MAUNA LOA, Hawaii – Scientists with the USGS Hawaiian Volcano Observatory released a summary of the Mauna Loa volcano monitoring data gathered through the month of April 2015. Mauna Loa is the largest active volcano on planet Earth, having most recently erupted in 1984. In recent months, the volcano has shown signs of unrest, but nothing yet to the scale of what was observed before eruptions in 1975 and 1984.

Seismicity Elevated

Seismicity at Mauna Loa remains elevated in several parts of the volcano, scientists say.

Earthquake rates on the Upper Southwest Rift Zone (Sulfur Cone) and Mokuʻāweoweo Crater remain elevated, with nearly 200 located earthquakes occurring in April. Though there were no swarms on the west flank of Mauna Loa, earthquake rates remained above background with approximately 13 earthquakes occurring in April. All earthquakes in the past month have been small relative to earthquake sequences observed before eruptions in 1975 and 1984.USGS Hawaiian Volcano Observatory – May 11, 2015

Inflation Continues

GPS stations recording deformation data in April indicate that inflation continues.

Velocities were similar to the average rates measured since the start of the current inflationary period in mid-2014. The pattern and rates are very similar to those observed in mid 2004-mid 2005, which, along with a short period in 2002, had been the time of highest observed velocities since GPS monitoring started in the mid-1990’s. USGS Hawaiian Volcano Observatory – May 11, 2015

Temperature Rises

Although no significant changes in SO2 or CO2 were recorded by the Mokuaweoweo gas and temperature monitors during April, scientists did note a temperature change.

Beginning around 03 April, fumarole temperature rose from ca. 79.5 deg C to approximately 83, by the end of the month. This the second such significant positive excursion since the station was installed in 2005, and the highest temperature recorded by the fumarole monitor, thus far. The last temperature event began in September 2014, with a low of 72.5 deg c, peaking at 79 deg in late November, before declining to 77 degrees in January.USGS Hawaiian Volcano Observatory – May 11, 2015