Search results
Results from the WOW.Com Content Network
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. [1] [2] The crust overlies the rigid uppermost layer of the mantle. The crust and the rigid upper mantle layer together constitute oceanic lithosphere. Oceanic crust is primarily ...
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 crust. The sima layer is also called the 'basal ...
Oceanic crust is denser than continental crust because it has less silicon and more of the heavier elements than continental crust. [11] [12] As a result of this density difference, oceanic crust generally lies below sea level, while continental crust buoyantly projects above sea level. Average oceanic lithosphere is typically 100 km (62 mi ...
In collisions between two oceanic plates, the cooler, denser oceanic lithosphere sinks beneath the warmer, less dense oceanic lithosphere. As the slab sinks deeper into the mantle, it releases water from dehydration of hydrous minerals in the oceanic crust.
Subduction zone physics: Sinking of the oceanic lithosphere (sediments, crust, mantle), by the contrast of density between the cold and old lithosphere and the hot asthenospheric mantle wedge, is the strongest force (but not the only one) needed to drive plate motion and is the dominant mode of mantle convection. [citation needed]
Isostasy (Greek ísos 'equal', stásis 'standstill') or isostatic equilibrium is the state of gravitational equilibrium between Earth's crust (or lithosphere) and mantle such that the crust "floats" at an elevation that depends on its thickness and density. This concept is invoked to explain how different topographic heights can exist at Earth ...
NASA/Goddard Space Flight Center The roughly 60,000-square-mile piece of crust has been hiding below the eastern Mediterranean Sea for about 340 million years (give or take 30 million years).
The thin parts are the oceanic crust, which underlies the ocean basins (5–10 km) and is mafic-rich [9] (dense iron-magnesium silicate mineral or igneous rock). [10] The thicker crust is the continental crust, which is less dense [11] and is felsic-rich (igneous rocks rich in elements that form feldspar and quartz). [12]