A phreatic eruption, also known as a steam-blast eruption, occurs when groundwater comes into contact with hot magma or lava, causing it to rapidly vaporize and explode. These eruptions are important for understanding volcanic hazards, particularly in areas with abundant groundwater or near hydrothermal systems.
Source Mastin, L. G. (1995). “Thermohydraulic Modeling of the Surface Eruptions at Mount St. Helens, 1980-1984.” Bulletin of Volcanology, 57(6), 509-516.