Subduction is a geological process where one tectonic plate moves under another and sinks into the Earth's mantle. This usually happens at convergent boundaries, where two plates collide. The denser oceanic plate often goes beneath the lighter continental plate, leading to the formation of deep ocean trenches and volcanic arcs. As the subducting plate descends, it melts and can cause magma to rise, resulting in volcanic eruptions. This process is crucial in shaping the Earth's landscape and is responsible for many natural phenomena, including earthquakes and the creation of mountain ranges like the Andes in South America.