Review Questions for

2^nd Lecture Test

Earth History and Global Change

GEOL-1122 Fall 2009

Section #1 ‑ Deformation, Structures and Mountain Building

Readings ‑ Chapter 10

1) What is Structural Geology? What important information can be derived from the study of geologic structures?

2) Define stress and strain. What is the difference between directed and lithostatic stress? Describe the types of directed stress (compressional, extensional and shear) and their causes.

3) Describe the three types of strain that result from stress. Which two types are most commonly used in determining the geologic history of an area?

4) What controls the style and degree of deformation or strain? Why does near-surface stress commonly result in brittle strain? In contrast, why do regional metamorphic rocks commonly display plastic deformation?

5) How is the 3‑dimensional orientation of a rock unit or structure measured? Why is this information important?

6) Compare and contrast the following geologic structures: anticline, syncline, monocline, basin, and dome. Which of these structures form by compressional stress and which form by vertical crustal movement?

7) Describe the four major types of faults (normal, reverse, strike-slip and thrust). Describe the stress type and orientation that is usually responsible for each fault type.

8) Why are thrust faults and folds commonly found in the same area? Along which types of plate tectonic boundaries are these structures most common?

9) How does a fault differ from a joint? Describe three ways in which joints form. Are all joints formed by mountain building and crustal deformation? Why do joints and faults most commonly form near or in the upper crust?

10) The San Andreas Fault is a right‑lateral strike‑slip fault. What does this mean? Describe the movement of the western fault block on which southern California is located. Which type of stress is most important along this boundary?

11) How do horsts and grabens form? What type of stress is responsible for these structures? Name a location in the United States that is characterized by horst and graben structures.

12) Define and describe Isostasy. Explain why isostatic rebound is important in the recent geologic history of the Appalachian Mountains and glaciated areas?

13) Define the following terms: strike, dip, plastic, brittle, elastic, columnar joints, sheeting, hanging and footwall blocks, terranes, orogeny, and fold.

Section #2 ‑ Plate Tectonics

Readings: Chapter 2

1) Describe some of the observations that Alfred Wegener and Alexander du Toit used to support their idea of Plate Tectonics and the supercontinents of Pangaea and Laurasia.

2) Describe how paleobiogeography is used as evidence for Plate Tectonics. List and describe specific examples that support the idea that the continents of South America and Africa were at one time joined.

3) When was the fit of the continents between South America and Africa first noticed? How can this fit be improved when these continents are joined and the present Atlantic Oceanic crust removed? Is this a valid assumption?

4) Name and describe several rock types that are used to determine paleoclimate data. Describe how paleoclimate data is used as evidence that the continents were located at different latitudes in the geologic past. In addition to movement of the continents, what other explanation can be used to describe the climatic changes recorded in the rock record of certain areas?

5) How is structural and rock age information also used to support the Plate Tectonic Theory? Give specific examples of these correlations.

6) What is the Gondwana Sequence? Where is it found? How is it used as evidence of plate tectonics? Make a simple sketch and write a short description of the sequence.

7) What is paleomagnetism? Describe the information that is recorded by paleo-magnetism. In which rock types is paleomagnetism best recorded? Are paleo-longitudes also recorded? Be able to determine paleolatitudes and rotation using paleomagnetic data.

8) Describe sea-floor spreading. Where does it occur? List and describe the evidence that indicates sea-floor spreading occurs.

9) What are magnetic reversals? Describe how magnetic reversals are used with heat‑flow and age data to prove the theory of sea‑floor spreading.

10) What is the Ring of Fire? How does this feature also support the theory of Plate Tectonics? Name and describe the two most important types of plate boundaries that form this area.

11) What are Benioff Zones? How are they recognized? How do they support the theory of Plate Tectonics? Why does the angle of these seismic zones vary?

12) What is a mantle hot spot? How are these used as evidence of plate movement? Describe how mantle hot spots can be used to estimate rates of plate movement? Give an example of a modern-day mantle hot spot.

13) What are some of the possible mechanisms responsible for plate movement? Which mechanism appears to be the most important? Describe the layers that are involved in this process.

14) Name two locations where we can directly measure the rate of plate movement. How fast do these plates move?

15) Name the three types of plate boundaries. Describe the characteristics of each type. Name geographic examples for each type.

16) Explain why the distribution of natural resources is largely controlled by plate tectonics.

17) Define the following terms: Plate Tectonics, transform margin, seafloor spreading, Mesosaurus, Glossopterus, Curie Point, lithosphere, asthenosphere, low‑velocity zone, magnetic inclination, subduction zone, and mid‑oceanic rises and ridges.