Tectonic plate movement and the occurrence of earthquakes

¶ … Continental Plates and Earthquakes

Natural events or disasters like earthquakes, tsunamis, and volcanoes are dangerous incidents given their significant impact on life and property. Given their devastating impacts, the causes of natural disasters have attracted considerable concern among the public and scientists. One of the most important ways to understand the causes of these events is by examining the science behind them. Even though these events differ in the manner in which they occur, they are largely attributable to tectonic plate movement. Since tectonic plate movement plays a major role in the occurrence of natural disasters, these incidents have relatively similar geological beginnings. An example of a natural disaster whose occurrence is brought by tectonic or continental plate movement is earthquake.

Overview of an Earthquake

An earthquake is basically regarded as a natural event that takes place when two blocks of the Earth slip past each other abruptly (Wald par, 1). The surface where blocks of the Earth slip past each other is known as the fault plane or fault whereas the location where the earthquake begins below the Earth's surface is known as the hypocenter. Since earthquakes take place after two blocks of the Earth slip past each other unexpectedly, they can occur anywhere in the globe. However, most of the earthquakes that take place tend to do so in the region where most of the volcanoes are found i.e. the Ring of Fire.

Earthquakes mostly occur in the Ring of Fire because this is the region where most of tectonic or continental plates of the Earth come together. Tectonic or continental plates are the many different pieces of the Earth's crust that combine together like a puzzle to cover the whole planet. These plates in turn comprise an outer layer of the Earth that is commonly known as the lithosphere that tends to function as a more or less rigid shell. The rigid plates in the Earth's lithosphere are in relative motion and affect humans in various means including generating volcanism, causes earthquakes, and mountain-building ("The Theory of Plate Tectonics" par, 1). Therefore, without plate tectonics and movement of continental plates, the Earth would have less volcanism, fewer earthquakes, and relatively no deep-sea trenches.

Continental Plates Movement and the Andes

The Earth has several major continental and oceanic plates including the Pacific plate, North American plate, South American plate, the Antarctic plate, and the Caribbean plate. The Andes is an example of an earthquake that was caused by the movement of the continental plates. This natural disaster can be traced to the movement of the Nazca plate, which was moving eastwards towards the South American plate at an estimated speed of 79mm per year as shown in Figure 1.

Figure 1: Movement of Nazca Plate

At the point of intersection between these two plates, Nazca's denser oceanic lithosphere is forced down and under the relatively floating continental lithosphere of the South American plate ("Oceanic/Continental: The Andes" par, 2). During this process, the Nazca plate is descending or moving at an angle into the Earth's mantle through a process commonly known as subduction. This is demonstrated on the ocean surface through the existence of the Atacama (or Peru-Chile) Trench. Subduction is a phenomenon that refers to the process in which a dense oceanic plate like Nazca plate collides with a thick continental plate and is forced under it.

The friction between Nazca plate and the South American plate when they meet prevents the oceanic plate from sliding smoothly though the plate is already subducting. Consequently, the Nazca plate drags against the overlying continental (South American) plate, which makes both plates to collapse and crack. The collapse and deformation of the continental and oceanic plates results in earthquakes that are initially shallow but deepen as Nazca plate continues to descend. The end result of this entire process brought by the movement of the continental and oceanic plates is Benioff zone, a zone of earthquake foci. This movement also affects water resources in the region through bringing sea water, which is already locked in the ocean crust, deep into the Earth's mantle.

In conclusion, Andes earthquake is an example of how the movement of continental plates causes an earthquake. An earthquake usually occurs when the edges of these plates unstuck on one of the plate boundaries. Andes earthquake occurred following a collision between an oceanic plate (Nazca plate) and continental plate (the South American plate). As shown in this example, the collision between continental or tectonic plates causes deformation and collapse of the Earth's major plates. The collapse and/or deformation in turn generate an earthquake, which has devastating impacts on life and property.