Ch. 1 Plate Tectonics Section 1 Earth’s Interior

Ch. 1 Plate TectonicsCh. 1 Plate Tectonics

Section 1 Earth’s InteriorSection 1 Earth’s Interior

Earth’s InteriorEarth’s Interior

• What does a geologist do?

• What are the characteristics of Earth’s crust, mantle, and core?

The Science of GeologyThe Science of Geology

• Geologists – Scientists who study the forces that make and shape planet Earth.– Rocks of the Earth’s surface– Map rock on and below the surface– Describe landforms formed in rock and soil by

water, wind, and waves.

The Science of GeologyThe Science of Geology

• Geologists study the processes that create Earth’s features and search for clues about Earth’s history.

Exploring Inside EarthExploring Inside Earth

• What is inside the Earth?

• Can we dig to the center of the Earth?– The deepest mine is 3.8 km, the center of the

Earth is over 6,000 km.

• Geologists have used two main types of evidence to learn about Earth’s interior:– Direct evidence from rocks– Indirect evidence from seismic waves

Evidence from Rock SamplesEvidence from Rock Samples

• Scientists have drilled holes as much as 12 km deep for rock samples.– Scientist make inferences about how and

where these rocks formed.

Evidence from Seismic WavesEvidence from Seismic Waves

• Geologists cannot look inside the earth, must rely on indirect methods.– Use Seismic Waves given off by earthquakes– The speed and paths the seismic waves

reveals the structure of the Earth.

Earth’s InteriorEarth’s Interior

A Journey to the Center of the A Journey to the Center of the EarthEarth

• What happens to the temperature as you travel into the Earth?

• For the first 20 meters or so the rock around you is quite cool.


• After 20 meters the temperature rises. Why does it rise?– Result of heat left over from the formation of the earth

and radioactive substances in the Earth.

• For every 40 meters you go down from then on, the temperature rises 1° Celsius.

• This increase in temperature continues for several kilometers. After that, the temperature increases more slowly, but steadily.


• Pressure– There is an increase in pressure the further

you go into the Earth.– Caused by the weight of the rock above.

• Just like there is more pressure the deeper you go in a swimming pool.


• As you go to the center of the Earth, you travel through several different layers.– Crust– Mantle– Core


The CrustThe Crust

• The crust is the outermost part of the Earth.– Rocks– Mountains– Soil– water.

The CrustThe Crust

• The crust ranges from 5 – 40 km thick.

• The crust beneath the ocean is called “oceanic crust.”– Consists mostly of a rock called BASALT.

The CrustThe Crust

• The crust that forms the continents is called “continental crust.”– Consists mostly of a rock called GRANITE.

The MantleThe Mantle

• Below the crust is the layer called the mantle.– Layer of hot rock– Mantle is about 3,000 km thick.


• The Lithosphere– The upper part of the mantle and the lower

part of the crust together form a solid layer called the lithosphere.

– About 100 km thick


• Asthenosphere– Below the lithosphere.– Hotter and under a lot of pressure– Softer, bendable rock (but still solid).


• The Lower Mantle– Beneath the asthenosphere, the mantle is

solid.– This solid material extends all the way to

Earth’s core.

The CoreThe Core

• The Core– Below the mantle– Made mostly of metals iron and nickel.– Made up of the inner and outer core– 3,486 km thick

The CoreThe Core

• Outer Core– Layer of molten metal that surrounds the inner

core.– Like thick liquid

• Inner Core– Dense ball of solid metal

• Very hot, but too much pressure to be a liquid

The CoreThe Core

• The outer and inner core make up about 1/3 (33%) of the Earth’s mass, but only 15% of its volume.

• The inner and outer core together are slightly smaller than the moon.

Earth’s Magnetic FieldEarth’s Magnetic Field

• The inner core is spinning at a slightly faster rate than the rest of the Earth.– This creates a magnetic field.– The force is strongest at the magnetic poles,

which is different than the geographical poles.

AssessmentAssessment

• Why is it hard to describe what the inner structure of the Earth?

• How are seismic waves used to provide evidence about Earth’s interior?

• What are the 3 main layers of the Earth?

• What is the difference between the lithosphere an the asthenosphere? In which layer is each located?

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Ch. 1 Plate Tectonics Section 1 Earth’s Interior