Volcano Watch: Playing with the Wire: Upcoming Investigations to Reveal Kīlauea’s Inner Workings

By U.S. Geological Survey Hawaiian Volcano Observatory / Research geophysicist Jim Kauahikaua.

Over the past several months, “Volcano Watch” articles have featured several research projects funded by the Disaster Relief Supplementary Act of 2019 (HR 2157). Each of these projects will help scientists better understand how Kīlauea Volcano works and how the 2018 Lower East Rift Zone eruption and Kīlauea’s summit collapse occurred.

Sources/Usage: Public domain. Photo of a helicopter with a loop hanging below it flying over Yellowstone National Park.

Two projects that will begin this summer use the flight of an oblong loop of wire and the burying of spools of wire. The target area is the entire Kīlauea Volcano – from the eastern tip of Kumukahi southwest almost to Punaluʻu. Warning: lots of acronyms to follow! Both projects will determine the distribution of subsurface electrical resistivities that can be used to map magma and hot rock, among others. The airborne project will also map variations in the magnetic field to determine how much of the Earth’s field is locked into Kīlauea’s magnetic minerals.

The first project will deploy electrodes and coils of wire buried at shallow depths to passively measure electromagnetic (EM) energy generated by lightning around the equator. The technique is called magnetotelluric (MT) sounding. Electrical storms are common in equatorial regions and these storms produce amazingly constant electromagnetic noise that travels around the globe in the atmosphere between the Earth’s surface and the ionosphere.

The earth’s response to this distant EM stimulation can tell us the electrical properties of the earth beneath the coils at depths of around 10 km (6 mi). The one square meter (yard) configuration will be moved to approximately 125 ground locations on the volcano. The resulting data will be used to develop a detailed picture of Kīlauea’s inner workings. This study will be carried out over two field seasons with the first season in 2022 during the months of May and June. The second season will take place in the summer of 2023.


The second part of this project will use a 15 by 25 m (50 by 80 ft) oval-shaped loop of wire suspended 30 m (100 ft) below a helicopter (Fig. 1) flying over most of the volcano. The loop assembly will transmit and receive very, very low frequency EM energy and must fly 35–50 m (115–165 ft) above the ground or treetops. A small sensor will also measure the strength of the magnetic field. The technique is called airborne electromagnetic and magnetic mapping (AEM).

Sources/Usage: Public domain.

AEM data will supplement MT data and allow imaging of the shallow (600 m or 2000 ft upper) structure of the volcano, including groundwater and weathering patterns caused by hydrothermal fluids such as those that have infiltrated. in the Halema’uma’u water lake in 2019-2020. The Earth’s magnetic field along the flight path will also map the cooling signature dyke which transported magma down Puna in 2018. This part of the project is also planned for 2022 during the months of June and July.

The currently planned flight lines do not fly over any residential areas or any other areas excluded by the Federal Aviation Administration or Hawaii Volcanoes National Park. Flights will take place during daylight hours and will be coordinated with the FAA. Experienced pilots specially trained and licensed for low altitude flying will fly the helicopter. None of the instruments of either part of the project poses a risk to human or animal health.

The MEA and Earth’s magnetic field were last mapped in 1978 at Kīlauea and Mauna Loa volcanoes. The 1978 results showed that Kīlauea’s east rift zone was clearly defined by strong magnetic field aberration typical of vertical levees that fed countless eruptions laterally from the summit area.


Equipment and software have been greatly improved over the past 20 years, and geophysicists overseeing the current project have successfully used the technique to map other US volcanoes. Our hopes are high that we will be able to image more clearly at greater depths in this new project to produce a picture of the entire Kīlauea magma system. The final products of this survey will be made public within a few years.

The AEM survey is expected to last about three weeks from the end of June. We understand that helicopter noise can be disruptive, so we will greatly appreciate the patience and understanding of affected residents as we collect this critically important data to help mitigate future eruption risks.

The feature shown in the photograph is a drainage outlet for the active lava lake of Halema’uma’u, a crater in the summit caldera of Kīlauea Volcano. The surface slabs of the active lake surface are driven into the outlet and churned. A small standing wave, about 1 meter or 1 meter high, is present in the center of the output structure. This photograph was taken during an observation field shift on the morning of May 18, 2022. USGS photograph by L. Gallant.

Volcanic activity updates

The Kīlauea volcano is erupting. Its USGS Volcanic Alert Level is at WATCH.

Over the past week lava has continued to erupt from the west vent in Halemaʻumaʻu crater. All lava is confined within Halema’uma’u Crater in Hawai’i Volcanoes National Park. sulfur dioxide emission rates remain high and were last measured at around 2,300 tonnes per day (tpd) on 22 May. Seismicity is high but stable, with few earthquakes and ongoing volcanic tremors. Summit tiltmeters showed two deflation-inflation cycles over the past week.

Mauna Loa is not erupting and remains at the ADVISORY Volcanic Alert Level. This alert level does not mean that an eruption is imminent or that progress to an eruption from the current level of unrest is certain.

Last week, about 50 low-magnitude earthquakes were recorded beneath the summit and upper flanks of Mauna Loa – the majority of them occurring at shallow depths less than 15 kilometers (9 miles) below the sea ​​level. Global Positioning System measurements show low rates of ground deformation over the past week. Gas concentrations and Fumarole temperatures at the summit and at Sulfur Cone on the southwest rift zone have remained stable over the past week. The webcams show no change in the landscape.

An earthquake was reported felt in the Hawaiian Islands during the past week: an M4.7 earthquake 3 km (1 mi) northwest of Hōlualoa at 9 km (5 mi) deep on May 21 at 11:49 p.m. HST.

HVO continues to closely monitor the ongoing eruption of Kīlauea and Mauna Loa for any signs of increased activity.

Volcano Watch is a weekly article and activity update written by the US Geological Survey Hawaii Volcano Observatory scientists and affiliates. This article was originally published on May 26, 2022.

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