Why Do Earthquakes Happen?

The movement of the plates away from each other can cause earthquakes, but they are relatively mild. The collision and transform boundary movements are much greater in terms of force and potential energy releases.

There are also fault planes near the convergence and transform boundaries of plates. Earthquakes occur most often along these fault lines. The movement of the plates in relation to each other has the potential to release large amounts of stored energy in the form of a quake. It is easiest to understand an earthquake when examining a meeting of plates that are interacting in transform boundary manner. The two plates are sliding along the edge of each other. If the edges were perfectly smooth and flat, there would be very little potential energy to release as the plates slide by each other.

This is not the case; instead, there are irregular edges along the plates. As one plate slides by the other, an outcropping on one plate may catch on the other plate, halting the progress.

As the plates continue to exert force to slide by, a great deal of potential energy builds along the fault that represents where the plates meet. When the force grows to the point where the plates slip by each other by overcoming the obstruction, the built up potential energy is released when the plate slides. This energy and the movement of the plates generate the quake.

It is as if the plates jerk by each other and the jarring of one plate against the other can create major damage to the areas around where the outcropping caught the plate movements. Once they have broken free, ending in an earthquake, they continue moving past each other until they are caught again.

Composition of the Earth's Core

The earth’s core is composed of four main sections: the lithosphere, the mantle, the liquid core and the solid inner core. In general, people group all of these sections together as the mantle (which encompasses the mantle and the lithosphere) and the core (which encompasses both the liquid and solid cores).

Core

The core of the planet is made up of a solid inner core that is surrounded on all sides by a liquid metal layer. The liquid metal layer is what people think of as molten lava. The lava is liquefied rock and metals that flow around the inner core.

The molten core is under tremendous pressure and is at a very high temperature. When the earth’s crust develops a weakened point or break, the material from the molten core is released through the mantle into the lithosphere. This is seen by those living in the lithosphere as a volcanic eruption or a release of lava.

Mantle

The mantle is made of the dirt and rock far beneath our feet and the lithosphere consists of the upper layer of the earth’s crust. The lithosphere reaches down about eighty kilometers and the mantle goes down another 2800 kilometers. Below this is the liquid core. The liquid core is 2300 kilometers thick and then the solid inner core is the remaining 1200 kilometers. Adding this up, the earth’s radius is about 6380 kilometers.

Plates of the Earth's Surface

The mantle of the earth is broken up into plates that allow the mantle layer to shift and float around on the molten core. Sixteen different plates comprise the earth’s surface. Of these plates, six are easily identified as the continents of Antarctica, North America, South America, Africa, Indo-Australia and Europe/Asia. The other plates are regions under the oceans of the world. For example, the Pacific plate is one major plate that is covered by most of the Pacific Ocean. This is the plate upon which the Japanese earthquake of 2011 occurred and caused so much devastation.

Movement of the Plates

Three types of movements can occur at points where the plates meet each other. They can meet in a collision, they can diverge or they can transform boundaries.

When plates collide or transform boundaries, earthquakes are inevitable. When plates diverge, the resulting effect is the formation of ocean rifts. As plates collide, deep ocean trenches form due to one plate being driven under the other plate.

Every island in the earth’s oceans has been formed by the release of lava from the mantle. On some Islands, eruptions continue. For example, in Hawaii, the Kilauea Volcano continually erupts. The release of lava flows down the mountain and into the ocean expanding the land mass of the Big Island, Hawaii.

Risks of Earthquakes

The biggest consequence of natural disasters such as earthquakes is the loss of human life. Many deaths can be caused by the collapsing of buildings. Social and economic consequences include unemployment, loss of shelter, poor economy and the waste of money and energy.

Many new structures are being designed and constructed to withstand earthquakes to a certain degree. Geotechnical engineers are knowledgeable about plate tectonics and are skilled in analyzing soil and rocks and can provide construction information to lessen the risks brought about by earthquakes.