(of a volcanic eruption) in which both magmatic gases and steam from groundwater are expelled.
- ‘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.’
- ‘After 1 August phreatomagmatic activity resumed and continued at a gradually diminishing rate until 5 August.’
- ‘These rafts were originally surface phreatomagmatic deposits, which were probably wet when they slumped into the vent complex.’
- ‘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.’
- ‘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.’
Mid 20th century: from Greek phrear, phreat- a well + magmatic (see magma).