GEOG-120 Lecture Notes - Lecture 30: Himalayas, Mafic, Gabbro
24 Sep 2020
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Document Summary
The outermost layer of the planet is the earth"s crust. It varies in thickness from 8 to 80 km and comprises the continents and ocean basins. The thickness of the crust is generally less than 10 km under the oceans and averages about 40 km for most continents. Approximately 10 percent of the crust exceeds 50 km, with the greatest thickness reported in the himalayas, where it is about 80 km. Differences within earth are not just solid vs. molten, but compositional as well. Inner areas (core) are largely iron and nickel, while outer mantle and crust are dominantly silica based. About 75% of earth"s crust is made of oxygen (47%) and silicon (28%) A mineral is a naturally occurring, inorganic substance that has a definite chemical composition and a characteristic atomic structure. This gives each mineral its distinctive properties, such as colour, lustre, hardness, and cleavage/fracture.
