Volcano Watch: High-altitude station maintenance on Mauna Loa

  • Sulphur Cone (left), viewed toward southwest, from 11,420 feet above sea level on Mauna Loa’s southwest rift zone. At right, an HVO geoscientist and technician rebuild volcanic gas monitoring equipment 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 10,000 feet altitude. Our field crew of six from Hawaiian Volcano Observatory (HVO) 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 Mokuaweoweo 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 Mauna Kea, 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 feet elevation contour of Mauna Loa, with an airborne perspective of the northwest flank. The long, jagged channel of the 1859 lava flow stretches 32 miles down to the sea south of Anaehoohalu 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 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 11,420 feet elevation. We are dropped off upwind of fumaroles emitting volcanic gases. The fumes have 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 (SO2), hydrogen sulfide (H2S), water vapor (H20), and carbon dioxide (CO2) 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 Mokuaweoweo Caldera.

My colleague hunts around with a thermometer. She locates a 95 Celsius (203 Fahrenheit) 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 down-rift, around the island, and onto HVO servers nearly instantly. The latency to the database is about 18 milliseconds.

I call HVO Hilo over 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 over the past week. Sulfur dioxide emission rates are low at the summit and below detection limits at Puu Oo and the lower East Rift Zone (LERZ). 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; please 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 that an eruption is imminent or that progression to an eruption is certain.

This past week, about 80 small-magnitude earthquakes (all less than M-2.2) 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 due to maintenance on the instrument sensors in mid-September.

Mauna Loa updates are issued weekly. For more info on the status of the volcano, visit 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 was recorded 9 miles south of Volcano at 1 mile in depth occurred at 8:55 p.m. HST Oct. 17. A magnitude-3.4 earthquake struck about 9 miles southeast of Volcano at 0 miles depth at 5:30 a.m. HST Oct. 17.

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


Visit www.volcanoes.usgs.gov/hvo for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake info, and more. Email questions to askHVO@usgs.gov.

Volcano Watch is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. This article is by HVO technician Frank Younger.

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