The type of rock that forms from previously existing rocks altered by heat and pressure is called metamorphic rock.

Here's why:

* Metamorphism is the process of changing existing rocks (igneous, sedimentary, or even other metamorphic rocks) into new forms through intense heat and pressure.

* Heat can come from the Earth's interior (magma intrusions) or from tectonic plate collisions.

* Pressure arises from the weight of overlying rock layers or from tectonic forces.

These intense conditions cause the minerals in the original rock to recrystallize and change their structure, resulting in a metamorphic rock with different properties.

Some common examples of metamorphic rocks include:

* Marble (from limestone)

* Slate (from shale)

* Gneiss (from granite)

* Quartzite (from sandstone)