We’re all familiar, or at least come across time and again, with the terms tectonic plates, fault lines and seismic zones. But there are quite a few of us who cannot make up the connection between these and basically answer the simple question of what causes earthquakes? How and why the tectonic plates move and what is it beneath the surface of the earth that makes all these hazardous movements to happen’ are two of the most pressing questions related to earthquakes.
Keep reading to get the aforementioned questions answered and get your hands on some essential knowledge about the basics of earthquakes.
Tectonic plates and fault lines
The planet Earth is composed of four layers, inner and outer core, mantle and the crust which is the outermost core. The outer/top-most part of the plastic-like mantle and crust make up a thin layer over the surface of the earth. In order to understand tectonic plates, it is essential to know that this thin outer layer is not a single piece; rather it is a number of pieces joined together. These pieces of crust, called tectonic plates, together with the block of the earth right beneath them, are not static; they move and slide at their boundaries against each other. These boundaries are referred to as ‘plate boundaries’. When we say the word fault line, we are basically referring to these boundaries collectively. It is here that the blocks of earth slide past each other causing the earthquake.
So, how does an earthquake happen?
As mentioned above, tectonic plates are not static. As their boundaries are joined or stuck with each other, it is easier for the plate itself to move than the respective boundary to move at the same pace because of higher friction. As plates move, pressure builds up on the plate boundaries causing energy to be increasingly stored in them. It is only when the pressure build-up from the plates’ movement overcomes the friction between the jagged plate boundaries that they are unstuck and slide past each other. This releases the energy being stored for far too long. The radiation of this released energy across the tectonic plate is what is scientifically called ‘Seismic Waves’. As these waves move past the earth, they shake the earth. Upon reaching the surface, they shake the surface of the earth.
The area below the surface of the earth, the origin of the earthquake, is called the hypocenter. Its corresponding area right on the surface of the earth is called epicenter. The path that the seismic waves travel from the hypocenter and epicenter is basically the fault plane, the movement of which against the neighboring plane causes the earthquake.
One major misconception about earthquakes is that the tectonic plates move only before/during the earthquake. This is not true. It is totally natural for the tectonic plates to keep having slight movements at all times, which do not escalate into an earthquake. As established above, it is only when the movement of tectonic plates is significant enough to overpower the friction holding the boundaries together that earthquake happens.