1. Oceanic Crust: This is found beneath the ocean basins and is relatively thin (about 5-10 km thick). It is primarily composed of basalt and gabbro, dense, and rich in iron and magnesium.

2. Continental Crust: This is found under the continents and is thicker (about 35-70 km thick). It is less dense than oceanic crust and consists mostly of granite and other felsic rocks, with a higher content of silica, sodium, and potassium.

These two crust types have different densities and compositions, which play a crucial role in plate tectonics.