The movement of the earth’s tectonic plates causes earthquakes. Earthquakes occur where plates meet along plate boundaries. F.e when two plates move towards each other, one plate can be pushed down beneath the other plate, into the mantle: this is a subduction zone. If this plate gets stuck under the other one, it causes a lot of pressure on the surrounding rocks. When this pressure will be released it will produce shock waves. These shock waves are called seismic waves. This is what we call an earthquake.
The place where two or more plates meet, is known as a plate boundary. There are four types of plate boundaries: constructive, destructive, conservative and collision plate boundaries.
Almost all earthquakes occur near to plate boundaries.
The earthquake in Chile was caused by subduction. At the west coast of Chile, three tectonic plates meet: Antarctic plate, South American plate and the Nazca plate. Chile is located at a convergent plate boundary (a destructive plate boundary). The Peru-Chile trench is caused by the subduction of the oceanic Nazca plate under the continental South American Plate. This movement causes seismicity and volcanism in Chile, producing amazing earthquakes. This is a typical example of a continental-oceanic subduction zone.
This earthquake was the biggest one that hit Chile in over 50 years.
The magnitude of an earthquake is measured with a seismometer. This machine measures movements in the surface of the earth.
The Richter scale measures earthquakes on a logarithmic scale. This means that an earthquake of 5 is ten times more powerful than one of 6 on the scale of Richter. Most people express the magnitude with this scale.
The 2010 Haiti earthquake had a catastrophic magnitude of 7.0.The Chile earthquake was measured 8.8, this means there is almost a widespread destruction. It was one of the strongest earthquakes that were ever recorded. If we must believe Chilean authorities, over 300 people have been killed.
4 This magnitude earthquake is widely felt and is strong enough to crack plaster.
5 A strong vibration shakes the earth, damaging chimneys and weak buildings.
6 This earthquake is strong enough to badly damage average buildings.
7 This earthquake is strong enough to destroy even well built structures.
8 Even special, earthquake-resistant buildings will be badly damaged.
9 There is widespread destruction.
Chile is a very active plate boundary, so it’s a perfect place for earthquakes. Chile is located in the so-called Ring of fire, an area in the Pacific where there are a lot of earthquakes and volcanic eruptions.
The names of the plates are in white. You can see the Nazca plate is causing subduction (blue line with triangles), because it goes under the South American plate (Amérique du Sud).
The earthquake happened near a plate boundary. Because of plate tectonics, one plate can sink deeper, so there becomes a difference in sea level.