ERTH308 Movie #1 Notes - Julia Boring
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Geology
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Apr 3, 2024
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1. What is the outermost layer of the Earth called? Do you take this for granted? Do you feel bad about that after watching the film?
It is called the Continental Crust. After watching the film, I do believe that I have taken this top layer for granted. I didn’t realize how much the earth’s crust provided for us and helped sustain life. I do feel bad about taking it for granted, and being more educated on how vital it is will help me be more aware going forward.
2. How old is the earth, according to this film? Do you buy it?
4.5 billion years old. I buy it. The evidence they put forward made sense, and I am no expert in dating planets. So it makes sense to me!
No question here, but notice the flowing lava beginning about 4 minutes in. The interactions of this moving solidified rock crust on top of a churning lake of lava is a good model of Plate Tectonics, speeded up so we can watch processes like rifting and subduction on our own time scale. Note which way the different “plates” are moving relative to one another; identify the "plate boundaries". 3. Which is older, continental crust or oceanic crust?
Continental crust is older than oceanic crust.
4. Where does the energy to drive Plate Tectonics come from?
The energy to drive Plate Tectonics comes from convection.
5. How much extension has occurred in the Basin and Range? How is this relevant to Oregon and the Pacific Northwest?
Sections of the Basin and Range have grown wider by %100. This is relevant because it is responsible for
creating new landscapes, and may progress to the ocean stage.
6. What is a xenolith? Where do they come from, and how do they get to the surface?
A Xenolith is a foreign rock fragment. They do not belong to the lava that brought them to the surface. They were once part of the bottom of the Earth’s crust, and even the mantle. When volcanoes become active, chunks from the lining get broken off and carried to the surface. 7. What is underplating of the crust? Why do you think magma rising from the mantle is likely to pause at the Moho, the boundary between the mantle and the crust?
Underplating occurs when rising magma gets trapped during its rise to the surface of the Moho. It is probably likely to pause or get stuck here because of the difference in density of the magma and the rock surrounding it.
8. Where does most of our knowledge of the deep interior of the Earth come from?
Most of the information about the deep interior of the Earth comes from aeromagnetic surveys. They detect the magnetic fields in crustal rocks. By doing this, scientists can discover unseen geological features. Note the magnetic survey data shown at minute 32:30. Contrast the simple striped pattern of the NE Pacific oceanic crust with the irregular blobs and generally chaotic arrangement on the continent.
9. Erosion reveals granitic batholiths by stripping away the overlying crust. What kind of crustal rocks were removed from above batholiths?
Thousands of feet of earth was removed from the top of the batholiths.
10. Where do pillow lavas form? Pay close attention to this process, you can see pillow lavas throughout Oregon.
Pillow lavas are formed where molten lava flowed into the ocean.
Note carefully the process of exotic terrane accretion starting at minute 41:40.
11. How much of Oregon is formed of exotic accreted terranes?
Exotic terranes are new pieces of continental crust that have been added through subduction. Most of the
land west of the American and Canadian rocky mountains (including Oregon) is made of this crust. 12. What is the goal or eventual result of erosion?
The eventual result of erosion is flatness, or an eventual level plane.
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