Geologic Time - their position • 3 main laws/principals...

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Geologic Time By Stephen Beisser
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Introduction Geological events by themselves have little meaning until they are put into a time perspective. Studying history, whether it be the Civil War or the age of dinosaurs, requires a calendar. Among geology’s major contributions to human knowledge is the geologic time scale and the discovery that earth history is exceedingly long.
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Geology needs a Time Scale In the 18 th century, geologists had no real way of knowing the age of the earth. Geologist John Wesley Powell realized that the key to earth’s history was in the rocks.
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Relative Dating—Key Principals Relative dating: a technique for determining the age of rocks based on
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Unformatted text preview: their position. • 3 main laws/principals of relative dating 1: Law of Superposition • In an underformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below. 2: Principal of Original Horizontality • Layers of sediment are generally deposited in a horizontal position. • Rock layers that are flat still have their original horizontality are not disturbed. • Layers folded or inclined in a steep angle have been moved in that position after original deposition. 3: Principal of Cross-Cutting Relationships • Faults and intrusions are younger than the layers of rock they are in....
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This note was uploaded on 01/13/2011 for the course GEO 1 taught by Professor Bleh during the Spring '10 term at Bergen Community College.

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Geologic Time - their position • 3 main laws/principals...

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