Homonym: crust (Bread)
The crust is the outermost layer of a planet, including Earth. It is composed of solid rock and varies in thickness, being thinner under oceans and thicker under continents. The Earth's crust is divided into tectonic plates, which float on the semi-fluid layer beneath called the mantle. These plates can move, leading to geological activities such as earthquakes and volcanic eruptions.
In addition to Earth, other celestial bodies like the Moon and Mars also have crusts. The crust of the Moon is covered with a layer of fine dust and rocky debris called regolith. Understanding the crust of different planets helps scientists learn about their formation and geological history.