USGS Volcano Hazards Program Volcano Update

HVO update page and observatory web site

Mauna Loa is not inflating. Seismicity rates were low.

Deformation: is occurring at slow rates, dominated by southeasterly motion of the southeast flank. If any inflation is occurring, it is at a very low rate. Upgrades of many Mauna Loa sites in late 2011 produced some apparent data offsets that will be corrected once a longer post-upgrade time series is available for analysis.

Seismicity: There was no unusual seismicity. HVO seismic networks detected 1 shallow event to the north and west of the summit, 4 shallow events within the upper southwest rift, 4 shallow event within the lower southwest rift, and 4 shallow events within the NW rift.

Gas: No significant changes in SO2, CO2 were recorded by the Mokuaweoweo gas and temperature monitors during the month. Fumarole temperature, after 5 months of slow decline totaling about 4 degrees C, reached 71 degrees C.
Background: Re-inflation of Mauna Loa's shallow magma storage reservoirs started immediately following the most recent eruption in 1984, then turned to deflation for almost a decade. In mid-2002, inflation started again, just after a brief swarm of deep long-period (LP) earthquakes. A more intense swarm of several thousand deep Long Period (LP) earthquakes occurred in late 2004, immediately preceding a dramatic increase in inflation rate. Inflation slowed again in 2006, ceased altogether in late 2009, and resumed slowly in late 2010.

Rising gradually to more than 4 km above sea level, Mauna Loa is the largest volcano on our planet. Its long submarine flanks descend to the sea floor an additional 5 km, and the sea floor in turn is depressed by Mauna Loa's great mass another 8 km. This makes the volcano's summit about 17 km (56,000 ft) above its base! The enormous volcano covers half of the Island of Hawai`i and by itself amounts to about 85 percent of all the other Hawaiian Islands combined.

Mauna Loa is among Earth's most active volcanoes, having erupted 33 times since its first well-documented historical eruption in 1843. Its most recent eruption was in 1984.

Update in Common Alerting Protocol (CAP) format