Oceanic trench
Trenches are active with earthquakes and resulting tsunamis. Most volcanism associated with trenches occurs on the continent and not on the sea floor. However, many of the ocean's volcanic islands and seamounts are found in what are called island arcs, bending chains of islands rising from the sea floor, usually paralleling the concave edges of an oceanic trench. The western Pacific has island arcism as do the Aleutian Islands.