Here's why:
* Crust: The crust is the outermost layer of the Earth, and it's primarily composed of igneous, sedimentary, and metamorphic rocks. These rocks are rich in silica (SiO2). The continental crust is generally thicker and has a higher silica content than the oceanic crust.
* Mantle: The mantle lies beneath the crust and is mostly composed of silicate minerals. While it contains a significant amount of silica, the overall percentage is lower than in the crust.
* Core: The Earth's core is primarily composed of iron and nickel, with very little silica.
Therefore, the crust, particularly the continental crust, holds the highest concentration of silica in the Earth's structure.
