Answer:
Step-by-step explanation:
The heat source for rock formation
Primordial heat: Some heat accumulated during the earth's formation and it is still available to drive the internal heat Engine of the earth. Some of these heat are used to melt rocks and produce magma.
Radioactive sources: Radioactive elements within the earth also serves as heat source for rock formation. Their spontaneous decay produce heat which are sufficient enough to generate enough thermal energy to melt and produce rocks.