the rock record
DESCRIPTION
The Rock Record. Chapter 8. Mr. Sierra's Earth Science. p.185. itarianism. Uniform. A principle that geologic processes that occurred in the past can be explained by current geologic processes. Volcanism and Erosion. p.186. Relative Age. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 8Chapter 8
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itarianism
A principle that geologic processes that occurred in the past can be explained by current geologic processes. Volcanism and Erosion
Uniformp.185
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Relative Age
The age of an object in relation to the age of other objects
p.186
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The law that a sedimentary rock layer is
older than the layers above it and younger than the layers below it if the layers are not disturbed.
Law of Superpositionp.187
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A break in the geologic record created
when rock layers are eroded or when sediment is not deposited for a long period of time.
Un ities p.189conform
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Absolute Age
The numeric age of an object or event, often stated in years before the present.
Using a process like “radiometric dating” or “carbon dating”
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Rates of Deposition
In general, about 30 cm of sedimentary rock are deposited over a period of 1,000 years.
However, a flood can deposit many meters of sediment in just one day.
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Radiometric Dating
A method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) and a stable (daughter) isotope.
Half-Life: the time required for half of a sample of a radioactive isotope to break down.
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Carbon-14 Dating
Plants absorb Carbon during Photosynthesis
Scientists compare the carbon isotopes 12C and 14C (radioactive)
This can be used to determine the ages of wood, bones, shells and other organic remains that are less than 7,000 years old.
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Pa
leonto
log
y The scientific study of fossils.
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Trace Fossils
Fossilized evidence of past movement of an animal such as tracks, footprints, borings and borrows.
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Index Fossils
A fossil that is used to establish the age of rock layers because it is: Distinct – features different from other
fossils Abundant – occurs in fairly large numbers Widespread – present in scattered rocks Existed only for a short span of
geologic time