COMPARE AND CONTRAST THE TOPOGRAPHICAL FEATURES AT DIVERGENT AND CONVERGENT PLATE MARGINS.
In order to compare and contrast the topographical features at divergent and convergent plate margins we must first define and understand the meaning of the term. The changes in surface such as valleys and mountains as well as features such as rivers and roads are what the broad term “topography” describes. It is basically a representation of the earth’s surface and is generally concerned with measuring and recording elevations and contours to produce a three-dimensional representation. The technique of topography can be used for a variety of applications such as geological explanation, military planning and it also provides detailed information about terrain and surface features. However, in this essay we look at the way in which it influences divergent and convergent plate margins. Figure 1 below shows an image of the earth’s surface to provide a better understanding via imagery.
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Figure: Topography features on the surface of the earth.
Source: https://sciencing.com/topography-5479604.htmlPlate tectonics is responsible for providing a basis for the understanding of the connection between processes that facilitates heat loss and ones that causes plate movements. Plate tectonics find its greatest success in the explanation of most of the earth’s topographic features specifically the ocean basin. Divergent and convergent margins are both part of the study of plate tectonics; this includes the study of the plates that make up the lithosphere and how its movements influence the surface structure. What causes the movement of these plates? Convection currents defined as the heat which lies at the core and is transferred to the mantle where hot material rises and cool air sinks. These currents facilitate either the spreading apart or the pushing together movements of these plates. The differences in features shown at each plate margin is determined by the type of movement and the types of plates involved known as oceanic and continental crusts.
Divergent plate margins refer to when the plates move apart from each other and this occurs above rising convection currents. These rising currents push upwards at the bottom of the lithosphere lifting it with its lateral flow causing the material above it to also flow in that direction. The topographical features that develop at this boundary are due to the extension of the plate boundaries which causes rifting in continental and oceanic crusts (Strahler, 2011, 419). This process stretches and thins the oceanic crusts until it eventually splits. There are several topographical features which lie at these divergent plate margins majority of which are due to faulting. As tectonic plates moves a fracture is formed on the earth’s crust and this is what is known as a fault. When one crust is raised higher than the other as it is pulled apart, is defined as a normal plate margin and here a cliff feature, fault scarp is formed. A graben is another feature formed when two normal faults occur on opposite sides of the lithosphere, creating rift valleys and a known example of this is the East African Rift Valley. Over a period of time these rift valleys can lead to the formation of new oceans when continental crusts are pulled apart currently being seen in the Red Sea (Strahler, 2011, 420-424). Figure 2 shows an image of a rift valley at divergent plate boundaries.
Figure 2: A rift valley at a divergent plate boundary.
Source: https://study.com/cimages/multimages/16/divergent_valley.pngIn divergent plate margins involving oceanic plates, mid ocean ridges are formed. The forces cause the lithosphere to stretch producing a gap. The super-heated material below (rising magma) does not fill the gap as the plates continue to drift apart causing the gap known as the ridge to develop. The Mid-Atlantic Ridge is a classic example of this type of plate boundary. Figure 3 is an image better explaining the formation of ridges.
Figure 3: Formation of an oceanic ridge.
Source: https://revisionworld.com/sites/revisionworld.com/files/rw_files/seafloor.jpgIn plate tectonics there are also convergent plate margins, which in comparison to divergent, the movement is the opposite. The plates move towards each other at these boundaries and the outcome of these slow-motion collisions depend on it locations. At this plate margin, the collision of these oceanic plates creates a subduction or one of the plates sinking beneath the other. This leads to the formation of deep sea trenches, a feature that develops directly above the subduction zone. Features such as deep sea trenches are formed here as they develop above the subduction zone. A common example is the Marianas Trench in the Pacific Ocean. Volcanoes and earthquakes are common along these plate margins, also seen by the famous “Ring of Fire”, in the Pacific Ocean. Figure 4 adds imagery to the understanding of the formation of trenches.
Figure 4: Formation of trenches.
Source: http://geology.com/records/ocean-trench.gifAt these plate margins faulting also exists just as in divergent margins. However instead of normal faulting, reverse faulting occurs. Due to compression, part of the crust rises above the other and this aspect has an influence on topography. Large Fold Mountains such as the Alps has formed due to the compaction of rocks upon rocks via compression forces. The diagram below demonstrates the formation of Fold Mountains.
Figure 5: The formation of Fold Mountains.
Source: https://i.ytimg.com/vi/4b81nXSVA34/hqdefault.jpgAfter defining and understanding these features and the processes that leads to its formation we can now compare and contrast. What makes these plates different? Its common difference is its movement, not only the direction that the plate is moving; either towards or away from each other, but it also includes the different types of crusts. Additionally, convergent plate margins unlike divergent can have the collision both a continental and oceanic plate. This also leads to the formation of more features such as deep sea trenches close to the shoreline and volcanoes further away from the shoreline.
Both of these margins play a major role in shaping the topography of the earth’s surface. Both of them lead to the formation of volcanoes and both also show faulting. However, divergent margins have normal faults and convergent has reversed all due to its direction of movement. Rift valleys and mountains are found only at divergent margins whereas deep sea trenches, volcanic islands and Fold Mountains are formed only at convergent margins.
REFERENCES:
“Topographical Features at Divergent and Convergent Plate Margins.” Topics, Sample Papers ; Articles Online for Free, Sep 13, 2016. Accessed October 11, 2018. https://studymoose.com/topographical-features-at-divergent-and-convergent-plate-margins-essayIrimia R, Gottschling M (2016) Taxonomic revision of Rochefortia Sw. (Ehretiaceae, Boraginales). Biodiversity Data Journal 4: e7720. https://doi.org/10.3897/BDJ.4.e7720Strahler, Arthur Newell, and Strahler, Alan H., Joint Author. Environmental Geoscience: Interaction between Natural Systems and Man by Arthur N. Strahler and Alan H. Strahler. Santa Barbara, Calif.: Hamilton Pub., 1973.
