Subduction of one oceanic plate beneath another leads to the formation of which feature?

• A. Subduction zone
• B. Ridge crest
• C. Mantle plume
• D. Transform boundary

Answer: (A)

When one oceanic plate sinks beneath another, the region that forms is a subduction zone. This convergent boundary features the sinking slab driving deep trenches at the surface, and the overlying plate often develops a volcanic arc as magma generated by fluids released from the subducting slab melts the mantle above it. Earthquakes are common as the slab bends and interactions with the mantle produce seismic activity. The reason this happens is that the descending plate releases water into the surrounding mantle, lowering the melting point and producing magma that rises to fuel volcanoes along the margin. The other options describe different tectonic settings: a ridge crest forms at divergent boundaries where new crust is created, a mantle plume is a deep mantle source for hotspots, and a transform boundary involves lateral sliding with little vertical subduction.