The Earth's surface is called the crust, and it is made up of about a dozen tectonic plates on which the continents and oceans rest. These plates are continually shifting because the surface beneath them is hot and soft, driven to keep moving by heat deep in the Earth's core. Sometimes they collide either by sliding past or crashing into each other, causing volcanoes and mountain ranges to form. The areas where they meet are called faults. The energy released at the faults travels through the Earth like waves, which we experience as an earthquake.
Earthquakes are measured by a machine called a seismograph that records and interprets the seismic waves of energy released during an earthquake. The seismic data is then applied to a measurement tool called the Richter scale to determine the length and intensity of an earthquake. On a scale of one to ten, four is considered minor while eight is a powerful earthquake that causes great destruction.
If you are indoors during an earthquake, drop to the ground and get under a table. Keep away from windows and anything that could fall on you. If you are outdoors, move away from buildings, streetlights, and utility wires. If you are trapped under debris, try to attract rescuers' attention by tapping on pipes or echoing objects around you. Have an earthquake kit ready. Each kit should contain water, dried food, blankets, a whistle to attract attention and a first aid kit, as well as a flashlight.
The strongest earthquake ever recorded was a magnitude 9.5 in Chile on May 22, 1960. The deadliest recorded earthquake took place in 1556 in central China killing an estimated 830,000 people. Tsunamis -- giant tidal waves that cause loss of life and devastation in coastal areas where they land -- are caused by earthquakes taking place in the ocean. Some parts of the world have more earthquakes than other areas. About 80 percent of the world's earthquakes take place around the massive Pacific Plate, an area known as the Pacific Rim of Fire, which stretches from South America to New Zealand. Up to a million earthquakes occur each year all around the world.