Seafloor spreading is the process where two young plates move away from one another, carrying islands with them. Seafloor spreading has few impacts on people, but when the Earth’s plates collide, there is cause for great concern. Such tectonic forces are among the planet’s greatest natural hazards. The most dangerous tectonic forces are related to seismic activity that causes earthquakes and tsunamis, and the volcanism often associated with plate movements.
When one plate “dives” below another in a process known as subduction. The descending lithosphere is melted again as it dives into the Earth’s superheated mantle along a deep linear feature known as a trench. This subduction process releases enormous amounts of energy. The great stress of one plate pushing beneath another is released in the form of an earthquake.