The outer layer of the Earth is called the crust. It is the thinnest layer compared to the mantle and core beneath it and consists of solid rock. The crust is divided into two types: the continental crust, which forms landmasses, and the oceanic crust, which underlies ocean basins. This layer plays a critical role in various geological processes, such as tectonic activity, earthquakes, and volcanic eruptions. It is also where all terrestrial life exists, housing various ecosystems and natural resources.