Answer:
Mount Merapi was formed by two converging plates. Subduction causes slabs of oceanic crust to sink through a deep-ocean trench into the mantle. The crust melts and forms magma, which then rises back toward the surface. It is located along the Sunda, or Java trench. When the magma from the melted crust erupts as lava, volcanoes are formed. Mount Merapi is located along an island arc.