The Earth's crust is the outermost layer of our planet, composed of solid rock. It varies in thickness, being thinner under oceans and thicker under continents. The crust is divided into large sections called tectonic plates, which float on the semi-fluid layer beneath them, known as the mantle. This layer is essential for life, as it contains minerals and resources necessary for ecosystems. The crust is also where we find landforms like mountains, valleys, and plains. Geological processes, such as volcanism and erosion, continually shape and change the crust over time.