Thursday, August 25, 2011

Earth's crust and the other delicious parts

Earth has an outer silicate (sand, Portland cement, and thousands of minerals are examples of silicates) solid crust, a highly viscous )between solid and liquid) mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core.

Scientific understanding of Earth's internal structure, says Wikipedia, is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of the gravity field of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth's deep interior.

Inner core: 4000 miles deep, super-hot but solid, iron & nickel.

outer core: liquid, super hot

mantle: silicon, aluminum, magnesium, iron, etc; "This mixture continually rises, cools, sinks warms up, and rises again, releasing 80% of the heat generated from the eartth's interior." - WG

crust: broken, rocky shell; plates of the crust float upon the upper mantle.

- continental drift theory
- plate tectonics, perhaps caused by interior heat.
- magma
- subduction: heavier sea plate slides beneath the lighter continental plate.
- accretion: adding to the material of the earth's crust.
- spreading: sea plates pulling apart, creating a rift (crack).
- folds: layers of rock that have been bent under pressure.
- faulting: cracks in the crust; associated with earthquakes.
- ring of fire: earthquake-prone zone that surrounds the Pacific.