Earthquakes Impact on the Spheres

When earthquakes occur they can cause damage to all or some of the spheres on Earth, including the lithosphere, atmosphere, hydrosphere and biosphere.

When one of the spheres is affected then at least one or more of the others will be affected as well because they all work together. For example, when ground breakage occurs in the lithosphere it creates new lakes in the hydrosphere.

What do these spheres represent?

Lithosphere: the solid portion of the earth including the crust and the upper mantle.

Under the metropolitan area in Adelaide you will find fairly stiff sediments that soften the impact of earthquakes. However if an earthquake happens in an area with less compacted sediments, damage to buildings can occur, including structures being destroyed and power lines falling. These incidents can cause fires and harm to civilians. Serve movement in the Earth's crust causes the ground near lakes and rivers to cause slumping.

  

Figure 1 - Diagram showing how slumping occurs.

Atmosphere: the gaseous envelope surrounding the earth; the air we breathe.

Earthquakes indirectly contribute the enhanced greenhouse effect.  They are known to release methane from pockets within the ground to the atmosphere by the movement of tectonic plates. Methane is one of the greenhouse gases that contribute to the enhanced greenhouse effect. Methane, as well as carbon dioxide, absorbs the sun’s radiation that is re-radiated from the Earth as infrared radiation. This warms the atmosphere and since the levels of these gases are higher than usual, the atmospheric temperature has been increasing.

If an earthquake is at an appropriately high magnitude they can increase the height of mountains by a few inches to a few metres. Evidence for this is seen at the Flinders Ranges in South Australia. This increase in mountains occurs due one side of the fault line moving up relative to the other side of the fault line, creating steep elevation referred to as a “scarp”.

Hydrosphere: the water on or surrounding the surface of the globe, including the water of the oceans and the in the atmosphere.

Confined and unconfined aquifers can both be affected by earthquakes. Confined aquifers that are within the area of the earthquake are more likely deform due to the movement of the earth, than unconfined aquifers. Groundwater level changes can be affected, which is evident in both types of aquifers.

Permanent deformation of aquifers lasts until pressure within the aquifer equalises with the water table. This equilibrium can be met at varying lengths of time. This only applies in the vicinity of the earthquake. The process and recovery of aquifers is still unknown.

Ground breakage creates new lakes also known as “sag ponds”. They increase groundwater flow from springs and displacing stream channels.

Figure 2 - Electronic diagram of the formation of sag ponds on the left and a real sag pong image taken from a helicopter along the San Andreas Fault on the right.

Biosphere: the part of the earth’s crust, waters and atmosphere that supports life and the ecosystem comprising the entire earth and the living organisms that inhabit it.

The intense shaking of the earth’s surface causes damage or loss of human and animal life. Earthquakes themselves do not kill or harm life, it’s when structures or certain flora collapse.

The creation of new springs and lakes created by ground breakage alters the surrounding environment. There is potential for flooding, changes in the food chain and can cause changes in animal behaviour in the area affected. In the long run, this can lead to new species being formed or the extinction of modern species.

Landslides release pathogenic microbes into the atmosphere impacting on human and animal health. This can have a devastating effect, such as becoming an epidemic or wiping out a species. Both situations lead to further alteration in the biosphere. 




Figure 3 - Damage to families homes and the effect of earthquakes on animals.

Comments