|
Earthquakes
Factfile |
 Earthquakes |
 |
How Earthquakes Happen
For most of the time, tectonic plates float or move on the mantle with no negative result. However, when two plates become jammed - usually through sliding past each other or crushing each other - over time, a lot of stress builds up in the surrounding rocks. Eventually this stress becomes too much to hold the two plates in place; they break and "snap" to a new position. In the process of releasing this tension, strong shock waves called seismic waves (giant waves of energy) are produced, which blast upwards and outwards - this is an earthquake.
The place where an earthquake starts underground is called the focus and shockwaves spread out from this point, getting weaker in strength the further away from the focus they move. The epicentre is immediately above the focus on the Earth's surface and this is where most damage will usually occur. The distance between the focus and the epicentre determines the depth of an earthquake. The focus can be very deep down (over 300km); medium deep (300-70km) or shallow (less than 70km).
Shallow earthquakes may cause a lot of damage at the epicentre but only cover a small area, while deep earthquakes are felt over huge distances. One of the deepest ever-recorded earthquakes was in Assam, India in 1897. Shocks from this earthquake were felt as far away as Edinburgh, Scotland.
While earthquakes do not produce volcanoes, volcanoes can create earthquakes. However, these are of such low intensity that any damage caused is very rare.
|
|
|
|
|
|
|
| |
|
|
