do now for thursday, feb. 28 how do geologists know what the earth is composed of?
TRANSCRIPT
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DO NOW FOR THURSDAY, FEB. 28
• How do geologists know what the Earth is composed of?
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PLATE TECTONICSChapter 4 – 1:Earth’s Interior
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What’s inside Earth & How do they know?
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Scientists use data from seismic waves to determine the anatomy of Earth.
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The deeper you go beneath Earth’s surface, both temperature and
pressure increase!
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Earth’s three main layers include the CRUST, MANTLE and CORE
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The CRUST
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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.
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The crust is composed of oxygen, silicon, aluminum, calcium, iron, sodium, potassium, and magnesium.
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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.
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The mantle is composed of silicon, oxygen, iron and magnesium.
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Finally, the CORE consists of the outer molten core and an inner solid core.
Both are composed of iron and nickel.
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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.
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Chapter 4 – 2 Convection Currents and the Mantle
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Remember! Heat is transferred in three different ways:
Conduction
Radiation
Convection
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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!
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Convection in the mantle
Hot material in the asthenosphere rises slowly towards the surface where it becomes cooler and eventually sinks down again.