# Tag Info

15

Most probably, he was referring to the Brunswick Magnetic Anomaly: http://www.geosociety.org/news/pr/2014/14-22.htm This is an area of lower-than-normal magnetism present in North America in the Southwestern United States. Note that altough it COULD be a piece of Africa, it could also be caused by something else.

9

The boundary between the upper and lower mantle is today believed to be due to the phase change because of increasing pressure of: $$\text{Ringwoodite} \xrightarrow{\text{660 km, about 24.5 GPa}} \text{Mg-Perovskite} + \text{Mg-Wüstite}$$ The boundary was originally found in the form of a seismic discontinuity (the "660 km discontinuity"). This information ...

9

The principle does not apply to all materials on earth as observed by us but is primarily concerned with sediments and rocks that form from sediments. Since sedimentation is a process driven by gravity grains settle one on top of others and there is no possibility to change that without adding additional processes. So from this perspective the principle is ...

7

No, we occasionally get fragments of upper mantle overthrust onto the Earth's crust, but then the specific gravity (density) contrast is not so great, roughly 2.7 to 3.0 for crust, about 3.2 for mantle. But the core is another matter. The density contrast is huge - the liquid outer core is between 9.9 and 12.2, whilst the solid core is estimated to be 12.6 ...

4

The diagram is perhaps a little mis-leading. Think of the ground/rock between the electrodes as a big resistor. The surrounding rock can be modeled as a set of parallel resistors. Most of the electrons will take a direct straight line route between the electrodes, but some of them flow through this surrounding rock, so increasing the current and reducing the ...

4

Here is another example where the law of superposition breaks. Mind you this is a natural process: meteorite impacts. A meteorite impact will excavate material from the bottom, and deposit it above the crater rims. Here's how: This will result in something that looks like this: Source for both images is http://www.lpi.usra.edu/exploration/education/...

4

As Peter correctly responds, for sedimentary rocks the principle of superposition is pretty much watertight except where tectonic superposition takes place. The latter can either repeat the sedimentary sequence, overturn it, or overthrust earlier sequences. There are many possible geometries, which creationists tend to misrepresent. The principle of ...

4

The inner core rotates slightly faster than the rest of the planet. This passage from National Geographic explains: The liquid outer core separates the inner core from the rest of the Earth, and as a result, the inner core rotates a little differently than the rest of the planet. It rotates eastward, like the surface, but it’s a little faster, making an ...

4

Im am currently doing my masters in geophysics (last semester) and before that I did a bachelor in geoscience. I assume by layers you mean the crust, the mantle and the core. These all have different composition and also different densities. But the earth rotates as a whole, not the individual layers, all layers have the same angular velocity. That means ...

3

The terrain examples show some striking similarities to what is referred to in the United States as "Badlands" - a type of terrain formed by layered sedimentary strata of rock that is soft enough to be eroded by wind and water into recognizably similar features. For example, here is South Dakota Badlands National Park: Anecdotally, I have seen similar ...

2

If you were hoping for a smooth succession from Archean all the way down to Quaternary, you're going to be disappointed. Geology is messier than rocks being serenely laid down continuously through time like that. A drive from the Appalachians to the East Coast would get you everything but the Archaean rocks, although the only Proterozoic rocks would be found ...

1

The divisions in the geologic time scale have evolved over time. Its origins can be traced back to Nicolaus Steno in 1669 described two basic geologic principles. The first stated that sedimentary rocks are laid down in a horizontal manner. The second stated that younger rock units were deposited on top of older rock units. Work by James Hutton, Charles ...

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