Silica and Alumina as the Main Mineral Constituents of the Continental Mass

The correct answer is option 'D', silica and alumina, as these two minerals are the main constituents of the continental mass. Let's understand why silica and alumina are considered the main mineral constituents of the continental mass in detail.

Silica:
Silica, also known as silicon dioxide (SiO2), is one of the most abundant minerals found in the Earth's crust. It is a major component of rocks and minerals, including quartz, feldspar, and mica. Silica is primarily composed of silicon and oxygen atoms and plays a crucial role in the formation and composition of continental landmasses.

Alumina:
Alumina, also known as aluminum oxide (Al2O3), is another important mineral found in the Earth's crust. It is a key component of various rocks and minerals, such as feldspars, clays, and bauxite. Alumina is composed of aluminum and oxygen atoms and contributes significantly to the formation and composition of continental landmasses.

Importance of Silica and Alumina in the Continental Mass:
1. Granite and Continental Crust:
Granite, a common type of intrusive igneous rock, is predominantly composed of silica and alumina. It is a major constituent of the continental crust, which forms the solid landmasses on Earth. The continental crust is thicker and less dense compared to the oceanic crust, primarily due to the presence of silica and alumina-rich rocks like granite.

2. Sial Layer:
The uppermost layer of the continental crust is known as the sial layer, which stands for silicon and aluminum. This layer is rich in silica and alumina-bearing minerals and is responsible for the higher elevation and lower density of the continental landmasses.

3. Continental Shield and Platform:
Continental shields and platforms are large, stable regions of the continental crust that have undergone minimal tectonic activity for millions of years. These regions typically consist of ancient rocks rich in silica and alumina. The presence of silica and alumina minerals contributes to the stability and strength of these continental landmasses.

4. Weathering and Erosion:
Silica and alumina minerals are also resistant to weathering and erosion. As a result, they tend to persist in the continental crust for longer periods, contributing to the overall composition and structure of the continental landmasses.

In conclusion, silica and alumina are considered the main mineral constituents of the continental mass due to their abundance in the Earth's crust, their presence in granite and other continental rocks, their contribution to the formation of the continental crust, and their resistance to weathering and erosion.