Metamorphic rock the foliation is called "gneissosity"), granoblastic (includes granulite, some marbles and quartzite), and hornfelsic (includes hornfels and skarn). Metamorphic rock Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure ( or more), causing profound physical or chemical change. The protolith may be a sedimentary, igneous, or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by
Heat rock Heat rock A heat rock is the common name for a type of heating source in enclosures for cold-blooded animals to supply heat, in the form of a false novelty rock plugged into an electrical socket. Keepers may notice that smaller reptiles prefer to rest on the heat rock most of the time, since it provides constant heat. Larger reptiles supplied with heat rocks often prefer to stay near their rock at all times, diminishing their novelty. Pet owners and keepers now usually recommended a non-direct contact UTH (under-the-tank-heater) or thermal tape which distributes heat through the enclosure’s substrate placed