Volcano Minute — Mauna Loa on the move

Aloha, it's your weekly Volcano Minute, brought to you by the USGS Hawaiian Volcano Observatory.

Today, we’re taking a look at how scientists track movement at Earth’s largest active volcano—Mauna Loa.

Each year, the USGS Hawaiian Volcano Observatory conducts a high‑precision Global Positioning System, or GPS, survey across the volcano. These measurements, combined with data from GPS stations that are located permanently across the landscape, allow scientists to monitor subtle changes in Mauna Loa’s shape over time. Some of these locations have been measured for decades, evolving from early leveling techniques to modern GPS instruments.

This summer, scientists surveyed twenty‑two benchmarks on Mauna Loa. Each station requires careful setup of an antenna that is precisely centered over a benchmark on the ground. The device is leveled, and aligned north, often on the rugged terrain of old lava flows. These instruments then record data continuously for several days before being packed up and redeployed with fresh batteries.

The results from this year show a familiar pattern. The summit has moved up and outward, while the flanks have shifted slightly down and away. This indicates ongoing slow inflation beneath Mauna Loa’s summit, consistent with about 2.9 inches of movement per year. Although magma continues to slowly accumulate, seismic activity and gas emissions remain low, and an eruption at Mauna Loa is not expected anytime soon.

Still, these annual measurements are critical. They could help us detect small changes below the surface that could indicate renewed volcanic unrest in the future, supporting our ongoing efforts to keep communities informed.

At neighboring Kīlauea volcano, inflationary summit ground motion indicates that another lava fountaining episode is likely.

Mahalo for listening, I’m Katie Mulliken and this was your weekly volcano minute brought to you by the USGS Hawaiian Volcano Observatory.