Understanding Plate Tectonics and Earthquakes: Movements, Causes, and Measurement

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Table of Contents

Introduction
Plate Tectonics
Conclusion
Reference List

Introduction

The earth is made up of four main layers which include; the outer layer, the inner layer, the mantle, and the crust. Another layer is the lithosphere which comprises the crust and the outer layer of the mantle. The lithosphere does not occur as a concrete piece but is broken into ten pieces that can move independently. The driving force of these movements is known as the convective forces which are created by the mantle (Mathez & Webster, 2004, p.84). During these movements, the plates can diverge with each other; others can converge while others can move past each other. Finally the plates grow and depart forming boundaries which act as the sites of earthquakes and volcanoes.

The essay seeks to give an elaborate discussion on plate margins and how they move in addition to exploring the events that cause earthquakes and how they can be measured.

Plate Tectonics

Movements of the Earth after quaking and shaking

Plate tectonics is the phenomenon that explains the structure and the movement of plates (Mathez & Webster, 2004, p.84). Due to plate movements, the Earth is also in a continuous motion. This involves different movements in the earth’s crust whereby, “North America moves stealthily away from Europe at 1 to 3 centimeters per year; huge regions of the Pacific seafloor plummet beneath the surrounding continents; while India pushes northwards into Asia, creating the Himalayas; and Arabia pulls away from Africa, thereby opening the Red Sea” (Mathez & Webster, 2004, p. 84). The edges of tectonic plates are known as boundaries. These boundaries are composed of numerous faults which are rough-edged in shape. During plate movement, the rough edges of the faults can stick together while the other parts of the plate move. After the plate has moved to a considerable distance over time, the edges of one of the faults can unstick thereby resulting in an earthquake.

The events that cause the earth to quake and shake

An earthquake can be defined as the shuddering and trembling of the ground as a result of release of stored energy from faulting that involves breakage of the rocks along weak joints. This involves plate movements whereby the rough edges of the faults stick together as the other parts of the plate move. This leads to the build-up of energy that would have otherwise been used to slide the plates past each other. Finally, the force of the moving plate trounces the friction forces of the stuck edges forcing them to unstuck and the energy that has accumulated is released. This energy is released from the faults in all directions producing patterns referred to as the seismic waves. These waves cause the earth to shake as they move from the center of the earth to the surface. They also cause the ground to shake as they emerge on the surface of the earth.

Scientists have identified “the elastic rebound theory” as the mechanism behind the release of stored energy from the rocks during the course of an earthquake (Monroe & Wicander, 2009, p.190). Earthquakes occur in rocks since they are capable of storing energy and they consist of fractures which are the points where rupture and therefore release of energy occurs first. When the fracture starts at a certain point on the rock, it moves along the fault at a very high speed usually in many kilometers per second. Therefore, the distance of the fracture will determine the intensity of the vibrations caused by the earthquake and the duration of the effect, that is, shaking the ground.

Measurement of Earthquakes

Seismology is the study of the characteristics of earthquakes. Scientists use equipment known as seismographs in measuring the intensity of vibrations caused by the earthquakes. These measurements are then recorded in form of seismograms. Currently seismographs are automated and they can record vibrations in a precise manner. They consist of an electronic sensor that sends signals to a computerized system that records the intensity of the earthquake precisely (Monroe & Wicander, 2009, p. 192). In other equipment, the vibrations can be measured manually. The earthquake is caused by the release of the energy accumulated in the faults which spread in all directions in form of seismic waves. The waves can cause the ground to shake. When the ground shakes, the base of the seismograph shakes too thereby allowing a string that suspends weight in the equipment to absorb these movements. Measurements are recorded by taking the distance between the base of the seismograph and the steady weight suspended by a string.

Types of body waves created by an Earthquake

Since the Earthquake occurs as a movement that shakes the ground, it creates various waves. These waves include; surface and body waves. The body waves originate from the Earthquakes’ epicenter and travel through the earth to the surface. The other forms of waves also known as shock waves include; the primary and secondary waves.

Primary waves are also known as pressure or P-waves be the fastest and can move through elements of matter causing forward and backward earth movements. On the other hand, secondary waves also referred to as Shear or S-waves are unable to move through liquids since they travel sideways causing a lot of damage by moving the ground horizontally. Upon reaching the Earth’s surface, some of the P- and S-waves are converted to surface waves which include the Long waves and the Rayleigh waves. These are known to travel slowly through the surface of the Earth but they do cause a lot of damage.

An example of a place prone to earthquakes in the United States is Alaska which records the highest number of earthquakes per year most especially in the remote areas of the Aleutian Island.

Conclusion

The essay has given an extensive discussion on plate margins and their relationship with earthquakes. The discussion also did touch on the ways of measuring the intensity of the vibrations caused by earthquakes. These measurements are important in predicting the intensity of any future earthquakes so that the people affected could prepare themselves adequately. These should also be coupled with predictions of the earthquake which can be indicated by changes in conductance and unusual animal noises.

Reference List

Mathez, E. A. & Webster, D. J. (2004). The earth machine: the science of a dynamic planet. New York: Columbia University Press. Web.
Monroe, S. J. & Wicander, R. (2009). The changing earth: exploring geology and evolution. Brooks/ Cole, Cengage Learning. Web.

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