What transformation occurs to limestone when it is subjected to immense heat?

When limestone is subjected to immense heat, a process known as metamorphism occurs, transforming it into marble. This transformation happens because the calcite minerals within limestone recrystallize under high temperature and pressure, leading to the formation of the interlocking crystalline structure characteristic of marble.

Marble is a metamorphic rock that retains the chemical composition of limestone, primarily composed of calcium carbonate, but exhibits different physical properties due to the changes in its structure. The heat and pressure cause the individual carbonate crystals to grow larger, resulting in the fine-grained, often polished appearance of marble. This process is an excellent example of how geological phenomena shape materials over time, significantly altering their properties and uses.

The other options represent different rocks or processes that do not correlate with the metamorphism of limestone, explaining why they are not the correct choice.