Maunaloa volcano (Hawaiʻi): Swelling slowly continues, no significant change

Unlike her neighbor Kīlauea to the south, Maunaloa is not erupting, and yet has been arguably more visible in the mainstream news this past month.
While a combination of earthquake clusters and an article on preparedness have drawn attention to the volcano, its monitored status and alert level remains unchanged with “no significant change in deformation rates or patterns that would indicate increased volcanic hazard at this time”, according to the USGS Hawaiian Volcano Observatory.


Last week on Maunaloa:

-GPS distance across summit switches from contraction to extension
-Ground tilt shows a small, but similar change
-No SO2 emissions, fumarole temperatures stable below 100 degrees C / 212 deg F
-220 small-magnitude earthquakes, all less than M2.5, 188 of them below the summit and upper-elevation flanks at depths of less than 8 km / 5 mi below ground level
-Earthquakes spike 1 week ago on April 9 with ~70 events, otherwise all days since show background levels below ~30 events per day

Discussion: Monitoring signals and recent InSAR imagery suggest that magma continues to fill slowly underground, triggering the observed seismic adjustments on Maunaloa's flanks over the past few weeks. Cycles of summit filling and flank adjustment are common on the volcano, and a switch back to the filling phase is consistent with GPS data. There is potential for the resumption of shallow seismicity around the volcano's summit, along with some reduction of flank adjustment earthquakes in the short term, until the cycle repeats. For now, the deformation rates are not indicative of any rapid or imminent change on Maunaloa.

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