as I know. RUC might write values on its own... not really sure if it uses the VEGPARM.TBL or not. I'm sure there are experienced WRF modelers out there that can give you more detailed information, e.g. on the WRF modelers forum.


Is there a piece of upside down foreign crust in the USA? When I studied earth science, a lecturer mentioned that one of the anomalies that earth science hasn’t been able to explain is a piece of crust in the USA.

This piece of crust appeared to match very well with the crust of another continent, if turned upside down, and didn’t match the surrounding crust in the USA.

I can't find any information about this and I can't forget about it. Is there any basis for this claim?

Most probably, he was referring to the Brunswick Magnetic Anomaly: http://www.geosociety.org/news/pr/2014/14-22.htm

This is an area of lower-than-normal magnetism present in North America in the Southwestern United States. Note that altough it COULD be a piece of Africa, it could also be caused by something else.


How do we allocate partial CO2 doublings for Empirical Climate Sensitivity? How do we allocate partial CO2 doublings for Empirical Climate Sensitivity? I applied partial doublings on a linear basis, is this correct?

Climate Threat to the Planet:Implications for Energy Policy and Intergenerational Justice Jim Hansen December 17, 2008
http://www.columbia.edu/~jeh1/2008/AGUBjerknes20081217.pdf

Empirical Climate Sensitivity 3 ± 0.5C for 2 x CO2
(Hanson said it could be 6C in the longer term)
http://www.columbia.edu/~jeh1/2008/TargetCO2_20080407.pdf

If we assume that the formula above still holds and
assume the current rate of CO2 increasing at 1.9% per year
and assume 280 PPM as the CO2 base.
and assume that partial doublings can be allocated linearly.

Years.......CO2
From.......Per.......CO2
Now........Year......Total
....0..........3.00......410
....4..........3.17......420.....1.5C
...17.........4.05......467.....2.0C
...27.........4.89......513.....2.5C
...36.........5.80......560.....3.0C

Keith McClary provided this link, which provided the data below it:
https://en.wikipedia.org/wiki/Climate_sensitivity#Estimating_climate_sensitivity

IPCC Fifth Assessment Report 2014
66% likely: Empirical Climate Sensitivity 3 ± 1.5C for 2 x CO2
Possible: Empirical Climate Sensitivity 1C to 6C for 2 x CO2

The best information available provided above shows the climate sensitivity. The next thing that we need is the procedure for allocating fractional doubling.

https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter1_Low_Res.pdf
SPECIAL REPORT: GLOBAL WARMING OF 1.5 ºC
CH 01
Framing and Context  The following is on page 66
Expert judgement based on the available evidence (including model simulations, radiative forcing and climate sensitivity) suggests that if all anthropogenic emissions were reduced to zero immediately, any further warming beyond the 1°C already experienced would likely be less than 0.5°C over the next two to three decades, and also likely less than 0.5°C on a century time scale.

It seems we already missed the 1.5C target: 3 * log2(410/280) degree increase, or about 1.65°C

To get a rough estimate you should be using a logarithmic interpolation rather than a linear interpolation. The response to added $\text{CO}_2$ would be linear if the atmosphere had barely any $\text{CO}_2$ in it. Even 280 ppm does not qualify as "very little". "Very little" would mean a handful of parts per million, at most.

The issue is that the atmosphere is rather opaque at those frequencies where $\text{CO}_2$ absorbs and emits thermal infrared radiation. Instead of a linear response, the response in terms of radiative forcing is roughly logarithmic. This is why climatologists talk about the effect of a doubling the $\text{CO}_2$ levels. The radiative forcing of an increase from 140 ppm $\text{CO}_2$ to 280 ppm is more or less the same as the response to an increase from 280 ppm to 560 ppm, or to an increase from 560 ppm to 1120 ppm.


Why doesn't the earth become superheated? One day I was sitting in an Atlanta traffic jam wondering about all the engine exhaust heat warming the localised environment. Later that night, things will have cooled down. Where did the heat go?  On a global scale, I understand our sun heats the earth via radiation, not conduction as  the intervening vacuum of space cannot transfer heat. So if the sun has been beaming gazillions of watts of energy into the earth over the last few billion years, and energy is conserved and the earth does not radiate out daily a material proportion of the radiation it has absorbed, where has all that energy gone?

A body has to emit as much thermal energy as it absobs to remain in thermal equilibrium. The Earth has been doing the same since  its formation, i.e, it absorbs solar  shorwave radiation by its atmosphere, solid earth and water body, and releases it in the form of longwave radiation. The amount that is released has to be equal to the amount that is absorbed to maintain same temperature. However, due to much emission of greenhouse gases in to the atmosphere (or according to sceptics of such concept due to solar activity, volcanic emission), some amount that the Earth has to release is absorbed by the gases in the atmosphere and are causing the Earth to warm by few degrees every year.


Sun's Effect on Water Vapor in the Air If the air temperature remains the same, will adding more sun reduce the amount of water vapor in the air - that is, does the sun have any impact on water vapor in the air when temperature is removed as a variable?

You need to define what you mean by 'adding more sun'. I'm asuming you mean 'increase the solar constant'.

The amount of water vapour in the air is, as a first order approximation, related to temperature - every degree of temperature rise gives us 7% more water vapour.  So if 'adding more sun' increases the temperature then it automatically increases water vapour.

Now, to add more sun without increasing the temperature, you'd have to compensate by doing something like painting large areas of land white; this would increase the Earth's albedo, reflecting the extra solar radiation. No temperature change overall, so no water vapor change.

The only direct effect of the sun on water vapor is something entirely different - through photo-dissociation. This is where the sun's UV rays directly break up water molecules.  However, in order to have an appreciable effect on the day to day concentration of water vapour, you'd need to replace the Sun with a much bigger and hotter star that blasted out far more UV radiation. The problem here is that everyone would die.

So as far as the question can be answered, it would be no under any realistic scenario.


Terrestrial Day vs. Venusian Day: Why the Huge Time Difference? The diameters of Venus (7,520.8 miles) and Earth (7,917.5 miles) are comparable, but the disparity of the length of the day for each planet - as expressed in terrestrial hours - is enormous; a day on Venus lasts 2802 hours vs. an Earth day lasting 24 hours (its 116.750 times that of Earth).

How can there be such a great difference when the size of the two planets is nearly the same? Does the fact that Venus’ rotation is retrograde to all of the other planets in our solar system affect the length of it's day?

There is no reason why the day length should be the same. From the time of planetary formation, some 4.6 Bn years ago there has been some degree of slowing of day length due to tidal friction, which is much higher on Earth than on Venus, so the original contrast in day length may have been even greater than today.

There are three major reasons for differencial spin rates. Firstly, the initial planetary rotation rate was a function of the net angular momentum of the planetesimals, gas, and miscellaneous debris from that part of the solar nebula from which the planet condensed (in accordance with the conservation of angular momentum). There is no reason to suppose that that the original solar nebula consisted of a nicely ordered, evenly distributed mass/velocity distribution. Rather, there is every reason to think that it was a highly chaotic heterogeneous cloud of matter undergoing gravitational mayhem - probably including large scale gravitational disruption by gas giants much closer to the sun than we see them today. From such chaos one could model almost any distribution of relative rotation speeds amongst the final planets.

Secondly, there is strong evidence that proto-Earth collided with a 'trojan' named 'Theia', about the size of Mars, about 4.3 Bn years ago. This is the 'giant impact hypothesis', which provides a good explanation for Earth having such a large moon. We don't know the relative angular momentum of either proto-planet, their relative motions, or the angle of impact (head on? glancing?), so it is probably impossible to reconstruct the event. However, it is (relatively) easy to envisage how such an impact could radically change the Earth's angular momentum. The spin could have been hugely accelerated or decelerated according to the physics of the impact.

Thirdly, Venus's relative proximity to the sun could have resulted in its undergoing rotational capture, such that eventually one face of Venus will perpetually face the sun. This gravitational locking of Venus is probably the most significant reason for its' long day. As you rightly note, the retrograde spin of Venus is curious. Therefore we may infer that Venus's spin history is more complex than we can account for by simple planetary accretion.


Reults of the glacials and interglacials of the ice age on the soil I have read that the Earth has undergone five ice ages, the latest one is the Quaternary glaciation. I know that in the ice age there are glacial periods and interglacial periods, and we are currently in an interglacial, I want to make sense what is the effect of those succsessive periods on the life on Earth. Because in my text book I read that the soil has grown and become fertile since 20 thousand years ago, since the interglacial period started. But what made this change in the soil? and why it became suitable for farming? And is it a costant thing that the soil become rich and good in the interglacials of all ice ages?

First a comment on the number of ice ages - one could say 5 to 7 major ice ages, depending upon how one defines an ice age, and several more minor ice-ages, with some debate as to whether some are sufficiently separated in time to be regarded as two ice ages.
Most of the northern hemisphere has been emerging from the most recent ice age over the past 10000 to 12,000 years, but by no means at a constant rate, with some short-term reversals. As regards soil formation, it is only the most recent ice age that is of relevance - older palaeosols have been either eroded or lithified.

How long does it take for soil to form? That is primarily a function of climate, and secondarily a function of weathering lithology. That is, many millennia for cold dry climates, or as little as a decade or so for hot wet conditions. Soils take many years to form on limestone, quartzite, granite and some other resistant rocks, but are rapid on recent basic rocks such as volcanic ash. The weathering rate of different minerals varies over many orders of magnitude, and is a combination of chemical and biological processes which is far too complicated to discuss here. I suggest you read a good book on weathering processes.

Regarding soil fertility, this is also rather complex, but obviously continuous cropping will tend to remove organic carbon, organically available phosphate and potassium, not to mention other trace elements, thereby leaving the soil less fertile unless very well managed.

Ice ages are not 'normal' in the geological history, and it will take tens to hundreds of millennia for a normal soil quasi-equilibrium to be reached. This 'equilibrium will also be lost both by human intervention and by accelerated climate change.


Why did sinkholes emerge in Pakistan? Here is a video.

Why did the sinkhole emerge in Pakistan? Is this because of the heavy exploitation of groundwater?

What could be the solution?

Reference

In pictures: Chaos as rain continues to lash Lahore
NDMA sends out monsoon alert, expects more urban flooding in Lahore, Rawalpindi
Sinkhole emerges near GPO on Mall Road
Those responsible for Lahore sinkhole will be punished: Interim transport minister

I was about to ask a question whether this should be classified as a sinkhole or not. This is because this so-called 'sinkhole' is not entirely because of a natural process. It seems that it was the underground GPO Station (or the tunnel) of Orange Line Metro Train Station that collapsed.

I can't seem to find an article that specifically mentions this. One news article I found isn't exactly very clear about it, but suggests this to be the case.

I think you can blame the 'sinkhole' (or collapse) or the failure of the underground structure. One of your source's title "Those responsible for Lahore sinkhole will be punished" also seems to suggest that it has only man-made causes, and not natural.

Further sources:
Punjab Mass Transit Authority - Orange Line Metro

P.S. I live here. :)


How CO$_2$ warming effect stays overnight? Water vapor looses it energy at night (no sun, no UV) and this is deposited as dew.  Change of state requires a massive energy change, in general.  Is the greenhouse effect of CO$_2$ not lost when it gets dark and there is no UV entering the Earth? If not how is the energy stored in the atmosphere by CO$_2$? None of the research I can find, even from the 1950's or 1960's, has addressed this.

I am a doubter, but I do see that CO$_2$ has the ability to warm. Just can't see how this is maintained overnight since there are about 12 hours of darkness daily.  This seems to be the case with water vapor loosing energy daily or it would be 150 degrees (or more) in the South (USA) by July. I am a chemist with a strong thermodynamics background. Thanks.

CO$_2$ doesn't significantly interact with solar radiation or UV, and doesn't store any significant amount of heat. What CO$_2$ effectively does is scattering infrared radiation emitted by the Earth, and such radiation is emitted day and night. Let me explain this:

All objects emit a type of radiation called black body radiation. And the color (wavelength) and power of that radiation depends on temperature.
This radiation becomes evident to the eyes only at temperatures above 500 °C, when stuff start to glow, as amber, the heating element of a stove, the filament of a incandescent light bulb, or the Sun itself. However, this radiation is emitted also by colder objects, as the human body, the ocean and even glaciers and ice cubes. But we can't see that radiation because is very faint and mostly composed of infrared radiation that is invisible to the eye.

However it can be detected with cameras, and that's why military and surveillance thermal infrared cameras are capable to see in the night, because they see the radiation the human body emits. Here an example:

[picture from Videoblocks]

The interesting fact to keep in mind, is that for Earth to be in thermal equilibrium (meaning that the mean temperature is stable or changing very slowly), the amount of infrared radiation that Earth's emits have to be equal to the amount of radiation it receives from the Sun, so it is a lot!.

The effect of CO$_2$

Now, the effect of CO$_2$ is not to store any energy, it just blindly absorb and re-emit infrared radiation (foot note 1), there is no significant storage. The key point is that most of the infrared radiation it absorbs comes from the surface, and then it re-emits it in a random direction. As consequence of this, half of the radiation that was escaping to space is sent back to the surface, and that's the origin of the warming effect of CO$_2$.

So the effect of CO$_2$ is similar to that of a survival blanket like this one:

[image from Aliexpress]

This blankets don't produce or store heat, it is not good insulators either. This blanket just reflect back some of the infrared radiation that is leaving the body, effectively keeping it warmer. That's the same effect of greenhouse gases.

Let's imagine an atmosphere with no greenhouse gases. The radiation balance would look like this:

In this case the equilibrium temperature of Earth would be that on which the outgoing energy is equal to the incoming energy. That equilibrium would happen when the Earth's surface is at -18 °C, because at that temperature (according to Stefan-Boltzmann law that say that emitted energy $=\sigma T^4$), in average,  the black body radiation of Earth's (working day and night) would be powerful enough to equal the amount of energy we receive from the Sun during the day. So in this scenario Earth's mean temperature would be a freezing -18°C (like in the Moon).

But thankfully we have greenhouse gases, and the actual radiation balance of Earth looks more like this:

Here, half of the energy radiated by the surface is sent back to the surface by greenhouse gases (as a survival blanket does). This effect (greenhouse effect) warms up the surface. And it will warm the surface up until it emits enough energy such that the half of it that can actually escape to space is enough to equal the incoming radiation and reestablish the balance. Does that make sense?

In this simplified scenario that balance would happen at a nice and warm 30°C. Now, if we have too much geenhouse gases, this heating effect will overshoot and we will be too hot. That's what have people worried about: we are putting too many "blankets" on Earth.

Foot notes

1.- As a Chemist you might be interested that this infrared absorption capacity is related to the asymmetry of the CO$_2$ molecule and it's associated vibrational modes).


Why does the frost depth increase when the surface temperature warms up? We've had an unusual winter this year, with a late cold snap that is causing people's underground water lines to freeze. Now that the weather has warmed up quite a bit, even more people's lines are freezing, because the frost is being pushed down even deeper by the thawing ground above it.

What causes this phenomenon? Why does the frost not simply thaw from top to bottom after it warms up? Why does it continue to go deeper?

That's is due to the slow diffusion of heat into the ground. Unlike a liquid, pieces of soil can't move around, therefore, in the absence of liquid water, heat can only be transferred by conduction, a process that follows the diffusion equations and it is very slow.

This means that if there is a heat wave, or a cold snap, their effect will reach deep layers of the soil with a delay, the deeper the longer the delay and the more dampened the wave will arrive.

This figure shows a heat wave in the soil

(figure from Soil Temperature at ScienceDirect)

As you can see, the plot shows that there was a peak in temperature of about 27°C at the surface (0m) at time t=6h, but that peak in temperature slowly diffused downwards, such that at a depth of 0.2 m, the peak happened at time t=8h reaching only about 23°C, and at a depth of 0.4 m it arrived even later, at about t=18h and reached only 21°C.

In you case, what is happening that the cold snap is still "traveling" down the ground.

An alternative way to understand this, is that the cold snap cooled the ground so that a layer below the surface can be now at, let's say -5°C, and it is on top of a deeper layer at +1°C, where the water pipe is located. What that deeper layer feels is not what happens in the surface, that is nice and warm, it feels the temperature of the layer right on top of it, that is still very cold. So that deeper layer will cool down and eventually freeze. Freezing as well  the water line with it.

That said, and to address some great comments. The current freezing of underground water lines responds to a past forcing. Therefore, it have nothing to do with current weather and is not the thawing ground what pushes the frost down. It is just the normal curse of events in the propagation of a cold/hot wave down into the ground.


To what extent do the levels of UVA, UVB and UVC radiations on the earth surface increase during solar flares? To what extent do the levels of UVA, UVB and UVC radiations on the earth surface increase during solar flares?

During a powerful solar flare the amount of x-ray radiation can increase up to 110% in the boundry layer of the atmosphere/space,very little of this will reach the earths surface but it can be measured from high flying planes.

UVC is stopped by the upper layer of the atmosphere so this will never reach the ground,It might be possible to measure some UVC in antarctica because of the ozone hole but it is very weak so one will need special equipment to measure it.

UVB will change very little during a solar flare and only in the shortest wavelenght of the UVB spectrum will additional radiation be measurable.

UVA radiation will not change at ground level.

During a solar flare only the shorter wavelenghts of the electromagnetic spectrum will be affected,hard x-rays the most and the longer wavelenghts will be less affected.

source https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005JA011507

source for more detailed information https://en.wikipedia.org/wiki/Ultraviolet

i do not have the source for this picture but i think it is free to use.


Can I use diamonds as fossil fuel? Aside from cultural implications (correct me if I'm wrong but artificial diamonds are not so hard to obtain, right?) diamonds are pure carbon and are more unstable than graphite. So, why not use diamonds as fuel?

My approach: steel melts at 1500°C at least (and there are better steel that melt at higher temperatures). It is pretty high compared with diamond combustion temperature that is just 800°C and once you get to that point combustion will generate enough energy to burn diamond itself. So you can burn it in a steel piston.

Ok, I admit 800°C is pretty high compared with paper and wood (233–400°C) but it is a clean combustion (you obtain only CO2, assuming a constant oxygen input). From this point of view hydrogen is the only competitor but it rise to 500°C, that is not little.

So, what is the practical limitation in the use of diamonds as fossil fuel?

Diamonds are expensive. Really expensive. Even "cheap" synthetic diamonds are orders of magnitude more expensive than conventional fossil fuel. By using them as fuel, you will increase demand, thus increasing their price even more. And synthetic diamonds have to be made somehow, and you need energy for that.
Diamonds burn, but they don't burn well. For example, look at this video of diamonds burning in pure oxygen. The burning sustains for about a minute after the heat source is removed, but then it stops. So then, you need to apply a constant source of heat, and this requires energy. You will probably have to put in more energy than you get from the combustion of diamonds. Kinetically, diamonds just don't burn as well as other things with carbon (like fuel or wood or coal).
One of your arguments is that diamonds burn "cleanly" (let's not forget that CO2 is a pollutant as well). Burning of natural gas emits only CO2 and H2O, so it's a much better alternative when pollution is a consideration.
Diamonds are so much more useful for other things. Don't waste diamonds on energy production!


The youngest and oldest source rock for hydrocarbons in economic quantities Most famous and productive source rocks for hydrocarbons are Paleozoic or Mesozoic, but there are also examples from the Neogene. Time is needed for the rock to reach the right depth and temperature for hydrocarbon generation. Younger formations are typically in an active tectonic setting; old source rock risks becoming over-matured.

What are the youngest and oldest source rocks that are generating hydrocarbons in economic quantities today?

According "The youngest natural oil on earth" Doklady Chemistry vol. 438, pages 144-147:

Prior to this paper, it was known that oil of the Guaymas basin is from young sediments and is 5000 years old.

However, their work shows that oil in the Kamchatka volcanic area is "less than 50 years old".  Oil is shown through carbon dating to have formed between 1962 and 1973.

At the opposite extreme, this 1986 New York times article reports:

  A team of geologists working for the Australian Government's Bureau of Mineral Resources reports in the journal Nature that it has discovered oil formed from the decayed remains of organisms that lived 1.4 billion years ago, when the earth was young. After the group drilled a 1,100-foot-deep test hole beneath the McArthur Basin in northern Australia, the oldest oil of its kind ever found bubbled to the surface.

Tiny amounts of oil as old as 3.2 billion years have been found more recently.


Temperature of the earth What are the main factors that contribute to the temperature fluctuations/cycles of a location? Is the earth's temperature cycle dictated mainly by the temperature cycle of the ocean? How does the ocean's heat storage affect the temperature of the atmosphere and thus the seasonality that we human's feel?

The oceans have a huge effect on the climate and temperature of the various regions of the world. Climates fall into two categories: marine and continental. In Britain we have a marine climate, which protects us from the extremes of the European continental climate. Our winters are milder, our summers cooler, because of the proximity of the Atlantic and the warm Gulf Stream coming up from the Gulf of Mexico. It also gives us a damper climate, with more mist and rain. This moderating effect and increased dampness and humidity is characteristic of marine climates. In the S.Pacific they have El Nino, a strange subtropical current which reverses every ten years or so, causing droughts and other adverse effects for the countries of the region.

The Galapagos archipelago is another example of a marine climate, in this case cooled by the Humboldt Current coming up the coast of Chile from the Southern Ocean. The Galapagos Islands are on the equator, yet the climate is only subtropical and the waters are cool enough for penguins to thrive. These cold currents, like the Benguela current coming up the west coast of S.Africa, are rich in nutrients and in fish. The Benguela Current has strange effects on the climate of Namibia.


How do geologists measure green house gass emmissions from large regions I read here that volcanoes release about "0.6 billion metric tons of carbon dioxide per year". I wonder though, how scientists can estimate the emissions from large regions with geological features that release carbon dioxide and methane. For example, here in the Czech Republic, we have countless springs with carbonated water. Some have only a few bubbles while others shoot out like a freshly opened bottle of sparkling wine. Since the Czech republic has an area of 78 870km² it seems impossible that geologists could ever count and measure the output from all these springs, especially since the vast majority of them probably seep their carbon into underground caves, which then leak into the surface soil and eventually the atmosphere. It seems to me, that there is probably carbon seeping into the atmosphere from every m² of land in the country, and at wildly varying rates. What kind of methods to geologist use to get even a rough estimate? Do they try like covering the ground with 100m² tarps and try gathering the carbon that comes up? I'm just guessing here...

Tracking atmospheric species over the entire planet really is comparatively easy via satellites, compared to plastering entire swathes of land with measurement stations.
You make one infrared image from an imaging satellite at the right wavelength and you got the entire country covered. The right wavelength to choose has to be

originating from the molecule in emission at the right altitude and
be optically thin. If you know your emission is optically thin, the flux in your image is directly proportional to the mass that is emitting this flux. If it's not optically thin, complications apply, but the idea is the same.

An example of the observational fleet that NASA has in orbit can be found here (scroll down the page). There it also becomes clear, that various instruments are needed to cover the entire range of interesting atmospheric species, which necessitates a number of observation platforms/satellites.


What does it take to make a diamond? I have constantly been told through my K-12 Education that diamonds are a product of carbon, time, pressure, and temperature. If this is true, what is stopping someone from building a high-pressure, high-temperature system and dumping graphite in and making millions of diamonds?

It seems my exact strategy is listed here: https://en.wikipedia.org/wiki/Synthetic_diamond#High_pressure.2C_high_temperature . But this is under the article "synthetic diamond." How can one tell a difference between a synthetic diamond and a "real" diamond? What is stopping someone from making these HPHT machines and making tons of money?

Update: I watched the BBC special on synthetic diamonds (https://www.youtube.com/watch?v=5d2WebdMpBQ) and De Beers shows you can tell the difference between synthetic and real diamonds by their reaction to UV radiation. I am still interested in how I can make a DIY diamond if anyone has details on that. And to make this more on topic, how best I can simulate the Earth's formation of diamond? Why is the Earth's formation of diamond different from these HPHT and CVD diamonds?

what is stopping someone from building a high-pressure, high-temperature system and dumping graphite in and making millions of diamonds?

  What is stopping someone from making these HPHT machines and making tons of money?

No one, and it is done. First of all, synthetic diamonds have been out on the market for quite some time now and it's a well established business. You've heard of diamond saws, diamond drills, diamond polishing paste and all kinds of other diamond products. So people make them, sell them, and make money.

It's not even that hard: In our own lab we got a machine that can make diamonds (among other HPHT) stuff. Someone once even put some peanut butter and made diamonds out of it (micrometre sized, though). Here's a picture of the machine (called a piston cylinder):

Here's a picture of how this might look:

Note that this one is not from our lab, but it's a really nice picture of how this stuff looks when you make it in such machines. This one's from this paper. The diamond crystals are about 30 μm across. Not something you'd put on a ring.

The big question is how do you make gemstone quality diamonds. Chemical vapour deposition seems like the most successful method. There are other methods, but it's pretty easy to distinguish them from natural diamonds (example). It is still quite hard to do it: it's not something anyone can just do in their backyard. With technology it becomes easier though. Here comes the question of regulation. Gemesis, one of the companies that makes them, engraves a serial number using laser on each synthetic gem-quality diamond they make. But what about some evil diamond makers who want to simulate natural stones? As with any other synthetic material, there are imperfections that are different from imperfections found in natural stones.  Moreover, each mine or region where diamonds come from has a different fingerprint (they use that to trace blood diamonds). There are methods to analyse the diamonds to detect this. UV and IR spectroscopy, laser ablation, isotope analysis, cathodoluminescence and others. Some are easier and cheaper than others.

So you can't just make up impurities to say "look it's natural", they have to be consistent with a specific diamond source you're trying to imitate. And that's - not very easy. Likely impossible with today's technology.


Why does a subduction zone produce a serpentinization diapir rather than volcanism? The classic Troodos Ophiolite in Cyprus has been uplifted by a 'serpentinization event'. Upper mantle (peridotite) has been serpentinized creating a buoyant diapir. This has uplifted the ocean crust sufficiently for it to be thrust over continental crust (underlying continental crust has been inferred from gravitational surveys).

The last sentence of the abstract of "Tertiary uplift history of the Troodos massif, Cyprus", AHF Robertson says:

  The dominant driving force may have involved the liberation of water
  from a subduction zone dipping northward beneath Cyprus.

This makes sense - serpentinization is the alteration process of olivine -> serpentine in the presence of water. And, as we know, subduction slabs release fluids (primarily water) into the overlying mantle wedge.

These fluids usually promote partial melting leading to andesite arc volcanism. However, Cyprus has this big serpentinite diapir instead of volcanism. Why?

What causes the fluids from the subducting slab to occasionally result in serpentinization of the mantle wedge instead of partial melting?

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

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


The Size Hierarchy of a Landmass If we judge a hierarchy of a landmass by size, here is what, in my knowledge, it would have looked like, from largest to smallest:

Continent

Subcontinent

???

Island

Islet

In regards to size, is there a transition of landmasses between (sub)continent and island?

Caveat: I'm answering this in a popular context. There may be more technical definitions, which I'd be interested in hearing about.

It seems to be generally accepted that continents are not, themselves, islands. This is a common confusion in pub quiz questions, where people argue over whether the largest island in the world is Greenland, Australia, or (if somebody especially pedantic is around) the combined landmass of Europe, Asia and Africa.

So the question comes down to "what is a continent"? It's more of a political / historical / geographical unit than a topological one. If continents were demarcated by coastlines, then Europe, Africa and Asia would all be one. Additionally, many small mid-ocean islands, which are not on continental shelves, would end up being continents.
It's tempting to think of continents as relating to tectonic plates, but even if we disregard mid-continent faults and "complicated" areas, Europe and Asia are hard to separate.... and the 6 continents as currently thought of were pretty much set before plate tectonics was advanced as a theory. Wikipedia has an interesting article on historic boundaries between continents; the one between Europe and Asia is especially ambiguous.

I'm not aware of any definition of "subcontinent", and have never heard this term used for anything other than the area around India, so I suspect this is also a political and historical term.

So to answer the question: No, there is not a size-based distinction between islands and continents, although the smallest continent is indeed bigger than the largest island. The definition of an island would seem to be "a landmass surrounded by water that is not thought of as a continent".

As for "islet", again, I'm not aware of any formal definition. However, the UN Convention on the Law of the Sea does distinguish between islands and "rocks", where the latter are islets that are too small to be habitable. This is an important definition, because unlike islands, rocks are not considered when defining a nation's exclusive economic zone (the area in which they may control who fishes, drills for oil, and so forth).


Unusual light at sunset? This evening in Boston there was quite a spectacular sunset. However, many people noticed this odd vertical "stripe" in the west.

Has anyone seen this before?

It looked as though it was projected on the clouds from somewhere near where I was standing (as though a reflection of the sun). This would make sense (the city of Boston, with it's tall glass towers, was right next to us), but could the reflection really reach so far and be described so clearly on the clouds?

What you saw was a crepuscular ray. They occur when the Sun's rays stream through gaps in clouds. Such rays tend to appear as parallel columns.

If you look closely at the picture you took, there is a subtle angled crepuscular column above the short building near the middle of the picture.


Calculate the Top of a Cloud So, I'm trying to find the Height of the Top of a cloud from basic weather information (ie. temperature on the ground, altitude, pressure, humidity, dew point, etc.)

I'm looking for an equation that will give or at least estimate the cloud top. Doing some searching, I've found this equation:

  The Cloud top height can be calculated by the formula
           h [km] = -8 * LOGS (cloud_top_press [hPa]/1013).

From this site. My question is, will this equation produce the height of a cloud and what does "LOGS" mean in this equation?

The formula you found comes from the barometric formula. It assumes a hydrostatic atmosphere (no vertical accelerations), a constant temperature with height (or a mean temperature) and uses the ideal gas law:

$$h= -\frac{RT}{g} \cdot \log \frac{p}{p_{sfc}}
$$
where h is height above ground, R is the ideal gas constant, T is the mean temperature, g is the gravitational constant, p is the pressure of the cloud top in your case and $p_{sfc}$ is surface pressure (not reduced)

The first factor comes down to a value of $-8$km if $T \approx 273$ K. This value is also known as scale height. $p_{sfc}$ is approx. 1013 hPa if you're at sea level.

So LOGS would most probably mean the natural logarithm.

I don't think there is a simple equation for the cloud top height from ground observations because e.g. how high a cumulus grows depends on the temperature of the surrounding air.

Cloud base height and cloud top height are two totally different things. The cloud base height formula does not depend on the on the upper air temperature.

Whether a thermal (which evolves into the cloud later on) reaches its cloud base or not, is not sure. As long as it's warmer than its surroundings, it rises. The same for the cloud: It rises up as long as it is warmer than its surroundings. You may know what's the temperature of the cloud at each height, but how cold the air at, say 15,000 ft is, varies a lot.


Average Aragonite:Calcite ratio in biogenic CaCO3 in the oceans I wonder what the average ratio between aragonite and calcite is during the precipitation of biogenic calcium carbonate in seawater. I know some species are aragonite-favouring and some perfer using calcite. I also know that aragonite is about 50% more soluble than calcite, and therefore less common.

If any of you would know a (coarse) average between these two (with references if possible)?

After some more research, the conclusion is that aragonite is somewhere between 10 and 50% of total CaCO3 production:

Aragonite, calcite-Mg and calcite are the 3 main species of marine CaCO3. Aragonite is unlikely to be a major component of the total CaCO3 flux (Berelson, 2007), though the exact contribution is uncertain and falls in the range of 10-50% of global CaCO3 production (Gangstø, 2008). Minimum values of 12% (Berner and Honjo, 1981) and 13% (Fabry and Deuser, 1992) have been reported based on sediment traps. Calcite-Mg contributes ~8% (Fabry and Deuser, 1992) to 24% (Morse, 2006) to CaCO3 production. The sediment trap-based contribution of aragonite of ~12% is thought to be lower than the actual contribution of aragonite to CaCO3 production because aragonite is about 1.5 times more soluble than calcite and therefore more depleted than calcite in the sediment trap records.

An educated guess of me would therefore be ~20% aragonite, ~10% calcite-Mg and ~70% calcite globally on average.


Why is the core of the earth thought to be iron rather than metallic oxygen? The pressure at the top of the core is about 1 million bar. That should be enough to create metallic oxygen. So why is the core thought to be iron rather than just metallic oxygen?

1) The density of the core approximately matches that of high pressure Ni-Fe, but is way denser than solid oxygen (roughly 1.4).

2) If the core was oxygen then the overall elemental abundance of the Earth would be nothing like the elemental abundance of anything else in the Solar System (or anywhere else in the known universe).

3) The elemental abundance in meteorites, thought to be left-overs of the original accretionary disk, closely matches Earth with an Fe core - doesn't resemble in any way any supposed metallic oxygen core.

4) The seismic data works well if we assume a liquid / solid iron core. If the core was solid oxygen, then the P-wave shadow would be configured completely differently, because seismic refraction at the core-mantle boundary would bend to make shallower refracted waves, not deeper.

5) A metallic oxygen core would could not explain the Earth's magnetism.

6) It would be bizarre for an oxygen core to have evolved when there are much heavier elements in the mantle.


What is this strange formation near Râmnicu Vâlcea? So I was browsing Google Earth the other day and I found this strange formation near Râmnicu Vâlcea, at about 45°07'N 24°16'E

It's an almost circular region, about 40 km in diameter which to my eyes looks like a multi ringed impact crater, but then again it's near a mountain chain so it could be just some random feature created by the converging tectonic plates. But what could cause the hills to be arranged in this strange manner?

Elevation profiles

North-South:

East-West

My guess is streams fed by mountains that have been tectonically compressed and is undergoing some rotation. Near Italy are 3 tectonic boundary. Convergent, transform, and divergent. Due to the plate motion of the Eurasian plate, to the African plate, and the Arabian plate, it is causing compression and what I can describe as some rotation the land. It appears to be an involved relationship. I used Google Earth to create this map:

I hope I helped or gave you a direction to look. As you can see by the arrows, there are areas of convergence that are oblique and related in a way, that his geologic feature is not at all impossible.

Other sources

Google search
Earthquakes in Italy


Is there a differential angular rotation on Earth? I asked a question about solar day difference between two latitudes on the same longitude here on the Earth surface. The answer was clear due to constant angular rotation time is the same. Tangential speed is different in the two points though. Then I came up with another question here that was the reason for my previous question. Gaseous bodies like the sun have different angular rotations from the equator to the poles. Others may still argue that the Earth is rocky and solid but we have a fluid atmosphere  that can have differential rotational impact on Earth's rotation. So, my question is anyone aware of the differential angular rotation on Earth as a result of solid earth and fluid atmosphere interaction? If so, what is its latitudinal gradient?

The Earth's atmosphere rotates at more or less the same rate as the Earth as a whole. Note my use of "more or less". That does not mean exactly the same.

The air does rotate pretty much at the same rate as the Earth near the equator. These are the doldrums. Getting stuck in the doldrums was a big problem for ships in the days when ships used sails.

Moving northward or southward, the air near the surface of the Earth tends to rotate slightly less than the solid Earth's rotation rate. These are the trade winds. Sailing ships used the trade winds to go from Europe to the western hemisphere. The coriolis effect means that the trade winds stop at about 30° north and south latitude. These are the horse latitudes, another area where the atmosphere pretty much does rotates with the Earth. Sailing ships had problems here, too.

Moving even further north in the northern hemisphere / south in the southern hemisphere brings one to the region where surface winds blow predominantly from the west, so faster than the Earth's rotation rate. Sailing ships used these winds to return to Europe from the western hemisphere. Finally, even further from the equator (at roughly 60° north or south latitude), yet another transition occurs. This is the polar cell.

  So, my question is anyone aware of the differential angular rotation on Earth as a result of solid earth and fluid atmosphere interaction?

I mentioned sailing ships. People have been aware of how the winds blow locally since sailing started. People probably started sailing before they started writing. The Portuguese discovered the importance of the trade winds before Columbus sailed to the Americas.

So far I've only written about winds near the surface. The winds are different well above the surface. There are jet streams at the boundaries between where the trade winds and prevailing westerlies flow and at the boundaries of the polar cells.

The Japanese discovered these jet streams during World War II and used this to their advantage. They launched fire balloons from near Tokyo to drop a bomb on the US about three days later. Nowadays, we use the jet streams for more peaceful purposes.


What do the researchers in Antarctica wear if they must go outside during winter? The Vostok station can observe temperatures as low -90 C during winter.  Human skin gets frozen wounds on the spot on direct contact with such cold air and precautions must be made to avoid open exposed skin during outdoor operations at these temperatures.

I don't thing going outside is possible, but also I think that they must have some solution in case going outside can't be avoided. Especially because the possible problems of heating and similar infrastructure are in their case life-threating consequences.

What do they wear? I think something similar to a space suit, but instead of compression it contains heated internal atmosphere, should work. Do they have something like this?

The US Antarctica Program publishes information about the required extreme cold weather gear. It's provided by the government and has to be returned after your deployment ends. The list is here along with other information. Here's another document that discuses clothing. I've extracted the list below.

Jackets
1 each GOR-TEX® wind jacket
1 each Helly Hansen® rain jacket
1 each polar fleece jacket
1 each Carhartt® jacket optional
1 each Carhartt vest optional
1 each red down parka optional

Pants
1 each GOR-TEX bib coveralls for grantees only
1 each Helly Hansen rain pants
1 each polar fleece pants
1 each Carhartt bib coveralls optional
1 each Carhartt pants

Thermal
2 each thermal top
2 each thermal bottoms

Hat and Neck
1 each Balaklava
1 each neck gaiter
1 each polar fleece cap

Gloves
1 pair leather work gloves (unlined)
1 pair leather work gloves (insulated)
1 pair rubber gloves (with liners)
1 pair GOR-TEX mitts
1 pair polypropylene gloves
1 pair wool gloves

Footwear
2 pair tube socks
1 pair snow boots (Sorel™ or LaCrosse®)
1 each fisherman boots (rubber or steel-toed) optional

Miscellaneous
1 pair goggles
1 each duffle bag


What causes these banded clouds? A set of banded clouds can be seen in MODIS imagery during several days in January and February over the Gulf of Maine. They tend to occur with very cold winds from the NW following storms.

There are several similar examples: 17 January and 6, 20 and 24 February

What causes these features? Why are they of that size?

These are most certainly boundary layer rolls and not gravity waves. While there exists a visual similarity between the two phenomena, and both may exist in similar atmospheric conditions, they can be distinguished by two key characteristics:

Unlike gravity waves, which develop in the downwave direction (perpendicular to the crest), boundary layer rolls develop downwind (parallel to the apparent "crest");
Unlike gravity waves, whose crest propagates with intrinsic phase speed (related to interfacial density difference and gravitational acceleration) and whose energy propagates with intrinsic group velocity, the large-scale structure of boundary layer rolls is quasi-stationary.

Despite the visual resemblence between gravity waves and boundary layer rolls and possible interactions reported in the literature, it is my opinion that stating that boundary layer rolls are a form of gravity waves is incorrect and misleading.

It is clear based on the satellite picture that the wind is northwesterly because of the distance from land that the convection occurs over the ocean, which is approximately 50 km from the coast uniformly in the SW-NE direction. As the cold and dry air moves over (relatively) warm water, air rises and saturates with water vapor, forming clouds downwind from the coast. For these to be gravity waves, wind would have to be perpendicular to the wave crest, i.e.  in the SW-NE direction, which is not the case.

Now that we agree that the wind is northwesterly, we see that the convective lines, the so-called "cloud streets", are aligned with the wind. They are long rolls of counter-rotating air that stretch the depth of the atmospheric boundary layer in height (~1 km) and are of width between 1 and 10 km. Water vapor condensation and cloud formation happens on the upward side of the roll, and evaporation happens on the downward side of the roll. Notice that in this particular example, they start off very thin, and become wider downwind. While these rolls are still not very well understood, the main mechanism for formation is likely to be a combination of rotation and friction (Ekman spirals) in presence of thermally unstable bottom boundary layer, and stable boundary layer cap, thus constraining the circulation into organized cells.

A review paper on boundary layer rolls by Etling and Brown (1993) can be found here.


Equator and Hours of Daylight Since the equator is closest to the sun, would it have more daylight hours compared to, say, the Tropic of Cancer?

I am using an example, however, would it be true if the farther one is from the equator, the less daylight hours?

The Earth's equator is about 0.006% closer to the sun than the Earth's mean spin axis, so the effect of proximity to the sun on daylight hours is so small that my calculator - which has a register of 10 significant figures - can't even discern any difference. A rough back of an envelope hand calculation indicates less than a millionth of a second difference in daylight hours between equator and the Earth's mean spin axis. So the effect on the weather would be indeterminate, and vastly less than caused by orbital variations, solar storms, fluctuations in solar luminosity, seasonal cloud variation, etc.


What behaviour does an ice sheet exhibit in crossing a cliff? I've not come up against clear explanations when trying to think about a situation where an ice sheet is advancing and comes up against a cliff. What happens next? How does the ice sheet cross the cliff? Does the base get stuck?

Does it create some landforms into the original cliff-face? The forcing that would apply should be very strong (and perhaps it will continue to apply over a very long time period). Also, how does the flow of the glacier happen in these locations? Will the cliff-face be exposed to liquid water flow throughout the period that the ice sheet has covered it, and won't this cause very rapid erosion of the cliff-surface?

From a geologic perspective, this would have been happening across the Baltic Clint though most of these cliffs are in the range of 15–25 meters—in other words, relatively small for an ice sheet to cross. However, there are also some exposed (presently above-water) parts which are slightly higher.

I've put a small map (20m DEM; generally one front of cliffs by the modern coastline and then occasional ones further inland) below which illustrates where this would have been happening during the last glaciation period based on the example of Tallinn, Estonia, though by no means is this the only place where such a situation would have occurred.

Of course, the DEM has further problems, including that ~20k years of isostatic uplift has raised these a fair bit since so the actual obstacle that the ice sheets met should have been smaller (perhaps was: are the remnant limestone mounds the part that didn't get washed away?).

I also find the sentence (from the above Wikipedia page) weird:

  However it is not known to which degree the Baltic Klint originated in postglacial time or if it evolved from cliff-like forms sculpted by the Fennoscandian Ice Sheet. In Gotland 20th century cliff retreat rates have been estimated at 0.15 to 0.78 cm/year.

I don't see how the ice sheet's advance/retreat could have caused such a cliff if the limestone plateau did not exist there beforehand.

I'm not expecting an answer based on this location specifically, but rather perhaps there are some imaged cliff-faces in Greenland/Antarctica where this behaviour has been recorded presently? I tried some searches and found this which seems relevant but I wasn't able to access the full text.

This depends on a few things.

If the cliff is small but widespread or the glacier is a huge, the glacier flows uphill until the cliff is gone.

If the cliff is large the glacier flows around it, is diverted by it, or piles up behind it depending on the land around it.

Glaciers are pushed along by back pressure, like toothpaste out of a tube. As long as there is enough accumulation the toe of a glacier can be driven uphill, but like anything else glaciers take the path of least resistance so if it can be diverted by the cliff it will.

Note that the forces on the cliff will be huge, and exactly the forces rock is weak against, so the cliff is over topped it will be stripped away very quickly.


Why does Earth have two kinds of crusts? Why does Earth have two clearly differentiated kinds of crusts, namely continental and oceanic? How did they differentiate initially and why don't they get mixed up over time?

First they do get slowly mixed at the plate boundaries but the mixing is minimal compared to the amount of crust there is. They do not mix easily since they have different densities, they tend to separate out when melted so most mixing is done in their solid states.

An easy way to think of it is there is not enough continental crust to cover the entire planet so oceanic crust is filling in the gaps. A better analogy is to think of continental crust as scum on pond (or foam in a tub). The uppermost portion of the mantle and oceanic crust are basically the same thing, oceanic crust is just colder, while continental crust is different in composition it is lighter and floats on top but as I said there is not enough of it to cover the entire planet so like scum on a pond it forms clumps and gets pushed around by the underlying currents. And just like pond scum they separate out because they have different densities than the "water" so they collect on the surface.


Why does vertical diffusivity increase with depth in the ocean? In Talley et al.'s Descriptive Physical Oceanography, figure S7.4, it seems that vertical Eddy diffusivity increases with depth between 0 and 30 degrees latitude. Why is this? I thought that diffusivity increases with increasing temperature, but here the opposite seems to be true.

I think you are confusing eddy diffusivity with molecular diffusivity. Whereas the latter increases with temperature, for the former there is no such relationship. Eddy diffusivity describes momentum transport due to eddies. The strength of the eddy diffusivity increases with decreasing buoyancy frequency, which is the case, when moving from the bottom of the mixed layer further downwards in the ocean.


Why is there so much more silicon than carbon in the Earth's crust? Some arguments I've seen about the viability of silicon-based life involve the relative abundance of silicon vs carbon. In the universe as a whole, there's a lot more carbon than silicon around. Yet, on Earth, silicon is far more common. So how did this happen? This question partially answers why there seems to be a lot of silicon in the Earth's crust, but it doesn't explain where all the carbon went.

So where did it go?

So where did it go?

Carbon was never there (or here) to begin with. You need to look at this from the opposite way. By asking "where did it go" you assuming the Earth was here first, with carbon, and then the carbon was removed somehow. But, Earth formed from a gaseous solar nebula that had all the elements.

As the Earth-forming materials started condensing, they consisted primarily of the refractory elements (i.e., elements that form compounds with high melting and boiling points). The volatile elements (i.e., elements that form compounds that you would mostly recognise as gas or liquid).

These volatile elements never accreted to Earth in any significant amounts. They "boiled" away. They were removed by the solar wind farther away. Carbon was mostly in CO, CH4, CO2, etc. These are volatile compounds that never accreted to the Earth, and by the time Earth was large enough to have a gravity to sustain a proper atmosphere, the carbon was all gone.

It's not only carbon. Neon is one of the most abundant elements in the solar system, but there's almost none on Earth. Nitrogen - we only have it in the atmosphere, which is a negligible component of Earth's total mass. Same with hydrogen. Just a small crust of ocean on the surface.

That's why Earth is made of Si, Al, Mg, Fe and Ca oxides. Oxygen bonded to those elements makes very refractory solid minerals.

Further reading

https://en.wikipedia.org/wiki/Frost_line_(astrophysics)

https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Earth


Considering the thin piece of material on the surface of Mars in the image below, is there anything like it on Earth? The above is a magnified part of the original image below captured by the Curiosity rover on Mars on sol 1729 (June 17, 2017).
 From the added information with that raw image it can be estimated that the distance between the lens and the target was about 14 cm.

Below another image of the thin piece with surroundings in the sunshine.
Click (or double click) on the image for magnification.

Asking about the chemical composition of this piece of material on space exploration SE, it appeared from the answers that most likely it is CaSO$_4$, perhaps the hydrated form gypsum.
I've seen many other raw images from Mars, but not anything like this.

What could this thin piece of material be, does it resemble anything on Earth ?

What you can see in the bottom picture is sandstone/mudstone/claystone.

If you look at the bottom picture top right you can see a thin rock that has split off, this is how a rock splits after it has been heated and then suddenly gets cooled down as it does on Mars when the Sun goes down.

On Earth the change in temperature is too slow for this to happen in nature, but you can see this if a fire has been burning on top of a rock/stone and it has been rapidly cooled down.

This is how mining was done before explosives where invented, heating up the rock until it is "glowing" hot and then throwing water on the rock to suddenly cool it down so it fractures.


Have the oceans dissolved water vapour? The oceans have dissolved gases as N2 or O2.

Henry's law establishes there is an equilibrium between the atmospheric concentration of a gas and its concentration in the ocean.

The atmosphere has H2O(g).

Is there H2O(g) dissolved in the oceans or Henry's law does not apply because the water is also H2O?

The answer is no, yes and then, perhaps, no.

No: water vapour is not "dissolved" in the oceans, rather it becomes part of the oceans through a phase change from vapour to liquid (possibly via an intermediary stage as ice). The process of "dissolving" refers to a substance entering a "solution", which is defined as stable mixture of two or more substances in which the state of the solution is determined, generally, by the solvent (the liquid water in this case). For example, see the wikipedia article on "solution". When water vapour enters the ocean, it is just adding to the volume of liquid water. Water vapour bubbles suspended in the ocean is another issue. When a gas is dissolved in a liquid, it ceases to be a gas. So we do not have "O2 gas" dissolved in the ocean, we have O2, which is a gas in the atmosphere, present in the ocean as a solute.

Yes: on the other hand, there is continuous exchange of water between the atmosphere and the ocean: sometimes water passes from the atmosphere to the ocean, sometimes the other way around, depending on the weather conditions. This is nothing to do the the process of being "dissolved", but, if the question is motivated by an interest in the exchange of compounds between the atmosphere and the ocean, this cycling of water between the two, which is described more below, will be of interest.

Finally, perhaps, no: the water vapour in the atmosphere is not in equilibrium with liquid water in the ocean (see wikipeadia foe discussion of equilibrium between liquid and gas phases). Generally speaking, the partial pressure of water vapour above the ocean will be below equilibrium, so there will be an evaporative flux of water from the ocean into the atmosphere. The steady evaporation of water from the surface of the oceans is balanced by precipitation (rain, sleet and snow) out of the atmosphere which falls on the oceans or falls on land and then drains into the oceans (see The Fundamentals of the Water Cycle).


How Can We Establish Precisely What Earth's Core is Made Of? The consensus view is that that the Earths core is composed mainly of iron alloyed with about 10 percent nickel and traces of other heavy metals, but I have seen at least one account which says it is partly iron sulphide. Has the iron sulphide theory been discredited, or is it a view still held by some geologists? There is a recent theory that about 5 percent of the core is composed of silicon. How valid is this, and will we ever be able to establish more precisely what the core is made of?

We know the density of the core from seismology.
We also know the density of pure iron at given pressure (P) and temperature (T).
From these two, people have long noticed that there is a discrepancy: the actual core is lighter than a theoretical core made of pure iron. This is known as the Core Density Deficit (CDD). To explain this CDD, we need to add light elements in the core composition. There are many candidates, such as sulphur, carbon, silicon, oxygen, etc.

This is actually needed by geochemists, who try to relate the Earth's composition to that of chondrite. They find that the Bulk Silicate Earth (BSE = crust + mantle) is depleted in some elements compared to the chondritic reference, and have to invoke a hidden reservoir to explain this. For some elements, this reservoir could be the core.

To further constrain this, petrologists run some high-P/high-T experiments to see the behaviour of elements during the Earth differentiation. Some elements are said to be lithophile, meaning they will stay in the BSE, while other elements are considered siderophile, hence should have joined the metal phase during segregation of the core. The problem is that some experiments disagree with others, as the behaviour of a given element can change depending on the conditions. For instance, niobium and tantalum are considered lithophile, but can be siderophile in reduced conditions.

I'm afraid the bottom-line of all this is: there is no simple answer to this question...


Is this platinum ore? Was found in central Mexico. It's very metallic, shiny, showing some streaks of gold and quartz.

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

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

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

Layered chromtite ore looks significantly different.  Reference.

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