AST 111 Lecture Notes - Lecture 11: Allende Meteorite, Radiometric Dating, Outer Core
6 Jun 2020
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Document Summary
Earth and other planets formed by a process of accretion from small dust grains within the solar nebular. Earth was hit by a mars size object early in its history to form the moon. Dates can be assigned to rocks and minerals through radiometric dating. Certain radioactive elements (such as uranium) decay with well determined half life to form a daughter element in this case lead. By measuring the uranium and lead content in certain minerals the time since the mineral crystallized can be determined. Uranium has two isotopes with different half life"s providing an independent check on such dates. In one half life, half the uranium will decay to lead. In two half life"s, half the remained will decay (3/4 in total) Understanding of the earth was revolutionized in the 1950s and 60s by the discovery of plate tectonics. Long before this, there had been evidence to suggest that continents moved around on the earth"s surfac.
