What two layers make up most of the geosphere?

The geosphere is primarily composed of two layers: the crust and the mantle. The crust is the thin, outermost layer where we find land and oceans, while the mantle lies beneath it, making up the bulk of the Earth's volume. The mantle is composed of semi-solid rock that flows slowly over geological timescales, allowing for tectonic activity. Together, these layers play a crucial role in the dynamics of the Earth's surface.