How do earthquakes change the land?

Answer 1

Depending on the environment they are in when they occur, earthquakes can:

- create faults and folds in the earth's crust

- trigger local volcanoes

- create tsunamis

- destroy local man-made buildings and/or structures

Answer 2

This largely depends on the magnitude of the earthquake and the composition and structure of the earth's surface in a particular area.

Earthquakes cause seismic waves to radiate out away from the epicentre. These seismic waves cause the Earth's surface to move in waves, a bit like those seen on the ocean (however they can also cause the earth's surface to move in a side to side motion as well)

If the Earth's surface was a uniform homogeneous isotropic material (it had all the same properties in all directions) then the seismic waves would uniformly reduce in amplitude as they radiated away from the epicentre.

However Earth's surface is not uniform. It is composed of different materials with differing strength, stiffness and other properties (such as density). Because of this the amplitude (or height) of the seismic waves can vary from location to location.

For example in strong, stiff rockmasses the amplitude of seismic waves is kept to a minimum, whereas in weak soft, poorly consolidated ground such as soils the amplitude of seismic waves is much larger. As such they can do more damage to any buildings or structures founded on soft ground.

So what other effects can earthquakes have on the Earth's surface?

Well if the earthquake is large enough it can actually cause enough movement along a fault plane to cause the two sides of the fault to move several metres relative to each other in one instant. This may be vertical or horizontal or a combination of the two. Vertical movement will create a "fault scarp" which is essentially like a small cliff where land on one side of the fault has moved down relative to the other. Horizontal movement can cause linear features to be moved out of alignment where they cross the fault (for example roads or fences).

Earthquakes can also cause a phenomenon known as liquefaction. This typically occurs in poorly drained, poorly compacted, coarse grained soils with water in the pore spaces (i.e. a sandy soil overlying much lower permeability clay soil). When the seismic waves reach the soil described above the vibrations cause the soil grains to move around. This ultimately results in them becoming more closely packed. In other words the individual grains fit together more closely which reduces the size of the pores (which are the gaps between the soil grains where the water is). This would normally cause the water to be forced out from between the soil grains.

However because of the presence of the low permeability layer below them, the water can not go anywhere. As such when the soil grains push against the water, the water (which is relatively incompressible - i.e. very resistant to being squashed) pushes back against the soil grains (this is known more technically as an increase in pore water pressure). This happens very rapidly and the pore water pressure can become so high that it effectively counteracts the self weight of the soil grains (in technical terms, the effective stress in the soil becomes zero) making them buoyant. At this point the soil is no longer behaving as a solid but as a liquid. As such it loses the ability to support loads such as those imposed by building foundations (a loss of bearing capacity). This can cause subsidence leading to potentially severe damage to structures.

In summary:

Earthquakes cause the earth's surface to move in waves. These waves can cause severe damage to human infrastructure such as buildings. These waves can also cause liquefaction where soils behave essentially as liquids rather than solids. They can also cause movement of the Earth's surface near a fault zone due to elastic rebound when the elastic strain is released during an earthquake.

Answer 3

They make the road go off track and split the land where the plates are

Answer 4

Earthquakes change the earth's surface by creating mountains, valleys, etc.

Answer 5

That depends on the magnitude of the earthquake. Small ones can do next to no damage / weaken structures. Larger ones can destroy almost anything on land.

Answer 6

because the ground moves when theirs an earthquake which causes change in landforms retard