Which option correctly identifies the primary mechanism for recycling older crustal rocks in the crust?

Which option correctly identifies the primary mechanism for recycling older crustal rocks in the crust?

• A. Plate tectonics including subduction
• B. Erosion and wind
• C. Volcanic activity
• D. Meteorite impacts

Answer: (A)

Plate tectonics with subduction is the primary way older crust gets recycled. Oceanic crust forms at mid-ocean ridges, ages as it moves away, and when it reaches a subduction zone it sinks back into the mantle. There, it melts and interacts with mantle rocks, producing magma that rises to form new crust elsewhere. Erosion and wind remove and relocate surface rocks but don’t return them deep into the mantle, volcanic activity mainly reshuffles material at the surface or through localized melting, and meteorite impacts are far too small in scale to drive global crustal recycling.

Plate tectonics with subduction is the primary way older crust gets recycled. Oceanic crust forms at mid-ocean ridges, ages as it moves away, and when it reaches a subduction zone it sinks back into the mantle. There, it melts and interacts with mantle rocks, producing magma that rises to form new crust elsewhere. Erosion and wind remove and relocate surface rocks but don’t return them deep into the mantle, volcanic activity mainly reshuffles material at the surface or through localized melting, and meteorite impacts are far too small in scale to drive global crustal recycling.