Plate Tectonism, Oceanic Ridges and Rises Coursework

Plate Tectonism, Oceanic Ridges and Rises - Coursework Example Similarities and differences between a continental arc and island arc will be provided. In general, oceanic ridges is referring to â€Å"a mountainous chain of young basaltic rock at the active spreading center of an ocean† (Garrison, 2010: 116) whereas oceanic rises are referring to â€Å"a long, broad elevation which can be found at the bottom of the ocean". Oceanic ridges are â€Å"sources of the new ocean floor where lithospheric plates diverge† (ibid). A good example of oceanic ridges includes the Bowers Ridge and Shirshove Ridge which can be found in the Bering Sea close to Alaska, Kamchatka, and Siberia. There are significant differences between oceanic ridges and oceanic rises. Although often mistaken as one, oceanic rises often have a gentler topography as compared to oceanic ridges. Furthermore, oceanic rises also are not characterized by the presence of wide central rift valleys which are often found in oceanic ridges (Garrison, 2010: 116). In fact, oceanic ridges reach its widest when active. The two hypotheses that laid the foundation for plate tectonism a.k.a. plate structure includes: the continental drift and seafloor spreading. To understand the theory behind plate tectonics, it is important to take note of the following features: (1) the Earth’s surface is composed of 7 large crustal plates (i.e. African, North American, South American, Eurasian, Australian, Antarctic, and Pacific plates); (2) ocean floors continuously move in different directions (i.e. vertical and horizontal movements); (3) convection currents underneath the plates causes the movement of crustal plates; and (4) heat that triggers convection currents is radioactively rooted in the Earth’s mantle.