Geotime - William E. Ferguson Geologic Time Geologic Time A...

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Unformatted text preview: William E. Ferguson Geologic Time Geologic Time A major difference between geologists and most other scientists is their attitude about time. A "long" time may not be important unless it is > 1 million years. Amount of Time Amount of Time Required for Required for Some Geologic Some Geologic Processes and Processes and Events Events Some geologic processes can be documented using historical records (brown area is new land from 1887-1988) Uniformitarianism Uniformitarianism The present is the key to the past. James Hutton James Hutton Natural laws do not change however, rates and intensity of processes may. Two ways to date Two ways to date geologic events geologic events 1 RELATIVE DATING (relative position of fossils, structure, geomagnetics) 2 ABSOLUTE DATING (isotopic, tree rings, varves, etc.) RELATIVE GEOLOGIC RELATIVE GEOLOGIC TIME TIME Steno Laws (1669) developed to arrange rock units in time-order Principle of Superposition Principle of Original Horizontality Law of Cross -Cutting Relationships Law of Inclusions Laws apply to both sedimentary and volcanic rocks. Principle of Superposition Principle of Superposition In a sequence of undisturbed layered rocks, the oldest rocks are on the bottom. Jim Steinberg/Photo Researchers Oldest rocks Oldest rocks Youngest rocks Youngest rocks Principle of Superposition Principle of Original Principle of Original Horizontality Horizontality Layered strata are deposited horizontal or nearly horizontal or nearly parallel to the Earths surface. Principles of original Principles of original horizontality and superposition horizontality and superposition Law of Cross-Cutting Law of Cross-Cutting Relationships Relationships A rock or feature is younger than any rock or feature it cuts across. Law of Law of Cross-cutting Relationships Cross-cutting Relationships LAW OF INCLUSIONS LAW OF INCLUSIONS Included rocks are older than surrounding rocks. PRINCIPLE OF FAUNAL...
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This note was uploaded on 04/19/2011 for the course GG 103 taught by Professor Herrero-bervera during the Summer '10 term at University of Hawaii, Manoa.

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Geotime - William E. Ferguson Geologic Time Geologic Time A...

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