GEOL 1401 - Lab 7 Directions and Questions
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Wayland Baptist University, Plainview *
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Course
1401
Subject
Geology
Date
Dec 6, 2023
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docx
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GEOL 1401 Directions – Lab 7
Objectives:
This assignment is designed to introduce student to concepts of plate tectonics and mountain building.
Materials needed:
1.
Access to Master Geology activities through Blackboard menu item Pearson’s MyLab & MasteringGeology
2.
The file Homework 7 – Worksheet should be downloaded from Blackboard.
3.
Maps, tables, and figures listed below for Parts II and III.
Part I: Chapter Study (25 Points)
1.
After reading through chapters 2 and 14 from your textbook and reviewing the lecture notes, go to
Pearson’s
MyLab & MasteringGeology
.
Click
Mastering Assignments
then “Week 7” to start. For credit, complete all items
within the Week 6 assignment. Points will be downloaded from this website and input into the Homework 7
column within Blackboard.
Part II: Plate Densities
By now you can see many different lines of evidence that the tectonic plates are moving. To build a theory we
need an explanation or a mechanism that explains the patterns that we see. The theory of plate tectonics states that the
outer rigid layer of the earth (the lithosphere) is broken into pieces called tectonic plates (Figure 4.3) and that these plates
move independently above the flowing plastic-like portion of the mantle (Asthenosphere).
Tectonic plates are composed of the crust and the upper most mantle that functions as a brittle solid. These
plates can be composed of oceanic crust, continental crust, or a mixture of both. The Oceanic Crust is thinner and normally
underlies the world’s oceans, while the Continental Crust is thicker and like its name consists of the continents. The
interaction of these plates is controlled by the relative motion of two plates (moving together, apart, or sliding past) as well
as the composition of the crustal portion of the plate (continental or ocean crust). Continental crust has an overall
composition similar to igneous rocks such as granite, which is a solid, silica-rich crystalline rock, with a mixture of feldspar,
quartz, and biotite minerals. Oceanic crust is primarily composed of the igneous rock gabbro, which is a solid, iron and
magnesium-rich crystalline rock with a mixture of pyroxene and feldspars.
An important property of geological plates is their density (mass/volume). Remember the asthenosphere has
fluid-like properties, such that tectonic plates ‘float’ relative to their density. Therefore, the relative density of two plates
can control how they interact at a boundary and the types of geological features found along the border between the two
plates. Measuring the density of rocks is easy and can be done by first weighing the rocks and then calculating their
volume. The latter is best done by a method called fluid displacement using a graduated cylinder. Water is added to the
cylinder and the level is recorded, a rock is then added to the cylinder and the difference in water levels equals the volume
of the rock. Density is then calculated as the mass divided by the volume (Figure 1).
Figure 1.
Method to find the density of a rock. First the weight is measured on a digital scale and then the fluid displacement method is used to determine
the volume.
The information needed to calculate density was collected (Figure 2) for four rocks and can be used to answer the
questions under Part II on the Week 7 Homework Worksheet. Note: each line on the graduated cylinder represents 10 ml.
When measuring the volume please round to the nearest 10 milliliter line on the graduated cylinder. Hint: Surface tension
will often cause the water level to curve up near the edges of the graduated cylinder creating a feature called a meniscus.
To accurately measure the volume, use the lowest point the water looks to occupy.
Figure 2.
The first row shows images of the four rocks. The second and third rows show the volume (in milliliters) of material in the graduated cylinder
before and after the rock was added. The last row shows the mass (in grams) of the four rocks.
Part III: Plate Boundary Identification
Tectonic plates can interact in three different ways they can come together, they can pull apart, or they can slide
by each other. The other factor that can be important is the composition of the plates (oceanic or continental crust) that
are interacting as was explored in the previous section. These three types of motions along with the type of plates on each
side of the boundary can produce vastly different structures and geologic events (Table 4.1). Review the types of plate
boundries using the figures below and from your lectures and textbook to answer the questions for Part III.
GEOL 1401 Lab 7 Worksheet
Part II: Plate Densities
1. The rock that most closely resembles the composition of continental crust based on the description in the previous
section is:
a.
A
b.
B
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c.
C
d.
D
2.
Based on the choice you made for question 1, what is the density of the rocks that make up continental crust? Please
give your answer in grams/milliliter. (Refer to Part II in the Directions for density calculation).
Answer:
3.
The rock that most closely resembles the composition of oceanic crust based on the description in the previous section
is:
a.
A
b.
B
c.
C
d.
D
4.
Based on the choice you made for question 5, what is the density of the rocks that make up oceanic crust? Please give
your answer in grams/milliliter.
Answer:
5.
Remember, because of isostasy the denser plate will be lower than the less dense plate. If oceanic and continental crust
collided, based on their densities the __________ crust would sink below the ________crust. a. continental; oceanic
b. oceanic; continental
Part III: Plate Boundary Identification
6. What type of tectonic plates are present in image A (below)?
a.
Ocean-Ocean
b.
Ocean-Continent
c.
Continent-Continent
7. What type of plate boundary is present in image A?
a.
Convergent
b.
Divergent C. Transform
A
8. What type of process is occurring at the location in image B (below)?
a.
Seafloor Spreading
b.
Continent Rifting
c.
Subduction
9. What features would you expect to occur at the location in image B?
a.
Earthquakes and a trench
b.
Volcanoes and a valley
c.
Mountains and landslides
d.
Earthquakes and offset rivers
B
10. What type of tectonic plates are present in image C (below)?
a.
Ocean-Ocean
b.
Ocean-Continent
c.
Continent-Continent
11. What type of plate boundary is present in image C?
a.
Convergent
b.
Divergent C. Transform
12. What type of tectonic plates are present in image D (below)?
a.
Ocean-Ocean
b.
Ocean-Continent
c.
Continent-Continent
C
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Zoomed in
D