Layers of Earth

Thursday, March 6

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Bell Work #94

1. The __________ Era began with the early invertebrates, such as trilobites and brachiopods; continued to develop early vertebrate fish, then arachnids and insects; later came the first amphibians, and near the era’s end the reptiles became dominant.
2. Early land _____ included simple mosses, ferns, and then cone-bearing plants.
3. By the end of the era, _______ plants were common.
4. The mass _________that ended the era caused most marine invertebrates as well as amphibians to disappear.
5. A major geologic event of the Paleozoic era was the formation of the supercontinent of ___________.

Paleozoic

Pangaea

extinction

seed

plants

Classwork:

• Bell work #94
• Notes on Layers of the Earth
• Crossword Puzzle

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Layers of the Earth Song (2:45)

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Earth is Divided into Four Main Layers

1. Crust
2. Mantle
3. Outer Core
4. Inner Core

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*From surface to center, the Earth is about 6,400 km or 4,000 mi deep.

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1. Earth’s Crust

• Composed mostly of oxygen (O₂ ), silicon (Si), aluminum (Al) rock
• Thinnest layer (5km -70km or 3mi - 44 mi)
• Like the skin of an apple or shell of hard boiled egg
• Solid top layer where we live
• Least dense layer
• 70% covered by water
• Temperature ranges from 200 C 500 C

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Two Types of Crust

Oceanic Crust

• Made mostly of igneous rock basalt
• Found beneath oceans
• Thinner of the two types of crust
• Denser of the two types of crust due to higher iron content
• Younger (newer) crust

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Two Types of Crust

Continental Crust

• Made mostly of igneous rock granite
• Found beneath continents
• Thicker than oceanic crust
• Less dense than oceanic crust
• Older than Oceanic Crust

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2. Earth’s Mantle

• Composed mostly of oxygen, silicon, magnesium (Mg), and iron (Fe) rock
• Thickest layer- about 2,900 km or 1,802 mi
• Mostly solid, but partially semi-solid, plastic
• Between the crust and outer core
• Density, pressure, and temperature all increase the deeper you go
• Temperature ranges from 500C to 2,200C
• Has three layers: upper, middle, and lower
• 84% of Earth’s volume

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Lithosphere-Asthenosphere Boundary

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Lithosphere

• Crust and upper mantle
• Hard, solid layer
• Broken up into plates

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Lithosphere-Asthenosphere Boundary

Asthenosphere

• Middle mantle, just below the lithosphere
• Where the plates “float”
• Slow moving “silly putty layer” (semi-solid, plastic)
• Moves as slowly as your finger nails grow

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Lower Mantle

• Below asthenosphere
• Solid rock
• Hotter than middle and upper mantle
• Pressure in this layer is so great that melting does not occur
• Temperature ranges from 1,690 C to 2,200 C

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3. Earth’s Outer Core

• Composed mostly of iron with a small amount of nickel (Ni)
• About 2,250 km or 1,398 mi thick
• Liquid metal (iron and nickel) magma
• Temperature ranges from 2,200 C - 5,000 C–the deeper the hotter

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4. Earth’s Inner Core

• Composed mostly of iron with a small amount of nickel
• About 1,280 km or 795 mi thick
• Solid metal core due to high pressure
• Temperature reaches 6,000 C
• Most dense layer
• Spins slightly faster than the Earth rotates

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Structure of Earth

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How Deep Have Humans Dug?

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How do we know about Earth’s composition?

• We cannot see the interior of Earth, or drill to the core, so we use seismic waves.
• Seismic waves are vibrations produced from earthquakes.
• Travel at different speeds depending on composition and density of material through which they travel

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Homework:

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• Earth’s Layers Quiz Thursday 3/14
• Earth’s Layers Test Tuesday, 3/26

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