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Time is not part of rock cycle, but is implied

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Time is not part of rock cycle, but is implied - PowerPoint PPT Presentation


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Time is not part of rock cycle, but is implied. Example : a granite could be weathered and the particles eventually become part of a sandstone. The sandstone could later be metamorphosed to become a quartzite. How fast these events happen would determine what ages the rocks were.

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slide1

Time is not part of rock cycle, but is implied

Example: a granite could be weathered and the particles

eventually become part of a sandstone. The sandstone

could later be metamorphosed to become a quartzite.

How fast these events happen would determine

what ages the rocks were.

slide5

RELATIVE DATING OF GEOLOGIC

  • EVENTS / MATERIALS:
  • PRINCIPLES
    • Superposition
    • Original Horizontality
    • Cross-cutting relationships
slide13

Event Principle

Deposition of 1 – 5 Superposition

Folding of 1 – 5 Original Horizontality

Erosion Superposition / Cross-cutting

Deposition of 7 – 9 Superposition

time

slide16

Layer H

Layer F

Layer G

Layer E

Layer D

Layer C

Layer B

Layer A

Figure 18.4

.5

slide20

Uranium-238

Unstable parent

Rn-222

Radon gas

Lead 206

Stable daughter

radiometric dating example 1
radiometric dating – example 1
  • A granite is collected and analyzed
  • Contains 50% U-235 and 50% Pb-207
  • Half-life of U-235 is 713 million years
  • How old is the granite?
radiometric dating example 11
radiometric dating – example 1
  • Refer to Figure 18.14
  • 50% parent, 50% daughter corresponds to 1 half-life
  • Half-life of U-235 is 713 million years
  • Thus, granite is 713 years old
radiometric dating example 2
radiometric dating – example 2
  • A granite is collected and analyzed
  • Contains 2 micrograms of U-235 and 6 micrograms of Pb-207
  • Half-life of U-235 is 713 million years
  • How old is the granite?
radiometric dating example 21
radiometric dating – example 2
  • 8 micrograms of parent + daughter
    • 2/8 micrograms = 1/4 = 25% U-235
    • 6/8 micrograms = 3/4 = 75% Pb-207
  • Refer to Figure 18.14
  • 25% parent / 75% daughter corresponds to

2 half lives.

  • Half-life of U-235 is 713 million years
  • Thus, granite is 2 x 713 = 1,426

million years old = 1.4 billion yrs.

  • What if U-235 = 75%, Pb-207 = 25%?
slide29

Europe

Modern humans

Present time

Asia

13,000 years

Archaic humans

incl. Neanderthals

33,000 years

Small Archaic

Humans

95,000 years

Evolution of humans

~3 million years ago

Africa

slide31

Correlation: establishing equivalence

between rock layers that were once

continuous

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