EVSC 2800 Study Guide - Midterm Guide: Radioactive Decay, Magnesium
12 May 2016
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Document Summary
Earth formed 4. 56 billion years ago: violent collisions of accreting planetesimals created impact energy which was converted to heat, radioactive decay of unstable nuclei such as uranium and thorium released heat. Early earth was a molten body- a magma ocean: heated by asteroid impacts, the heavy elements sunk to the center which added more heat. Earth"s oldest rocks are 4. 4 billion years old. From longest time ago to most recent: oldest known rocks, blue-green algae, shelled marine organisms, land plants, reptiles, mammals, extinction of dinosaurs, hominids, modern humans, tj founded uva. They are crystalline substances meaning they have a regular internal arrangements of atoms, repeating in an orderly 3d array (called a lattice: the regular internal arrangement is expressed in an external crystalline shape or habit. Minerals are inorganic: not composed of organic carbon but can be made by organisms.
