What causes earthquakes?
On a larger scale an explosion can cause the earth to shake for a considerable distance. Scientists use seismographs to monitor nuclear tests. People in Las Vegas could feel the shaking caused by underground nuclear tests in the desert miles away. The government analyzes the shock waves (earthquakes) produced by nuclear explosions to study the effects of nuclear tests and to monitor tests elsewhere in the world.
Here are the exact words from my book about geology. Most earthquakes are caused by a sudden, violent shift of the Earth’s tectonic plates. Rocks at the edge of the plates break underground. The motion spreads out from the break in waves like the ripples in a pond when a stone is dropped. Large earthquakes can be very destructive.
The hard ground of the earth sits on plates that occasionally move due to the hot molten lava inside of the earth. Pressure builds up inside and needs to be released. When that occurs the plates shift and move causing earthquakes. http://weirdsciencekids.
