
An explosive volcanic eruption caused when water and heated volcanic rocks interact to produce a violent expulsion of steam and pulverized rocks. Magma is not involved.
Found on
http://volcano.oregonstate.edu/glossary/1

Phreatic eruption at the summit of Mount St. Helens, Washington. Hundreds of these steam-driven explosive eruptions occurred as magma steadily rose into the cone and boiled groundwater. These phreatic eruptions preceded the volcano's plinian eruption on 18 May 1980. Credit: D. A. Swanson / U.S. Geol...
Found on
http://www.daviddarling.info/encyclopedia/P/phreatic_eruption.html

A volcanic eruption or explosion of steam, mud or other material that is not incandescent; this form of eruption is caused by the heating and consequent expansion of ground water due to an adjacent igneous heat source.
Found on
http://www.solarviews.com/eng/terms.htm
No exact match found.