# Tag Info

31

It is the pressure gradient that is proportional to the local gravitational force. When that force is integrated over a distance, the pressure gradient is integrated to accumulate a total pressure. The maximum occurs at the point towards which gravity is directed in a spherical mass, which is the center. True, gravity at that point is zero, but it and ...

30

Part 1 The Democratic Republic of the Congo's Katanga Province contains almost 40% of the world's reserves of cobalt [1]. Why are deposits concentrated so strongly in such a small portion of the earth? Cobalt isn't as unevenly distributed as it seems. It is correct that most of the world's cobalt reserves are in DRC, but most of the cobalt resources are ...

25

Metals occur on every continent . The issue is whether or not they occur in sufficiently large deposits for them to be mined economically. The difference between a mineral deposit and an ore body is economics: can it be mined for a profit? One of the issues with mineral resources is that once they've been mined, they're gone. Cornwall and Devon, in the UK, ...

21

There is actually an hypothesis that large asteroid impacts can trigger volcanism at the antipodal point, where the seismic energy of the impact focuses. On Earth, it has been suggested that the Chicxulub impact could have triggered the main phase of the antipodal (and synchronous) Deccan Traps eruption (Richards et al., 2015). On Mars, the same process has ...

17

Maybe but it will depend on the state of the magma chamber under the caldera. If the magma chamber is already under enough pressure and has a super-eruptive quantity of liquid melt in it then the shock of a large bolide impact may act to "pop the cork" so to speak initiating a super eruption. I can also make an argument for shock nucleation of gas ...

16

All stable elements (and the radioactive U and Th) exist everywhere on Earth. They're in the sand underneath your feet, they're in your bones, they're in the dust in the air, they're in the ocean. The question is how much. There are some estimates on the concentration of each element, and there's a nice table that lists all of them in Wikipedia article ...

15

The effects of Earth's past climate variations on the landscape, especially glaciation, cannot be underestimated. The multiple glacial advances and retreats over the last 4 million years or so have been a major (and sometimes the principal) force that shaped the current landscape. We're actually living in one of the temporary glacial minima - there will be ...

13

Pumice does not contain any gas, the vesicles are empty1. The magma which generated the pumice used to contain gas, mostly water and CO2 like you said. But this gas was lost during the eruption. Most of the vesicles are actually connected, allowing the gas to escape. The connectivity $C$ is defined as: $C = \frac{\phi'}{\phi}$ where $\phi'$ is the connected ...

12

Roughly put, it's the same thing that makes a density step function when you try to combine oil and water: Source The components do not mix with or dissolve into each other, so gravity makes the denser material -- water -- settle to the bottom. The density as a function of height jumps up from the oil density to the water density when you go below the ...

12

The previous answers do a fine job already. But I'll try to add a simple thought experiment. Imagine three objects floating in space, clumping together by gravity: ### ### #A#|c|#B# ### ### Mass A, the negligible mass c and mass B, equal to A. The center is attracted to A and B and their gravity cancels out. However, A presses against c, because it is ...

9

Pressure at the center of the earth is non-zero. You're correct that there's no gravitational force at the center of the earth, but that doesn't mean pressure is zero - the pressure comes from the many miles of rock sitting above the center of the earth. As an analogy, think of a balloon. The pressure inside is higher than ambient because the elastic skin of ...

9

Bennu is about 470m diameter, and will impact at a "mere" 11.3km/s. At the impact site it would blast a crater some 3 miles wide and 1500 ft deep, a very respectable impact indeed. The energy of impact is equivalent to a 6.6 moment magnitude earthquake at the surface at the impact location. 500 miles away, the impact will be neither felt not heard ...

8

Its not that cobalt is less abundant or wide spread. What you are noticing is that gold has been mined for far longer than cobalt and is far more valuable. Gold has been mined even in antiquity and even poor deposits are usually worth extracting, so most of the large easy deposits were mined out ages ago. Cobalt on the the other hand was only discovered in ...

7

The transformation of sand into sandstone per se cannot be directly witnessed, as it's happening deep in the earth. However, there are types of cementation that happen quickly and in plain view: A ScienceDirect article on Cementation says: Cementation is the precipitation of a binding material around grains, thereby filling the pores of a sediment. Berner (...

7

I changed your model solution a little bit; but it's like Ingvar Lukas wrote in his answer: you redefined xi and yi in the process, so when you later on define the netCDF values for lat and lon you try to fill small 1D arrays with a 2D array. That is the source of your error. import numpy as np from scipy.interpolate import griddata import xarray as xr ...

6

This is not a four- digit number but four separare numbers called Bravais-Miller indices. Bravais-Miller indices descrive the orientation of a crystal plane relative to the symmetry axes of a crystal, as described in Wikipedia. Put very briefly, a zero index means the plane is parallel to that axis, while nonzero indices encode the relative values of the ...

6

By far most naturally occurring hydrates are methane hydrates. However, Dillon[1] documents hydration of other gases including carbon dioxide in some places such as the Gulf of Mexico: Many gas hydrates are stable in the deep ocean conditions, but methane hydrate is by far the dominant type, making up >99% of gas hydrate in the ocean floor. The methane ...

6

You have a shape mismatch, as you are overwritingxi and yi using np.meshgrid, then assigning wrong dimensions with dim_lat and dim_lon and eventually trying to fill latitude and longitude with your initial values of length 6. Try modifying the grid preparation and interpolation # prepare a grid for interpolation xi = np.arange(6.0, 14.0, 0.001) yi = np....

5

it was simply an older stone smoothed by water that had fallen into sediment. This is exactly what happened. There's a name for that: a conglomerate.

5

Skarn is metamorphosed sedimentary rock, it's iron deposits are in the form of sulfides. This means two things; There almost certainly will be iron oxide contamination throughout the unit, at least I have never seen a sedimentary rock that didn't have staining from iron oxides. In my Earth Science classes we were always told that copper, and particularly ...

5

We don't know for sure because A. the evidence has almost all been erased by the continued crustal shortening of the area where the volcanic arc(s) would have been. B. the region is huge and volcanism will have varied in duration greatly across the range as a whole. The "core range" of the Himalaya has lost on the order of 6000km (~2500 miles) of ...

5

The work of Formenti et al. in Earth and Planetary Science Letters 214 (2003) 561 disagrees with the idea that pumice can never retain original gases (emphasis added): Our observations show that dense blocks derived from lava domes are commonly not able to retain gas because essentially all the vesicles are interconnected, as also found by Le Pennec et al. [...

4

In English, the word fluvial comes from the Latin word for river. Fluvial processes are processes associated with rivers or streams and the deposits and forms created by them. River terraces and fluvial terraces are the same thing.

4

Part of the problem is in the question itself. In the title, you ask about "in every continent" while in the text, you imply that you are talking about smaller areas. One premise we can safely assume is that most elements are distributed unevenly. That is a far more relaxed question than you are asking, though. For an example, look at hydrogen. You ...

4

Quartz is a silicate at the most used Dana and Strunz classifications of minerals. Several websites and mineralogists classify it as silicate. The structure of quartz is similar to other silicates with Si-O tetrahedres. Quartz structure. quartzpage.de

4

Select the objectives you want to use on your microscope altogether with your camera. If the camera is not a permanent installation, ensure that the mount reliably establishes again and again the same position and alignment in respect to the optical axis of the microscope. See if your group has a stage micrometer, a slide with fine regular markings: (...

4

You could mention the fact that the solid Earth (i.e., not the atmosphere) is slowly cooling down, as the two main sources of heat, primordial and radioactive, are slowly decaying. Because of this, the planet may become tectonically dead at some point. Gradual change over long periods of time is known as uniformitarianism, and has been opposed to ...

4

As I understand it, the current explanation for these deposits' existence is the carboniferous period when plants basically evolved woody structures that allowed them to grow trunks and grow tall. This is a minor point, but you're writing about coal rather than petroleum. Most geologists think petroleum is also of biogenic origin, but resulted from sea-...

4

The approach adopted by Charles Lyell (and other writers in a similar timeframe), in his book 'Principles of Geology' which was first published in the 1830s was to look at processes in the modern landscape where the rate of change could be determined by observation or from historical evidence, and assuming that similar processes operated at similar rates in ...

4

Ignoring the effect of overgrazing by animals, you have already touched on many things that affect where grass will grow: elevation, slope, geology - particularly soil cover, water erosion and wind. Three others are ground moisture, for which soil plays a very important role, temperature and exposure to sun light - particularly where surface features can ...

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