A sometimes violent movement of the earth is produced when tectonic plates grind or slip past each other at fault.

Researchers believe that the Earth’s crust is cracked into huge pieces that fit together like a giant puzzle. The broken sections, called tectonic plates, are supported by the oozing, soft rocks of the mantle beneath the Earth’s crust.

The unstable borders between the plates are known as rings of fire. These areas are danger zones for both volcanoes and earthquakes.

A volcano is an opening in the Earth’s crust that allows red hot magma (molten rock) from the mantle to escape onto Earth’s surface. An earthquake is a shaking of the ground caused by movements of rocks beneath the Earth’s surface.

Measuring earthquakes: Seismologists use measuring instruments called seismographs to record the pattern of an earthquake’s seismic waves and determine the earthquake’s strength and duration.

The Richter scale: The best-known method of recording the magnitude of earthquakes is the Richter Scale. American seismologist, Charles F. Richter, developed this numbering system in 1935.

Earthquake depths: The focus, the starting point, of most earthquakes is less than 50 miles / 80.46 km below the Earth’s surface.

Largest recorded earthquake: On May 22, 1960, an earthquake of 9.5 magnitudes on the Richter Scale struck the coast of Chile, South America. Seismographs recorded seismic waves traveling around the whole world for many days afterward.

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