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• How do geologists know what the Earth is composed of?

PLATE TECTONICSChapter 4 – 1:Earth’s Interior

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What’s inside Earth & How do they know?

Scientists use data from seismic waves to determine the anatomy of Earth.

The deeper you go beneath Earth’s surface, both temperature and

pressure increase!

Earth’s three main layers include the CRUST, MANTLE and CORE

The CRUST

The crust is the layer of rock that forms the Earth’s skin. It is between 5 and 40 km thick and extends under the

ocean (oceanic), mostly as basalt and on land (continental) mostly as granite.

The crust is composed of oxygen, silicon, aluminum, calcium, iron, sodium, potassium, and magnesium.

The MANTLE is nearly a 3,000 km thick boundary of hot rock.

The uppermost part is the Lithosphere, a rigid “stone” layer of 100 km.

Underneath is the Asthenosphere, a soft layer that flows and is nearly 3,000 km thick.

The mantle is composed of silicon, oxygen, iron and magnesium.

Finally, the CORE consists of the outer molten core and an inner solid core.

Both are composed of iron and nickel.

Currents in the Earth’s outer core cause the inner core to spin at a rate faster than the planet. These currents also

give Earth it’s magnetic poles, North and South Pole.

Chapter 4 – 2 Convection Currents and the Mantle

Remember! Heat is transferred in three different ways:

Conduction

Radiation

Convection

Radiation is the transfer of heat through empty space.Conduction is the transfer of heat through direct contact.

Convection is heat transferred by the movement of a heated fluid.

As a fluid is heated, it becomes less dense, it’s mass in relation to it’s volume decreases. This is why hot air rises and cold air sinks!

Convection in the mantle

Hot material in the asthenosphere rises slowly towards the surface where it becomes cooler and eventually sinks down again.