Volcano Watch: A field trip to the Mountain of Water

  • E.F. YOUNGER/USGS photo This photo captured this month shows a midwinter dawn at Halema‘uma‘u crater on Kilauea. Steaming cracks tell of water and heat interacting beneath the summit caldera of the volcano. In the background, the first rays of sunlight illuminate Uekahuna Bluff.

The field day begins with a summit weather check at first light. It is a reflective moment at 6:15 a.m. atop Kilauea Volcano, and the fumarole cracks are steaming like the coffee from my thermos. The weather at Halema‘uma‘u crater is cool and dry, with light trade winds from the northeast.

We hope for these mornings.


I text my workmates at the U.S. Geological Survey Hawaiian Volcano Observatory in Hilo. The plans are a “go” — our sampling crew is heading to Keller Well. My checklist for today’s field work reads: water, rain jacket, extra-long tape measure … .

I am one of a team of volcano scientists and technicians making this trip. Our destination is a 1,262 m (4,140 ft) deep borehole, locally called Keller Well, which is the only one of its kind on Kilauea’s summit. Since it was drilled in 1973, it has provided researchers with a view into the hydrology and history of an active volcano.

Our mission today is to measure the groundwater level in the well, 506 m (1,660 ft) beneath the surface (where the groundwater level was when it was last measured nine months ago) and to bring up a scalding hot water sample. I continue checking my list: 2 m (6 ft) metal sampler tube, clean sample bottles … .

My HVO and USGS Volcano Science Center colleagues and I will be accessing a restricted area of Hawaii Volcanoes National Park. We check our safety gear: helmets, respirators, SO2 sensor badges, satellite tracker and our National Park Service permit.

Keller Well, located in the southern portion of the Kilauea caldera, sits at 1,102 m (3,615 ft) above sea level. The rim of the Halema‘uma‘u lava lake of 2008-18 used to be about 1 km (0.62 mi) to the north.

Distance from rim to well narrowed dramatically during the eruption of this past summer, as caldera collapse explosions shook Halema‘uma‘u and the lava lake drained out of sight. The steaming pit is now nearly a cubic kilometer (0.25 cu mi) larger, the rocky bottom is 500 m (1,640 ft) deeper and the crater rim expanded about 250 m (820 ft) toward the wellhead.

Across the chasm from Keller Well, the evacuated HVO tower looms empty; a silent host of cameras keeping watch over Kilauea.

We will find out today if Keller Well survived the 2018 eruption. Will it continue to yield data on Kilauea’s hydrothermal depths, or has the story been pinched off?

At the wellhead, a capped stub of pipe protrudes from the barren, ash-caked landscape. We set up the large tape measure reel and lower the electric continuity sensor into the well. It descends quickly as we spool out the calibrated graduations into the darkness below.

Down through the porous rock, we follow the path of a fallen raindrop, moving through varied layers. Some are highly porous, while others are choked by mineralization that formed as liquid water was converted to steam by geothermal heat. Ash layers confine the free movement of the groundwater, while cracks and other voids can conduct large flows.

Suddenly, the alarm at the surface buzzes madly, signaling the tape circuit is complete. The downhole sensor has reached the water table!

We have arrived at the Mountain of Water.

Hidden beneath the surface of the volcano island, this mountain within has a character all its own. Its topography is constantly changing, seeking balance between discharge and recharge, pressure and heat.

Beneath Kilauea’s summit, the altitude of the water mountain is remarkably high compared to nearby areas outside the volcanic rift zones. We measure the tape, 508 m (1,667 ft) to the reference mark on the wellhead; the groundwater is 2.1m (7 ft) lower than it was in March, before this year’s eruption.

The Mountain of Water’s composition is diverse. It is fresh and salt, liquid and steam, and it carries an abundance of dissolved chemicals. We withdraw the sampler, kettle-hot, and carefully bottle the sample for laboratory analyses of sulfate (SO4), chloride (Cl), sodium (Na), and potassium (K).

Today’s field work marks one new data point in a long series of observations at Keller Well. Only time and concerted effort will reveal its context within the larger story.

Volcano activity updates

Kilauea is not erupting. Rates of seismicity, deformation and gas release have not changed significantly during the past week.

There was one event with three or more felt reports in the Hawaiian Islands during the past week. At 1:44 a.m. Dec. 18, a magnitude-2.8 earthquake occurred 12 km (7 mi) SSE of Volcano at 3 km (2 mi) depth.

Deformation signals are consistent with refilling of the middle ERZ. Sulfur dioxide emission rates have been below detection limits in the lower ERZ since early September, though minor amounts of volcanic gas are still present. Sulfur dioxide emission rates were last measured at ~35 t/d at the summit and ERZ, consistent with the past few months of emissions from Kilauea.

Hazardous conditions still exist at the lower ERZ and summit. Residents in the lower Puna District and Kilauea summit areas should stay informed and heed Hawaii County Civil Defense closures, warnings and messages (http://www.hawaiicounty.gov/active-alerts).

The USGS Volcano Alert level for Mauna Loa remains at Normal.


Visit HVO’s website (https://volcanoes.usgs.gov/hvo) for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake info, and more. Call 808-967-8862 for weekly Kilauea updates. Email questions to askHVO@usgs.gov.

Volcano Watch (https://volcanoes.usgs.gov/hvo/hvo_volcano_watch.html) is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

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