GLG110_Lab1_Final(1) (1)
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California State University, Long Beach *
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106
Subject
Geology
Date
Apr 3, 2024
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8
Uploaded by DukeLapwingMaster237
GLG110: Introduction to Geology and PLATE TECTONICS NAME: _ Layers of the Earth
The planet Earth is divided into spheres that define different parts of our Earth system. The atmosphere is the layer of gases that surround out planet. The rest of the planet beneath our feet can be divided in one of two different ways. If divided by chemical composition, the Earth can be broken into layers that include the crust
, which is the uppermost rocks and is less than 70 kilometers thick and forms less than 1% of the total volume. Beneath the crust is the mantle
that makes up the majority of the planet (up to 85% of Earth’s volume). And the center of Earth is called the core
. The crust is rich in potassium and silicon, while the mantle contains large abundances of iron and magnesium. The core is mostly made of nickel and iron. There is a second way to divide up the Earth’s layers that is based on the mechanical properties of the rocks. The uppermost rocks are rigid. If we hit them with a hammer, they’d break. We call this the lithosphere
. It contains all of the crust and the uppermost portion of the mantle. Beneath the lithosphere is the asthenosphere. Asthenosphere
means “weak” and these rocks flow like hot plastic. Asthenospheric rocks aren’t molten. They are just hot enough to flow when a force is applied, whereas lithospheric rocks are rigid and break. The asthenosphere is part of the mantle and the remaining mantle beneath is called the lower mantle
. The core is also divided into the liquid outer core and solid inner core
. Tectonic plates
The lithosphere is what makes up Earth’s tectonic plates
. Because the lithosphere is rigid and can hold together when force is applied to it, these lithospheric plates move around together. Because different parts of these plates are different compositions and temperatures, they are constantly sinking, moving, and colliding. All of these processes happen at the margins of the tectonic plates. In this exercise, you are going to use the characteristics of each type of plate margin or boundary
to determine the type of plate boundaries present across the globe. There are three types of boundaries: divergent (moving away from each other), convergent (moving towards each other), and transform (sliding past). Plate “rides” On the asthenosphere
1.)
Divergent plate boundaries
:
Divergent plate boundaries are the margins where two tectonic plates are moving away from each other, and the mantle beneath is moving up to the surface and crystallizing into new lithosphere, creating new parts of a tectonic plate. Divergent boundaries have many small to medium sized volcanoes
, numerous earthquakes
, and plates are moving in the opposite direction
. The boundary is typically an elevated set of ridges with a central valley in the middle
. Rocks along the edges of the boundary are very young (less than 10 million years old)
, and get older further away from the margin. On your map, color . Example: The Mid-Atlantic Ridge
in the middle of the Atlantic Ocean and the East African Rift
are examples of divergent boundaries (see Globe 2
), where two plates are moving apart.
STATION 1 VIRTUAL REALITY HEADSET:
The image in the headset is from Thingvellir National Park in Iceland. If you look down the central valley, the rocks to the right are part of the North American tectonic plate. The rocks to the left are part of Europe (or the Eurasian tectonic plate). This location is one of the only places above the surface of the ocean where two tectonic plates can be observed at a divergent boundary. NOTE: There are ocean-ocean and continent-continent divergent boundaries. Although many of these have existed in the past, and many more will occur in the future, there are only a handful of active continent-continent divergent boundaries (known as rifts
) right now. In this exercise we will not split them out, so label all divergent boundaries the same. Convergent plate boundaries: Convergent boundaries are margins where tectonic plates are colliding. Convergent boundaries are characterized by many earthquakes
and
high relief mountain ranges
. Rocks on one side of the boundary are typically less than 500 million years old
. Plates are moving towards each other. There are two types of convergent plate boundaries: Continent-continent convergent boundaries: few to no volcanoes, many earthquakes, and between two continental plates. High elevation mountains.
On your map, color
.
Continent-continent boundaries continued: Example: Himalayan Mountains of Asia are the result of the Indian and Eurasian tectonic plates colliding. See Globe 3.
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b.) Ocean-continent convergent boundaries: many volcanoes in an “arc” or linear shape that parallels the margin.
These boundaries separate oceanic and continental lithosphere. On your map, color .
Example:
Andes Mountains of South America are a ocean-continent convergent boundary where the East. Globe 2.
c.) Ocean-ocean convergent boundaries
: an arc of volcanoes on the ocean floor of the over-riding plate. Deep trench is present along the boundary. Many earthquakes.
On your map, color
.
Example: Marianas islands in the Pacific Ocean are an ocean-ocean convergent boundary, where the Pacific plate is subducting beneath a small part of the Philippine Sea plate (a “subplate” known as the Marianas plate). Globe 1 and 2
3.) Transform plate boundaries:
Transform boundaries, where plate slide past each other, are plate margins that commonly have many earthquakes
, but few volcanoes
. The ages of the rocks on either side of the boundary can vary, but less than 300 million years old
, and the plate are moving in directions that are parallel, but the opposite direction
.
On your map, color . Example: The San Andreas fault in southern and central California is a transform boundary that runs from the Gulf of California, through the LA and San Francisco metro areas, and back into the eastern Pacific Ocean near Bodega Bay, California. Globe 1 DETERMINE THE TYPE OF PLATE BOUNDARY Access the maps required by scanning the QR code with the camera on your smartphone. Printouts are available from your TA. What you are given: 1.)
Map of large magnitude global earthquakes over the past ~3000 years. Purple circles represent major earthquakes. Black lines are plate boundaries. Globe 1
2.)
Map of global volcanism over the past ~15,000 years. Red triangles represent an active or recently active volcano. Black lines are plate boundaries. Globe 2
3.)
Map of global elevations. Higher elevations are white and red. Intermediate elevations are orange and yellow. Lower elevations are green and purple. Globe 3
4.)
Plate boundaries (black lines) without earthquakes or volcanoes. A print out of this map is located on the last page. Fill in this map to complete the exercise. Globe/Map 4
*note: the maps on the globes in Sketchfab
are slightly distorted at the polar regions. Interested in why? Ask your TA! What you will need to complete for this project: 1.)
A colored and labeled map of the types of plate boundaries. Map 4
2.)
Complete the assessment questions (1-10). ASSESSEMENT: 1. What feature was the most distinctive in determining the type of plate boundaries around the globe and why? 2. Where are the majority of volcanoes located? 3. Look at the San Andreas fault in southern and central California (
GLOBE 1
). This area is a transform boundary. Do you think the plate boundary in southern and central California has always been a transform boundary? Why or why not? 4. Look at the Alps in west-central Europe and then track the mountain range and plate margin to the east (
GLOBE 3
). What mountain belt does it link up with? Do you think those mountains are related? Are they the same boundary type?
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5. Using your map, which type of plate boundary is most common on land? 6. Which type of plate boundary is most common under the sea (submarine)? 7. Why do you think some margins change from one type of boundary to another? 8. Look at the Juan De Fuca plate off the coast of Washington and Oregon (
GLOBE 4)
. There are two types of margins. What are they? a.) b.) 9. In the geologic future, what do you predict will happen with the Juan De Fuca plate and the plate boundaries in the region? 10. Take a look at the Appalachian Mountains in the eastern United States (
GLOBE 3
). These mountains were once very high, like the Himalayan Mountains of today. The Appalachian Mountains are not near an active plate boundary today. How is this possible?
MAP4: color and label the plate boundaries as divergent, convergent (specify which type), and transform.