The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) recently completed its 2026 annual campaign Global Positioning Satellite (GPS) survey of Mauna Loa, revealing continued ground inflation indicative of magma accumulation beneath the volcano's summit.
HVO utilizes a combination of a dense network of permanent GPS stations and annual campaign surveys to collect high-precision data at benchmark locations across the island. This practice, which began with GPS instruments in 1994 after earlier survey techniques, is essential given Mauna Loa's history of producing large, fast-moving lava flows, with its most recent eruption occurring from November to December 2022.
The data from these surveys significantly increases the spatial coverage of HVO's geodetic network, enhancing understanding of Mauna Loa's long-term deformation field. Patterns of ground motion, such as movements away from the summit indicating inflation or magma rise, are critical for preparing scientists for potential hazards and enabling effective communication with nearby communities for safety efforts. The 2026 survey involved a staged deployment to measure 22 benchmarks, requiring precise equipment setup over several days.
Survey results from 2025-2026 align with trends from the past decade, showing all benchmarks around the summit moving up and away from their original locations, consistent with continued inflation directly beneath the Mokuʻāweoweo caldera. The average rate of ground motion at the summit is approximately 2.9 inches (7.4 cm) per year. While Mauna Loa continues to slowly accumulate magma, seismicity and gas emissions have remained low, indicating no immediate eruption is expected. HVO scientists maintain continuous monitoring to detect subtle changes and provide early warnings to Hawaii residents. Kīlauea, meanwhile, continues episodic eruptions within its summit caldera, with another fountaining episode possible between July 25 and 29.