Littoral hydrovolcanic explosions: a case study of lava–seawater interaction at Kilauea Volcano

Abstract

A variety of hydrovolcanic explosions may occur as basaltic lava flows into the ocean. Observations and measurements were made during a two-year span of unusually explosive littoral activity as tube-fed pahoehoe from Kilauea Volcano inundated the southeast coastline of the island of Hawai'i. Our observations suggest that explosive interactions require high Ž 3 . entrance fluxes G 4 m rs and are most often initiated by collapse of a developing lava delta. Two types of interactions were observed. ''Open mixing'' of lava and seawater occurred when delta collapse exposed the mouth of a severed lava tube or incandescent fault scarp to wave action. The ensuing explosions produced unconsolidated deposits of glassy lava fragments or lithic debris. Interactions under ''confined mixing'' conditions occurred when a lava tube situated at or below sea level fractured. Explosions ruptured the roof of the tube and produced circular mounds of welded spatter. We estimate a waterrrock mass ratio of 0.15 for the most common type of littoral explosion and a kinetic energy release of 0.07-1.3 kJrkg for the range of events witnessed.

The airborne lava–seawater interaction plume at Kīlauea Volcano, Hawaiʻi

“…OP FTS measurements were made 80 m northeast of the lava ocean entry on 21 and 28 July 2004 ( February the lava entry into the sea was vigorous; on 20 February 2005, the flux of lava reaching the sea appeared greatly diminished. Estimates of the mean lava flux into the sea are derived from calculations of the volume of lava necessary to account for the SO 2 released from Puʻu ʻŌʻō [7].…”

“…For this to happen, it is essential that the HCl of the interface films is separated from the brucite and periclase products in order to prevent retrograde neutralization reactions. Investigations (by SEM/EDX, FTIR spectroscopy, X-ray powder photography, refractive-index measurements, and chemical staining tests) of samples of molten lava splashed with seawater showed that the solid products of these reactions (Mg(OH) 2 and MgO) formed coatings on the lava surfaces, together with abundant NaCl and other salts [14]. This suggests that similar deposits stick to the surfaces of ocean entry lava fragments which sink to the sea floor or are released as particles into a submarine lava-seawater interaction plume, an area of light-coloured seawater generally visible several miles westward down the coast.…”

“…Brine enriched in magnesium, potassium, sodium and chloride seeped into the holes [16] and deposits of magnesium chloride salts, Mg(OH) 2 , and MgO formed on the high-temperature end of heaters where vaporisation was most intense, while hydrochloric acid condensate formed on heater components at lower temperatures, causing extensive corrosion [17].…”

“…At Kīlauea Volcano, Hawaiʻi, basaltic lava usually flows into the sea in a passive manner, with the interaction confined to the boiling of seawater. Occasionally, larger lava ocean entries are associated with explosive activity as seawater invades confined lava tubes [2]. This paper focuses on the chemical interactions which take place as seawater boils and evaporates extensively at the low pressures of the ocean surface and creates a halogenrich, acidic, airborne plume [1,3,4].…”

Icelandic pseudocraters as analogs to some volcanic cones on Mars

“…This would require repose periods between explosions to provide sufficient time for thermal interaction with the water to achieve further vaporization and pressurization. Alternatively, efficient mixing of the lava and substrate water could produce high pressures on short timescales and more sustained activity [Mattox and Mangan, 1997]. However, even if the larger pressures were unable to develop, longer clast ranges could be produced with lower gas pressures (i.e., lava strengths) provided that sufficient driving gas was drawn from a larger vaporrich region.…”