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A few sample MC on metamorphic rocks…. Marble is a metamorphic rock that forms from __________? A. granite B. limestone C. sandstone D. shale Answer =

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Presentation on theme: "A few sample MC on metamorphic rocks…. Marble is a metamorphic rock that forms from __________? A. granite B. limestone C. sandstone D. shale Answer ="— Presentation transcript:

1 A few sample MC on metamorphic rocks…. Marble is a metamorphic rock that forms from __________? A. granite B. limestone C. sandstone D. shale Answer = B (page 193)

2 A few sample MC on metamorphic rocks…. What is the pressure on a rock at 15 kilometers depth in the Earths crust? A. approximately 4 times atmospheric pressure B. approximately 40 times atmospheric pressure C. approximately 400 times atmospheric pressure D. approximately 4000 times atmospheric pressure Answer = D (page 195)

3 A few sample MC on metamorphic rocks…. Which of the following processes will cause metamorphism? A. an increase in pressure B. an increase in temperature C. interaction with hydrothermal fluids D. all of the above Answer = D (page 194)

4 A few sample MC on metamorphic rocks…. What type of metamorphism is caused by high temperature and high pressure imposed over a large volume of crust? A. burial B. contact C. regional D. shock Answer = C (page 197)

5 A few sample MC on metamorphic rocks…. Which of the following is not used to classify foliated rocks? A. the metamorphic grade B. the nature of the foliation C. the size of the crystals D. the texture of the parent rock Answer = D (pages 199-202)

6 A few sample MC on metamorphic rocks…. Which of the following statements about the metamorphism of a shale is false? A. With increasing metamorphism, clay minerals break down to form micas. B. With increasing metamorphism, the grain size of the rock gets smaller. C. With increasing metamorphism, foliation develops. D. With increasing metamorphism, the amount of water in the rock decreases. Answer = B (page 200)

7 TODAY: Chapter 10 Geologic Time 1) Relative dating principles 2) Correlation of rock layers 3) Absolute dating w/ radioactivity 4) Geologic time scale

8 Chapter 10 Study questions 1.What is the difference between absolute and relative dates, and how are they determined? Know the principles of original horizontality and superposition. 2.Learn the basics of fossils and how theyre used, concepts of faunal succession, formation. 3.How do we correlate rock layers in different regions? 4.What are the different types of unconformities, how do you apply cross- cutting relationships to determine the relative sequence of strata? 5.How was the geologic time-scale created? Study the most important divisions (eons, eras) of the geological time scale and extinctions between major divisions. 6.How do apply radioactive decay of some elements to add absolute dates to the geologic time scale (radiometric dating)?

9 Telling time geologically v Earths history concealed in rocks v Goal of geology: unraveling Earths history v Principle time keeping devices: Relative dating - putting rocks/events in proper order Absolute dating - determining rocks/events actual age 1. Relative Dating: Key principles

10 Law of superposition Principle of original horizontality Principle of cross-cutting relationships InclusionsUnconformities T&L Figure 8.2 A bed of rock is older than that above, younger than that below

11 Superposition is well illustrated by the strata in the Grand Canyon

12 Law of superposition Principle of original horizontality Principle of cross-cutting relationships InclusionsUnconformities A bed of rock is older than that above, younger than that below T&L Figure 8.3 1. Relative Dating: Key principles Sedimentary layers deposited flat

13 Law of superposition Principle of original horizontality Principle of cross-cutting relationships Unconformities A bed of rock is older than that above, younger than that below Sedimentary layers deposited flat Faults & dikes are younger than beds they cross 1. Relative Dating: Key principles See Figure Story 10.11

14 Unconformities (Conformable layers: deposited w/out interruption) 1. Relative Dating: Key principles An unconformity is a break in the rock record produced by erosion and/or nondeposition of rock units

15 1. Relative Dating: Key principles Example: Grand Canyon Has record of a huge expanse in time, and multitude of sedimentary environments… But: The record of time is not continuous because of geological processes that happened after deposition. Movie: watch for terminology of different kinds of Unconformities and relative dating methods

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17 Relative Dating: Key principles Unconformities 3 types v Angular unconformity v Disconformity v Nonconformity

18 Relative Dating: Key principles Unconformities 3 types v Angular unconformity v Disconformity v Nonconformity Tilted/folded sedimentary rocks overlain by younger, more flat layers See Fig. 10.6

19 Deposition Folding/Uplift Erosion Subsidence/more erosion Recipe for an angular unconformity See Fig. 10.8

20 Relative Dating: Key principles Unconformities 3 types v Angular unconformity v Disconformity v Nonconformity Layers on either side of unconformity are parallel See Fig. 10.7

21 Relative Dating: Key principles Unconformities 3 types v Angular unconformity v Disconformity v Nonconformity Interface between sedimentary layers and metamorphic or igneous rock


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