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
Pressure cooking boiling point of water increases as the pressure rises, resulting in superheated water. At a pressure of 1 bar or approximately above the existing atmospheric pressure, water in a pressure cooker will reach a temperature of . The boiling temperature of water (and water-based liquids) is determined by the ambient atmospheric pressure. Pressure cookers always require liquid in order to cook food under pressure. Inside a pressure cooker, once the water (liquid) is boiling and the steam is trapped, the pressure from the steam increases and pushes on the liquid, which increases its boiling temperature. The heat applied to the