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## PowerPoint Slideshow about ' Geologic Time' - binah

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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

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