GEOL 1010 Chapter Notes - Chapter 12: Richard Dixon Oldham, Outer Core, Wave Power
by Jake Smooke
Course CodeGEOL 1010
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Geology Chapter 12 Key Terms
Mineral phase change is a change that occurs when a mineral is subjected to intense pressure.
In this change, the structure of a mineral may become unstable, causing its atoms to rearrange
into a denser and more stable structure.
The increase in density of mantle rocks is due both to the compression of existing minerals and
the formation of new high-pressure minerals.
Seismic waves are large enough to go through the earth and come out the other side, making
them very visible. They allow us to see into our planet. Seismic waves travel fastest when the
rock is rigid. Seismic waves are reflected and refracted when traveling through the Earth and do
not travel in a straight line.
Reflection is the redirection of some waves back to the surface when seismic waves hit a
boundary between different Earth materials.
Refraction is the remaining wave energy that is bent. This is the path we normally see seismic
The D Layer is the boundary layer between the rocky mantle and the liquid outer core. The
base of the D Layer is partially molten because it is so hot.
The Lower Mantle is between the transition one and the liquid core.
Richard Dixon Oldham discovered Earth’s core. He believed the core created a shadow zone,
the zone between 105-140 degrees from an earthquake’s epicenter. Direct waves do not
penetrate the shadow zone because of direct refraction.
The core-mantle boundary causes P wave velocity to drop, and does not allow S waves to
penetrate the core.
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