Why does subduction occur

These hazards affect millions of people around the world, particularly around the edges of the Pacific Ocean, which mainly consist of subduction zones. The largest earthquakes on Earth occur at the interface between the two plates, called the megathrust.

Recent examples include the magnitude 8. Earthquakes are caused by movement over an area of the plate interface called the seismogenic zone. It is then released catastrophically in one or more earthquakes.

Instead, the less dense material slips into a trench behind the denser oceanic crust where it gets stuck. The pressure continues to build until the trench flips over and the less dense plate slips underneath the one with the continent. It is possible for a whole tectonic plate to disappear. This happens when the plate goes through subduction faster than new material can be added to the plate through seafloor spreading. The spreading pushes the plate slowly toward the subduction zone until the whole thing disappears.

When this happens, the other tectonic plates rearrange to cover the area. Subduction zones are mainly located in the Pacific Ocean. This is because seafloor spreading — the process by which new oceanic crust is created — occurs mostly in the Pacific. Thus the new material pushes the older plates outward and then they need to undergo subduction.

This also explains why so many earthquakes originate in the Pacific Ocean near the Ring of Fire. That is where the subduction zones are concentrated. Continental plates also converge, but this is not considered subduction because these plates do not have different densities and thicknesses to subduct. Landforms such as the Himalayas are formed from these convergences though.

Science Explorer. Multimedia Gallery. Park Passes. Technical Announcements. Employees in the News. Emergency Management. Survey Manual. These plates collide, slide past, and move apart from each other. Where they collide and one plate is thrust beneath another a subduction zone , the most powerful earthquakes, tsunamis, volcanic eruptions, and landslides occur.

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