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ScienceNet Questions and Answers
Question Number: 275
What is the Earth made of?
1.
How are the plates of the Earth’s crust similar to frozen peas in a boiling pot
of water?
Plates float on a semi-molten mantle of hotter rocks.
Circulation of the molten rock causes the plates to move
across the surface of the Earth where they can be dragged
under at the edges of other plates just like the peas moving in
boiling water.
2.
The rate at which plates move is about 2 - 5 cm/yr .
3.
How were the Alps and Himalayan mountain ranges formed?
The Alps were formed when Africa crashed into Europe about
100 million years ago.
The Himalayas were formed when India crashed into Asia 60
million years ago.
4.
Name the three basic types of rocks and give examples of each.
Sedimentary – limestone
Metamorphic – marble (made from limestone)
Igneous – granite (w/ large crystals)
basalt (w/ small crystals)
5.
Explain how the study of earthquake waves improves our understanding of the
Earth’s interior.
Earthquake waves pass through different parts of the Earth's
interior at different speeds and when they pass through
different layers they change direction slightly. The place that
the wave emerges on the other side of the Earth, and the time it
takes to get there, tells us something about the Earth's interior.