Silica and Magnesium
Explanation
The Earth's crust is chemically differentiated into two main types: the continental crust and the oceanic crust. These layers differ significantly in thickness, density, and mineral composition.
- Oceanic Crust: This layer is thinner (approximately 5–10 km) and denser than the continental crust. It is primarily composed of basaltic rocks. The main mineral constituents are Silica and Magnesium. Due to this composition, it is often referred to as SIMA (Si for Silica, Ma for Magnesium).
- Continental Crust: This layer is thicker and less dense, composed largely of granitic rocks. Its primary constituents are Silica and Alumina, leading to the acronym SIAL.
- Core: The innermost part of the Earth is composed mainly of Nickel and Iron, referred to as NIFE.
Key Takeaway: The oceanic crust is characterized by a mafic composition (Silica and Magnesium - SIMA), while the continental crust is characterized by a felsic composition (Silica and Alumina - SIAL).