Volcano Watch: Snowshoeing on the Big Island’s Kīlauea? High fountain episodes pose new challenges to volcano monitoring

“Volcano Watch” is a weekly article and volcano activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

U.S. Geological Survey Hawaiian Volcano Observatory maintains a network of nearly 150 monitoring instruments — that track activity above and below the surface — on Hawaiʻi Island’s Kīlauea volcano.

The high lava fountain episodes of the ongoing episodic eruption in Halemaʻumaʻu Crater within Kaluapele, the volcano’s summit caldera, that started Dec. 23, 2024, present new challenges to maintaining parts of the Kīlauea summit monitoring network near and immediately downwind of the two eruptive vents.

Episode 28 — the most recent in the sequence so far — fired off geysers of molten rock rock for about 9 continuous hours July 9, with 8 of them being high fountaining, reaching a maximum height of about 1,200 feet.

Hawaiian Volcano Observatory field engineers the next day, on July 10, strapped on snowshoes as they prepared to work in the closed area of Hawaiʻi Volcanoes National Park, southwest of the eruptive vents.

With each step, the ground crunched and their feet sunk a little.

Large footprints of snowshoes kept the field engineers on top of the frothy pumice everywhere rather than stepping through. A soft sound of clinking could be heard as tiny pieces of volcanic glass floated through air, shimmering in the sunlight.

Engineers wore full-face respirators for protection from these particles — known as tephra.

Tephra is any volcanic material erupted that travels through the air before landing on the ground. It includes very small particles such as volcanic ash, light and frothy rocks full of holes called reticulite, more robust rocks such as scoria, larger pieces called bombs and ever-present Pele’s hair.

Lava fountains of the ongoing episodic eruption have created a growing tephra blanket downwind of the eruptive vents.

On the crater rim closest to the vents, the tephra is as thick as 80 feet deep.

Lava flows fed by the 28 fountaining episodes of the ongoing eruption have covered nearly 850 acres of the Halemaʻumaʻu Crater floor — up to 236 feet thick in some areas.

Hawaiian Volcano Observatory staff have moved several monitoring stations that were too close to lava flows or buried by falling tephra.

The instruments themselves remained functional, and most — including the F1 thermal camera, KWcam, B1cam and continuous laser rangefinder — have been redeployed near the V1 streaming camera in an area less likely to be impacted by the eruption.

The B2cam on the crater floor underwent a full melt down, but its solar power supply survived and was airlifted to the south rim to power the new V3 livestream camera.

Several other monitoring stations are located farther away from the vents but still impacted by the eruption.

The instruments at these stations — many of which measure volcanic gas — are positioned southwest of the summit because that direction is usually downwind of summit eruptions during common trade wind conditions.

Being downwind of the ongoing eruption means, in addition to the gas they are designed to measure, the stations are subjected to tephra fall.

Infrastructure at monitoring stations in this area can be covered by tephra depending on wind direction during an eruptive episode. Hawaiian Volcano Observatory staff have visited these sites following eruptive episodes to dig them out and remove tephra from solar panels, restoring power to the station.

Sulfur dioxide emission rates, which the observatory measures to help track eruptive activity, are not possible when this part of the network is down.

Hawaiian Volcano Observatory scientists are exploring other methods for obtaining sulfur dioxide emission rates. In the meantime, numerous measurements during past pauses and eruptive episodes allow us to generally estimate emission rates during different types of activity.

Sulfur dioxide emission rates during past pauses between fountaining episodes were measured at about 1,200 to 1,500 tonnes per day. Those during eruptive episodes were measured up to 75,000 tonnes per day.

It’s likely sulfur dioxide emission rates have been even higher during recent eruptive episodes; although, measurements have not been possible.

High lava fountains can also temporarily block radio telemetry, preventing data flow from monitoring stations.

Most telemetry paths have been re-routed to avoid this issue, but several instruments — including the Sandhill tiltmeter, Cone Peak global positioning system and several seismic stations — might continue to be affected during high fountaining episodes.

The area southwest of eruptive vents can be difficult to access.

Depending on wind direction during fountaining episodes, more tephra can blanket the landscape — and access road — to the southwest.

Hawaiian Volcano Observatory staff assess the feasibility of visiting monitoring sites after each eruptive episode, with staff safety being the primary priority.

A small portion of the Kīlauea monitoring network is being impacted by the ongoing summit eruption, but the observatory is still able to adequately monitor the volcano.

Maintaining the instrument network during eruptions is one of the challenges that comes with monitoring one of the most active volcanoes on Earth.

Volcano Activity Updates

Kīlauea has been erupting episodically within its summit caldera since Dec. 23, 2024. Its U.S. Geological Survey Volcano Alert Level remains at Watch.

Episode 28 of the summit eruption in Halemaʻumaʻu Crater happened July 9, with about 9 hours of fountaining from the north vent. The south vent did not activate and was completely covered by new volcanic deposits.

Summit region inflation since the end of Episode 28, along with persistent tremor, suggests another eruptive episode is possible, though more time — and data — are needed before a forecast can be made.

Sulfur dioxide emission rates are elevated in the summit region during active eruption episodes.

No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

Mauna Loa is not erupting. Its U.S. Geological Survey Volcano Alert Level remains at Normal.

One earthquake was reported felt in the Hawaiian Islands during the past week:

• MAGNITUDE-2.9 located 6 miles south of Volcano at a depth of 3 miles at 5:04 a.m. July 6.

Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Mauna Loa.

Visit the observatory website for past “Volcano Watch” articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake information and more. Email questions to askHVO@usgs.gov.