geologictime

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Geologic Time Notes Page 3 : 

Geologic Time Notes Page 3 Geologic Time ©Mark Place, 2009-2010 www.LearnEarthScience.com

Fossils can only be found in rocks. : 

Fossils can only be found in rocks. sedimentary

Slide 3: 

On to the next question...

Why is this statement false: “The caveman had dinosaur for breakfast.”? : 

Why is this statement false: “The caveman had dinosaur for breakfast.”? man and dinosaurs never lived at the same time

Slide 5: 

On to page 4.... Answers to Questions on Page 3

Slide 6: 

Relative Age If a sedimentary rock outcrop has not been overturned, which layer would be the oldest? What is this principle known as?

Slide 7: 

Principle of Superposition oldest rock layers are on bottom

Slide 8: 

Using this principle, label the strata below from oldest to youngest. oldest youngest

Slide 9: 

On to the next question...

Faults are always (older, younger) than the rocks they cut through. : 

Faults are always (older, younger) than the rocks they cut through.

Slide 12: 

Which is older: F or S How do you know? F cuts through S S must have been there first (it's older)

Slide 13: 

On to the next question...

If a geologist finds an igneous sill, how can she determine if the sill is an intrusion or an extrusion? : 

If a geologist finds an igneous sill, how can she determine if the sill is an intrusion or an extrusion?

Intrusions : 

Intrusions contact metamorphism on all sides

extrusions : 

extrusions no contact metamorphism on top

Slide 18: 

Is “H” an intrusion or extrusion?How can you tell?

Slide 19: 

H is an intrusion.Contact metamorphism on top

Slide 20: 

On to the next question...

Slide 21: 

What is an unconformity? a buried erosional surface a part of the rock record is missing How does it complicate the relative dating of rock layers?

Slide 22: 

What processes could lead to an unconformity? weathering and erosion

Slide 23: 

Using the diagram to the left, identify where the unconformity is located by drawing an arrow and writing the word “unconformity” next to it.

Slide 24: 

On to the next question...

What characteristics must fossils have in order to be good index fossils? : 

What characteristics must fossils have in order to be good index fossils? lived over a large geographic area (large horizontal distribution) lived for a short period of time (small vertical distribution)

In the diagram below, a geologist has matched up rock layers based on index fossils. : 

In the diagram below, a geologist has matched up rock layers based on index fossils. In geology, this is referred to as CORRELATION

Slide 27: 

On to the next question...

Slide 28: 

Evolution Explain the theory of evolution. organisms adapt to their environment in order to survive

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Evolution Explain how the fossil record supports this theory can see that different organisms have changed over time

Slide 31: 

Answers to Questions on Page 3

Slide 32: 

Absolute Age Why are radioactive isotopes useful in determining the absolute age of a rock? their half-lives are constant

Slide 33: 

Absolute Age What can be done to change the half-life of a radioactive isotope? Why is this important? NOTHING! it is reliable to calculate age

Slide 34: 

Draw the generic graph for the half-life of a radioactive isotope. unstable atoms stable atoms

Slide 35: 

Absolute Age What radioactive isotope could be used to determine the absolute age of material that was recently living? carbon-14

Slide 36: 

Please answer the two questions on page 7 of your Notes What is the half life of uranium-238? 4.5 x 109 4,500,000,000 4.5 billion years choice (c)

Slide 37: 

Please answer the two questions on page 7 of your Notes If there is a 100g sample of C14, how many grams of C14 would remain after three half-lives? How long would this take? Show all work. 100g 50g 25g 12.5g    3 half-lives x (5.7 x 103) =1.71 x 104 = 17,100 years

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