Volcano Watch: Taking Kīlauea’s temperature

“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. Today’s article is by Hawaiian Volcano Observatory geologist Kendra Lynn.

Geochemical analysis of erupted tephra samples during the past decade help scientists understand the temperature of Kīlauea’s shallow magma system under the summit — and things have been “heating up!”

Do you know how hot erupting basaltic lava is at our Hawaiian volcanoes?

This value is usually about 2,100 to 2,190 degrees and can be measured in a few different ways. Calibrated thermal cameras/images can provide temperature estimates of active lava flows, and field geologists can manually measure the temperature using a device called a thermocouple — basically a thermometer inserted into the active lava flow.

Using field-based observations, past generations of volcano scientists calibrated a laboratory-based thermometer to calculate eruptive temperatures based on magnesium oxide in lavas and tephra.

Hawaiian Volcano Observatory scientists used magnesium oxide values in near real-time during the past decade as a geochemical monitoring tool, conducted as part of a cooperative agreement with University of Hawai‘i at Hilo Geology Department.

By examining changes in magnesium oxide — and thus changes in eruptive temperatures — for tephra from summit eruptions from 2008 to present, we can determine whether the magmatic system is cooling down or heating up.

More simply — this is how Hawaiian Volcano Observatory scientists take Kīlauea’s temperature.

This is done using several analytical techniques and instruments, but we summarize results from measuring magnesium oxide in tephra glasses using an electron microprobe.

This glassy material rapidly cools after it erupts and is the best representation of the magma.

In April and May 2018 — prior to summit collapse — the lava lake in Halemaʻumaʻu Crater had glass 6.7 to 7 weight percent magnesium oxide, reflecting temperatures of 2,118 to 2,129 degrees.

After summit collapse, the 2020-23 Halemaʻumaʻu eruptions had a larger magnesium oxide range of 6 to 7.2 weight percent, reflecting a wider temperature range of 2,091 to 2,138 degrees, but with a similar maximum.

During the first 42 episodes of the ongoing lava fountaining eruption in Halemaʻumaʻu, which began Dec. 23, 2024, the magmatic system has been hotter, with glass magnesium oxide higher at 7 to 8.2 weight percent, meaning temperatures are at least 50°F warmer (range of 2,129 to 2,176 degrees).

Thus, lava erupting now is hotter than eruptions from 2018 to 2023.

These measurements reflect the temperature of the lava at the Earth’s surface — in our ambient atmosphere, which on a delightful day at Kaluapele, Kīlauea’s summit caldera, might be about 75 degrees.

Once magma reaches the surface to erupt as lava, rapid and dramatic cooling occurs in seconds to minutes.

How do we measure pre-eruptive temperature of Kīlauea’s magmas?

Hawaiian Volcano Observatory scientists use a few laboratory methods to determine the pre-eruptive temperature of Kīlauea’s magmas and thus can characterize the thermal state of the shallow magmatic system.

Erupted lavas and tephra contain olivine crystals — the common green mineral found in Hawaiian basaltic rocks — and their chemistry is sensitive to the magma temperatures.

When Hawaiian Volcano Observatory scientists looked at olivine chemistry from the 2008-18 lava lake, the 2020-23 summit eruptions and the ongoing lava fountain episodes in Halema‘uma‘u, they found that olivine tracks an increase in temperature of about 60 to 70 degrees.

The increase in temperature of glass, a liquid component, and olivine show us that Kīlauea’s shallow magma reservoirs have been heating up during the past decade and continued to show these signals through Episode 42.

What does this mean for the long-term behavior of Kīlauea?

It’s possible that increasing temperatures observed for the current eruption might have to do with its prolonged episodic nature — hotter, fresher magmas entering the system are driving repeated eruptive episodes.

With temperatures still elevated, it could mean the episodic activity will continue for some time. It may also reflect somewhat high rates of magma supply to the shallow reservoir beneath Kīlauea’s summit, which could lead to continued episodes or an eruption elsewhere on the volcano.

Hawaiian Volcano Observatory’s team of interdisciplinary scientists are carefully monitoring Kīlauea to detect any changes to the pattern of episodic eruptions.

Laboratory-based work and near real-time geochemical monitoring are important perspectives that will help detect changes to the thermal state of the system.

VOLCANO ACTIVITY UPDATES

KĪLAUEA volcano

VOLCANO ALERT LEVEL: Watch

Kīlauea has been erupting episodically Dec. 23, 2024, within the summit caldera. Episode 43 of lava fountaining happened for 9 hours March 10. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

WHAT’S NEXT? Summit region inflation since the end of Episode 43 indicates another fountaining episode is possible; however, power and storm related outages affected instrumentation used to model the start time frames for the next episode and an offset had to be applied to the modeling data, which suggest Episode 44 could begin between April 5 and 15.

MAUNA LOA volcano

VOLCANO ALERT LEVEL: Normal

Mauna Loa is not erupting. Refer to the March 5 monthly update for additional information about activity at Mauna Loa.

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

EARTHQUAKES

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

• MAGNITUDE-3.4 earthquake at 2:33 p.m. March 20 located 2 miles south-southwest of Pāhala at at depth of 19 miles.

Visit the Hawaiian Volcano 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.