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Why is this statement false: The caveman had dinosaur for breakfast.? Why is this statement false: The caveman had dinosaur for breakfast.? man and.

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Presentation on theme: "Why is this statement false: The caveman had dinosaur for breakfast.? Why is this statement false: The caveman had dinosaur for breakfast.? man and."— Presentation transcript:

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3 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 man and dinosaurs never lived at the same time

4 Laws of geologic history SuperpositionOldest rocks on the bottom of an undisturbed sequence of rock Law of original horizontalityAll rocks are initially deposited in flat (horizontal) rows Cross-cutting relationshipsObjects which cross-cut rocks are younger than the rocks themselves (ex: fault or intrusion) SuperpositionOldest rocks on the bottom of an undisturbed sequence of rock Law of original horizontalityAll rocks are initially deposited in flat (horizontal) rows Cross-cutting relationshipsObjects which cross-cut rocks are younger than the rocks themselves (ex: fault or intrusion)

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6 Using superposition, label the strata below from oldest to youngest.

7 All rock layers are originally deposited in flat (horizontal) layers

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

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10 Which is older: F or S How do you know?

11 uniformitarianism. These laws are based on the assumption that the forces at work today are the same forces at work in history = uniformitarianism.

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

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14 Is H an intrusion or extrusion? How can you tell?

15 H is an intrusion. Contact metamorphism on top

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

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

19 What are

20 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) lived over a large geographic area (large horizontal distribution) lived for a short period of time (small vertical distribution)

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

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

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

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

27 What is the half life of uranium-238? 4.5 x ,500,000, billion years choice (c)

28 If there is a 100g sample of C 14, how many grams of C 14 would remain after three half-lives? How long would this take? Show all work. 100g50g25g12.5g 3 half-lives x (5.7 x 10 3 ) =1.71 x 10 4 = 17,100 years


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