Earthquakes are caused by the motion of tectonic platesindividual sections that make up the Earths surface like panels on a football. Immense strain accumulates along fault lines where adjacent plates meet. When the rock separating the plates gives way, sudden seismic ground-shaking movement occurs.
Of course, if we want to know why earthquakes happen, we need to dig a little deeper.
Centre of the Earth
The Earth is made up of three main layers: The core is at the centre of the Earth. The mantle is a mobile semi-molten layer around the core. The outer-shell of the Earth is called the crust. Scientists call this the lithosphereits the part were on now.
The crust is made up of 12 individual tectonic plates. Below the sea, they can measure three to six miles thick and under land this increases to 20-44 miles . Below the crust, radiation from the Earths core heats the semi-molten mantle to temperatures of over 5000C.
All fluids when heatedeven molten rockare affected by a process called convection. That makes hot liquid rise to displace cooler liquid, creating a current. Tectonic plates effectively float on the mantle, like croutons in a bowl of super-heated soup. But these plates and constantly move due to the convection current.
Of course, they creep along very slowlyroughly the same speed your fingernails grow. Even at this sub snail-pace, the effects can be devastating. The combined annual force of earthquakes is equal to 100,000 times the power of the atomic bombs that flattened Hiroshima.
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