Transformation by Heat
Transformation by heat describes how rock descending during subduction absorbs increasing thermal energy from the mantle until it melts into magma, completing the rock cycle and returning crustal material to a molten state ready to begin again. In Amplify Science (California) Grade 7, Chapter 3: Movement of Rock Formations, students learn that depth equals heat in driving rock transformation.
Key Concepts
Depth equals heat. As rock descends further during subduction, it absorbs increasing amounts of thermal energy from the surrounding mantle.
Eventually, the temperature overwhelms the rock's solid structure, causing a phase change. The solid rock melts into liquid magma . This completes the loop: material that once existed as cold sediment on the ocean floor is returned to a molten state, ready to begin the cycle again.
Common Questions
How does heat transform rock during subduction?
As rock descends during subduction, it absorbs increasing amounts of thermal energy from the surrounding mantle. Eventually the heat overwhelms the rock's solid structure, causing it to melt into magma.
Why does deeper rock get hotter?
Earth's interior generates heat from radioactive decay and residual heat from planetary formation. The deeper you go, the closer to this heat source, so temperature increases with depth.
What happens to subducted rock in the mantle?
Subducted rock absorbs mantle heat until it melts into magma. This magma may rise to fuel volcanoes or stay underground and cool slowly into new igneous rock, completing the rock cycle.
Where is transformation by heat covered in Amplify Science Grade 7?
Transformation by heat during subduction is covered in Amplify Science (California) Grade 7, Chapter 3: Movement of Rock Formations.