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oceanic crust, the outermost layer of Earth’s lithosphere that is found under the oceans and formed at spreading centres on oceanic ridges, which occur at divergent plate boundaries. Oceanic crust is about 6 km (4 miles) thick. It is composed of several layers, not including the overlying sediment.
1 Αυγ 2023 · The Crust. The crust is the Earth’s outermost layer and it’s where we live. It has an irregular thickness, varying from about 5 km beneath the oceans (oceanic crust) to about 30 km beneath the continents (continental crust). The crust mainly consists of lighter rocks, such as basalt in the oceanic crust and granite in the continental crust.
The differences between oceanic crust and continental crust are due to the different ways in which they are formed. Oceanic crust is formed from magma that rises from the mantle and cools at the ocean floor. Continental crust, on the other hand, is formed from the accumulation of sediments and the melting of rocks.
As we discussed in Chapter 10, oceanic crust is formed at sea-floor spreading ridges from magma generated by decompression melting of hot upward-moving mantle rock (Figure 10.18). About 10% of the mantle rock melts under these conditions, producing mafic magma.
Tectonic lithosphere plates consist of lithospheric mantle overlain by either or both of two types of crustal material:oceanic crust (in older texts called sima from silicon and magnesium) and continental crust (sial from silicon andaluminium). Average oceanic lithosphere is typically 100 km (62 mi) thick; its thickness is a function of its age ...
26 Απρ 2024 · The theory of plate tectonics states that Earth’s solid outer crust, the lithosphere, is separated into plates that move over the asthenosphere, the molten upper portion of the mantle. Oceanic and continental plates come together, spread apart, and interact at boundaries all over the planet.
24 Απρ 2024 · Why are the shelves on the eastern coast of North America so much wider than those along the west coast? The ocean trenches at some subduction zones are relatively shallow. What is one explanation for this? What are the main lithological components of oceanic crust, and how does this rock form?
