Discover

The term 'phreatic' is used in geology to refer to matters relating to ground water below the static water table (the word originates from the Greek ''phrear'', ''phreat-'' meaning "well" or "spring"). "Phreatic surface" is a synonym for "water table."
The 'phreatic zone' is the layer(s) of soil or rock below the water table in which voids are permanently saturated with groundwater, as opposed to the higher ''vadose zone'' in which the pore spaces are not completely filled with water.
'Phreatic action' forms cave passages by dissolving the limestone in all directions, as opposed to 'vadose action' whereby a stream running in a cave passage erodes a trench in the floor. Phreatic action usually takes place when the passage is below the water table (although it may happen if the passage is full of water and not saturated with calcium carbonate or calcium magnesium carbonate). A cave passage formed in this way is characteristically circular in cross-section as limestone is dissolved on all surfaces. Many cave passages are formed by a combination of phreatic followed by vadose action. Such passages form a keyhole cross section: a round shaped section at the top and a rectangular trench at the bottom.
'Phreatic eruptions' are certain types of extremely violent volcanic eruptions resulting from the interaction of ground water and magma.

Contents

See also

See also

★ Aquifer

★ Water content