Earth: Inside and Out

Key Ideas How is the Earth’s interior structured? How has the appearance of the Earth changed over time? What geologic Features are common near tectonic plate boundaries?

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Earth’s Interior Three parts: 1. Crust 2. Mantle 3. Core

Crust Only makes up 1% of Earth’s mass. Continental crust averages about miles deep. Oceanic crust averages about 3-5 miles deep.

Mantle Lays beneath the crust. Denser than the crust. Makes up 80% of the Earth’s interior. About 1800 miles deep. Humans have never drilled all the way to the mantle.

Core Core makes up 19% of Earth’s mass. Composed mainly of iron and nickel. Two layers – inner and outer core. Inner core – solid metal Outer core – liquid metal mlhttp:// ml

Hot, Hot, Hot!!! The temperature of the Earth increases with depth. The Earth’s interior contains radioactive isotopes. As uranium, thorium and potassium decay, they release energy that is stored in the core.

Plate Tectonics Alfred Wegener hypothesized that all of the continents might have been part of one landmass in the past before they drifted apart.

Plate Tectonics The continents fit together like pieces of a puzzle. The landmass was called Pangaea.

Plate Tectonics Fossil record showed that the continents were at one time, one landmass.

Plate Tectonics How did the continents get to their current location???

Continental Drift Continental Drift Theory is the theory that the Earth’s surface is made up of large moving plates.

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Continental Drift Where’s the evidence? Changing magnetic fields discovered on either side of the Mid-Atlantic Ridge. Suggests that the crust was moving away from the plate boundary in both directions.

Continental Drift Lithosphere = crust + upper portion of mantle Lithosphere is made up of 8 large plates(and 9 smaller plates) called tectonic plates. Tectonic plates move from 1-10cm per year.

What makes tectonic plates move? Hypothesis One – convection currents in the asthenosphere, the hot, plastic portion of the mantle moves the plates. Hypothesis Two – plates are driven by the force of gravity acting on their own massive weight.

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