Test: Our Changing Earth

The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken into tectonic plates also known as Lithospheric plates.

The Earth's lithosphere is composed of seven or eight major plates and many minor plates.

The lithosphere is broken into a number of plates known as the lithospheric plates. These plates move around very slowly because of the movement of the molten magma inside the earth which moves in a circular manner.

The earth's movements are divided on the basis of the forces which cause them to move.

• The forces which act in the interior of the earth are called Endogenic forces.
• The forces that work on the surface of the earth are called Exogenic forces.

Endogenic forces are those forces that act in the interior of the earth.
Example: volcanoes and earthquakes causing mass destruction over the surface of the earth.

• Exogenic (a.k.a. exogenetic) refers to external processes and phenomena that occur on or above the surface of the earth.
  Example: Comet and meteoroid impacts, the tidal force of the moon, and the radiation from the sun, Weathering effects, and erosion.
• Running water, wind, snow and waves are agents in exogenous processes, and these agents are also known as “Geomorphic agents”.
• ​Whereas, sudden movements such as volcanos are caused by endogenous force.

Thus, option A is correct.

Endogenic forces cause sudden movements like earthquakes, volcanoes, landslides which cause mass destruction over the earth's surface.

A volcano is an opening in the Earth's crust that allows molten rock, gases, and debris to escape to the surface.

The place in the crust where the movement starts is called the focus. The place on the surface above the focus is called the epicenter. Vibrations travel outwards from the epicenter as waves. The greatest damage is usually closest to the epicenter and the strength of the earthquake decreases away from the center.

When the Lithospheric plates move, the surface of the earth vibrates. The vibrations can travel all round the earth. These vibrations are called earthquakes.