Volcano Watch: Recent events at Mauna Loa remind us to be prepared for quick changes

  • Hawaiian Volcano Observatory Mauna Loa monitoring data showing increased ground deformation rates (top) and earthquake rates (bottom) from August 8 through October 5, 2022. The distance (line length) between GPS stations MOKP and MLES (blue circles) lengthened by about 2 cm (less than 1 inch), indicating that Mauna Loa is expanding as more magma accumulates beneath the surface. MOKP is located just Northwest of Mokuʻāweoweo (Mauna Loa’s summit caldera) and MLES is located on Mauna Loa’s upper southeast flank. Tiltmeter measurements (green line) also show increased ground motions (the daily oscillations in tilt are due to local heating and cooling cycles). There were less than 20 earthquakes per day (blue bars) from early August through mid-September. The rate increased to about 40-50 earthquakes per day over the past two weeks, with peaks of over 100 earthquakes per day on September 23rd and 29th. (USGS graphic)

The last eruption of Mauna Loa occurred in 1984 and began in a style typical of the volcano. At 10:55 p.m. on March 24, 1984, the rate of earthquakes under Mauna Loa started to rapidly pick up. While rates of earthquakes were already above normal, they quickly rose to 2-3 earthquakes per minute.