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Geology Week 2 Notes

In week two we discuss the layers of the earth and plate tectonics, ta...
Course

Geology (GEOG 2100)

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Academic year: 2022/2023
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Fitchburg State University

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The Layers of the Earth (Day 4, Week 2)

Earth’s Crust - Continental Crust - Thick (6-50 mi thick) - Silicon + oxygen rich - Less dense - Older in age - Oceanic Crust - Thin (4-5 mi thick) - Iron + magnesium rich - More dense - Younger in age

The Mantle - Ultramafic composition (high Fe, Mg, Si) - 2900 km thick (1800 miles); thickest layer of the earth - Malleable (rock can change shape)

What Does Recent Research Say About The Mantle? - The mantle has blobs within it that are hotter than their surroundings - One under Africa, one under the Pacific Ocean - These blobs move around (through geologic time) and may help explain past plate tectonics - Warmer blobs rise and colder blobs sink within the mantle (convection) - The bottom of the mantle has a layer called the D’’ layer - A very dense region at the boundary with the core - May be the “graveyard” of old tectonic plates

Outer Core - Liquid Fe + Ni - 7000 °F - Generates Earth’s magnetic field

Inner Core - Solid Fe + Ni - 8500 °F - 10,000°F - 3,000,000 atm (pressure)

What Does Recent Research Say About The Inner Core? - The inner core oscillates every 6 years or so (rotation changes direction) - we don’t know why yet - There may be an inner - inner core - Iron crystals point N-S in outer inner core but E-W in inner inner core - Hypothesis? Earth cooled in two stages when originally forming

Lithosphere – Asthenosphere - Lithosphere / asthenosphere = based on rocks’ ability to flow - Lithosphere = brittle (breaks); crust + upper mantle - Asthenosphere = plastic / ductile (flows); part of the upper mantle - Rigid lithosphere “floats” on the asthenosphere

Take Home Messages - The earth has three layers - crust, mantle, core - The outer core is liquid and the inner core is solid - oceanic crust is thinner, but more dense than continental crust

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Geology Week 2 Notes

Course: Geology (GEOG 2100)

7 Documents
Students shared 7 documents in this course

University: Fitchburg State University

Was this document helpful?
The Layers of the Earth (Day 4, Week 2)
Earth’s Crust
- Continental Crust
- Thick (6-50 mi thick)
- Silicon + oxygen rich
- Less dense
- Older in age
- Oceanic Crust
- Thin (4-5 mi thick)
- Iron + magnesium rich
- More dense
- Younger in age
The Mantle
- Ultramafic composition (high Fe, Mg, Si)
- 2900 km thick (1800 miles); thickest layer of the earth
- Malleable (rock can change shape)
What Does Recent Research Say About The Mantle?
- The mantle has blobs within it that are hotter than their surroundings
- One under Africa, one under the Pacific Ocean
- These blobs move around (through geologic time) and may help explain past
plate tectonics
- Warmer blobs rise and colder blobs sink within the mantle (convection)
- The bottom of the mantle has a layer called the D’’ layer
- A very dense region at the boundary with the core
- May be the “graveyard” of old tectonic plates
Outer Core
- Liquid Fe + Ni
- 7000℉
- Generates Earth’s magnetic field
Inner Core
- Solid Fe + Ni
- 8500℉ - 10,000℉
- 3,000,000 atm (pressure)

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