Earthquake is simply a sudden violent shaking of the ground causing great destruction e.g loss of lives, loss of properties, destruction of buildings, etc. Earthquake is one the natural disasters we have on the Earth. Earthquake sometimes happens under the sea. When this happens, it leads to Tsunami.
What causes Earthquakes?
Earthquakes are not caused by “witches and wizards” as might be proclaimed by some villagers. From scientific points of view, some parts of our Earth are not stable. Those unstable parts of the Earth are the regions that are plagued with Earthquakes. We need to know the unstable regions, we need to identify them and we need to know what to do to mitigate the effects of the Earthquakes. So, what causes the instability in those regions of the world?
The Earth is made up of Lithosphere and Asthenosphere. Lithosphere is the rigid part of the Earth – the Crust. Asthenosphere is made up the molten rock called Magma. The Lithosphere lies on the Asthenosphere. The Lithosphere is broken up into pieces called Tectonic Plates. There are seven major tectonic plates namely: Eurasian Plate, Pacific Plate, Indo-Australian Plate, African Plate , Antarctic Plate, South American Plate and North American Plate. Apart from these, there are other minor plates e.g Somali plate, Philippines plate , Arabian plate , Caribbean plate etc.
These plates have boundaries between them. The boundaries are called Plate Boundaries. The plate boundaries are of three types namely: (1) Convergent Boundary (2) Divergent boundary (3) Transform Fault Zone.
For the convergent boundaries, the plates move towards each other, just like head-on collision between two vehicles. While the two plates are colliding, great pressure is being built up around the converging zone. The pressure building up here takes geologic years. Also, mountains are being developed at the same time. Mountain development here is technically called Orogeny. When the pressure becomes too much for the rock therein to retain, then, the pressure is released and this causes Earthquake around that region. It’s like pumping air into a balloon until the balloon bursts.
For the divergent boundaries, the plates move away from each other. Here, there is no mountain building or pressure building up, like it is in convergent boundaries. As the plates are moving away from each other, molten rock(magma) from beneath comes up to fill the vacuum created. The molten rock becomes solidified and a new land is created here. This is called Sea-Floor Spreading. It is called Sea-Floor Spreading because it is usually associated with sea floor.
For the Transform Fault Zone, the plates slip past each other. While the two plates are slipping past each other, great pressure is also being built up around this zone. This built up pressure is also released one day and it causes an Earthquake around the region. The first point of rupture of the built up pressure in the rock during Earthquake is called Epifocus. A point on the surface of the Earth that is directly above the Epifocus is called Epicentre.
So, we need to identify the places in the world that are around the plate boundaries. Check the picture “Earth’s Major Tectonic Plates” above.
What can we do to mitigate the effects of Earthquakes?
In Earthquake prone areas, we can do the following:
(1) If we can avoid the Earthquake prone areas, then, we should.
(2) For the tourists, the Government and citizens of Earthquake prone areas, we should study the Earthquake Cycle of that area. Knowing the Earthquake Cycle of an Earthquake prone area, we can predict when the Earthquake will strike. When the time for the Earthquake to strike is approaching, we pack our things and leave the area. After the Earthquake must have taken its natural cause, we can come back. Tourists may not visit, when the time for the Earthquake to strike is approaching, to play safe. (Note: Earthquake Cycle is simply the time interval between two Earthquakes. Just like menstrual cycle in women. In some Earthquake prone areas, the Earthquake Cycle is every 10 years. In some, it is every 5 years. Etc.)
(3) Only Earthquake resistant buildings should be constructed.
(4) Heavy objects should be removed from high places.
(5) All the emergency exits should always be kept free of obstacles.
(6) In a multiple-story building, no one should try to evacuate using the elevator. If the elevator gets destroyed
by the Earthquake while the person is still inside, you can guess what will happen!
(7) Medical supplies and emergency aids/materials should always be made readily available in case of an unexpected
(8) Students/kids should be taught safety measures during Earthquakes. These can be incorporated into the school’s
(9) Seismologists should be employed by the the Government to check regularly to know if an Earthquake is impending or not! With this, people can be directed on what to do if an Earthquake is imminent.
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