Destruction of Rock
Destruction of Rock is a Grade 7 science topic from Amplify Science (California) Chapter 2: Understanding Plate Boundaries, explaining how convergent plate boundaries destroy rock. As a subducting plate sinks into the mantle, intense friction and heat cause the rock to melt or merge back into mantle material, recycling old crust to balance new rock creation at divergent boundaries.
Key Concepts
Unlike divergent boundaries where rock is made, convergent boundaries are where rock is destroyed. As the subducting plate sinks deep into the mantle, it creates a massive amount of friction and encounters extreme heat.
The edge of the plate eventually melts or is incorporated back into the mantle material. This explains why Earth does not grow larger despite new rock being made elsewhere; the recycling of old plates balances the creation of new ones.
Common Questions
How is rock destroyed at convergent boundaries?
At convergent boundaries, one tectonic plate sinks (subducts) under another into the mantle, where intense heat and pressure cause the rock to melt or be absorbed back into mantle material.
Why does Earth not grow larger if new rock is constantly being made?
Earth stays the same size because old plates are destroyed at convergent boundaries at the same rate new rock forms at divergent boundaries, creating a continuous recycling system.
What happens to a subducting plate in the mantle?
As a plate subducts, it sinks deeper where extreme heat melts the rock or incorporates it back into the mantle, effectively destroying the old crust.
What is the difference between divergent and convergent plate boundaries?
Divergent boundaries create new rock as plates separate and magma fills the gap, while convergent boundaries destroy rock as one plate subducts under another and melts back into the mantle.