Quiz 1: Rocks and Minerals

NAME: ______

12.001 QUIZ 2: Structure and Mapping

MARCH 23, 2007

ANSWER ALL QUESTIONS IN THIS QUIZ BOOKLET AND HAND IN NOTHING BUT THIS BOOKLET.

YOU HAVE UNTIL 1:55 TO COMPLETE THIS QUIZ.

Rocks ___/30

Strike/Dip ___/20

Question 1 ___/30

Question 2 ___/30

Question 3 ___/20

Question 4 ___/10

Question 5 ___/30

Question 6 ___/30

(Bonus ___/25)

Total ___/200

Part I: Identification of Rocks and Minerals (30 Pts)

You have 3 minutes per sample to identify 3 rocks. Samples will be passed around the room and rotated every three minutes.

Rock 3 special bonus: Give the complete formation name for this rock, if you know it.

______

Part II: Orientation (20 Pts)

Using a Brunton compass, measure the orientation of the bedding planes of the rock at the back of the class. Come to the back and measure the rock as soon as you are finished with the rock identifications. North is as defined by the compass (not the front of the room).

Strike:

Dip:
Part III: Short Answer

Question 1: Create Your Own Topographic Map (30 Pts)

1a. (25 Pts) In the box below, create a topographic map. Some advance planning will help you out and make it go faster (scratch paper is available). Your map must include a scale, a stated contour interval, and at least 6 contour levels. Represent the following landforms:

·  3 high points (for example, hills, mountains, pinnacles…)

·  3 major streams flowing off the boundaries of your map (traced in blue pencil)

·  contour lines that reflect the streams

1b. (5 Pts) Use a red pencil to draw the divides between each of the three major streams.

Question 2: Surface Trace of a Planar Layer (15 Pts) and drainages (15 Pts)

On the topographic map below, a thin planar layer in the bedrock crops out at the ground surface at Points 1 and 2 on the east and west edges of the map. This layer has an east-west strike and dips 30° to the north.

2a. (10 pts) Draw the qualitative surface trace of the layer between Points 1 and 2 on the map. Remember the rule of the V’s.

2b. (5 pts) Identify two points along the surface trace, in addition to Point 1, through which you can be certain that the surface trace passes. Label them A and B.

2c. (10 pts) Draw in blue pencil the streams you expect to find on this map.

2d. (5 pts) Are the valleys on this map all carved by streams, all by glaciers, or some of each? Why?
Question 3: Surface Expression of Folded Layers (20 Pts)

The map below shows a low-relief area underlain by folded sedimentary rock units. Answer the following questions.

3a. (3 Pts) Draw the traces of the axial planes on the map.

3b. (3 Pts) In which direction do the folds plunge (recall that “plunge” is the dip of a line, in this case, the

trace of the axial plane of the fold)? Circle one direction.

N NE E SE S SW W NW

3c. (3 Pts) Which is the oldest unit in the map area?

B

A

3d. (11 pts) Draw a cross-section of the map from A to B, assuming the ground surface is flat.

A B

Question 4: Faults (10 Pts)

Below is a map of an approximately horizontal land area, showing the surface trace of a fault that cuts and offsets a distinctive thin planar rock unit. The dip of the fault plane is as shown.

4a. (8 Pts) Indicate with a check mark which of the following situations are possible.

4b. (2 Pts) Assume the fault is a strike-slip fault. From the information given on the map, what is the displacement on the fault?

Question 5: (30 Pts)

(2 Pts) What is the age of the earth?

(2 Pts) What is the age of the oldest continental crust?

(4 Pts) What is the upper mantle made of, and is it solid or liquid?

(2 Pts) What kind of contact exists between a sandstone and a granite?

(4 Pts) Name two types of contacts that can exist between a gneiss and a limestone.

(6 Pts) Name three factors that affect how a rock responds to stress:

(4 Pts) What word describes a rock that breaks apart or erodes or weathers readily, and what word describes a rock that is strong and does not erode readily?

(4 Pts) Label A and B in the diagram below.

(2 Pts) Circle the type of stress that causes this pattern of faulting:

compressional extensional shear

Question 6: Relative Time (30 Pts)

The figure below shows a hypothetical cross-section through the Earth’s crust. Apply the principles of original horizontality, superposition and cross-cutting relationships to determine the relative timing of geologic events in this area.

6a. (20 Pts) List these units and events by letter (A through R) from oldest to youngest (using scrap paper is a

good idea here).

6b. (10 Pts) Which letters correspond to unconformities on the diagram? What types of unconformities are

each of these?

BONUSES:

B1. (5 pts each) Clearly and neatly draw three impossible geologic relationships, and explain why they are impossible.

B2. (10 pts) Draw a diagram of stress (y-axis) vs. strain (x-axis). Label and define the elastic region, the plastic region, and the fracture point.

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