Layers of the Earth

Compositional Layers –Divided by what they are made out of –planetary differentiation – the process of separating out distinct layers of a planet due to differences in the density of the materials –There are 3 Compositional Layers Structural Layers –Divided by how they “work” –There are 5 Structural Layers

Compositional Layers (made out of) Crust - silica & oxygen-rich rocks –Oceanic Crust Thinner Younger (180 million or less) More dense –Continental Crust Thicker Older (up to 4 billion years old) Less dense

Compositional Layers Mantle silicate rocks with iron & magnesium –Under crust –More dense than crust –2/3 of Earth’s total mass Core nickel and iron –center of Earth –divided into two layers

Structural Layers (work) Lithosphere –Crust + Upper Mantle –Cool, Rigid –Makes up plates Asthenosphere –Plastic (like clay) –Contains magma –Has convection currents which move the plates

Structural Layers Mesosphere –“Middle” sphere –Solid mantle rock

Structural Layers Outer Core –Dense Liquid –Source of magnetosphere Inner Core –Solid –1/3 of Earth’s mass

Ready to sing?

How do scientists “know” that the earth has these layers?

How about drilling? Continental Crust: –The Kola Superdeep Borehole on the Kola peninsula of Russia reached km (~7.62 mi) and is the deepest penetration of the Earth's solid surface. –The dig began in 1970 and continued for 19 years, stopping only when the 180°C (356°F) temperature made further digging impossible Oceanic Crust: –We have drilled down 1.7 km (~1 mi) into the seafloor. We have penetrated only the upper 25% of either crust.

Why can’t we dig deeper? HEAT: At 5 km deep, the temperature reaches 70 degrees Celsius (158 F) and therefore massive cooling equipment is needed to allow workers to survive at such depths. Remember the deepest hole reached 180°C (356°F). ROCK WEIGHT: At 3.5 km the pressure of rocks above you is 9,500 tons per meter squared. When rock is removed through mining this pressure triples in the surrounding rock. This effect (coupled with the cooling of the rock) causes a phenomenon known as rock bursts, which accounts for many of the 250 deaths in South African mines every year. PRESSURE OF MAGMA: Once you break through the crust, you would release pressurized magma– instant volcano – destroying equipment, killing workers, etc.

So – what “tool” do scientists use to learn about the layers…

Scientists use data from earthquakes – using seismometers – to learn about what is below us.

Seismograms

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