phreatomagmatic
/frɪˌatə(ʊ)maɡˈmatɪk
/adjective Geology
(Of a volcanic eruption) in which both magmatic gases and steam from groundwater are expelled.These are commonly present as pyroclastic deposits rather than lava because their early arrival favours interaction with groundwater to produce phreatomagmatic eruptions, and/or because they have higher volatile contents....
- Mud and sand volcanoes are positive topographic features that have many of the aspects of normal phreatomagmatic volcanism resulting from explosive interaction between hot magma and water.
- A similar degree of compositional variation between pyroclast glasses of phreatomagmatic pyroclastic rocks and intruding dykes has been recognized from the vent remnant of Szigliget, western Hungary.
Origin
Mid 20th century: from Greek phrear, phreat- 'a well' + magmatic (see magma).