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White laze plumes, southeast coast of Kilauea Volcano Photograph by T.N. Mattox April 23, 1993	Pahoehoe lava enters sea. Extreme heat from lava entering the sea rapidly boils and vaporizes seawater, leading to a series of chemical reactions. The boiling and reactions produce a large white plume, locally known as lava haze or laze, which contains a mixture of hydrochloric acid (HCl) and concentrated seawater.
In this photo, lava flows ooze into the sea on the southeast coast of Kilauea Volcano; the discrete plumes form above the most energetic entry sites. The red traffic cones on the left side of the photograph were placed by rangers of the Hawai`i Volcanoes National Park to mark the hazardous area where lava is entering the sea.

The hydrochloric acid (HCl) comes from the breakdown of seawater-derived chlorides during sudden boiling. Because the lava is largely degassed by the time it reaches the sea, any HCL coming from it is insignificant by comparison. Analyzed samples of the plume show that is is a brine with a salinity of about 2.3 times that of seawater and a pH of 1.5-2.0.

Key seawater chloride breakdown reactions that produce HCl gas

• MgCl₂ (sea salt) + H₂O (steam) = MgO (periclase) + 2HCl (HCl gas)
   
• 2 NaCl (sea salt) + H₂O (steam) = Na₂O (sodium oxide) + 2 HCL (HCl gas)
   
• CaCl₂ (sea salt) + H₂O (steam) = CaO (lime) + 2 HCL (HCl gas)

Laze plumes are very acidic

Photograph by C.C. Heliker February 10, 1994

Avoid standing beneath a laze plume. Dense laze plumes contain as much as 10-15 parts per million of hydrochloric acid. These values drop off sharply as the plume moves away from the lava entry areas. During along-shore or on-shore winds, this plume produces acid rain that may fall on people and land along the coast. This rain (pH 1.5 to 2), often more acidic that lime juice or stomach acid, is very corrosive to the skin and clothing. Visitors to the lava entry areas should avoid standing directly in, under, or downwind of the laze plume.

Gerlach, T.M., Krumhansl, J.L., Fournier, R.O., Kjargaard, J., 1989, Acid rain from the heating and evaporation of seawater by molten lava: a new volcanic hazard [abs.]: Transactions of the American Geophysical Union (EOS), v. 70, p. 1421-1422.

Sutton, A.J., and Elias, T., 1993, Volcanic gases create air pollution on the Island of Hawai`i: U.S. Geological Survey Earthquakes and Volcanoes, v. 24, no. 4, pp. 178-196.