Which rock type is formed under high pressure and temperature conditions?

Metamorphic rock is formed under conditions of high pressure and temperature, which lead to significant changes in the mineral composition and structure of pre-existing rocks. This transformation occurs deep within the Earth's crust, where tectonic forces generate immense pressure and heat, causing the original rock, known as the parent rock or protolith, to recrystallize without melting.

During this metamorphic process, the arrangement of minerals can become more compact, and new minerals may form. Examples of metamorphic rocks include schist, gneiss, and marble, all of which illustrate how the textures and mineralogy of the parent rocks have been altered significantly under those intense conditions.

In contrast, igneous rocks form from the cooling and solidification of molten material (magma or lava), sedimentary rocks are created from the accumulation and compaction of sediments, and volcanic rocks are a subset of igneous rocks that are specifically formed from lava that cools quickly at the Earth's surface. These processes are distinct from that of metamorphism, which is driven primarily by elevated pressure and temperature rather than by processes involving melting or sedimentation.