Explanation:
Earthquakes are natural calamities that are caused by the movement of the Earth's tectonic plates. These plates are massive slabs of rock that float on the semi-fluid mantle layer beneath them. The Earth's lithosphere, which includes these tectonic plates, is divided into several large and small pieces that constantly move and interact with each other.

What are tectonic plates?
Tectonic plates are pieces of the Earth's lithosphere that fit together like a jigsaw puzzle. There are several major tectonic plates, such as the Pacific Plate, the Eurasian Plate, the African Plate, and the North American Plate, among others. These plates are constantly moving, albeit very slowly, due to convection currents in the mantle beneath them.

How do earthquakes occur?
When tectonic plates interact, they can either move apart, move towards each other, or slide past each other. It is at the boundaries of these plates where most earthquakes occur. There are three types of plate boundaries:

1. Divergent boundaries: At divergent boundaries, plates move apart from each other. This movement creates a gap, and magma from the mantle rises to fill the space, creating new crust. Earthquakes can occur when the newly formed crust fractures and moves.

2. Convergent boundaries: At convergent boundaries, plates move towards each other. When two plates collide, one can be forced beneath the other, creating a subduction zone. The intense pressure and friction at the subduction zone can cause earthquakes.

3. Transform boundaries: At transform boundaries, plates slide past each other horizontally. The friction between the plates can cause them to lock together, and when the stress becomes too great, they suddenly slip, releasing energy in the form of an earthquake.

Impact of earthquakes:
Earthquakes can have devastating impacts. They can cause buildings and infrastructure to collapse, leading to loss of life and property. They can trigger landslides, tsunamis, and in some cases, volcanic eruptions. The severity of an earthquake is measured using the Richter scale.

In conclusion, earthquakes are natural calamities caused by the movement of the Earth's tectonic plates. Understanding the causes and effects of earthquakes is important for scientists and engineers to mitigate their impact and improve the safety of communities living in seismically active areas.