A subduction zone is an area where one tectonic plate is moving towards another and becoming pushed underneath, causing the subducting plate to be recycled into the Earth's liquid mantle. This is called a convergent boundary, and is part of the science of plate tectonics. Subduction zones occur both on landmass and under the ocean; each type can cause earthquakes, volcanic activity, and create mountains over long periods of time. Mountains are created when the subducting plate pushes a larger mass against the overriding plate, causing the overriding plate to be pushed upwards (Wikipedia). Subduction zones are responsible for most of the earthquakes in the world, as well as causing volcanic arcs, long stretches of volcanic activity that is extremely dangerous because of their mixture of water and molten rock.