The Pacific Ocean is surrounded by convergent plate boundaries. When the heavy oceanic crust of the Pacific Plate sinks into the mantle, it carries water and sediment that lower the melting point of the rocks above. This generates massive amounts of magma that rise to form volcanic island arcs (like the Aleutians and Japan) and volcanic mountain ranges (like the Andes). This tectonic “recycling” makes the Pacific margins the most active volcanic laboratory on Earth, contrasting with the much calmer Atlantic or Indian Oceans, which have fewer subduction zones.