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Oceanic: 5 – 10 km (3 – 6 mi) thick [4] and composed primarily of denser, more mafic rocks, such as basalt, diabase, and gabbro. The average thickness of the crust is about 15 – 20 km (9 – 12 mi). [5] Because both the continental and oceanic crust are less dense than the mantle below, both types of crust "float" on the mantle.
The oceanic crust displays a pattern of magnetic lines, parallel to the ocean ridges, frozen in the basalt. A symmetrical pattern of positive and negative magnetic lines emanates from the mid-ocean ridge. [24] New rock is formed by magma at the mid-ocean ridges, and the ocean floor spreads out from this point.
Erosion differentiates granite, separating it into clay on the ocean floor, sandstone on the edge of the continent, and dissolved minerals in ocean waters. Metamorphism and anatexis (partial melting of crustal rocks) can mix these elements together again. In the ocean, biological organisms can cause chemical differentiation, while dissolution ...
Granite (/ ˈ ɡ r æ n ɪ t / GRAN-it) is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase.It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground.
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor.These particles either have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea, or they are biogenic deposits from marine organisms or from ...
Sima often takes the form of basalt when on the surface. In geology, sima (/ ˈ s aɪ m ə /) is an antiquated [1] blended term for the lower layer of Earth's crust. This layer is made of rocks rich in magnesium silicate minerals. Typically, when the sima comes to the surface, it is basalt, so sometimes this layer is called the 'ocean layer' of ...
The age is often equal to L/V, where L is the distance from the spreading centre of mid-ocean ridge, and V is velocity of the lithospheric plate. [11] Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years but after this becomes increasingly denser than asthenosphere.
Only beneath mid-ocean ridges does it define the lithosphere–asthenosphere boundary (the depth at which the mantle becomes significantly ductile). The Mohorovičić discontinuity is 5 to 10 kilometres (3–6 mi) below the ocean floor , and 20 to 90 kilometres (10–60 mi) beneath typical continental crusts, with an average of 35 kilometres ...