(https://en.wikipedia.org/wiki/Sima_(geology))In geology, sima is the name for the lower layer of the 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 'basalt layer' of the crust. The sima layer is also called the 'basal crust' or 'basal layer' because it is the lowest layer of the crust. Because the ocean floors are mainly sima, it is also sometimes called the 'oceanic crust'.The name 'sima' was taken from the first two letters of silica and of magnesium. Comparable is the name 'sial' which is the name for the upper layer of the Earth's continental crust.
Properties
- Density: 2800-3300 kg/m3 (higher than Sial)
Sima is more dense than Sial because it has higher concentrations of iron and magnesium, while having a decreased concentration of aluminum. When Sima gets pushed up to the surface it forms Mafic rocks. The more denser Sima, that has less Silica, forms Ultramafic rocks
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