How do earthquakes occur?

 Hi everybody and welcome back to my blog! Have you wondered how earthquakes happen? Well, that's what I did for writing! For writing this week we have to pick a topic and write an explanation text on that topic. My topic was on how earthquakes occur. Here is my writing.

How do earthquakes occur?

You might have seen earthquakes where you live. Earthquakes happen in some places and avoid others. But have you ever wondered what causes them and how?

The tectonic plates

The Earth is divided into three main layers: The crust ( which is the ground we step on), the mantle (this is where the tectonic plates move around), the outer core and the inner core. It is also divided into seven plates: African, Antarctic, Eurasian, Indo-Australian, North American, Pacific and South American. These move around so slowly that you can’t even feel them moving. These are what causes an earthquake.

How do earthquakes occur?

If you have seen weird cracks on the ground, these are known as fault lines, this is where two plates meet. Fault lines can be formed by two plates colliding, subducting, spreading or slipping.  As the plates grind together, they get stuck and pressure builds up. Finally, the pressure between the plates is so great that they break loose. Depending on how much pressure has built up, the ground may tremble slightly or shake forcefully.

Can earthquakes be cause by reservoirs and dams?

Earthquakes can be affected by reservoirs and dams.New reservoirs could cause earthquakes due to the change in stress because of the weight of water, or by increased groundwater pore pressure that decreases the effective strength of the rock under the reservoir. Globally, there are over 100 identified cases of earthquakes that scientists believe were triggered by reservoirs (see Gupta 2002). The most serious case may be the 7.9-magnitude Sichuan earthquake in May 2008, which killed an estimated 80,000 people and has been linked to the construction of the Zipingpu Dam.

In conclusion, there are many reasons why earthquakes happen.They are either caused by the tectonic plates or by humans. But how do stop these earthquakes from happening? We can’t stop earthquakes, but we can get help from seismologists, who will be able to predict them and give us warning. 

Glossary:

tectonic plates: A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Plate thickness also varies greatly, ranging from less than 15 km for young oceanic lithosphere to about 200 km or more for ancient continental lithosphere (for example, the interior parts of North and South America).

Seismologist: Scientists who study earthquakes.

I hope you enjoy. What was your topic?