The plastic yield point of granite is a function of pressure, temperature and the presence of water and/or carbon dioxide. It happens at a pressure of about 5.5 kilobars and a temperature of about 900˚-1000˚ C. This occurs at about 10 km depth and seems to be related to the T˚- P˚ combination at which water enters its supercritical phase and becomes a vigorous solvent.