Quickly breeding oysters to combat oceanic pollution? I've been doing some wikipedia binging and it's come to my realization that it may be in the Earth's best interest to raise the world oyster population as quickly as possible. The basis for this is for several reasons:

  [They hold] promise for relieving pressure on land-based protein sources.

also,

  [They] provide shoreline protection and sediment stabilization,
  nutrient cycling and sequestration, and habitat for other organisms.

and most importantly:

  sources state that a single oyster can filter 24–96 liters a day (1–4 liters per hour). With 750,000 oysters in one acre, 18,000,000-72,000,000 liters of water can be filtered, removing most forms of particulate matter suspended in the water column.
  (Source)

What I'm curious about, however, is the potential downstream impacts of the overpopulation of oysters.
They seem to have so many ecological benefits, I'd like to see if there's a hard detriment to everyone breeding thousands of oysters in their free time to help the ocean.

What I'm particularly concerned about is other filter feeders that may become threatened by a strong prevalence of the oyster population.

To summarize my question; is this a reasonable solution, and what potential risks exist should the world try to greatly increase the oyster populations where they exist currently already?

As @Fred pointed out in the comments, precautions would/should be taken to ensure endemic oysters are used to be as minimally invasive as possible, and responsibly bred for biodiversity to prevent viral catastrophe.

According to @AllInOne from the comments: This is currently what a project in New York City is trying to do.
Their listed goal on wikipedia is to get one billion live oysters in New York Harbor by 2035.

According to their website, they do this because of the following reasons:

  Oysters have a remarkable ability to filter nitrogen pollution from water as they eat. This is a heroic feat, because excessive nitrogen
  triggers algal blooms that deplete the water of oxygen and create
  “dead zones.”
  “Once all but extinct in New York City’s waters, the whales are undeniably back.” –Popular Science Oysters play a key role in
  attracting life. They earn their nickname as “ecosystem engineers”
  because we see biodiversity levels increase dramatically surrounding
  oyster reefs.
  Oyster reefs can help to protect New York City from storm damage—softening the blow of large waves, reducing flooding, and
  preventing erosion.

the website also carries on to state that 1 million pounds of shells have also been recycled as a result of this initiative.

Other comments suggest that in order to prevent invasive species, one would want to do this with oysters that already exist in the region.


What is the error in bathymetric observations in the presence of vegetation? How can we determine the error associated with bathymetric measurements when we survey over submerged vegetation? Let's say we are using single-beam echo-sounder over a patch of Posidonia, what are the expected errors and how can we determine them?

As noted in the comments, this is actually a much more complex question than it might seem at first. Answering fully would require a very involved and technical discussion of single-beam surveying's inherent errors and their causes (water velocity, side slope reflection, highly transmissive hydrocarbon-rich anthropocene silt, and other such complications). I will skip those topics—thankfully, I think—and simply focus on the OP's question of what errors Posidonia sea grass might introduce to a hypothetical singlebeam survey. As such this may be more of a partial answer.

Let's say you're using a singlebeam instrument with a fairly narrow pulse angle, like 3º. (Your vessel should not roll too much with this narrow a beam, but it will give higher resolution). You're surveying over a colony of Posidonia on a flat seabed. Posidonia leaves have a density fairly similar to that of the water column. Depending on the frequency of sound you are surveying with, you may get a ping with a slightly different shape from surveying over an area of "bare ground". This is, at least in theory, due to the slight variation in density between the water column and Posidonia leaf blades causing small amounts of reflection and refraction to the sound wave before it hits the root mat and the top of sediment. Just for imagination's sake, I've included the conceptual "bare ground" model below.

  Behavior of P-waves and S-waves at a impedance change boundary. Image reproduced from Dragoset, B., A historical reflection on reflections, The Leading Edge, 2005, v. 24, p. S46-S71, Box 1.

A good singlebeam acquisition program will allow you to choose the method of bottom tracking. Often these methods are not associated with the first return but rather the "strongest" part of the first return within some specified distance from the last known bottom position. This allows the minimization of error created by, for example, fish swimming in the path of the beam (see image below), and also the weaker first returns of soft vegetation.

  Fish in the water column as seen on a singlebeam survey. A red band indicates the strongest return amplitude. An acquisition program would likely classify the bottom at or near the top of the red band. Image reproduced from the University of New Hampshire Ongoing Education website.

So, if we assume that the acquisition program's bottom tracking capability is acceptable, the errors that Posidonia's leaves introduce will be minuscule, because the leaves do not present a large change in impedance and thus will not reflect much of the beam. You're left with deciding whether or not you want to classify the "bottom" of the water column as Posidonia's root mat, which may be several inches thick in a large colony, or the top of the sediment below. This is where your uncertainty will likely lie. What I don't know, and what may be difficult to figure out without some rather clinical testing, is whether or not the root mat provides a strong-enough first return to trigger the bottom tracking. I suspect it would, but I can't say that with any confidence without looking at a controlled test survey. I imagine companies like Odom and Kongsberg do this regularly and might be able to give you a more specific answer.

Tobbe also correctly notes that lower frequencies won't be affected as much by vegetation as higher frequencies. If you were going to try to run a bathymetric survey over Posidonia—or any area with high concentrations of seafloor plant life—you would want to consider using a device capable of lower frequency surveys...at the cost of diminishing your resolution.


What is the basis for the Geologic Time Scale The Geologic time scale was completed in the mid to late 1800s. What methods were used to date the various subdivisions?

Here is an answer that matches the wording in this question.

Nice summary from http://hyperphysics.phy-astr.gsu.edu

Principles for Relative Dating of Geological Features
From over two hundred years of careful field explorations by geologists, a number of practical principles for determining the relative dates of geologic features have emerged. The assignment of numerical ages to these relative dates had to await the development of radiometric dating.

Law of Superposition**: For sedimentary rocks, each bed is older than the one above it and younger than the one below it.
Principle of Original Horizontality. Layers of sediment are generally deposited in a horizontal position. This is useful even if beds of sedimentary rock have been subsequently tilted.
Principle of cross-cutting relationships. A fault or intrusion is younger than the rocks affected by it.
Inclusions: the rock mass containing the inclusions is older than the rock providing the included material.
Unconformities: interruptions of sedimentation with removal of material by erosion and then a resumption of deposition can place rock strata in contact that have a gap of time and material between them.
Principle of fossil succession: fossil organisms succeed one another in a definite order. The fossils observed help to identify the time period in which the organism lived.

Does anyone know if there a published book that gives a comprehensive history of geologic time scale (looking for more than summary that is presented in countless text books)?


What are some of the strongest theories against the existence of mantle plumes? Among the people I interact with in the geodynamics community, it seems that almost all of us are in full support of the mantle plume theory. What are the strongest arguments against this theory? Is the earth science community not as divided on this subject as some people have led me to believe ?

The best argument I've heard supporting strong skepticism of plumes, if not total dismissal, is that the theory is too flexible. To put it more bluntly, this amounts to saying that it is unfalsifiable and therefore not helpful (in Popper's words, "A theory that explains everything, explains nothing.").

Erik Lundin, a Norwegian geologist, is a fairly vociferous (and sarcastic) proponent of this view. He likes to point out that you can explain almost any tectonic anomaly with plumes. Have a look at his articles The Iceland “Anomaly” – An Outcome of Plate Tectonics and Phanerozoic fold belts and volcanic passive margins: a causal relationship? on Gillian Foulger's site mantleplumes.org — where you'll find lots of other evidence for and against plumes.

My own view is that there seems to be some clear cases of plume-like things being a good explanation for observations — the Hawaiian–Emperor chain comes to mind. And then there's the rest of the infinitely complex earth, with thousands of competing and interacting forces, convection currents being just one.


Why are the Great Lakes not considered a sea? From me looking at maps, excluding the Caspian sea and the Great Lakes, I see these in common for seas and lakes:

Seas

Most are saltwater
Connected to the rest of the ocean via either an isthmus, strait, river, or
gulf
Bigger and deeper than lakes

Lakes

Most are freshwater
Landlocked
Not nearly as big or deep as any sea

So back to these 2 bodies of water in question. Some people consider the Caspian sea to be a lake and others consider it to be a sea. While historically, it might have been part of a sea, it is landlocked now so it would be more suited to call this the Caspian Salt Lake, thus making it the largest lake on Earth and also the largest saline lake.

The Great Lakes are also in question, to me at least. While the majority of the world considers them lakes and they were historically a lake (really, the rivers and small lakes in that area connecting them are so small in comparison that it is basically 1 body of water), the Erie canal has since then connected the lakes to the St. Lawrence River. So it would be more suited to call this the Great Freshwater Sea. I have no idea how this would rank up to other seas like the Mediterranean Sea in area but it would be one of the world's few freshwater seas (Joining the Sea of Galilee).

So why are the Great Lakes not considered a freshwater sea when other than the freshwater, they are essentially like any other sea?

"Sea" versus "lake" versus "just part of the ocean" is a bit fuzzy, but there are two things that are universal about seas:

They are saline.
They are either endorheic or have a sea-level (tidally-influenced) connection to the ocean.

Now, let's see how the Great Lakes look under these criteria.

Saline?  No, salinity is 0, give or take measurement error.  Even the Baltic Sea, the least-salty of the generally-recognized seas, is far more saline, at 0.5%.
Endorheic?  No, they're connected to the ocean by way of the Saint Lawrence River, and have been for at least 10,000 years.
Sea-level connection?  No, the Saint Lawrence River has about 500 km of non-tidal flow below the outlet of Lake Ontario, over which it descends 75 meters.

Score: 0 out of 3.  Not surprising that the Great Lakes are considered lakes, not seas.


reverse time migration for wave equation PDE using SBP-SAT I'm stuck implementing a reverse time migration technique, the PDE(partial differential equation) being implemented is an acoustic wave equation, The numerical method being used is a FD(finite difference method) using SBP(summation by parts) property to ensure stability across the domain,i.e., this changes the coefficients that the FD use in the boundary and near boundary points, in addition to the SAT(simultaneous approximation terms) that will mimic how the continuous energy method is implemented and that would guarantee long time stability across the model. i need help with implementing the SAT for a 2D grid, each time i run the model with the SAT I've implemented it diverges at the last time-steps. IS there any well known acoustic-2D-wave equation that includes SAT to weakly enforce boundary conditions ??

I have no experience with SBP-SAT methods, but you may try and go through the references in (and potentially contact the authors of) this paper https://arxiv.org/pdf/1802.06123.pdf .

Personally, I don't see a strict need for using such 'complicated' modelling methods for RTM. In the ideal case, you have deghosted (i.e., upgoing) recorded data and a smooth velocity model. Then, using standard low-order finite-difference modelling on a uniform grid should already provide fairly good results at fairly little cost. Likely, you'll achieve better results by optimizing the data & velocity model than improving your numerical code beyond the standards. This simple MATLAB code https://csim.kaust.edu.sa/files/ErSE328.2013/LAB/WE_LABS/index.html already does a brilliant job using 2nd order accuracy in time and 8th order accuracy in space, using a simple FD method.

Of course, if you are doing state-of-the-art (academic) research or are dealing with a very atypical velocity model with an extreme dynamic range, these are interesting topics to look into, and I hope that someone may be able to help you... But I hope that my answer may help you right now.


How much climate history can be reconstructed using marine sediment cores? Today I learnt in college that marine sediments can be used to reconstruct the climate up to 500 million years back. I find that number very strange because in another class we learnt that the ocean floor "recycles" every few million years as a result of plate tectonics, and that the oldest ocean floor is 200 million years old.

I asked the lecturer about this, but he said he did not know. So I was hoping anyone here could tell me how many years old the climate we can recover through marine sediment cores is and why.

The oldest in situ marine sediments recovered by IODP (International Ocean Drilling Program; formerly ODP and DSDP) was (from memory) Late Triassic (so ca. 200 to 230 Ma) and it is as old as in situ marine sediments go, since indeed, as the marine crust gets older, it gets denser and thus is more prone to be subducted. However we do have older marine sediments, that were lifted during various orogenies and that were somewhat metamorphosed but are still viable for paleoclimatic studies (to some reduced extent of course). These lifted and metamorphosed sediments (along with the crust below them and even the upper mantle dragged along) are referred to as ophiolites, and they indeed date as far back as the earliest Phanerozoic (so 500 Ma). As most of the climatic information we are getting from them depends on the planktonic or benthic eukaryotic activity at the time of sedimentation, we cannot really go further back with these.


Is weathering of rock a primary means of $\text{CO}_2$ scrubbing on primordial Earth? I read somewhere that the reason Venus has a runaway greenhouse effect and Earth doesn't is because Venus failed to develop tectonic plates and instead formed a full tectonic plate enveloping the entire planet. And as such, Venus cannot scrub $\mathrm{CO}_2$ from its atmosphere by burying the weathered rock back into the mantle while Earth can, which eventually caused a positive feedback loop of high temperature softening plate preventing fracture which prevents burying of $\mathrm{CO}_2$, which puts more $\mathrm{CO}_2$ in the atmosphere, which raises the temperature even more. Regardless of the truthfulness of this theory, is the weathering of rock a primary mechanism of $\mathrm{CO}_2$ scrubbing on red-hot primordial Earth long before life occurred?

NO, it's not a very major sink on our planet, red is the extra carbon from human activities: https://jancovici.com/en/climate-change/ghg-and-carbon-cycle/wont-the-carbon-sinks-absorb-the-extra-co2/

Cool theory about Venus. It lacks a strong magnetosphere, so the solar wind carries away more light elements like hydrogen, and water vapor, the solar wind has carried away all the seas of venus since about 2 billion years ago, probably aided by the sun being 30% bigger and hotter there.
So, if Venus had kept it's CO2 levels in check, it would probably have sunk them in limestone, and also weathering if there was tectonic activity. Weathering does account for 0.2 to 1 gigaton of CO2 sink every year, compared to 30 gigatons released every year from fossil fuels.
The primary store of carbon in the earth's surface is in limestone, comprising about 60,000,000 gigatons of carbon, and coal and oil. the total amount of carbon near the surface of the earth is source 120 million GtC. Life exists on our planet since about 3.8 billion years, so it could have survived in Venusian oceans until about 2 billion years ago. That's the same time that the first major limestone layers appear on earth about 2.4-2.8 billion years ago. https://www.skepticalscience.com/weathering.html#significance


Will global warming lead to agriculture in the Arctic? From what I understand, global warming will make growing food a lot harder in areas like the American Midwest because temperatures will become too high for most crops. At the same time, Arctic (and Antarctic) regions will heat up and permafrost will melt. Would areas like Alaska, Siberia, and northern Canada then become suitable for large-scale agriculture? And if so, would this be enough to make up for the lost production in warmer areas? Or are there other factors in those areas that would make farming impractical?

The agricultural regions of Canada:

are located on suitable soil types:

Much of the unfarmed area is the Canadian Shield (shades of red below):

The current surface expression of the Shield is one of very thin soil
lying on top of the bedrock, with many bare outcrops. This arrangement
was caused by severe glaciation during the ice age, which covered the
Shield and scraped the rock clean. The lowlands of the Canadian Shield
have a very dense soil that is not suitable for forestation; it also
contains many marshes and bogs (muskegs). The rest of the region has
coarse soil that does not retain moisture well and is frozen with
permafrost throughout the year.

I think the "coarse soil" is Glacial Till.

This is melting permafrost. I don't think it will be suitable for agriculture.

CLIMATE CHANGE ADAPTATION AND CANADA’S CROPS AND FOOD SUPPLY (2013) (122 pages) discusses warming, precipitation, soils and other factors.

There is definitely potential for a northern expansion of agriculture
as a result of changes in heat and moisture in [the western prairies],
although most of these lands will remain only marginally suitable for
farming because of poor soil conditions.

Edit:
An eroding coastline exposes permafrost along the Mackenzie Delta. Photo: Roger McLeod / Natural Resources Canada
High resolution version from Arctic tundra is 80 per cent permafrost. What happens when it thaws? - The Narwhal:
https://thenarwhal.ca/wp-content/uploads/2019/03/Coastal-Erosion-Permafrost-Roger-McLeod-NRCan--e1551913545654-1920x1080.jpeg
Edit, Oct., 2020:
Canada could be a huge climate change winner when it comes to farmland

In this map from the study, areas that transition from no current suitability for major commodity crops to suitability for one or more crops are depicted in blue, while currently uncultivated areas that transition to suitability for multiple major commodity crops are shown in red. (Hannah et al, 2020)

KC acknowledged the study looked only at climate as a factor when determining where crops could be grown in the future, and didn't take into account things like soil quality.

Soil scientist David Burton of Dalhousie University, who wasn't involved in the study, says that could have a big impact on how much of the potential new farmland is actually arable.
"The soils of Southern Canada have taken 10,000 years to develop," he said. "Rapid change wouldn't necessarily make soils in Northern Canada suitable for production."

Johanna Wandel, an associate professor of geography at the University of Waterloo who edited a book called Farming in a Changing Climate, agrees the soil in much of Canada would likely be unsuitable for growing crops, as it's too rocky or acidic.


Is sterescope still used to do cartography with orthophotography? I used this tool at my degree a couple of lusters ago to do cartography with aerial orthophotos. We used it on cartography and geomorphology subjets.

  Source: gumtree.com

The method consists on using two consecutive but overlaped orthophotos (on east-west direction) taken from a plane, so an optical effect allows you to see the relief. Then you can delimite units with a marcker pen on a transparent film. We after transpose the cartography to a topographic map.

My question is if this tool is still used at university and among working geologists.

I am working in an academic environment and I know these tools are still shown to undergrads along other modern photo-interpretation techniques.

Often, modern techniques are more straightforward and convenient. There is a wide coverage of decent, recent and cheap satellite images available, providing a lot to work with in a short amount of time, easily compared to the interpretation of orthophotos. Elevation models, multi-bands and high resolution are big plus for modern techniques in a GIS for instance. Not counting just bringing a drone and ortho-photograph everything.

Where available stereo-pairs are somewhat older (50's to 80's) and of a limited/specific coverage depending on the region of interest - so this need to be considered.

But I also use stereo-pairs when I go in a tent at the tip of the globe where technology break, battery drains and internet lack. Portable stereoscope work well in the field.


Weather conditions to create significant glacier growth I am fascinated at the rapid growth of Glacier Bay Glacier from 1600 to 1750, along with its rapid retreat from 1750 to 1900. I am interested in the local weather conditions during these times. What are the likely variations in the local temperatures and precipitation during these periods. How much colder was the average local temperature to create no retreat during the summer peak heat during the growth period.

I'm guessing the glacier grew for 8 months of the year, it was growing & moving seaward at a rate of 5-6 meters a day for a 100 years. How different and noticeably different would the climate have felt by citizen of near by Juneau if living during the rapid growth period of 1650. Was it harsh winter conditions almost year round, or ? How much did the average day time high change from what it is today. Can an average year round change in temperature of .5C or 2.5 or 4.5 degrees cause this huge change in glacier behaviour. What was going on with global climate at this time to cause this amazing growth during the maunder minimum? Why the temperature change during this period?

Hold on, you're talking about growth of the glacier's tongue, not necessarily the whole glacier itself. To my best knowledge, flow dynamics of ice in glaciers still are not wholly understood, meaning we do not really know, why sometimes glaciers seem to grow so rapidly (protruding their tongue).

A prerequisite is the presence of enough ice in the growth-area of the glacier (growth area is the part above the snowline), meaning above average snowfalls in the years or even decades before the easier observable tongue growth. More snow compacts to more ice, generating more pressure on the whole glacier body, finally causing the outflow of the tongue.


Why is Olympus Mons the largest volcano in the whole solar system? Why is it that the volcanoes found in the Tharsis Montes region near the Martian equator, (one of which is Olympus Mons) so much larger than those found on Earth. In comparison, Hawaii's Mauna Loa, the tallest volcano on Earth, only rises 10 km above the sea floor. Olympus Mons rises three times higher than Earth's highest mountain peak, Mount Everest. What makes these volcanoes rise to such enormous heights in Mars, when comparing to those found on Earth and the rest of the Solar System?

This is mostly due to the fact that Mars does not have plate tectonics. Therefore the plate stays above the hotspot without moving, allowing magma to rise and pile up at the same place for millions and millions of years. Above the Hawaii hotspot, the oceanic plate is moving, so volcanism tends to drift away with time (actually the volcanism happens at the exact same place from a mantle point a view, but its surface expression moves with the plate). It's why rocks of the Hawaiian-Emperor seamount chain are older in the West and younger in the East. This is true even at the scale of Hawaii island itself, where Kohala and Mauna Kea are extinct, while volcanism$-$or rather the plate$-$has shifted to Mauna Loa, Kīlauea and Lōʻihi.
Imagine if all the magma comprising these islands had piled up at the same place, it could have built a gigantic volcano like Olympus Mons! Well... not really. There is another parameter to account for: a theoretical limit to how high a mountain can possibly get, because of compressive strength of rock (or glacial erosion in some theories). See for instance answers in these questions:

How high can a mountain possibly get?
Why is Mauna Kea taller than the maximum height possible on Earth?

On Earth the limit is ~10 km. So even if magma kept piling up at the same place, the resulting mountain would start to laterally spread or collapse. But on Mars gravitational acceleration is lower, making the limit much higher.


Where can I find broadband seismic reflection data? or what type of companies should I contact to ask for the data?

This data would be produced from Seismic Vibroseis survey trucks which are mostly used to locate oil and gas.

I doubt most oil and gas companies would be willing to share the data, even with researchers, so I'm stuck.

Any ideas on how to obtain the digitized response data from several locations?

It depends on what purpose you need the data for.

This site https://wiki.seg.org/wiki/Open_data gives several sources of data. If it must be land acquisition (as opposed to marine) data then the Poland 2D, Teapot dome 3D, or Stratton 3D surveys might be of interest.

These free data sets are for pedagogical/research purposes, so if you'd like to 'strike-it-rich' these are not the droids you're looking for.

Hope this helps,
-D


What is a breadboard (retrieval) algorithm in the context of geophysical satellite retrievals/remote sensing? In a recent met-jobs job posting (different version here) for a researcher with a background in climatology/meteorology/hydrology or
environmental sciences, I saw the phrase breadboard retrieval algorithm (emphasis mine):

  Sentinel-4 Retrieval: This Research Fellow Opportunity aims at
  testing of breadboard retrieval algorithms. It is foreseen that
  synthetic satellite data, and possibly also real measurements data from
  airborne and satellite sensors will be used for this purpose. The
  activity might also cover the exploration of alternative retrieval
  approaches depending on the expertise and skills of the candidate.

What is a breadboard (retrieval) algorithm?  Google Search yields precious few results, mostly from ESA.  Another usage I found

Albert, Preusker, and Fischer (2012), ENVISAT workshop:

  Originally, three breadboard algorithms were developed at the
  Freie Universität Berlin, and the knowledge for their creation
  was  transferred  to  ESA  /  Bomem  for  the  creation  of  the  ESA  algorithms.  In  the  meantime,  the  original  look-up  table approach was replaced for the breadboard algorithms by the use of artificial neural networks, which significantly eases the interpolation  of  the  simulation  results  onto  the  actual  viewing geometry.

Wikipedia tells me that, in electronics, a breadboard is a construction base for prototyping electronics.  The details of the article do not appear relevant for the algorithm usage, but it makes me guess that the meaning of breadboard is related to prototyping.  However, from context, it is clear that the job ad or the ENVISAT paper has nothing to do with electronics.

What does breadboard mean in the context of Earth observation retrieval algorithm development (which are the only contexts I could find)?  Is it simply a synonym for prototype, or does it have a different meaning?

When determining the retrieval algorithm for a spectrometer that will be built, it is first done on highly mathematical software platforms.  The software allows to the best curve approximation fitting equations to be derived (across all detected wavelengths) that will work for the proposed optics.  This is important because the diffracted light that is detected will interfere with itself very uniquely, depending on the geometry of your optical setup.   The data from the spectrometer's detector needs to be interpreted with a good curve fitting function so that you can get good wavelength resolution from your instrument.

When building a spectrometer for operational use on a satellite, it is ideal to be able to process the retrieval algorithm using hardware, rather than software.  The hardware processor allows real time function that isn't dependent on an operating system that requires lot's of computational overhead.  So, you build a breadboard that you can connect to your spectrometer so that your retrieval algorithm is processed using integrated circuits that can be programmed.  You essentially hard-code your algorithm into hardware.

Search for "breadboard spectrometer" in Google and you will find many examples.

Now, to answer your question.  A breadboard algorithm is developed using software that is used to help engineer the actual breadboards to be built in the future.  The software allows you to predict the response of your proposed circuitry to the spectrometer detector without having to actually build the breadboard yet.  Once your breadboard algorithm is setup properly (confirmed by testing the software version of your needed hardware) you can go about building the actual breadboard spectrometer model.

Once a breadboard spectrometer model is built and passes quality control checks, you can evaluate the spectrometer performance and see if its worth optimizing and fabricating a standalone instrument payload that can be deployed in the field (or in space).


What woud happen to me if I touched the aurora? The Aurora Borealis (commonly known as the northern lights) is a mesmerizing and captivating sight to behold, so beautiful that I just want to touch it and feel it. Should I? Could it harm me?

The lowest reaches of an aurora is ~100 km in the air.  Your problem won't be the ionized gas, it'll be that the air pressure is close to zero.  Also, aurora are very diffuse, with at most a few glowing molecules per square centimeter.  I'm not sure at that density that you could tell you were actually in something.

If you're in a spacesuit to survive the lack of oxygen, you might worry about the high-energy electrons that sometimes make it through to those altitudes, but fundamentally your problem is that you won't really be "touching the aurora" because you're in a space-suit and you can't really see that you're in it.


Relationship between tides and earthquakes Ide et al. (2016) suggest that earthquakes (especially those of high magnitudes) are more probable during periods of high tidal stress (during full and new moons). While they show a comprehensive dataset and analysis to corroborate their claims, it contradicts previous findings (e.g., Kennedy et al., 2004). Their argument claiming that tides trigger the transformation from small fracture to the large rupture associated with large earthquakes seems counter-intuitive to me. Wouldn't it make more sense for the relatively small changes associated with the tidal stress to be more related to smaller earthquakes?

I don't find Ide et al's recent paper to be very convincing. They only studied three earthquakes - hardly a statistically representative sample. There are millions of earthquakes on record, and hundreds of really big ones, of more than about MM 7.0, so there is plenty of scope for a more rigorous study. They occur at all phases of the tides. Some have claimed a weak correlation between tidal maxima and earthquake occurrence, but these are only just detectable above randomness, so maybe tides have an influence, albeit very small. The additional shear stress caused by tides is 2 to 3 orders of magnitude less than the stress release of an earthquake, so clearly other factors are much more important, such as the extent and location of fluid lubrication, and heterogeneity of friction along the slip plane.


Are the length of seasons the same globally? Is the length of time, say months, for each season the same all over the world or can it vary?

As has been noted in a comment, it depends on how you define seasons (see https://earthscience.stackexchange.com/a/2603/111).

If seasons are defined in astronomical terms, then they have the same length everywhere on the planet. This is simply down to geometry.

However, the effects of astronomical seasons vary geographically in a number of ways. The magnitude of seasonal changes, for example changes in day/night lengths, is more pronounced in higher latitudes, so the effect of (for example) winter might be noticeable for a shorter time period in the tropics than the arctic, and hence some people might reasonably consider winter to be shorter there. There are other, less systematic variations that depend on local climate and weather. In weather terms, not everywhere in the world has the same 4-season cycle that temperate zones tend to experience - so when defining seasons in terms of observable effects one often has,  for example, a wet season and a dry season rather than spring /summer /etc.


Freely available and re-distributable weather observations over the US? I am looking for a (small) data set of weather observations for a few (say 5-20) weather stations in the US, with observations of precipitation, temperature and wind speed for the year 2016. The data should be freely available and downloadable - and, should be allowed to be re-distributed to third parties, since I would like to use it as an example data set in an R package to demonstrate some methodology I have implemented.

Is there such a data set?

Such a dataset can be found via the NCDC. Here is the main gateway. My 'go to' place for high temporal resolution data from NCDC is the 5-minute ASOS data.


Correlating the Caledonian and Appalachian Orogenies The Caledonian mountains and Appalachian mountains are recognised to be the roots of the same Palaeozoic orogenic belt. This has since been split in two with the opening of the Atlantic.

On the European side, two orogenies are recognised: the Caledonian and Variscan (or Hercynian). On the American side the Appalachians are also recognised to be made up of multiple orogenies, eg. the Taconic and Allegheny.

A parallel could be drawn with the present day Tethyan Belt - especially the Mediterranean length. Here we don't see one big mountain building episode but many as each sub-continent or large island is accreted onto Europe. Similarly, Pangaea was not formed in one big orogeny but multiple as sub-continents such as Avalonia were accreted on to what is now North America.

Can each orogenic episode on the European side be correlated with an orogenic episode on the North American side? I.e. having two names for the same orogeny?

Are correlations possible at a finer scale? For example the Caledonides in Scotland are marked by some very prominent ancient faults (Great Glen, Moine, and Highland Boundary Faults). The Appalachians also have some large fault systems. Can any of these be correlated across the Atlantic?
Can specific sedimentary sequences be correlated?
(I realise that big picture sequences in the late Palaeozoic are broadly similar, e.g. Permian Aeolian Sandstones, Carboniferous Deltaics & Coal, etc)

The article The Caledonian Orogeny redefined (McKerrow et al. 2000) have done exactly that - correlating the stratigraphic and orogenic aspects of all of the orogenic movements (as you have listed) that they define as being orogenic phases comprising the Caledonian Orogeny.

An important distinction the McKerrow et al. make is to state that the term 'Caledonian Orogeny' is not a single event, but rather comprised of all the tectonic movements that occurred in the ~200 million year development and closing of the ancient Iapetus Ocean, through the Cambrian to Devonian.

With this framework, the authors were able to determine a continuous stratigraphy through deposits of the tectonic events of the Caledonian Orogeny in the present day North American and European continents.


Best way to interpolate bathymetry with a directional component? I have a bathymetry dataset that has a small section missing. I need to fill in this section.

The bathymetry in this region has some strongly directional features (e.g. a canyon that runs through the missing region). Using a standard interpolation function would weaken these features.

Is there an appropriate method to estimate the missing values that gives more weight to known values along a given axis?

At the moment the data is a GeoTIFF, and I'm using QGIS, but I can convert as necessary. I have straightforward access to MATLAB and R, as well as all the GRASS and SAGA tools included in QGIS.

I had the same problem with surface DEM's. The best solution I found in Matlab was using the scatteredInterpolant class, it is inbuilt in Matlab. It allows Natural neighbour interpolation (that is a class of weighted distance interpolation as suggested in previous comments). The usage is like this:

% IF X and Y are the coords of each grid cell (you can use meshgrid to get
% those)
invalidValue=NaN; % or -99999 or whatever is in your case
gapIdxs= DEM==invalidValue; %Indexes of the void cells
interpolant = scatteredInterpolant(X(~gapIdxs),Y(~gapIdxs),DEM(~gapIdxs),'natural');
% interpolant is now a function, and we can evaluate it at any point you
% want, in this case we evaluate it in the void cells
interpolatedValues=interpolant(X(gapIdxs),Y(gapIdxs));
% Now we patch the DEM
patchedDEM=DEM;
patchedDEM(gapIdxs)=interpolatedValues;

That produce a result way better than cubic interpolation in my experience. If that is not enough, before you start doing manual picking of features you can explore Kriging interpolation.
Finally if you what to force directionality, you can rotate your data (using matlab imrotate) so that your main direction is vertical and then interpolate column by column (using matlab interp1).


How do geologists find ore deposits? From my research, there is lots of information on how to extract ore, but I can't find any information on how these ore deposits are found in the first place, apart from 'looking for surface formations'. So, what kind of formations would exist for different types of ore? Are there any other ways of finding ore?

That is the multimillion dollar question! "looking for surface formations" is indeed one way, and it was the main method of exploration in the past. This does not necessarily mean that you directly see the ore deposit in front of your eyes. Many ore-forming systems are accompanied by different kinds of alteration (for example potassic or argillic alteration) that are not too hard to see in the field. Once you see them, there is a possibility that an ore deposit is nearby.

Other surface methods include, among others, looking at rivers sediments. Since rivers transport soils and rocks from upstream, sampling the sediments may reveal an anomaly in a certain commodity of interest that may lie somewhere upstream. It is also possible to use satellite data - by looking at certain wavelengths it is possible to estimate the mineralogical composition of the surface. This may give hints on the possibility of mineralisation. I've even seen cases where people used different kinds of vegetation that grows on different lithologies!

Surface methods, however, require that the mineralisation will be close to the surface, and the truth is that most of the ore deposits that satisfy that requirement have already been found. This is where geophysical methods come into place. Gravimetric, magnetic and seismic studies probe the earth below the surface and may provide exploration targets, which are then drilled to see what's actually in there.

Mineral exploration is a hard business with much more failures than successes. That said, cases of serendipity are not unknown in exploration. Also, changes in global economics, production costs and increasing/decreasing metal prices may change what is actually an economically feasible ore deposit. The metals are always there - but is it actually worth taking them out?


How Can Smog in Metropolitan Cities like Delhi & Beijing Be Reduced? These two cities are facing the worst smog in Asia and I think in the world and people of these cities have no choice other than to wear masks when going outside. So what Advance technology that can be used by these two state government so that smog can be reduced to a minimum or can be eliminated?

these 2 counties can't avoid smog due to large no. of factories and farmer burning residual so what Technology that can be used to reduce/eliminate smog.

The first thing to do is to stop putting pollution in the air, particularly very small particulate matter that are produced by combustion.

For the Beijing Olympic Games of 2008, the Chinese government forced the polluting plants and factories in the vicinity of Beijing and nearby areas to stop operating for weeks prior to the games and during the games to ensure the air in Beijing was clear and had minimal pollution during the duration of the games. The measure was successful.

Burning wood, animal dung, coal, petroleum products (particularly diesel and heavy oil) produce soot and other small particulate matter which leads to poor air quality and smog.

This is an easy solution that results in clean air. The difficulty with this is that it is detrimental to the economy in the short term. For a longer term solution, energy sources need to be changed to ones that do not cause air pollution.


Are hot springs in non-volcanic areas radioactive? Hot springs in non-volcanic areas are attributed to the interaction of water with hot rocks deep in the earth's crust:

  In non-volcanic areas, the temperature of rocks within the Earth also increases with depth—this temperature increase is known as the Geothermal Gradient. If water percolates deeply enough into the crust, it comes into contact with hot rocks and can circulate to the surface to form hot springs.
  Hot Springs/Geothermal Features, National Park Service

If I understand correctly, this heat comes from the decay of radioactive isotopes:

  ... the vast majority of the heat in Earth's interior—up to 90 percent—is fueled by the decaying of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232 contained within the mantle.
  Probing Question: What heats the earth's core?

Hence...

Question: Are hot springs in non-volcanic areas radioactive?

I'm guessing the answer is either "no" or "yes, but not very", because people swim in them.  But it seems like radioactive isotopes should be seeping into the water.

The answer is contained within your own question. Virtually everything is radioactive, including your own body, the air you breathe, and everything you eat. The radioactivity is usually beta radiation (emission of energetic electrons), which is the least harmful form of radioactivity.

Radon gas, which is emitted from granite rocks containing uranium, sometimes builds up to dangerous levels in our homes and is an alpha emitter. Alpha radiation is very ionising and dangerous, but needs to be ingested into the body to cause serious harm.

The answer to your question, therefore, is yes, hot springs are radioactive, but so are cold springs. As hot springs are more likely to have passed through granite rocks, they are probably on average more radioactive than cold springs, but neither are radioactive enough to cause concern.

The radioactivity which is dangerous enough to cause concern is radon gas, which varies from place to place according to the underlying rocks. Maps of radon hotspots can be obtained from the internet. If you happen to live in a hotspot, you need to keep your house well ventilated, otherwise the radon will build up to dangerous levels, sometimes levels which would not be tolerated in a nuclear power station or research establishment.


Why is Ozone hole above single area of earth? Why that area? As titled. How does the hole fell specifically on that region of the stratosphere above the Antarctic and why?

Mostly temperature, leakage of CFCs(Chlorofluorocarbons), produced for early model refrigeration units thinned the ozone layer a bit all over the world but in Antarctica, and to a lesser extent over Scandinavia, CFCs were frozen into winter snowfall rather than effecting the ozone layer equally year round. Small amounts of ozone damage regenerated reasonably quickly, I understand the reaction is self catalysing but I'm not sure of that, but the flood of CFCs evaporating with the summer thaw in colder climates overwhelmed the natural increase and thus the massive hole down south. The Arctic isn't as badly effected due to the combination of fact that much of the melting ice turns to water which absorbs much of the CFC burden, continental Antarctica sees more ablation in summer months than melting, and the fact that global air currents concentrated much of the pollutant matter south of the equator in the first place.


What is the effect of rising sea level on measurements of elevation? If the earth's mean sea level rises, I assume that requires humans to adjust current measurements of elevation? For example, Mt Everest would no longer be 8,848 metres above sea level. Is there a more stable universal way to measure elevation such as on other celestial objects?

I know that zero altitude on Mars is defined as a specific atmospheric pressure of 610.5 Pascals, about six millibars which is the triple point of water on Mars, where it can exist as gas, liquid or solid.

The zero elevation point of the Moon is the average diameter since it has no atmosphere. So perhaps this is the most universal method to measure elevation?

Elevation can be measured against a tidal datum, in which case it is usually tied to some historic mean, or against a geodetic datum, which is statically defined.

Tidal datums, of which there are many flavours, are only useful locally and, as you thought, they drift over time. Here's what NOAA says:

  Tidal datums are used as references to measure local water levels and should not be extended into areas having differing oceanographic characteristics without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks. Tidal datums are also the basis for establishing privately owned land, state owned land, territorial sea, exclusive economic zone, and high seas boundaries.

For large (continental or global) areas of interest, you need geodetic datums.

In the UK, Ordnance Datum Newlyn was defined in 1956 as the mean sea-level at Newlyn, Cornwall, between 1915 and 1921. In the US, the North American Vertical Datum of 1988 prevails today (though several others are in use). It was pegged to the local mean sea level height at Rimouski, Quebec, Canada.

There are two types of reference surface, the earth's equivalent of the celestial ones you mentioned in your question: the geoid, and ellipsoids. The geoid is the surprisingly lumpy shape that the ocean surface would take in the absence of factors like tides. It can be measured with gravity anomalies, e.g. by GRACE. Since it's a natural surface, you could think of the geoid as the earth's absolute datum. Ellipsoids, on the other hand, are models of the geoid and, as mathematical surfaces, are smooth.

As shown in the figure, GPS uses the World Geodetic System of 1984 for its measurements, so elevation is measured against its ellipsoid. So one must correct GPS elevations  to this orthometric height (height above the geoid).

If you want to read more, this tutorial on datums from NOAA is pretty fantastic. And here's a nice piece on the height of Everest, with respect to various datums.

Image: Judson L. Ahern, University of Oklahoma, via Federal Geographic Data Committee.


Would a nuclear explosion over one of the Earth’s magnetic poles momentarily disrupt/weaken the Earth’s magnetic field? If say the Tsar Bomba had been detonated directly over one of the Earth’s magnetic poles at ground level, would the nuclear electromagnetic pulse generated from that blast have had any momentary effect on the strength of Earth’s magnetic field?

If a nuclear EMP cannot disrupt/weaken the Earth’s magnetic field, would it still be powerful enough to momentarily energize the Earth magnetic field and would this powerful electromagnetic discharge fry any sensitive electronics devices around the Earth and/or satellites in low Earth orbit?

There are a few different questions lurking here.

No, it would not have any lasting effect on the Earth's magnetic field. That field is not generated at the surface, at the poles or otherwise.
Yes, it would produce an electromagnetic pulse, and that could be harmful to unshielded electronics in at least a line-of-sight sense.
Yes, this EMP would definitely cause localized magnetic effects for a very brief moment, which one could argue constitute a change in the natural magnetic field.
I'm not sure whether there's any reason to think that the earth's magnetic field could help these effects to propagate beyond line of sight - which I think is what you're really asking. Perhaps a physicist could chime in...


Is there a hemisphere where there's more land than ocean? From a previous question, around 40% of the northern hemisphere is land. Would there be a plane splitting the earth into two equal parts, where in one part there are more land than ocean?

I wrote a little Matlab script to estimate this approximatively. Here is the result: colour denotes the total land area inside the hemisphere centred on a particular surface point. The red point is the maximum.

This gives me a maximum for the hemisphere centred on 1.7582°W longitude and 40.7692°N latitude, roughly in Guadalajara, Spain. If I calculated right this is 81% of all land, with 23.37% land area on the hemisphere (and 5.83% on the other hemisphere). So the answer to the question is no, there is no hemisphere with more land than ocean. There isn't even one with more than half land.

(Updated 2019-06-23 with higher resolution estimation, which moved the point south a bit.)


How can oceanic Rossby waves move from East to West? I can find several examples of Rossby waves, mainly atmospheric, moving towards East. Is it possible that they also move towards West?

Yes it is. In fact Rossby waves always move westward in the absence of a zonal mean flow. Before going into detail lets try to explain this qualitatively. In a barotropic fluid the absolute vorticity is conserved. The absolute vorticity is composed of the relative vorticity $\zeta$ and the planetary vorticity $f$ ($f$ is also called the Coriolis parameter). $\zeta$ is the rotation of the fluid as you would observe on earth. $\zeta + f$ is the rotation of the fluid as someone from space would observe. Conservation means that the sum $\zeta + f$ must always stay the same no matter where a fluid parcel moves. I.e. $D(\zeta + f)/D t = 0.$ Notice that $f = 2 \Omega \sin \varphi$ increases the further we move away from the equator. $\Omega$ is earths angular frequency and $\varphi$ is the latitude.

Now imagine a line of connected fluid parcels that is initially at rest (horizontal line in the figure below). Lets say on the northern hemisphere at a line of constant latitude. If we displace the parcels to the sine like line, the following happens: If we move northwards to the pole the planetary vorticity increases ($f$ increases), but if absolute vorticity is conserved, $\zeta$ must decrease. If the parcels were initially at rest (as observed by someone standing on earth) $\zeta$ is now negative - inducing a clockwise rotation. If we displace parcels southward the converse happens. $f$ decreses and $\zeta$ increases, inducing an anti-clockwise rotation. If we move even further in time the rotation induced before will translate the wave to the sine like dashed wave. Think of the arrows in the figure as "pushing" the solid sine like line to the dashed sine like line. This describes a motion of the wave from east to west!

What is needed to make the wave move eastward? Imagine the horizontal line moves towards the east (i.e. we have a zonal flow), the wave itself will move eastward if the zonal flow is faster than than the westward movement of the phase which I described above. The details are a little more complicated but I will state them below.

Lets take a look at the details. Maybe the simplest setting to study Rossby waves is based on the barotropic vorticity equation (BVE) which describes the flow of incompressible, non-divergent, constant density flow on a rotating sphere. If you are not interested in the derivation here just take a look at the part denoted "Dispersion relation", which will describe the phenomenon.  The relative vorticity $\zeta$ is given by $\zeta = \partial v / \partial x - \partial u/ \partial y$, where $v$ is the the northward component of the velocity and $u$ is the eastward component of the velocity.

The equation of motion (BVE) is given by:

$\left( \frac{\partial }{\partial t} + u \frac{\partial }{\partial x} + v \frac{\partial}{\partial y}\right)\zeta + \beta v = 0.$

This equation is equivalent to $D(\zeta + f)/D t = 0$ as described above. The first term ($\partial \zeta/\partial t$) is the local change of relative vorticity, followed the advection of relative vorticity and finally there is the advection of planetary vorticity $v\beta$ ($\beta = \partial f / \partial y$), which is the contribution to the rotation of the fluid by the earth itself. Solutions to this equation can be interpreted as Rossby waves. However to admit solutions including zonal flow we must linearize the equation about a basic state plus perturbations. We do this by letting $u = \overline{u} + u'$ and $v = v'$. So we have a zonal mean flow $\overline{u}$ and perturbations $u'$ and $v'$. The perturbation vorticity is then $\zeta' = \partial v' / \partial x - \partial u'/ \partial y $. Introducing a stream function $\psi$ that is related to the relative vorticity by $\nabla^2 \psi = \zeta'$ we can write the linearized BVE as

$\left(\frac{\partial}{\partial t} + \overline{u} \frac{\partial }{\partial x} \right) \nabla^2 \psi + \beta \frac{\partial \psi}{\partial x} = 0.$

In the equation above terms involving products of perturbation (e.g. $u'v'$) where neglected because they are assumed to be small (something small squared is even smaller).

Dispersion relation:
A wave like solution to the perturbed BVE is given by

$\psi = Re(\psi_0 e^{i \phi})$,

where $\psi_0$ determines the maximum amplitude and the phase $\phi = kx + ly - \nu t $. $k,l$ are zonal, meridional wavevectors and $\nu$ is the frequency of the wave. Substituting the proposed solution into the perturbed BVE yields the dispersion relation

$\nu = \overline{u}k - \frac{\beta k}{k^2+l^2}$.

Recall from elementary physics that the zonal phase speed is given by$ c = \nu/k$. This allows to write the dispersion relation in the desired form, answering your question:

$c = \overline{u}- \frac{\beta}{k^2+l^2}$.

Notice that $c$ determines whether the Rossby wave moves eastward (c>0) or westward (c<0). In the case of $\overline{u} = 0$, $c$ is negative and therefore, the wave moves from east to west. In fact a Rossby wave can only travel from west to east in the presence of a zonal flow that is also directed eastward. More precisely if $\overline{u}>\beta/(k^2+l^2)$. This also explains the answer of gansub: long waves have small wave numbers, therefore $\beta/(k^2+l^2)$ is greater compared to smaller waves. Thus, it is more likely for the waves to travel westward.

My answer can be found almost identically in Holton, Hakim - Dynamic Meteorology, 5th edition, page 161 onwards. So credit the book rather than me.


Why can Thomsen's parameter $\epsilon$ be negative in VTI media? I just got several well log curves, some of which are Thomsen's parameters. They are a result of interpretation of Sonic Scanner tool measurements (Schlumberger). Negative epsilon values appear quite frequently, which is not physical for VTI media (as far as I can conclude from books). Am I right?

The question is not about measurements with a specific tool, but rather about the physical and geological interpretation of negative epsilon values. Gamma is also negative, by the way.

Negative values are physical and are expected.

Indeed, Thomsen's 1986 paper has several negative values for $\delta$, $\epsilon$, and $\gamma$ — look at the data in Table 1. He also discusses negative values, at least for $\delta$ (e.g. on page 1961) . You can quickly get a sense of how common negative values are from his Figure 4:

As for physical meaning, it depends on the parameter. I recently wrote this about the physical meaning of the Thomsen parameters (edited for brevity):

  $\delta$ or delta — the short offset effect — captures the
  relationship between the velocity required to flatten gathers (the NMO
  velocity) and the zero-offset average velocity as recorded by checkshots.
  $\epsilon$ or epsilon — the long offset effect — is,
  according to Thomsen himself:  "the fractional difference between
  vertical and horizontal P velocities; i.e., it is the parameter
  usually referred to as 'the' anisotropy of a rock".
  $\gamma$ or gamma — the shear wave effect — relates, as rock physics
  meister Colin Sayers put it on Twitter, a horizontal shear wave with
  horizontal polarization to a vertical shear wave.

Usually these parameters are, at a gross scale anyway, positive, because usually velocity is faster along bedding (roughly horizontally) than across it (roughly vertically). But it's easy to imagine scenarios where the relationship is reversed, especially if we're talking about small scales — as in log measurements.

Intuitively, we can draw these conclusions about negative parameters:

A rock with $\delta < 0$ has the zero-offset reflections 'seeing' faster velocities than the long-offset reflections.
A rock with $\epsilon < 0$ has a faster vertical velocity than horizontal velocity.
A rock with $\gamma < 0$ has a faster vertical shear velocity than horizontal shear velocity.

Reference

Thomsen, L (1986). Weak elastic anisotropy. Geophysics 51 (10), 1954–1966. DOI 10.1190/1.1442051.


What is the predictability of El Niño/La Niña? What is the maximum period of time into the future that an El Niño event can be forecasted with reasonable accuracy and what are the limitations in predicting the time limit?

All season forecast systems are subject to uncertainty. The uncertainty arises from an imperfect initial state, such as initial conditions, and from imperfect models, such as uncertainty due to, numerical methods, parametric models, data sampling. Forecasting systems utilize ensembles and their spread to quantify uncertainty.

See the spread in forecasts for El Niño produced by a number of international models:

When considering large scale processes varying on interannual scales ENSO, which is the coupled process of El Niño/La Niña SST anomalies and the Southern Oscillation, is relatively well predictable. However, the fidelity of the forecasting is modulated by the season, the phase and intensity of ENSO. For example, there is a decrease in skill during the so called "spring predictability barrier" where, during the boreal spring when SST anomalies are abnormally variable. Model drift (such as SST drift as the forecast progresses) and bias especially for a couple-model such as the ENSO, is a very real issue. After only a season the bias inherent in the results renders the forecasting unreliable to the point where the model may be unable to recognize different types of ENSO (such as classical East Pacific versus central Pacific ENSO events).

So unfortunately at this time your specific question is still very hard to answer with any degree of satisfactory precision. But at least we know that it is not more than one season in the future.

Source:

Alves, Oscar, et al. "Seasonal and decadal prediction." Operational Oceanography in the 21st Century. Springer Netherlands, 2011. 513-542.


What happens to global temperature when we stop all the vehicles for a year? I know this is a very simple or naive question but am just being curious.

How would the global temperature change if all vehicles stopped for a whole year?

Not much at first. The damage has already been done. Humanity has added at least 100 gigatonnes of carbon to the atmosphere since the start of the industrial age. Natural sequestration of that excess carbon is a slow process. Suppose all human production of carbon ceases (and note that vehicular production of CO2 is but a fraction of the total). It will take centuries to return to pre-industrial levels, and temperatures will continue to rise for decades to come.

Humanity will not countenance a decree to stop using vehicles. You would somehow need to magically dispense the laws of physics, at least those that pertain to internal combustion engines. Food shipments would stop. Riots would ensue within a week of your use of your magic wand.  Your magic want is a death sentence for a huge portion of humanity. People will die in droves. Killing off 90% of humanity is of course one long term solution to the anthropogenic warming problem. It's not a very nice solution.


Understanding the color coding of a weather map I came across an infrared weather map like this

I couldn't find any legend on the colorbar's color convention. Initially, I thought that might be the
color for reflected light's wavelength, but there was no way to find out.
This image is obtained from https://mausam.imd.gov.in/imd_latest/contents/satellite.php#.

Unfortunately it's common for satellite data services to show these types of images qualitatively, omitting the units or even a colorbar.
This is an infrared image from the 10.8 micron channel (TIR1) of INSAT-3D.  That website you link to is a bit misleading because (for me at least) following the link puts the text describing the 0.65 micron visible channel under the image.  If you click "Infrared" in the sidebar of that page the text is replaced with the correct text about the 10.8 micron channel.
Given that TIR1 records are stored as 10-bit values (i.e., in the range 0 to 1023) and the color scale maxes out at 939, I suspect that they are just plotting the raw count data.  This is normally transformed into radiances by applying a linear scale and offset to put the data in physical units.
I had a quick look at the equivalent 10.8 micron image from Meteosat over the Indian Ocean (see below) and I get a similar count range and a similar image when I apply their color scale.  I also suspect that they've inverted their data, e.g., plotted count_inv = 1024 - count, to fit with the viewers' expectation that cold clouds appear white.


What are the phenomenon (artificial and natural) in play in this photograph "350m beneath Berezniki in Russia"? This image is from the BBC Culture article Striking photos of human scars on Earth. It is accompanied by the text and captions below.
But I still don't understand what I'm looking at at all. Can someone recognize what's happening here? What are the phenomenon (artificial and natural) in play?

Burtynsky categorises himself as an environmentalist, and has dedicated his life to bearing witness to “the indelible marks left by humankind on the geological face of our planet”. In other words, the increasingly ambitious scars and blemishes created by industry and large-scale human habitation, such as the vividly coloured layers from an ancient sea floor exposed by tunnelling machines 350m beneath Berezniki in Russia.

Caption: "Uralkali Potash Mine #4, Berezniki, Russia, 2017 (Credit: Edward Burtynsky, courtesy Flowers Gallery, London/Metivier Gallery, Toronto)" [Source][1].
Click for full size.

Update: I found another view of this in the BBC's video The photographer capturing mankind's impact on planet Earth

Edward Burtynsky travels the world trying to capture striking images of humanity's impact on the planet, from the fossil-like shapes left behind by drills in a Potash mine to the luminescent colours of lithium ponds.
The Canadian photographic artist has spent 40 years focusing on large-scale human activities such as mining, quarrying, agriculture and deforestation - but he says he doesn't see himself as an environmentalist.
His latest project, Anthropocene, is a collaboration with film-makers Jennifer Baichwal and Nicholas de Pencier, exploring the idea proposed by some scientists that a geological epoch shaped by human activity has begun.
It includes a travelling exhibition, a book and feature-length documentary, which was premiered last year in Canada and goes on theatrical release in the US next week.
Images: Edward Burtynsky, courtesy of Flowers Gallery, London / Nicholas Metivier Gallery, Toronto. Video by Heather Sharp and Laura Foster

As stated in the caption for the picture this is an inside view of a potash mine.

Mining professionals regard potash, like most coal, to be a soft rock; unlike hard rock such as most metal sulfides.

With hard rock mining, the rock is mined by drilling holes and using explosives to break up the rock. The rock is then loaded and transported out of the mine.

Most soft rock mines, and particularly potash mines, do not use drilling and blasting as the main means of removing rock. Instead they use specialized cutting machines to cut the rock. The shapes left in the rock, in the picture are marks created by the cutting heads of such machines. Usage of such a machine can be seen at the 3:30 mark in this You Tube video.

I answered the question What would you call this mining vehicle? (Ural-20R, used in mining) on SE Engineering two years ago, when someone asked about the purpose of an unusual mining machine.

Such machines are typically called continuous miners.


What are the physical upper bounds on the magnitude of an earthquake? Given what we know about the physical mechanisms underlying earthquakes, what do the theoretical upper bounds on the magnitude of an earthquake look like? What physical phenomena impose those upper bounds?
Assume that we're talking about the "modern" Earth, i.e. from the past 4 billion years, after the Earth was fully formed. Also assume that only natural phenomena are involved - no nuclear weapons or Deep Children or anything of the sort.
If it makes a difference, I would like to know what the answer looks like in two cases:

No impact events are involved - the earthquake is generated by purely terrestrial phenomena
Arbitrarily large impact events are involved, provided that the Earth still looks "roughly the same" (defined however makes sense to you) after the impact

We have a trivial upper bound of moment magnitude ~25 for the former case, since the energy released by a magnitude-25 earthquake is roughly equal to the total mass-energy of the Earth1 - but I'm sure you folks know of tighter bounds than that. :)
(cf. the question Are Richter-magnitude 10 earthquakes possible? - but most of the answers there are from a statistical perspective, not a physical perspective.)

Notes
1 As we know, the total mass-energy content of a system is given by
$$E = \sqrt{(mc^2)^2 + (pc)^2}$$
Since the Earth's motion (both translational and rotational) is non-relativistic, we discard the momentum term as negligible and simply write $E = m_\text{Earth}c^2$. Using $m_\text{Earth} = 6 \times 10^{24}\ \mathrm{kg}$, this gives us $E = 5 \times 10^{41}\ \mathrm{J}$. Converting this to a moment magnitude using
$$M = \frac{2}{3} \log_{10} \left(\frac{E}{1\ \mathrm{N} \cdot \mathrm{m}}\right) - 2.9$$
we get $\boxed{M \approx 25}$.

Earthquakes involve slip on faults, most of which occur on plate boundaries.

Now the width of a fault is usually limited by the downdip limit of the brittle ductile transition. E.g., in case of vertical strike slip faults this limit is between 10-20 km. In subduction zones this limit can be larger as the fault/interface is inclined.

The theoretical length of the fault is limited by the length of the plate boundary. It is impossible to have a fault with a length greater than the circumference of earth.

The final variable is slip. Average slip, based on empirical relationships, doesn't exceed more than 5-15m (rocks can accumulate only so much strain). Though locally it is possible to have slip as high as 50m (e.g., in the case of the Tohoku earthquake.

So for a plate boundary fault which exactly splits the earths brittle upper crust into two halves (in a single earthquake) with an average slip of 15 m, assuming a modulus of rigidity of 30GPa (mean for upper crust) we have:

Moment = Fault_area x rigidity x slip

which for our hypothetical scenario is equal to

= ((2*pi*6371000)*20000)*(30e9)*(15)

or

3.6E23 Nm

which is about Mw9.7.


Why are many fossils found in deserts? Why are deserts famous for fossils? Is it a coincidence? Some examples:

Giant Catfish Fossil Found in Egyptian Desert

Chile's stunning fossil whale graveyard explained

Giant Dinosaur Fossil Found in Sahara Desert

Bones don't last very long in jungles. Or in forests. Or almost anywhere.

Fossils are the consequence of one highly unlikely fluke after another. Darwin himself commented on this. It takes just-right circumstances to have the bones of a recently deceased animal not be eaten by scavengers or turned into rot by bacteria. It takes yet another set of just-right circumstances for those bones to turn into fossils. It takes yet another set of just-right circumstances for those fossils to be brought back to surface level. It takes yet one more set of just-right circumstances for those nearly exposed fossils to survive the ravages of time and weathering.

The last coincidence is where deserts come into play. Water is an extremely powerful weathering agent. The key characteristic of deserts is an extreme lack of water. Fossils are much more likely to survive the savages of time without that weathering by water.


Actual thickness of permafrost vs theoretical maximum possibly permafrost thickness I came across a question in my notes about why the actual thickness of permafrost is much less than the theoretical maximum possible permafrost thickness value.

The actual permafrost measure on sites were much less thick than the maximum possible thickness.

So the actual permafrost thickness had values ranging from 0-15m. But the maximum possible permafrost thickness had values froom 75, to 375m. We determined the maximum possible thickness by using the formula $z=(T_s)(k/q)$. With $T_s$ which was -3 and we took the absolute value of this so 3. Then K was the thermal conductivity $W/m$ and Q was the heat flux which was $.04w/m^2$. So why was the actual thickness much less than the theoretical max possible? Clearly the max possibly max is going to be higher than the actual thickness because this gives a end range for the thickness of the permafrost but besides that I am not quite sure

Edit: as an example, the following values are for Newfoundland and Labrador.  The maximum possible thickness was calculated by that equation I gave up above.

Material, Max Possible Thickness, Actual Permafrost Thickness:
granite, 75m, 0m
sandstone, 150m, 1m,
glacial till, 113m,1m
esker gravel, 188m,0m
marine silt, 375m,15m
river sand, 225m, 0m
fen peat, 300m, 10m

I could not recover my account so here is some additional information for you. This area is Newfoundland and Labrador.  The maximum possible thickness was calculated by that equation I gave up above

Material, Max Possible Thickness, Actual Permafrost Thickness:
granite, 75m, 0m
sandstone, 150m, 1m,
glacial till, 113m,1m
esker gravel, 188m,0m
marine silt, 375m,15m
river sand, 225m, 0m
fen pea,t 300m, 10m


Why are parts of the Atlas Mountains in Morocco flat? A couple of months ago I traveled into the Moroccan Atlas Mountains. Many times I have seen pictures of landmarks like this one of Aït Benhaddou which show apparently unnaturally flat mountain formations stretching across the horizon.

My guess is that this is a vestige of the ice age or a huge water reservoir. Unfortunately, I could not find any good source on how they were formed. Thus my question is:

How can these formations be explained?

Once the sediments (mainly silt and sand) have been deposited as layers in an ocean, when the sea level was much higher. Thus, each layer is very homogeneous in its texture, hardness and stability against weathering and erosion. Therefore vertical forces of erosion have a uniform effect on the entire surface and the ridge remains flat when there is no deformation due to tectonic strain. But lateral erosion has different effects on the different hard layers and so you see ribs on the mountains flanks. So it is mainly due to the layer homogenity and due to the absence of tectonic deformation that you see in the background.


Is there a table available for the maximum potential intensity of hurricanes? The maximum potential intensity (MPI) is a computed quantity that often sets a maximum bound for maximum hurricane wind speed, though rarely, the wind speeds observed can exceed it. MPI is based off of the idea that hurricanes effectively work as Carnot engines. Has there been a table produced with historic MPI calculations (reanalysis or forecast based)?
Also, is there a source that calculates MPI for each model and each hurricane?
For reference, $$v_{MPI}=\sqrt{\frac{C_k(T_s-T_0)}{C_dT_0}\Delta k}=\sqrt{\frac{T_sC_k}{T_0C_d}(CAPE_s-CAPE_b)}$$
where $v_{MPI}$ is the theoretical maximum speed (MPI), $C_k$ is the surface drag coefficient of enthalpy, $C_D$ is the surface drag coefficient, $\Delta k$ is the change in enthalpy between the surface and environment, $T_s$ is the sea surface temperature, $T_0$ is the outflow temperature, $CAPE_s$ is the convective available potential energy (CAPE) from sea level and $CAPE_b$ is the
CAPE of the boundary layer air.

This perhaps only indirectly addresses the question, but maybe it might be helpful. According to Kerry Emmanuel's book "Divine Wind", a hurricane can, in a sense, achieve super-Carnot efficiency without violating the Second Law of Thermodynamics. A hurricane's heat reservoir is the ocean surface at temperature Th and its cold reservoir is the tropopause at temperature Tc. Heat flow Q, mainly via water evaporating from the warm ocean and condensing in the cold upper troposphere is, according to the Carnot efficiency (Th - Tc)/Th, converted into work W as per W = Q(Th - Tc)/Th. But a hurricane's work output is the kinetic energy generation for its winds. With a hurricane in steady sate (constant wind speeds) kinetic energy generation is matched by frictional dissipation. Frictional dissipation of W into the hot reservoir reduces the net heat input required from the hot reservoir from Qh to Qh - W = Qc and raises the hurricane's efficiency to (Th - Tc)/Th X Qh/(Qh - W) = (Th - Tc)/Th X Qh/Qc = (Th - Tc)/Th X Th/Tc = (Th - Tc)/Tc. The Second Law of Thermodynamics is not violated because it allows work to be dissipated via friction as heat at any temperature --- at Th as well as at Tc. Of course the above assumes perfect or reversible operation. Like all real heat engines, hurricanes are imperfect. But perhaps it at least illustrates the point.


Why are the seas difficult to navigate at the "southern edge" of land? The question was inspired by an answer to this question on History SE, which referred to the "at times enormous waves" at the Cape of Good Hope in South Africa, and the even more "treacherous" passage around Cape Horn.

Why is the sea so hard to navigate at the southern extremities of the land masses.?Cape Horn, with a latitude in the high 50's, is easy to understand, but the Cape of Good Hope is in the 30s. Yet from what I understand, "navigability" does not extend far south of the Cape of Good Hope.

Is southern Australia and Tasmania (in the 40s latitudes) similarly hard to navigate? Would it be fore the same reasons?

Fetch.  The longer the wind has to act on the water the larger and more developed the waves become, see this site from the NOAA.  If you look at the southern portion of our planet you will note that there are few land masses to affect the wind or the wave development.  In the Wikipedia entry about prevailing winds you can see that the Southern Westerly winds are only affected by the Cape of Good Hope, Cape Horn, and to a lesser extent Australia.  Contrast this to the Northern hemisphere where North America, Europe and Asia divide the seas into smaller isolated sections.

There are additional factors involved particularly around the capes.  If you look at the prevailing ocean currents, see global map on this site you will see there are strong currents, driven by the wind, around the southern pole region.  At the capes, these currents become more chaotic and lead to eddies.  Sometimes the eddies make the current flow against the wind.  This results in even larger and less predictable sea states.


What, if any, paleoclimate data can be derived from stromatolite fossils? Stromatolite fossils have a layered structure vaguely reminiscent of tree rings, which are a well-known source for climate data. Although the formation process of stromatolite layers is less seasonal than that of tree rings, it seems plausible that some information about environment conditions and changes in those conditions might be derived from stromatolite fossils. Having very close modern analogues in modern stromatolites might make interpreting such observations easier than for growth data from other fossils, and the great age of some stromatilite fossils might give at least a blurry window into such ancient environments.

Is there any potential for using stromatolite fossils to infer climatic (or other) conditions from billions of years ago?

Stromatolites have indeed been used in palaeoclimatic investigations. Here are a couple of papers I found through Google Scholar:

Paul I. Abell, Stanley M. Awramik, Robert H. Osborne, Sterling Tomellini, Plio-pleistocene lacustrine stromatolites from lake Turkana, Kenya: Morphology, stratigraphy and stable isotopes, Sedimentary Geology, Volume 32, Issues 1–2, May 1982, Pages 1-26, ISSN 0037-0738, http://dx.doi.org/10.1016/0037-0738(82)90011-2.

Andrews, J. E. and Brasier, A. T. (2005), Seasonal records of climatic change in annually laminated tufas: short review and future prospects. J. Quaternary Sci., 20: 411–421. doi: 10.1002/jqs.942 http://dx.doi.org/10.1002/jqs.942

As you'll notice, though, these are both relatively young records. I don't know if similar studies have been attempted for Precambrian stromatolites.


The magnetite is in which type of magma In which type of magma can I find magnetite? Peraluminous or peralkaline? I've been looking and the peraluminous magma have a lot of oxides so I thought it would be reduced magma so it would have magnetite but I'm not pretty sure.

Probably both but I'd expect to see more in a peraluminous melt. The more mafic the melt the more iron based mineralisation you're going to see.


Centripetal Force Perfect Ball and Water I made a question in WolrdBuilding as I was directed to.

There a user said that with a perfect ball all water would pool to the equator because of centripetal force.

What I do not understand is how would the earth being perfect ball have all the water pooled to the equator when it does not do so now?

A perfect ball would have less difference between the radius close to the poles and the radius around the equator than what the current earth has.

In short, weird things happen when you combine things that don't combine in nature:

the Earth as a perfect sphere
the Earth spinning on an axis

Einstein's equivalence principle tells us that accelerations are all the same, no matter what's causing them. So you just add the acceleration vectors up.

The (real) Earth has an equatorial bulge because a stable surface can only exist where those vectors sum to zero:

gravity
residual ("centrifugal") acceleration from the Earth's rotation
the ground holding you up

This is called an equipotential surface and because of the centrifugal acceleration, on a spinning Earth this surface is an ellipsoid (well, mostly; there are small adjustments due to mass distribution).

The constraint of having a perfect sphere means that the materials making up the Earth your fictional planet are strong enough to keep it from ballooning out and filling an equipotential surface.

So if you make your fictional planet a perfect sphere, what you're really doing is changing where #3 happens but leaving #1 and #2 the same.

In other words, you're creating a 26 km deep valley encircling the globe.

Water runs downhill.

So eventually, all of the water will flow down into the giant equatorial valley...


Where can I find solar radiation data for specific land areas? NOAA has solar radiation data for 1991-2010 http://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/solar-radiation But I need data for Nov 1 2012-present! Is this data available?

Will I have to generate it myself? I have the software to do it, it is just a time/processor consuming task.

The Measurement and Instrumentation Data Center (MIDC, http://www.nrel.gov/midc/) provides Irradiance and other Meteorological Data from several stations. Have you also check in: https://mapsbeta.nrel.gov/nsrdb-data-viewer/? Some of the data maybe until the end of 2012 used to be in http://rredc.nrel.gov/solar/old_data/nsrdb/. Good luck!


What sort of a plate is the Sunda plate? I have read that the islands of Sumatra & Java have resulted from the subduction of oceanic crust of the Indo-Australian plate beneath the Sunda plate. I want to know whether this boundary is ocean-ocean convergence or ocean-continent convergence.

Are islands of Sumatra and Java like Mariana Islands which result from the subduction of the oceanic Pacific Plate beneath the oceanic Mariana plate? Or are they like the Andean volcanic continental Arc which results from the subduction of the oceanic Nazca plate beneath the South American plate.

Well, in short, it's mainly continental, (oceanic-continental convergence).
But in regards to the "type of plate" that the Sunda plate is, is minor plate or tertiary plate. Meaning it's not very big etc. Because 1 tectonic plate can have both oceanic or continental crust. Tectonic plate and crust are slightly different concepts. So, The Sunda plate is mainly comprised of continental crust. There might be a bit of oceanic crust, but less.
Map of oceanic crust on earth: https://www.ngdc.noaa.gov/mgg/ocean_age/data/2008/ngdc-generated_images/whole_world/2008_age_of_oceans_plates.jpg


How to calculate gps location based on direction and distance? I need to calculate the gps coordinates of a point "North 52° West 2.67 chains" from a known location. What's the process to make this calculation? If possible, start with 37N-91W.

There's an answer to this on Mathematics on a plane. That answer, plus knowing degrees/meter around my location will provide a sufficiently accurate answer for the short distances in my case. Given that, this question is probably a good candidate to be closed.

The answer in a plane you linked works rather well in a sphere provided that the distance you want to measure is tiny compared with both the radius of Earth and the distance to the nearest pole - and 2.67 chains is that tiny.

For the remaining of the answer I'll be assuming that the Earth is an sphere, which quite accurate unless you need great accuracy - that is, enough accurate for nearly anything except for surveying.

The first step is to convert your distance and direction to easting and northing distances - as the linked answer tells.

The second step is to convert those two distances to degrees latitude and longitude, and you only need to know that one degree latitude measures $R_{Earth}\cdot\frac{\pi}{180}$ and a degree longitude measures $R_{Earth}\cdot\frac{\pi}{180}\cdot cos(latitude)$.

As a final step, you just need to sum those angles to the latitude and longitude of your position.

With your data:

> # Earth radius in chains
> (r <- 3958.8*80)
[1] 316704
>
> #bearing, latitude and longitude in radians
> (br <- -52/180*pi)
[1] -0.907571211
> (latr <- 37/180*pi)
[1] 0.6457718232
> (lonr <- -91/180*pi)
[1] -1.588249619
>
> #1 Distance to North and East in chains
> (east <- sin(br)*2.67)
[1] -2.103988712
> (north <- cos(br)*2.67)
[1] 1.643816139
>
> #One degree in chains
> (deglat <- r*pi/180)
[1] 5527.527554
> (deglon <- r*pi/180*cos(latr))
[1] 4414.479788
>
> #2 distance in degrees
> (dlat <- north/deglat)
[1] 0.0002973872356
> (dlon <- east/deglon)
[1] -0.000476610793
>
> #3 arriving point (GPS coordinates)
> (lat <- 37+dlat)
[1] 37.00029739
> (lon <- -91+dlon)
[1] -91.00047661


What is the meaning of integral of negative magnetic field (nT) over time? I have a plot of the magnetic field (y-axis) over time (x-axis), one measure each hour (Dst - Disturbance Storm-Time).

From time to time, there is a negative peak, which indicates a magnetic storm. The more it goes down the bigger the storm.

What is the physical meaning of the integral of it (nT x h)?

Disturbance storm time index is a measure of the weakened horizontal component of Earth magnetic field during great magnetic disturbances. The depression is often flanked by peaks, that initiates and ends the storm. Dst is published by Kyoto University and more information about the methods and references are available on the web page.

  The Dst index represents the axially symmetric disturbance magnetic field at the dipole equator on the Earth's surface. Major disturbances in Dst are negative, namely decreases in the geomagnetic field. These field decreases are produced mainly by the equatorial current system in the magnetosphere, usually referred to as the ring current. The neutral sheet current flowing across the magnetospheric tail makes a small contribution to the field decreases near the Earth. Positive variations in Dst are mostly caused by the compression of the magnetosphere from solar wind pressure increases.

Sugiura and Kamei, IAGA Bulletin No 40 (1991)

Measures are presented as the deviation from the average magnetic field strength, measured in the SI unit Tesla $T$ at time $t$. In this context, the magnetic field is very weak, so the nano prefix $n$ is usually used. Magnetic field strength can be derived from weight (in $kg$), electric charge (in Coulomb $C$) and time in second ($s$) as:

$T =\frac{kg}{C \times s}$

if you integrate with time (in seconds, $s$) you'll get for each unit:

$T \times s =\frac{kg}{C}$.

The relation of electric charge and weight is used as a measure of Radiation exposure, often given in röntgen ($R$) and related as:

$1 \frac{C}{kg} = 3876 R$

Technically, your integral will, therefore, be a measure of increased radiation exposure, kinetic energy released per unit mass, for the time you integrate over. You could convert it to röntgen ($2.58×10^{−4} C/kg = R$) but note that the calculated product describes the deviation, not the absolute ionization.


DC component: Seismic inversion Multiple papers (for example, Limitations on impedance inversion
of band-limited reflection data Gosh[2000]) and textbooks covering seismic inversion mention a necessary component of any seismic inversion: the DC (or zero frequency) component. For lack of a better question, what does a "zero frequency" component look like? Also, why is this considered a necessary component of any complete seismic inversion scheme?

The impedance inversion problem asks: "Recover acoustic impedance from seismic reflection waveforms". The forward modeling procedure from acoustic impedance to seismic reflection waveforms involves calculating reflection coefficients and then convolving these with a wavelet.

Let's assume, for now, that you have perfect seismic resolution and therefore your wavelet is of infinite bandwidth. This means that the inversion problem becomes: "Recover the acoustic impedance from a given set of reflection coefficients".

As shown by Peterson et al. (1955), for small contrasts in acoustic impedance, the reflection coefficient equation can be linearized as shown below. Linear problems are much much easier to solve computationally than non-linear. This makes the forward model calculation a simple difference, the discrete analog to a derivative. Note: this is for normal incidence but a similar analysis can be done for non-normal incidence.

So... if it takes a derivative to calculate the reflection coefficient, it must take an integral to calculate the acoustic impedance. However, as everyone knows, when you integrate any function, you inevitably run into the non-uniqueness caused by that dreaded +C at the end of all integrals.

That +C, in this context, means that there are an infinite number of acoustic impedance models that can give you the exact same reflection coefficients. So you need the +C (i.e. the DC, or zero frequency, or additive constant) information to do a complete inversion and really recover the true values of impedance in the earth. All you get from the seismic are the reflection coefficients (and that's with infinite resolution), so you will need to get this DC information from another independent source.

In practice, the inversion is not done by a simple integration but by setting up a linear system and iteratively converging (by something like conjugate gradient) to the answer that minimizes some misfit function between the forward model and the data. As complex as that sounds, deep down, we are pretty much just doing a careful integration.

Hope that helped.

Peterson, R. A., W. R. Fillippone, and F. B. Coker, 1955, The synthesis of
seismograms from well log data: Geophysics, 20 (3), 516–538.


GIS Data on climate types Where can I download GIS data delimiting global climate types?  For example mediterannean climate, temperate climate, etc.

Additionally, how similar are temperature profiles for various places in the same climate classification?

NOAA has climate division files in netcdf and shapefile format, though they may be just CONUS:

http://www.esrl.noaa.gov/psd/data/usclimdivs/boundaries.html

The most promising link looks like this source with paper citation below.  They have lots of freely available data in a variety of formats:

http://koeppen-geiger.vu-wien.ac.at/shifts.htm

Rubel, F., and M. Kottek, 2010: Observed and projected climate shifts 1901-2100 depicted by world maps of the Köppen-Geiger climate classification. Meteorol. Z., 19, 135-141. DOI: 10.1127/0941-2948/2010/0430.

There's also the ArcGIS Online map service that has Koppen-Geiger Observed and Predicted Climate Shifts:

http://www.arcgis.com/home/item.html?id=0b9f1f90f4f745daacbc35599609b59a

To answer your question about the types of temperature in a classification,  I suggest you refer to the paper above and the ranges of expected temperatures for each Koppen climate type which can be found here: https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification

For modeled and observed temperature, precipitation, etc. you might find the following resources helpful:

http://iridl.ldeo.columbia.edu/

http://gisclimatechange.ucar.edu/

http://www.worldclim.org/


Why is hydrogen formation in serpentinisation an exothermic reaction? In the process of serpentinisation, protons act as oxidising agents for ferrous ions, which results in the production of dihydrogen gas. How is that possible?
Dihydrogen being a strong reductor, I woud expect this reaction spontaneously going the opposite way.

Under normal circumstances your suggestion might be correct, but bear in mind that the serpentinization reaction takes place under very negative Eh, and very high pH conditions (pH 12 or more). This abnormal combination is right on the boundary of water-hydrogen stability conditions. In hyperalkaline springs, which result from the reaction water + peridotite = serpentine, there is hardly a free molecule of oxygen left in solution.


How Could Sheep Graze these Steep Hillsides Without Leaving any Marks? Here are two images of English hill figures (The Cerne Abbas giant and the Uffington white horse):

These hillsides, which are obviously grazed by sheep, show tracks that form numerous contour lines around the said hillsides. According to many people, however (e.g., Wikipedia), these contour lines are not generated by domestic livestock.

If that is the case, what causes these lines and why do they only appear on hills that are grazed by livestock? If, on the other hand, no livestock grazes these pastures, what keeps the grass so short and why are English farmers wasting such huge amounts of good grazing land? Are they mad? Some people, such as this answer, say the lines are caused by natural earth movements, but won't explain why they only occur on hills that are grazed by livestock. There are many more examples, and better ones, of chalk hill contour lines available on Wikipedia, but my simple explanation of how to find them has been deleted. The Long Man of Wilmington is a much better example than the two photos above, it shows the sheep as well as contour lines and is available on Wikipedia.

Those lines have nothing to do with animals.

Those lines are generated by solifluction and frost heave. It is sometimes referred to as cryoplanation or soil creep. Basically as the thin hillside soil freezes and thaws it expands and contracts and because there is a slop it moves downslope. In addition rain combined with how the surface thaws before the deeped ground causes a plane of weakness and movement. It can form a variety of patterns but on strong slopes it tends to form stripes or ripples.

That area of England is well known for such landform. Below is a picture from Dorset and another from the isle of wight. They don't only occur on grazed ground, but if ground has trees they act as anchors for the soil and you don't get the more noticeable lines and nobody is going to graze animals on ground with nothing but trees or hills with no soil which also will not have them.

1. Sugden, David E. (1971). "The significance of periglacial activity on some Scottish mountains"

2. frost creep and gelifluction features a review


Deserts and Humidity How is that a general rule of thumb that less humidity equals more rain? Deserts don’t get much rain and humidity is also very low. Rainforests get a lot of rain when the humidity is very high so how is that that less humidity equals more rain?

Humidity doesn't affect whether or not it rains. Rain clouds form on their own. Humidity does control whether or not the rain will touch the ground or not.

Sorry if I wasn't clear in my other answer.

Deserts. They don't get a lot of rain because rain clouds never make it to a desert. This can be due to a factor of many reasons. You can read more about it here: Why don't deserts get a lot of rain?

Rain forests. Like I said before, humidity doesn't really affect whether or not it will rain. Even though there is high humidity, rain clouds can still form, and it will still rain. Like I said in my other question, the surrounding air can't hold more water, so there will always be rain in a rain forest if rain clouds are present.

What I was trying to say in my other question, is that the surrounding humidity could play a role in whether or not the rain drops actually fall to the ground or not. But rain cloud formation is completely unrelated to humidity.

I'll be sure to edit that question to make it more concise. Sorry for the confusion.


Why does exhaust smells linger some days? Some days I can smell bad smelling exhaust 50 meters or more away from the bus stop. I think the air is usually moist those days.

Does exhaust gases linger longer if the air is moist near the ground? Is it smog I am smelling those days?

On morning 12 march it was about

Temperature: 4°C
Humidity:93%
Barometer:978 mbar
Wind:10 m/s

Looking at the data from earth.nullschool.net at a few hours before that morning I saw surface temperature of 5.1°C and 5.8°C at 1000hPa.

You can see this post for a more detailed discussion, but the typical answer to your question is air stagnation.  When the atmosphere is stable, there is little mixing, and the air can stagnate.  Typically this coincides with low wind speeds and a low boundary layer.  The boundary layer holds air near the surface like a blanket. The boundary layer collapses overnight, becoming shallow, and grows when the sun heats the surface of the Earth.  So, in the morning, the shallow boundary layer allows less vertical mixing to occur.

You might be noticing that on cloudy days, when clouds are low, there is little wind and no solar heating.  Air pollution has no place to go, so it sticks around.

Another aspect is that vehicles emit more emissions under cold-start conditions.  This is because vehicles get cold overnight and take a while to get up to normal temperature when they startup in the morning.  The cold vehicle will have a low combustion efficiency and catalytic converters won't work as well.