Internal and External Forces: Volcanoes and Earthquakes - Assignment Example

Harris Kamran Geography Review Paper 6 November Internal and External Forces: Volcanoes and Earthquakes The forces of nature that shape the landmarks on the earth’s surface can be grouped into two categories: external forces and internal forces (FCAT Science). The mechanism of action of the two groups of forces and the end results are quite different from each other, and both have played a part in the formation of the features of the earth as are known today (A Living Planet).

The external forces shape the superficial features of the earth’s surface, and form and reform the soil (A Living Planet 19). They also help in the determination of the distribution of the surface and ground water (A Living Planet 19), and the shape of the deserts and features such as sandbars (FCAT Science 187). The formation of the soil occurs as a result of erosion and weathering (A Living Planet 20). Erosion can be of many types, such as water erosion, wind erosion, glacial erosion, and loess formation (A Living Planet 20).

The process of weathering could be mechanical or chemical (A Living Planet 19). Other external forces include tornadoes, hurricanes, and water runoff (FCAT Science). On the other hand, the internal forces of the earth result in the formation of deep seafloor features (FCAT Science 175), along with the formation of landscape structures such as mountain ridges, fault lines, and phenomena such as volcanoes and earthquakes (FCAT Science 176).

The internal forces can be attributed to the movement of the lithosphere which is explained most satisfactorily by the plate tectonics theory (FCAT Science 178). It states that the crust or the lithosphere of the earth is divided into twenty plates (FCAT Science 178), which are dynamic in nature due to the movement of underlying magma in the asthenosphere below (FCAT Science 178). Their movements include sliding, colliding, convergent, and divergent movements (FCAT Science 178).

Divergent movements, in which the plates move away from each other (FCAT Science 179), have resulted in the formation of the Atlantic mid-ocean ridge and the Atlantic ocean seafloor (FCAT Science 179). As the crust is pulled apart, it results in earthquakes (FCAT Science 179). Convergent movements occur when the plates move towards each other (FCAT Science 180), resulting in the formation of mountain ridges such as the Himalayas, the Ural Mountains, and the Appalachian Mountains (FCAT Science 180).

Again, earthquakes occur as a result of the collisions (FCAT Science 180). An associated process to the convergent movement is that of subduction (FCAT Science 180), in which one plate, usually the heavier of the two, slides beneath the lighter continental plate (FCAT Science 180), resulting in the formation of deep sea trenches (FCAT Science 180) on the ocean floor, such as the Puerto Rico Trench (FCAT Science 180), and volcanoes on the external crust (FCAT Science 180).

The volcanoes are formed in the form of an island arc, which is essentially a series of volcanoes formed due to subduction (FCAT Science 180). Such arcs include those in the Atlantic and Indian Oceans, and the Ring of Fire in the Pacific Ocean (FCAT Science 180). The Marianas Islands and the Aleutian Islands have also been formed by this process (FCAT Science 180), and are volcanic in nature. The occurrence of volcanoes can be predicted relatively fairly (Earthquakes and Volcanoes) with the use of instruments such as seismometers and gravimeter (Predicting Eruptions).

The volcanic eruptions follow fixed patterns of increasing seismic activity (Earthquakes and Volcanoes), which can be measured on a seismometer (Predicting Eruptions). Also, gravimeters measure the pattern and rate of flow of magma (Predicting Eruptions). On the other hand, earthquakes are relatively harder to predict (Earthquakes and Volcanoes), since the seismic activity in this case is not fixed, and no pattern is followed (Earthquakes and Volcanoes).

Earthquakes are measured on a modified Richter Scale (Earthquakes and Volcanoes). However, their prediction is poorly established (Earthquakes and Volcanoes). Works Cited “Earthquakes and Volcanoes.” ModTech. UWinnipeg, 29 Sept. 1999. Web. 6 Nov. 2011. “Predicting Eruptions.” ThinkQuest. Education Foundation, n.d. Web. 6 Nov. 2011. “A Living Planet.” McDougal Littell Inc., n.d. Web. 6 Nov. 2011. “Forces that Change Earth’s Surface.” Preparing for FCAT Science, n.d. Web. 6 Nov. 2011.