The Structure of the Earth Earth’s Layers The Structure of the Earth

Layers of the Earth The layers of the Earth in order from the center out are. Inner core Outer core Mantle lower Middle upper Asthenosphere Lithosphere (crust)

The Crust The crust is the outermost layer of the Earth Most widely studied and understood Made up primarily of silicon and oxygen Very thin when compared to the other layers 3-5 miles or 8 km thick under the oceanic crust 32 km or 25miles thick under the continental crust

The Crust The crust is the thinnest layer of the earth. Oceanic crust The mantle is the thickest layer of the Earth Stretches from the lithosphere to the outer core

Continental Crust Composed mainly of granite Thicker than oceanic crust (30-50 km) Makes up only 25% of Earth’s surface Less dense than oceanic crust

Oceanic Crust Oceanic crust is composed of primarily basalt Basalt is much denser than the granite. The less dense continents ride on the denser oceanic plates Covered by water Makes up 75% of Earth’s crust. Thinner than the continental crust (5-10km)

The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the lithosphere.

Lithospheric Plates The crust of the Earth is broken into many pieces called (lithospheric) plate. The plates “float” on the soft, semi rigid asthenosphere

Mohorovicic Discontinuity The imaginary line of discontinuity that separates the brittle crust of the earth from the mantle is the Mohorovicic Discontinuity or MOHO for short. Boundary between the crust and the mantle in the earth. Depth where seismic waves change velocity and there is also a change in chemical composition

MOHO

The Mantle The mantle is the thickest layer of Earth. 2,885 km thick, the mantle is 82% of Earth’s volume. Upper mantle Middle mantle Asthenosphere Lower mantle Mesosphere (middle layer) Mantle composition is an ultramafic rock called peridotite. Solid rock layer between the crust and the core.

The Upper Mantle The uppermost mantle is connected to the crust and forms the asthenosphere, which composes Earth's tectonic plates. Part of the lithosphere

The Asthenosphere Middle Mantle The asthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight The movement of the middle mantle, asthenosphere, is the reason that the crustal plates of the Earth move.

Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again The cycle repeats over and over. The molten rock below Earth’s surface is known as magma

The Lower Mantle Called the Mesosphere because it is the middle layer of Earth. “middle” sphere 2,250 km thick lowest part of mantle

The Outer Core 1400 miles thick It is so hot that the metals in it are all in the liquid state. Composed of the melted metals of nickel and iron. The flow of the inner core creates Earth’s magnetic field

Earth’s Magnetic Field The flow of the fluid outer core around the solid inner core creates the Earth’s magnetic field

The Inner Core The inner core of the Earth has extremely high temperatures and pressures 4,000 - 5,000 °C 3 million atmospheres Pressure is so great that the metals are squeezed together and are not able. forced to vibrate in place like a solid. A ball of very hot metals. Inner core dimensions 3,248 km radius Composed of a sphere of hot, dense nickel and iron 1/3 of the Earth’s mass

Proof of Earth’s Structure Seismic Waves: the waves that travel through the Earth’s interior during an earthquake. Altered by the type of material that it travels through. Timing and strength of seismic waves gives us a picture of Earth’s interior Using the diagram which seismic wave travels through what type of substance?

Seismic Waves P-Waves S-Waves Travels through any substance Compression wave Any substance can be compressed Solid, liquid, gas S-Waves Transverse, shear waves Travels through solid only

Seismic Shadow Zone 104 -140 degrees from the epicenter No direct P-waves S-Waves are stopped entirely by the liquid core P-Waves are bent

Think, Pair, Share Write down the following question on a sheet of paper. Have we ever seen part of the Mantle? Explain. Include an illustration of the explanation. Discuss the question with your partner and write the answer down. Sit quietly until I say time is up