Earthquakes and volcanic activity are a result of that process. Plate tectonics is the area of science that explains why the Earth’s surface moves, and how those changes cause earthquakes and volcanic activity.
We Are Walking on Eggshells
Scientists say the surface of the Earth is cracked like a huge eggshell. They call these pieces tectonic plates. As many as 20 of them cover the Earth. The plates sometimes hit each other, and sometimes move away from each other. Because some continents are above two plates, the continents move when the plates do.
The movement of tectonic plates can cause earthquakes and volcanoes. Modern instruments show that about 90 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.
Some 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.
One example of this pressure is found on the west coast of the United States. 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