Definitions for "Phreatic"
That part of a cave environment that lies or once lay below the water-table. Also refers to the processes that act within the phreatic zone.
Cave passage formed when full of water
of or relating to ground water
Refers to a steam eruption that produces no fresh magma. A common precursor of eruptive activity, it is caused when groundwater, heated by a magmatic source, flashes into steam.
Phreatic explosions are caused by ground water being heated by rising magma to high temperatures. The phase change from superheated liquid to vapour close to the earth's surface causes explosive activity.
involving only gases (usually steam)
Subterranean; -- applied to sources supplying wells.