If two oceanic plates meet at a convergent boundary, which plate subducts?

If two oceanic plates meet at a convergent boundary, which plate subducts?

• A. The lighter one
• B. The older one
• C. The denser one
• D. Subduction does not occur

Answer: (C)

At a convergent boundary between oceanic plates, the plate with greater density sinks into the mantle. Oceanic lithosphere cools and thickens as it ages, becoming denser, so the older, cooler plate tends to subduct beneath the younger, warmer plate. This subduction drives the formation of deep trenches and volcanic arcs on the opposing plate and is accompanied by earthquakes. The idea that a lighter plate would sink doesn’t fit the physics, and subduction does occur at oceanic-oceanic boundaries, so the statement that it doesn’t is incorrect. Density, tied to age and temperature, is the key factor determining which plate subducts.

At a convergent boundary between oceanic plates, the plate with greater density sinks into the mantle. Oceanic lithosphere cools and thickens as it ages, becoming denser, so the older, cooler plate tends to subduct beneath the younger, warmer plate. This subduction drives the formation of deep trenches and volcanic arcs on the opposing plate and is accompanied by earthquakes. The idea that a lighter plate would sink doesn’t fit the physics, and subduction does occur at oceanic-oceanic boundaries, so the statement that it doesn’t is incorrect. Density, tied to age and temperature, is the key factor determining which plate subducts.