Transcript The Geologic Time Scale

The Geologic Time Scale
A Clock In the Rocks
Relative Dating
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A technique used to determine the age of a fossil by
comparing it to other fossils found in the layering of a
rock
Sedimentary rock = undisturbed
C
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Lower = oldest
Upper = newest
B
A
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Vertical geologic section.
Layer A is the oldest, layer C is the youngest.
Relative Dating (Cont)
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Time of appearance and disappearance
–
Determines relative times of organisms
Problems with Relative Dating
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Gaps in record
Quality of Fossils
Relative Dating
vs. Absolute
Dating
Radioactive Dating
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Absolute Dating
Rocks
–
Made of many elements
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Radioactive
–
Elements that decay
or break down at a
steady and
measurable rate
- Used to age fossils
and layers of Earth
Radioactive dating
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How is it measured?
–
Half-life- unit of
measurement of decay
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The amount of time
required for half of the
radioactive atoms to
decay
Radioactive Elements
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Each element has a
different half-life.
Radioactive
Isotope
Half-Life
Rubidium- 87
50 billion years
Thoruim- 232
13.9 billion years
Uranium- 238
4.5 billion years
Potassuim- 40
1.3 billion years
Uranium- 235
713 million years
Carbon-14
5770
Carbon-14
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Useful
–
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Dates once living
material
Drawback
–
60,000 years
Earth Age?

All this data helped scientists come to the
conclusion the earth is 4.5 billion years old
Image Sources
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http://3dparks.wr.usgs.gov/nyc/images/fig5.jpg
http://static.howstuffworks.com/gif/carbon-14.gif
http://qbx6.ltu.edu/s_schneider/courses/intro_astro/images/06-28.jpg
http://qbx6.ltu.edu/s_schneider/courses/intro_astro/images/06-28.jpg
http://www.uwlax.edu/MVAC/ProcessArch/ProcessArch/images/styles
W.jpg
http://upload.wikimedia.org/wikipedia/en/thumb/e/e8/Knightia.jpg/250p
x-Knightia.jpg
http://daneshnameh.roshd.ir/mavara/img/daneshnameh_up/4/4b/earthage.jpg
http://evolution.berkeley.edu/evosite/lines/images/strat_column.gif