A silicate planet, also known as a terrestrial planet, is a planet mostly composed of silicate rocks. These are also sometimes referred to as rocky planets. Silicate planets are often rich in metals. In the Solar System, all of the inner planets are silicate planets. Most terrestrial planets have canyons, volcanoes, craters, etc. Terrestrial planets are much different from gas giants, which lack a surface and are mostly composed of gasses like hydrogen, helium, water vapor, and ammonia. Ocean planets and carbon planets are neither silicate planets nor gas giants.