Beneath our feet, the earth's surface is a giant puzzle of tectonic plates. Each year, these plates move a few centimeters in different directions. In some areas of the planet, these plates rub together, releasing energy that can cause an earthquake. In 1935, the American scientist Charles Francis Richter created a scale that measures the strength of an earthquake: it is the Richter scale. The largest earthquake ever recorded occurred in Chile in 1960 and was 9.5 magnitude. Photo credit: Dan Meyers