Earthquakes are a result of that process. Plate tectonics is the area of science that explains why the surface of the Earth moves and how those changes cause earthquakes.
FAITH LAPIDUS: Scientists say the surface of the Earth is cracked like a giant eggshell. They call the pieces tectonic plates. As many as twenty of them cover the Earth. The plates slowly float around the Earth’s surface. They sometimes crash into each other, and sometimes move away from each other.
When the plates move, the continents move with them. Sometimes the continents are above two plates. The continents move as the plates move.
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STEVE EMBER: The movement of tectonic plates can cause earthquakes. Modern instruments show that about ninety percent of all earthquakes happen along a few lines in several places around the Earth.
These lines follow underwater mountains, where hot liquid rock flows up from deep inside the Earth. Sometimes the melted rock comes out with a great burst of pressure. This forces apart pieces of the Earth's surface in a violent earthquake.
Other earthquakes take place at the edges of continents. Pressure increases as two plates move against each other. When this happens, one plate moves past the other, suddenly causing the Earth’s surface to split open.
An earthquake monitoring station near the San Andreas Fault near Thermal, California
FAITH LAPIDUS: One example of this pressure is found on the west coast of the United States. One part of California is on what is known as the Pacific plate. The other part of the state is on what is known as the North American plate.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25