Oceanic crust rock composition. 18). . 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. Oceanic Crust Definition The oceanic crust is the thin, dense outermost layer of Earth that lies beneath the ocean basins. Oceanic crust is the outermost solid layer of the Earth beneath the ocean basins. [1][2] The crust lies above the rigid uppermost layer of the mantle. It is composed of several layers, not including the overlying sediment. It exhibits a standard layered structure and is characterized by features such as pillow lavas and flows, as well as intrusive rocks like gabbros and dunites at greater depths. 2 The Geology of the Oceanic Crust 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. Made mostly of mafic rocks such as basalt and gabbro, it forms Oceanic crust is defined as the thin, young, and magnesium-rich layer of the Earth's crust formed by the partial melting of the mantle at mid-ocean ridges, typically about 7 km thick and primarily composed of basalt. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. 18. Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. About 10% of the mantle rock melts under these conditions, producing mafic magma. Because oceanic crust is denser, it will get subducted beneath continental crust during collisions of plates. It is part of Earth's lithosphere and is distinct from the thicker, less dense continental crust that makes up the landmasses. AI Nov 21, 2023 ยท Oceanic crust is thinner than continental crust because its composition is denser. Additionally, oceanic crust can be created, or at least substantially thickened, when mantle plumes generate melt that erupts through the oceanic lithosphere, creating oce-anic islands or oceanic plateaus. fklmr ftjopr vbuv spkc plvq iig bmy yevcwebc okhkcg ilbq