5.9 Earthquakes

earthquakes sometimes happen in Québec. an earthquake feels like the whole world is shaking. they are normally brief and don’t do lot’s of damage but that is not the case elsewhere in the world.

What is an earthquake?

Definition of an earthquake: an earthquake is a shaking or a movement of the ground caused by a volcanic eruption, by the sudden movement if rocks along a fault (when two tectonic plates rub against each other) or by other similar events.

The birth of an earthquake

1) the movement of rocks can cause an earthquake. along the edge of two tectonic plates the earth’s crust can crack and even in the middle of two tectonic plates. these cracks can be several kilometres deep.

2) the crack grows wider and becomes a fault when masses of rock slide down a crack. rocks can move a few centimetres to a few metres at a time. they can get stuck or change shape when they slide past each other. this causes a massive shock that releases a large amount of energy which causes vibrations.

3) these vibrations spread in all directions to earth’s surface. these “quakes” can last up to a few seconds to a few minutes.

4) most of the time the movements inside the earth is what cause the earthquakes. “focus” is what the starting point of an earthquake is called. the area on the surface right above the focus is called an “epicentre”.

when describing an earthquake you must know what a “fault”, “focus” and “epicentre” are because they are key words for describing an earthquake.