Continental Rifting
Divergent boundaries can develop within a continent, in which case the landmass may split into two or more smaller segments separated by an ocean basin. Continental rifting begins when plate motions produce opposing (tensional) forces that pull and stretch the lithosphere. Stretching, in turn, thins the lithosphere, which promotes mantle upwelling and broad upwarping of the overlying lithosphere (Figure 2.14A). During this process, the lithosphere is thinned, and the brittle crustal rocks break into large blocks. As the tec- tonic forces continue to pull apart the crust, the broken crustal fragments sink, generating an elongated depres- sion called a continental rift, which eventually widens to form a narrow sea (Figure 2.14B,C) and then a new ocean basin (Figure 2.14D).
A modern example of an active continental rift is the East African Rift (Figure 2.15). Whether this rift will eventually result in the breakup of Africa is a topic of continued research. Nevertheless, the East African Rift is an excellent model of the initial stage in the breakup of a continent.
Continental RiftingDivergent boundaries can develop within a continent, in which case the landmass may split into two or more smaller segments separated by an ocean basin. Continental rifting begins when plate motions produce opposing (tensional) forces that pull and stretch the lithosphere. Stretching, in turn, thins the lithosphere, which promotes mantle upwelling and broad upwarping of the overlying lithosphere (Figure 2.14A). During this process, the lithosphere is thinned, and the brittle crustal rocks break into large blocks. As the tec- tonic forces continue to pull apart the crust, the broken crustal fragments sink, generating an elongated depres- sion called a continental rift, which eventually widens to form a narrow sea (Figure 2.14B,C) and then a new ocean basin (Figure 2.14D).A modern example of an active continental rift is the East African Rift (Figure 2.15). Whether this rift will eventually result in the breakup of Africa is a topic of continued research. Nevertheless, the East African Rift is an excellent model of the initial stage in the breakup of a continent.
การแปล กรุณารอสักครู่..