Structure.exercises.ONLINE.F22
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College of Charleston *
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105L
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Geology
Date
Feb 20, 2024
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5
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You will need: o
Internet o
“Chapter 4: Structural Geology” provided on
OAKS o
The Powerpoint provided on OAKS o
LABGEO3 ANIMVID: Animations found on OAKS
Environmental Geology 105L Name: Structural Geology Part 1: Plate Tectonics, Folds, and Faults Review Read Chapter 4: Structural Geology on OAKS to help you answer the questions below. Read Chapter 3: Geologic Time/Relative Time (pages 20-23). LABGEO3 ANIMVID: Animations. Scroll to Chapter 15: Interpreting Geologic Structures on Block Diagrams, Geologic Maps, and Cross-section. Click on the ANIMATION: FAULTS: NORMAL, REVERSE, STRIKE-SLIP (Note: you may have to copy/paste the link) IMPORTANT:
You will also need to know for this lab that in a stack of layered rocks the oldest is on the bottom, and the layers get younger upward. This is known as the Law of Superposition
. 1.
At convergent plate boundaries, tectonic plates come together, such as at continental collision zones and _? 2.
Convergent plate boundaries are the result of forces. TENSION COMPRESSION SHEAR 3.
Name an example of a convergent plate boundary somewhere on Earth. 4.
What types of faults would be associated with convergent plate boundaries? NORMAL FAULTS REVERSE/THRUST FAULTS STRIKE-SLIP FAULTS 5.
What type of plate motion occurs at divergent plate boundaries? 6.
Divergent plate boundaries are the result of _ forces. TENSION COMPRESSION SHEAR 7.
Name an example of a divergent plate boundary. 8.
What types of faults would be associated with divergent plate boundaries? NORMAL FAULTS REVERSE FAULTS STRIKE-SLIP FAULTS 9.
What type of plate motion occurs at transform plate boundaries? 10.
What type of fault is found at transform plate boundaries? NORMAL FAULTS REVERSE FAULTS STRIKE-SLIP FAULTS 11.
At what type of plate boundary are folds most likely to befound? 12.
Name the two types of folds described in this chapter. 13.
The Law of _ states that layered sedimentary strata are deposited as sediments with older layers on the bottom and younger layers on top of the older layers.
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Part 2: Folds Watch the animation found on OAKS: LABGEO3 ANIMVID: Animations. Scroll to Chapter 15: Interpreting Geologic Structures on Block Diagrams, Geologic Maps, and Cross-section. Click on the ANIMATION: FOLDS and watch the topics on Anticline and Syncline (Note: you may have to copy/paste the link) Slide 1: The Alps (Southern Europe) This photograph shows a portion of the Alps mountain range in southern Europe. These mountains resulted from the collision of the northward-moving African landmass with the Eurasian landmass during the Oligocene and Miocene epochs. 1.
Which set of Letters for the layers are in order from oldest to youngest. T –
X OR X –
T (Refer to Chapter 3, pages 20-23 regarding the Law of Superposition). 2.
There are 2 main folds in the photograph. Fold 1 on the left is a(n) ANTICLINE/SYNCLINE
. Fold 2 on the right is a(n) ANTICLINE/SYNCLINE 3.
At what kind of plate boundary would these types of folds likely occur? CONVERGENT/DIVERGENT/TRANSFORM 4.
Did the folding occur BEFORE OR AFTER the youngest bed was deposited? 5.
If there were faults present, what kind of faults would you also expect to see? NORMAL/REVERSE/STRIKE-SLIP Faults Watch the animation found on OAKS: LABGEO3 ANIMVID: Animations. Scroll to Chapter 15: Interpreting Geologic Structures on Block Diagrams, Geologic Maps, and Cross-section. Click on the ANIMATION: FAULTS: NORMAL, REVERSE, STRIKE-SLIP (Note: you may have to copy/paste the link) Slide 2: Basin and Range (Nevada) The photograph was taken of an exposed fault in the Basin and Range province of western North America, which extends from eastern California to western Colorado and from northern Nevada to central Mexico. The area results from the Earth's crust being stretched by the effect of the Pacific Plate moving north relative to the North American Plate (as well as other reasons we will not go into here). It is estimated that the earth’s crust here has been stretched up to 100% of its original width. 1.
Which set of Numbers shown on the layers are in order from oldest to youngest? 1 2 3 4 56 Or 6 5 4 3 2 1 2.
Which side is the hanging wall: A or B
? 3.
Which side is the footing wall: A or B
? 4.
The black layer that you see on either side of the fault used to be one continuous layer and has been offset by movement on the fault. By observing this offset, determine if the hanging wall has moved up relative to the footwall or down relative to the footwall. 5.
What kind of fault is this? NORMAL/REVERSE/STRIKE-SLIP
3
6.
Approximately how much offset (meaning how much movement) has occurred along this fault? Again, use the black layer to help you. The man in the photo is 6ft tall. 7.
These types of faults commonly occur in association with what kind of plate boundary? CONVERGENT/DIVERGENT/TRANSFORM Slide 3: The San Andreas Fault (California) 1.
This aerial photograph is of the famous San Andreas Fault in central California. The San Andreas fault system is over 800 miles long and is presently active (causing earthquakes!). The stream labelled in the image used to flow directly from east to west, but has been offset by motion along the fault; it now follows the fault for a short distance before continuing west. NOTE: THIS PHOTOGRAPH WAS TAKEN FROM THE NORTH, SO SOUTH IS AT THE TOP OF THIS IMAGE. 2.
Which direction has the North American plate moved –
NORTH OR SOUTH
? 3.
Which direction has the Pacific Plate moved –
NORTH OR SOUTH
? 4.
What type of fault is this? NORMAL/REVERSE/STRIKE-SLIP 5.
If you stood in the stream channel on the Pacific plate and looked at the North American plate, in which direction does it appear that the North American plate is moving? (Left or Right) 6.
Is this fault RIGHT OR LEFT LATERAL? (use Figure 7 in Marshak’s
Chapter 10: Interpreting Geologic Structures on Block Diagrams, Geologic Maps, and Cross Sections to help you) 7.
If the offset seen in the photo is 100 meters in length, and scientists determine that the stream is only 2000 years old, what is the maximum relative rate of movement (velocity) between the Pacific Plate and the North American Plate in meters per year (m/yr)? Remember velocity = distance / time. Show your work! Part 3: Block Diagrams Block diagrams are a way of showing geologic structures in 3 dimensions. Use the slides from the powerpoint to answer the questions below. You can also explore some 3D Block Diagrams here: https://app.visiblegeology.com/profile.html
. Go to the Geology tab and click View Models, then scroll down to look at 3D block diagrams of structures that you can rotate with your mouse! Slide 4 Block Diagrams 1.
What is the top surface of a block diagram called? 2.
What does a cross section show you? Slide 5 Horizontal Strata. This block diagram shows how undeformed, horizontal sedimentary rocks would look in 3 dimensions. 1.
On the map view of these beds, which layer(s) arevisible? 2.
On the front cross section face, which layer(s) arevisible?
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3.
On the side cross section face, which layer(s) are visible? 4.
List the beds in order from oldest to youngest. Slide 6 Dipping Strata. This block diagram shows how tilted strata would look in 3 dimensions. 1.
On the map view of these beds, which layer(s) arevisible? 2.
On the front cross section face, which layer(s) arevisible? 3.
On the side cross section face, which layer(s) are visible? 4.
Which cross section face shows the dip of the layers? FRONT or SIDE 5.
List the beds in order from oldest to youngest (assuming they have not been tilted by more than 90°, aka they are not overturned beds). Slide 7 Folds 1. This slide shows the sequence of how originally horizontal beds (a) can be deformed to create folds (b). As the top of these folds are eroded (c & d), the inner layers are exposed on the surface. Sometimes some layers are more resistant to erosion than others and will form a ridge (d). A real example of this is shown on slide 8. Slide 8 Aerial view of Appalachians 1. These mountains are made up of many anticlines and synclines. Some rock layers are more resistant, so they stick out as ridges while others are eroded away to form valleys. Slide 9 Anticline 1.
On the map view of these beds, which layer(s) arevisible? 2.
On the front cross section face, which layer(s) arevisible? 3.
On the side cross section face, which layer(s) are visible? 4.
How are the folds dipping around the axis of the anticline? TOWARDS THE AXIS or AWAY FROM THE AXIS 5.
On this block diagram, which face shows you the type of fold this is? FRONT or SIDE 6.
Where is the youngest bed on an anticline? Slide 10 Syncline 2.
On the map view of these beds, which layer(s) are visible? 3.
On the front cross section face, which layer(s) are visible? 4.
On the side cross section face, which layer(s) are visible? 5.
How are the folds dipping around the axis of thesyncline? TOWARDS THE AXIS or AWAY FROM THE AXIS 6.
On this block diagram, which face shows you the type of fold this is? FRONT or SIDE 7.
Where is youngest bed on a syncline?
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Part 4: Map Symbols Geologists usually use geologic maps to look at rock types and structures in an area. This would be like looking at the top section of the block diagram only. Without the cross-section view, geologists need a way to show on the map view what is going on below the surface. They use special symbols to show the direction that the strata is tilted and how much it is tilted from horizontal. This is called strike and dip. Refer to slide 11 of the PowerPoint slides and Chapter 4: Structural Geology Figure 4.7 on OAKS to help you answer the questions below. Choose from the map symbol images shown below to answer the following questions: 1.
Go back to block diagram on slide 5
. Which is the correct symbol (a, b, c, or d, above) for these layers of rock? 2.
Go back to block diagram on slide 6
. Which is the correct symbol (a, b, c, or d, above) for these layers of rock? 3.
Which direction are the beds dipping on slide 6
? TO THE EAST or TO THE WEST (Use the North arrow for reference)? 4.
Based on your answer to question 3, which image on slide 12 shows the correct strike and dip symbols? 5.
Go back to the block diagram on slide 9
. Which is the correct symbol (a, b, c, or d, above) for an anticline? 6.
Go back to the block diagram on slide 10
. Which is the correct symbol (a, b, c, or d, above) for a syncline? 7.
Look at the geologic map on slide 13
. It includes a map view and shows a cross section of the area along the line marked A-
A’
(diagonally from the NW corner of the map to the SE corner). The cross section is shown closer up on slide 14
. Based on the cross section, which of the maps on slide 15 would correctly show what the strike and dip symbols on the map should look like? 8.
Look at the geologic map on slide 16
. Imagine you had to draw a cross section from B-
B’ for the portion of the map shown close up in slide 17
. Using the strike and dip symbols on the map to help you, which of the images on slide 18 would correctly show what the cross section would look like?