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http://dewa.com/animated/. Geologic Time. A method of ordering and measuring past events. How Old is this Photograph?. How can you tell? What are some clues?. http://www.cartes.freeuk.com/time/date.htm. http://www.familychronicle.com/dating40.htm.
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http://dewa.com/animated/ Geologic Time A method of ordering and measuring past events
How Old is this Photograph? • How can you tell? • What are some clues? http://www.cartes.freeuk.com/time/date.htm
http://www.familychronicle.com/dating40.htm http://www.familychronicle.com/dating60.htm
Eon • Longest unit of geological time • Measured in billions of years • Present eon: Phanerozoic
Era • Second longest geological time measurement • Hundreds of millions of years • Present era: Cenozoic
Period • Third longest geological time measurement • Measured in tens of millions to hundreds of millions of years • Defined by the life forms that were abundant or became extinct • Present: Quaternary
Epoch • Fourth geological time measurement • Measured in million to tens of million of years • Present epoch: Holocene
http://www.geology.wisc.edu/~museum/old/geotime.html http://www.geology.wisc.edu/~museum/old/geotime.html
Relative Dating • Determines the order in which geological events occurred based on stratigraphic principles, fossils and bands of rock
Absolute Dating • Provides a numerical age for the material tested
The Principle of Superposition http://homepage.usask.ca/~mjr347/prog/geoe118/geoe118.039.html
The Principle of Original Horizontality http://en.wikipedia.org/wiki/Sedimentary
The Principle of Lateral Continuity http://www.library.csi.cuny.edu/dept/as/strat/lc.htm
The Principle of Cross-cuttining http://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.html
The Principle of Intrusion/Inclusion http://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.html
Principle of Deformation/Unconformity http://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.html
Correlation: Similar Rock Patterns http://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.html
Correlation: Fossils http://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.html
http://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.htmlhttp://homepage.usask.ca/~mjr347//prog/geoe118/geoe118.039.html
Geological Records with Strong Annual Cyclicity • Tree growth rings • Coral growth rings • Varves (annual clay sediment layers)
http://www.calacademy.org/exhibits/california_hotspot/habitat_redwoods.htmhttp://www.calacademy.org/exhibits/california_hotspot/habitat_redwoods.htm
Coral Annual Ring Growth http://earthobservatory.nasa.gov/Study/Paleoclimatology_CloseUp/paleoclimatology_closeup_2.html
Varves http://www.indiana.edu/~ensiweb/lessons/varves.html
Radiometric Dating • Methods relying on the decay of naturally occurring radioisotopes
Most Common Radioisotope Decay • Carbon-14 -> Nitrogen-14 • Potassium-40 -> Argon-40 • Uranium-235 -> Lead-207 • Uranium-238 -> Lead-206 • Thorium-232 -> Lead-208 • Rubidium-87 -> Strontium-87