A few sample MC on metamorphic rocks…. Marble is a metamorphic rock that forms from __________? A....

A few sample MC on metamorphic rocks….

Marble is a metamorphic rock that forms from __________?

A. graniteB. limestoneC. sandstoneD. shale

Answer = B (page 193)

A few sample MC on metamorphic rocks….

What is the pressure on a rock at 15 kilometers depth in the Earth’s crust?

A. approximately 4 times atmospheric pressureB. approximately 40 times atmospheric pressureC. approximately 400 times atmospheric pressureD. approximately 4000 times atmospheric pressure

Answer = D (page 195)

A few sample MC on metamorphic rocks….

Which of the following processes will cause metamorphism?

A. an increase in pressureB. an increase in temperatureC. interaction with hydrothermal fluidsD. all of the above

Answer = D (page 194)

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. burialB. contactC. regionalD. shock

Answer = C (page 197)

A few sample MC on metamorphic rocks….

 Which of the following is not used to classify foliated rocks?

A. the metamorphic gradeB. the nature of the foliationC. the size of the crystalsD. the texture of the parent rock

Answer = D (pages 199-202)

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)

TODAY: Chapter 10

Geologic Time 1) Relative dating principles2) Correlation of rock layers3) Absolute dating w/ radioactivity4) Geologic time scale 

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 they’re 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)?

“Telling time geologically”

Earth’s history concealed in rocks

Goal of geology: unraveling Earth’s history

Principle time keeping devices:

Relative dating - putting rocks/events in proper order

Absolute dating - determining rocks/event’s actual age

1. Relative Dating: Key principles

1. Relative Dating: Key principles

Law of superpositionLaw of superposition

Principle of original horizontalityPrinciple of original horizontality

Principle of cross-cutting relationshipsPrinciple of cross-cutting relationships

InclusionsInclusions

UnconformitiesUnconformities

T&L Figure 8.2

A bed of rock is older than that above, younger than that belowA bed of rock is older than that above, younger than that below

Superposition is well illustrated by the strata in the Grand Canyon

Law of superpositionLaw of superposition

Principle of original horizontalityPrinciple of original horizontality

Principle of cross-cutting relationshipsPrinciple of cross-cutting relationships

InclusionsInclusions

UnconformitiesUnconformities

A bed of rock is older than that above, younger than that belowA 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 flatSedimentary layers deposited flat

Law of superpositionLaw of superposition

Principle of original horizontalityPrinciple of original horizontality

Principle of cross-cutting relationshipsPrinciple of cross-cutting relationships

UnconformitiesUnconformities

A bed of rock is older than that above, younger than that belowA bed of rock is older than that above, younger than that below

Sedimentary layers deposited flatSedimentary layers deposited flat

Faults & dikes are younger than beds they crossFaults & dikes are younger than beds they cross

1. Relative Dating: Key principles

See Figure Story 10.11

UnconformitiesUnconformities

(Conformable layers: deposited w/out interruption)

1. Relative Dating: Key principles

An unconformity is a break in the rock record produced An unconformity is a break in the rock record produced by erosion and/or nondeposition of rock unitsby erosion and/or nondeposition of rock units

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

Relative Dating: Key principles UnconformitiesUnconformities

3 types

Angular unconformity

Disconformity

Nonconformity

Relative Dating: Key principles UnconformitiesUnconformities

3 types

Angular unconformity

Disconformity

Nonconformity

Tilted/folded sedimentary rocks overlain by younger, more flat layers

See Fig. 10.6

Deposition

Folding/Uplift

Erosion

Subsidence/more erosion

Recipe for an angular unconformity

See Fig. 10.8

Relative Dating: Key principles UnconformitiesUnconformities

3 types

Angular unconformity

Disconformity

Nonconformity

Layers on either side of unconformity are parallel

See Fig. 10.7

Relative Dating: Key principles UnconformitiesUnconformities

3 types

Angular unconformity

Disconformity

NonconformityInterface between sedimentary layers and metamorphic or igneous rock