fossils & relative dating
DESCRIPTION
FOSSILS & RELATIVE DATING. GEOLOGIC TIME SCALE. a series of time intervals that divides Earth ’ s history. Each layer of rock represents specific interval of time Index fossils help determine specific period Time periods divided by specific events like mass extinctions. ROCKS TELL A STORY. - PowerPoint PPT PresentationTRANSCRIPT
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FOSSILS & RELATIVE DATING
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GEOLOGIC TIME SCALEa series of time intervals that divides Earth’s history
• Each layer of rock represents specific interval of time
• Index fossils help determine specific period
• Time periods divided by specific events like mass extinctions
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ROCKS TELL A STORY Rocks can tell where they were made and
when Sedimentary rocks can have fossils in them Rocks can tell when mass extinctions
happened
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LAW OF SUPERPOSITIONFor undisturbed rocks, the oldest layer is on the bottom and the youngest is on top
Supai is oldest – WHY?
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PALEONTOLOGYthe study of fossils remains of ancient life
Body fossils vs. trace fossils Body = remain of organism, like bones; Trace = evidence of organism, like footprints
Scientific dating Absolute dating (gives age in years)
uses radiometric / radioactive dating (isotopes) Relative dating (gives age before, after, during)
uses observation of rock layers
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FOSSILS Traces and preserved remains of
ancient life found within rock layersFossils show:
Biodiversity How species have changed over time Correlation between rock layers from around the
world Relative ages to particular strata Evidence for the geological time scale
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SCIENTIFIC DATINGAbsolute Dating: numerical
dating to give rocks an actual date or date range, in number of years
Relative Dating: compare how old something is in comparison to something else; used to put rocks and geological events in correct chronological order
HOW?Use sedimentary rocksUse fossilsStudy strata
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INDEX FOSSIL Fossil that defines and identifies
geologic periods; often in only one layer of rock
Easily recognizable Exists over a short
geologic time range(found only in a few layers of rock)
Wide distribution(geographic rangeis world-wide)
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Ex/ INDEX FOSSIL: AMMONITE
Ammonite fossils are found worldwide, existed for only a very
specific period of time
This means ammonites are found in very specific layers of rock;
Once we know the ammonites, then we can determine the age of any fossil found next an ammonite fossil.
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What kind of rocks are these fossils in?
Which layer is oldest?
Which layer is youngest?
How do you know?
Quiz yourself!