The sima layer is located in the lower layer of the Earth's crust.
According to older geological terminology, Sima refers specifically to this lower portion of the crust. It is distinct from the upper crust, often termed Sial (rich in silicon and aluminum).
Composition and Characteristics of the Sima Layer
The sima layer is primarily made up of magnesium silicate minerals-rich rocks. This composition is denser than the rocks found in the upper crust.
- Composition: Predominantly magnesium silicate minerals.
- Density: Generally denser than the Sial layer above it.
The "Ocean Layer" Connection
The sima layer often reaches the surface, particularly in oceanic regions, where it cools to form basaltic rock. Because of this common occurrence as basalt in the ocean basins, this layer is frequently referred to as the crust's "ocean layer".
- Association with Basalt: Sima material erupts as basalt.
- Location: Forms the bulk of the oceanic crust.
In essence, while the Earth's crust is now typically discussed in terms of oceanic and continental crust, the sima conceptually corresponds largely to the denser, lower part of the crust that forms the foundation of continents and makes up most of the oceanic crust.
