Chapter 4 - Plate Tectonics Inside the Earth Restless Continents The Theory of Plate Tectonics Deforming the Earth’s Crust

Inside the Earth

Earth’s Layers Inner Core Outer Core Mantle Crust

The Earth’s Crust Outermost layer of the Earth 5 – 100km thick Less than 1% of the mass of the Earth, yet humans have not ever drilled all the way through it. Two types: Continental Crust Oceanic Crust

Mantle Continental Crust - Thicker and less dense Oceanic Crust - Thinner and more dense

The Earth’s Mantle Between the crust and the core 2900 km thick 67% of the Earth’s mass Three parts Lithosphere (half in the crust) Asthenosphere Mesosphere

Layers of the Mantle

Layers of the Mantle -- Lithosphere is the rigid layer of the Earth that includes the crust and the upper part of the mantle.

Layers of the Mantle -- Asthenosphere is the soft plastic-like layer of the mantle on which the pieces of the lithosphere float.

Layers of the Mantle -- Mesosphere is the strong lower part of the mantle.

The Core Innermost layer of the Earth 3430 km radius 33% of Earth’s mass Made mostly of iron Two layers Outer core Inner core

Layers of the Core -- Outer Core is liquid

Layers of the Core -- Inner Core is solid

Tectonic Plates Pieces of the lithosphere that move around on top of the asthenosphere These plates are made up of both continental crust and oceanic crust.

Mapping the Earth’s Interior Scientists have figured out what the Earth’s interior looks like by studying how earthquake (seismic) waves travel through the Earth.

Seismic waves travel at different speeds when they travel through materials with different densities.

Scientists measure how long it takes the waves to travel through the Earth to different locations, then make calculations to figure out what the inside of the Earth is composed of.

Seismologists can then use the distances and travel times to calculate the density and thickness of each layer of the Earth.

USGS Earthquake Hazards Program: Animation of Seismic Waves: CENTRAL ALASKA

Seismograph Scientists us a device called a seismograph to measure arrival time and magnitude of seismic waves around the Earth.

Seismograph