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A scheme of a phreatic eruption: 1: water-vapor cloud, 2: magma conduit, 3: layers of lava and ash, 4: stratum, 5: water table, 6: explosion, 7: magma chamberPhreatic eruption at the summit of Mount St. Helens, Washington, in the spring of 1980
A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption,[1] occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from 500 to 1,170 °C (930 to 2,100 °F)) causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs.[2] At Mount St. Helens in Washington state, hundreds of steam explosions preceded the 1980 Plinian eruption of the volcano.[2] A less intense geothermal event may result in a mud volcano.[citation needed]
Phreatic eruptions typically include steam and rock fragments; the inclusion of liquid lava is unusual. The temperature of the fragments can range from cold to incandescent. If molten magma is included, volcanologists classify the event as a phreatomagmatic eruption. These eruptions occasionally create broad, low-relief craters called maars. Phreatic explosions can be accompanied by carbon dioxide or hydrogen sulfide gas-emissions. Carbon dioxide can asphyxiate at sufficient concentration; hydrogen sulfide acts as a broad-spectrum poison. A 1979 phreatic eruption on the island of Java killed 140 people, most of whom were overcome by poisonous gases.[3]
^Mullineaux, D.R. et al. (1987) Volcanic Hazards in the Hawaiian Islands in Volcanism in Hawaii, volume 1, USGS Professional Paper 1350, page 602.
^ ab"VHP Photo Glossary: Phreatic eruption". Volcano Hazards Program. U.S. Geological Survey. Retrieved 13 November 2010.
^
"On February 20th, 1979, 142 inhabitants of Dieng Plateau (Indonesia) were asphyxiated by poisonous gases during a mild phreatic eruption. From later fields gas collection and analysis, the casualties are considered to be due to CO2 rich volcanic gases." F. Le Guern, H. Tazieff and R. Faivre Pierret, "An example of health hazard: People killed by gas during a phreatic eruption: Diëng plateau (Java, Indonesia), February 20th 1979", Bulletin of Volcanology45 (1982): 153–156.
Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions...
volcano produced a surprise phreaticeruption lasting 73 seconds. Ash, steam and rock were produced during this eruption. Ash clouds reached 500 meters...
everything in their path". "Dangerous water vapor: phreaticeruptions". "VHP Photo Glossary: Phreaticeruption". Volcano Hazards Program. U.S. Geological Survey...
passages, and in volcanology to refer to a type of volcanic eruption. The term phreatic (the word originates from the Greek phrear, phreat- meaning "well"...
century, behind only the 1912 eruption of Novarupta in Alaska. Eruptive activity began on April 2 as a series of phreatic explosions from a fissure that...
were deposited during the second phase. The third and final phase was phreatic and produced interbedded pyroclastic fallout and surge deposits. 1790 Footprints...
VEI-7 eruption. Although the Mount Tambora eruption reached a violent climax on 10 April 1815, increased steaming and small phreaticeruptions occurred...
advisories were given to low-flying aircraft against the dangers of sudden phreaticeruptions, and to local residents near rivers and streams in case of lahar flows...
is a list of volcanic eruptions in the 21st century with a volcanic explosivity index (VEI) of 4 or higher, and smaller eruptions that resulted in fatalities...
Merapi had experienced several smaller eruptions, most noticeably two phreaticeruptions which occurred on 18 November 2013 and 11 May 2018. The first and...
emergency on 29 October. On 21 November, activity increased once again. A phreaticeruption took place, with the ash cloud top reaching 3,842 metres (12,605 ft)...
eruption. 24 November 2021: Small phreaticeruption occurred with the ash plume height yet to be known. On 11 July 2022, the first magmatic eruption in...
earthquakes that might have warned authorities in the lead up to the phreaticeruption—caused by ground water flashing to steam in a hydrothermal explosion...
The 1883 eruption of Krakatoa (Indonesian: Letusan Krakatau 1883) in the Sunda Strait occurred from 20 May until 21 October 1883, peaking in the late morning...
did not involve a magmatic eruption, as suggested by researchers, rather, they were phreatomagmatic or phreaticeruptions. Its collapse characteristic...
Volcanology and Seismology (PHIVOLCS). Twenty-one of these have had historical eruptions. The three exceptions are Cabalian, which is a strongly fumarolic volcano;[further...
possibly in April 1994.[b] Many of these eruptions involved a central vent eruption, a flank vent eruption, and a phreatic (steam) explosion. Ruiz is the second-most...
to the main eruption. The third one was the largest, at around magnitude 5. At 07:45, while the ground was still moving, a phreaticeruption began at the...
flank; it formed mud streams and appears to have originated in a phreaticeruption. The last known volcanic activity prior to 2017 was in 1769. Future...
later confirmed it was a phreatic explosion produced by hydrothermal fluids near the surface, rather than a magmatic eruption. The word pinatubo could...
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