# Volcano Watch — HVO scientists to study hydro fluids

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The Hawaiian Volcano Observatory's primary purpose is to understand how volcanic systems operate. All of the work we do in defining geological hazards posed by the volcanoes, and short-term monitoring of eruptions and lava flows, is made possible by developing this fundamental understanding of volcanic systems.

The Hawaiian Volcano Observatory's primary purpose is to understand how volcanic systems operate. All of the work we do in defining geological hazards posed by the volcanoes, and short-term monitoring of eruptions and lava flows, is made possible by developing this fundamental understanding of volcanic systems. One way to develop such understanding is to study the hydrothermal systems associated with the underground storage of magma. Hydrothermal fluids extract heat from magma, thereby cooling and crystalizing it within the volcano. In addition to cooling magma and surrounding hot rock, these fluids react chemically with the surrounding lavas, thereby changing the composition of both the fluid and the rock. The key to unraveling these complex hydrothermal processes is to study the chemistry of the fluid and the altered rock. However, such study is not easily done, as the only way to obtain such fluids and altered rock is by drilling wells.

Puna Geothermal Ventures has generously allowed the U.S. Geological Survey to obtain samples of the hydrothermal fluid from their KS-8 well during the flow-test that began this past week. We will be obtaining, and publicly releasing, an independent analysis of these fluids to support our research efforts to understand the hydrothermal system in the lower East Rift Zone. The fluids will be sampled at the wellhead for the duration of the flow test by a specialist from our office in Menlo Park, California.

The sampled fluids, both brine and steam, will then be analyzed using the most reliable techniques available, for a wide range of chemical, gas, and isotopic components in the laboratories of the U.S. Geological Survey. We will analyze for pH; hydrogen sulfide, carbon dioxide, hydrogen, methane, ammonia, nitrogen, argon, and helium gases; and aluminum, sodium, potassium, calcium, magnesium, lithium, strontium, arsenic, iron, manganese, rubidium, cesium, silicon, chlorine, sulfate, bromine, carbonate, bicarbonate, and ammonium. In addition, a number of isotopic analyses will be performed for deuterium, tritium, oxygen, carbon, and sulfur. Additional analyses may be performed on isotopes of helium, boron, lithium, strontium, and nitrogen.

This first stage of our analysis program is aimed at characterizing the size, temperature, flow regime, origin of fluids, and extent of water-rock interaction of this hydrothermal system. A second phase of analysis, to be undertaken in the future, will concentrate on minor constituents and will help to refine the models developed from the earlier analysis.

### Volcano Activity Update

Kīlauea's ongoing eruption is once again inactive. The last eruptive interval from the episode 51 vents lasted from early in the morning on July 27 until the morning of August 12. The vents are located just west of the Puu Oo cinder and spatter cone on the East Rift Zone of Kīlauea Volcano. Episode 51 has been punctuated by periods of inactivity that have always lasted less than one week, generally less than 4-5 days. The eruptive activity has been intermittent since it began on March 7, and we expect the eruption to resume within the next few days from the same vents.

The most recent flows did not reoccupy the tubes formed during the previous eruptive period, and the development of a new tube system slowed the advance of flows. The area of active flows was confined to the south side of the low lava shield that formed during episodes 50 and 51, and the latest flows stopped at about the 2,100-foot level. No structures are threatened by these or by future flows from the same vents.

The lava lake inside Puu Oo remains active and glows at night; its large plume can be seen from Highway 11, or from the lookout atop Puu Huluhulu on the Napau Trail in Hawaii Volcanoes National Park.