Chapter 7

The Earth’s inner core consists of liquid metals. Plate tectonics is a theory that describes how large slabs of the lithosphere are moved.

Built-up energy is released along a fault during an earthquake. Intense vibrations felt through Earth’s crust during an earthquake are called seismic waves.

Magma is melted rock found beneath Earth’s surface. Both earthquakes and volcanoes often occur along faults, which are cracks in Earth’s crust.

The mantle is the thickest of Earth’s layers. Most of Earth’s volcanoes and earthquakes occur along plate boundaries.

Surface waves produced by an earthquake move more slowly than body waves.

Evidence of temperatures below the Earth’s surface: Scientist encounter higher temperatures when they drill. Rocks melt below the Earth’s surface. Geysers spew hot water from beneath the surface.

Rocks along converging boundaries Plates collide and rocks compress and break. One plate may move below the other plate.

Besides plate movement, other processes can alter the structure of Earth’s mantle. Weathering (or erosion, disposition) can create plateaus (or mesas, caves, sand dunes, alluvial fans, barrier islands).

Fossils can provide evidence to support the theory of plate tectonics. Fossils of tropical plants and animals may be found in polar regions. Fossils of marine animals may be found in moutainous regions.

Compare earthquake damage to volcano damage. Which is more dangerous? Earthquakes can level buildings, cause landslides, and generate huge ocean waves. Volcanoes can cover large areas with lava and volcanic ash and rocks, destroy forest, and emit dangerous gases into the atmosphere. Both are dangerous.

Ways scientists can learn more about what goes on beneath the Earth’s surface. Scientist can drill holes. They can study lava, rock debris, and ashes from volcanoes. They can monitor the activity of natural geysers. They can set up seismographs. They can design laboratory experiments to expose surface rock to intense heat and pressure.

Possible effects of a city near the epicenter of an earthquake: Earthquakes might cause huge ocean waves that flood the city and destroy buildings and bridges. Earthquakes could re-route rivers and cause flooding.

Measurements indicate that the distance between Africa and South America is increasing. Africa and South America are located on different plates. There is a diverging boundary between two places. Melted rock from the mantle is rising to the surface along the boundary.