09 GEOS 1004 - GEOS 1004 SPOTILA Lecture 8 Geologic...

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GEOS 1004, SPOTILA Lecture 8, 9/22/09 Geologic principles II: the rock record and geologic time *One of the most important contributions of geoscience has been discovering the age and history of the earth. It is as important as the discovery that the sun is the center of the solar system, or that the universe extends far beyond the solar system. Age of Earth = 4.6 billion years (4.6 Byr = 4.6 Ga = 4,600,000,000 = 4.6x109 yrs) *What is this based on? Dated by a meteorite geologic timescale = -variable resolution, eons, eras, periods, epochs -resolution decreases back in time (more divisions towards the present) WHY? -terminology is based on original timescale which was relative WHY? Relative geologic time Sequence of events based on the record preserved in the rocks; not ages in years. Rules to establish a sequence: 1) superposition -stack of sedimentary layers -oldest on the bottom, youngest on top -what is another word for the layers? 1b) fossils
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09 GEOS 1004 - GEOS 1004 SPOTILA Lecture 8 Geologic...

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