Volcano Watch: High-altitude station maintenance on Mauna Loa

  • USGS photo Sulphur Cone, left, viewed toward the southwest from 3,480 m (11,420 ft) above sea level on Mauna Loa’s southwest rift zone. At right, an HVO geoscientist and technician rebuild volcanic gas monitoring equipment installed near an outgassing fissure.

U.S. Geological Survey trucks pull off the shoulder of Mauna Loa Observatory Road before dawn.

I park the Jeep at the helicopter staging area, a flat rubble strip flanked by a‘a lava. The air is cool and thin at 3,048 m (10,000 ft) altitude. Our field crew of six from Hawaiian Volcano Observatory keep warm unloading gear. We clear the landing zone for the inbound pilot. We organize packs, tools and equipment by checklist for the helicopter.


Today’s flight plan will disperse us across Moku‘aweoweo Caldera and the upper flank of the volcano to rebuild five remote Mauna Loa monitoring stations. Our team of technicians ensures the continuous transmission of seismic, deformation and gas emission data from the active, but not currently erupting, volcano.

Two geoscientists and I are heading to Sulphur Cone on the Southwest Rift Zone within the boundaries of Hawaii Volcanoes National Park.

The first light of day spreads over Hawaii Island. The natural colors of Maunakea, Hualalai and Kohala come alive in the warmth of the sun.

Across the channel, the heights of Haleakala rise above ocean clouds.

I hear beating chopper blades approaching. The helicopter lands in a roaring downdraft. We load cargo for Sulphur Cone, and I strap myself in next to the pilot. He throttles for takeoff, keys coordinates on the GPS and pulls rotor pitch with his control.

The helicopter lifts into the trade wind, banks westward and nods into forward acceleration.

We navigate along the 10,000-ft (3,048-m) elevation contour of Mauna Loa, with an airborne perspective of the northwest flank. The long, jagged channel of the 1859 lava flow stretches 52 km (32 miles) down to the sea south of Anaeho‘omalu Bay.

Crossing the west flank, we fly above an atmospheric inversion layer. Cloud-swept pahoehoe cradles patches of hardy native pukeawe shrub. We hurtle over the trackless wilderness at 110 knots (126 mph). The dark ridgeline of the Southwest Rift Zone dominates the horizon ahead.

The Sulphur Cone area stands out in bright contrast. It’s a steaming section of the 1950 eruptive fissure at 3,480-m (11,420-ft) elevation. We are dropped off upwind of fumaroles emitting volcanic gases. The fumes created crystals, including snow-white calcite and canary-yellow sulfur, that cover the surroundings.

Our crew hikes over altered rock to monitoring equipment installed near an outgassing fissure. Station MG14_SCN clicks and whirs beneath protective rocks.

The MultiGAS technology inside was developed by USGS Volcano Science Center researchers. It is a field-deployed gas laboratory the size of a suitcase. Sensors measure sulfur dioxide, hydrogen sulfide, water vapor and carbon dioxide gas concentrations. Automatic calibration is used to correct sensor drift.

We bring in a replacement MultiGAS to relieve the veteran station instrument. It is scheduled for preventative maintenance at HVO’s Keaau workshop, then redeployment to Moku‘aweoweo Caldera.

My colleague hunts around with a thermometer. She locates a 95-degree C (203-degree F) fumarole and wires a station thermocouple to continuously measure near-surface temperature.

I tend the power station, cleaning solar panels. The wet rag comes away yellow with insoluble sulfur. The anemometer atop the mast gets a scrub, too. I inspect the welded frame and antenna grid for any deterioration beneath a fine coat of crystals.

Our team lead installs the new MultiGAS and communicates with it via laptop. She notes parameters and triggers a calibration cycle. We listen and test the plumbing of pumps and valves as they operate — all look and sound healthy. She swaps cylinders of calibration gases and replaces desiccant and scrubbing media. I check the tubing manifold connections and raise the sample intake pipe.

We initiate the program for automatic operation. The station will sample and analyze ambient volcanic gases around the clock. Now back online, the data are transmitted on HVO’s radio telemetry network.

Data flows downrift, around the island and onto HVO servers nearly instantly. The latency to the database is about 18 milliseconds.

I call HVO Hilo via satellite phone. Our flight follower verifies network connectivity and data quality. I get updates on the other crews’ status around the summit. The mission is running smoothly.

Confident in our work, we request helicopter extraction.

Volcano activity updates

Kilauea Volcano is not erupting and its USGS Volcano Alert level remains at Normal (https://volcanoes.usgs.gov/vhp/about_alerts.html). Updates for Kilauea are now issued monthly.

Kilauea deformation and seismicity showed no notable changes during the past week. Sulfur dioxide emission rates are low at the summit and below detection limits at Pu‘u ‘O‘o and the lower East Rift Zone. The water pond at the bottom of Halema‘uma‘u continues to slowly expand and deepen.

At or near the 2018 LERZ eruptive fissures, elevated ground temperatures and minor releases of gas (steam, tiny amounts of hydrogen sulfide and carbon dioxide) persist. These are typical post-eruption conditions and are expected to be long-term.

Hazards remain at the LERZ and summit of Kilauea. Closures and warnings in these areas should be heeded. The 2018 lava flows are primarily on private property; be respectful and do not enter or park on private property.

Mauna Loa is not erupting. Its USGS Volcano Alert level remains at Advisory. This alert level does not mean an eruption is imminent or progression to an eruption is certain.

This past week, about 80 small-magnitude earthquakes (all less than M2.2) were detected beneath the upper elevations of Mauna Loa. Deformation measurements show continued summit inflation. Volcanic gas emission and fumarole temperature readings have been slightly elevated from measurements several weeks ago because of maintenance on the instrument sensors in mid-September.

Mauna Loa updates are issued weekly. For more information about the status of the volcano, go to: https://volcanoes.usgs.gov/volcanoes/mauna_loa/status.html

There were two events with three or more felt reports in the Hawaiian Islands during the past week. A magnitude-3.0 earthquake 14 km (9 mi) south of Volcano at 2 km (1 mi) depth occurred at 8:55 p.m. Oct. 17. A magnitude-3.4 earthquake 14 km (9 mi) southeast of Volcano at 0 km (0 mi) depth occurred at 5:30 a.m. Oct. 17.

HVO continues to closely monitor Kilauea and Mauna Loa for any signs of increased activity.


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

Volcano Watch (https://volcanoes.usgs.gov/observatories/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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