Introduction
Tectonic Plate refers to a massive, slab of solid rock that is irregularly shaped, and it is composed of both oceanic and continental lithosphere.
Definitions
Mid-Ocean Ridge refers to an underwater mountain range that forms due to plate tectonics. This structure is formed through two tectonic processes, ridge-push and slab pull that cause the spreading at mid-ocean ridges.
Basin and Range topography refers to structure that is characterized by sudden changes in sloping and is alternating in between the narrow chains of faulted mountain and flat arid basins or valleys. They are formed by crustal extension or extensional tectonics.
Island Arcs refers to long and curved chain of the oceanic islands that are associated with seismic and intense volcanic activity and mountain-building processes. They are formed mostly when there is subduction of one oceanic tectonic plate under the other, and in most instances, producing magma underneath the over-riding plate.
A deep-sea trench refers to any long, narrow as well as steep-sided depression in the bottom of the ocean whereby there is occurrence of maximum depths of the ocean of approximately 24,000-36,000 feet. They form in places where there is subduction of one tectonic place under another.
Coast volcanic chains refers to volcanoes that are active in nature, especially those occurring in island arcs and marked with individual mountains that are high and separated by large expansions of gentle and low topography. They are formed by subduction of one tectonic plate in the ocean under another.
Fold Mountains refers to mountains that are formed mainly by folding effects taking place on the layers inside the upper part of Earth’s crust. It is formed when two tectonic plates jointly move (convergent plate boundary). It is usually formed through the accumulation of sedimentary rocks along the continents’ margins.
Subduction Zones are formed when two oceanic plates collide with each other, resulting to one plate running over the other causing it to sink into the mantle.
Triple Junction refers to the meeting point of three tectonic plates’ boundaries. At this junction, each of the three joined boundary will one of the three types: trench (T), transform fault (F), or ridge (R). Triple junction is formed according to the types of the plate margin that meet at its place such as Ridge-Ridge-Ridge or Transform-Transform-Transform.
Depending on the definition of the plate tectonics, there are seven major plates and many other minor plates (primary plates-7; secondary plates-8 and tertiary plate-many). They consist of either continental crust or oceanic crust.
Lithosphere refers to the outermost rigid shell of the Earth’s rocky planet (consist of crush and uppermost mantle). It remains to be rigid over a very long geologic time periods in which it will deform elastically and by brittle failure. On the other hand, asthenosphere refers to highly viscous, ductile and mechanically weak, deforming upper mantle region of the Earth. It is involved in the movement as well as isostatic adjustments of the tectonic plate.
The movements are classified as follow: Convergent movement refers to plates moving towards each other; Divergent movement refers to plates moving away from each other; and Transform movement refers to plates sliding past each other.
Active plate margins are found in areas around subduction zones where there is collision of two plates of the crust after many years, while passive plate margins found in place where there if formation of new ocean.
The evidences of plate tectonics include the following: the discovery of similar fossils in masses of rock that are separated as continents (meaning continents were once together); the matching of the coastlines of different continents (meaning continents were once together); and the paleomagnetism (studies showing magnetic field characteristics in rock strata as identical) and also the map shows that the shape of the continents count fit each other..
The North American continent is believed to have been created around 1.8 billion years ago as a result of the fusion of older Baltic and the Ukrainian cratons (which is about two billion years old), Greenland as well as the older Arctica continent (North America and Siberia). The study shows that there has been addition of continental lithosphere since the formed original North American craton was scraped off as it plunged under the continent, and not deposited from the bottom by plumes of material that was hot welling up via the mantle (Sanders, 2010).
Wilson Cycle refers to the process of opening and closing of the ocean basin as a result of the movement of the Earth’s plates.
References
Sanders, R. (2010). North American continent is a layer cake, scientists discover. Retrieved from http://newscenter.berkeley.edu/2010/08/25/north_american_craton_layer_cake/
