The ground on which we walk is not made of one simple sheet of earth - - our planet's exterior is covered in gigantic plates of rock (called tectonic plates) that carry the continents and the ocean floors. Earthquakes occur when a fault in the Earth (where tectonic plates meet) slips, releasing waves of incredible energy that move through the ground and cause the surface to shift and vibrate. Areas near these fault lines are the most vulnerable to earthquakes and other seismic activity.
Many scientists believe that the entire continent of South America is drifting westward, which is causing the land mass (and the tectonic plate on which it rests) to press up against the Pacific Ocean's crustal slab. The pressure that the two plates apply to one another is responsible for many of the earthquakes in South America. This includes the earthquake that hit just off the western coast of Peru on May 31, 1970. Measuring 7.9 on the Richter scale, the earthquake killed 66,000 people and caused more than $500 million in damage.
The most powerful earthquake in history to date, as measured by the Richter scale, occurred on May 22, 1960, just off the coast of Chile. The earthquake had a magnitude of 9.5 and caused a chain reaction of damage as far away as Hawaii and the Philippines. This earthquake was actually a series of earthquakes, all occurring within a few hours, and they led to a number of other natural disasters. A monstrous tsunami followed the earthquake and ravaged the Chilean coast. It then traveled across the Pacific Ocean, where it pulverized Hawaii. This earthquake is also believed to have caused the eruption of the Puyehue volcano, which occurred just two days later.
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