Sometimes we see that all the trees, buildings and other objects beside us are shaking heavily where we are standing. We all call it an earthquake.
Though we are aware of this phenomenon, do you know what the actual reason behind this unusual phenomenon is? So, let us discuss this below.
Earthquakes result from sudden movement related to a few specific faults within the Earth. This movement usually releases a specific kind of energy, known as the ‘elastic strain’ in the form of seismic waves. This propagates through our Earth and causes the ground surface to shake noticeably.
This kind of movement that is faulty is a response to the buildup of stress and even long-term deformation. So, we can say that the main reason behind this earthquake is the specific structure of the Earth.
The Earth’s Structure
Seismic waves originating from notable earthquakes that pass throughout our Earth. These waves carry crucial information related to the internal structure of the Earth.
When seismic waves pass through our Earth, they are bent or refracted, such as the rays of light bending when they mainly pass through a particular glass prism.
As the speed of these seismic waves relies a lot on density, we can easily use the time of travel of those waves to determine a change in density with depth and can show us that our Earth is made of several layers.
Plate Tectonics
The outermost layer of our Earth is fragmented into around 15 major slabs, which are known as tectonic plates. The lithosphere is formed with these slabs, which comprise the crust and the upper part of the mantle.
The Earth’s tectonic plates move very slowly relative to each other, usually a few centimeters per year. However, this procedure can cause a huge amount of deformation at the boundaries of those plates, which eventually leads to incidents known as earthquakes.
Many observations show that almost all of these earthquakes are related to those tectonic plate boundaries and can explain the global distribution of earthquakes. However, some of the characteristics of earthquakes may be explained with the help of a simple elastic rebound theory.
What Forces The Tectonic Plates To Move?
Below these tectonic plates lies the asthenosphere of our Earth. This mainly behaves like a specific fluid over very long-time scales. There are several types of competing theories that are used to explain what can drive the movement of those plates, usually tell about three main forces, such as:
Slab pull: These colder and older plates sink at subduction zones.
Mantle Convection Currents: These warm mantle currents drive and carry lithosphere plates, similar to a conveyor belt.
Ridge Push: Plates that are newly formed at the oceanic ridges. As they are warm, these have a higher elevation at the ridge than the colder ones.
Thus, in this article, we learn some fantastic facts and reasons behind earthquakes.
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