Volcano Watch — Tuning in to Mauna Loa

Our Hawaiian Volcano Observatory (HVO) Web site (http://hvo.wr.usgs.gov/multimedia/main.html) also provides snapshots of the activity - sometimes rather spectacular as lava makes its way downslope and enters the ocean.

Away from the hot stuff, a lot of our work this summer is focused on Mauna Loa. With our present monitoring capabilities, we are able to appreciate Mauna Loa as an active, though not presently erupting, volcano. With data from Global Positioning System (GPS) stations, we continue to measure the increase in distance that started in mid-2002 across Mauna Loa's summit caldera. We interpret this increase as showing a possible magmatic inflation of the caldera region. Small earthquakes continue to be recorded from beneath Mauna Loa, though not in patterns necessarily associated with imminent eruption.

As we anticipate Mauna Loa's next eruption, HVO's staff is working to bolster and upgrade some of our key monitoring capabilities. This week brought the installation of a new, continuously operating GPS station on Mauna Loa. Data from this station will be transmitted to HVO and incorporated into data-processing streams that calculate positions for all of HVO's permanent GPS stations. This information can then be used to infer possible changes in Mauna Loa's surface shape that could result from earthquakes or magma movement leading to eruption. By summer's end, a total of 7 new GPS stations will be installed and their data added to our geodetic analysis and monitoring routines.

Repairs and upgrades are also being performed to a number of Mauna Loa seismographic stations. Because information is derived from seismic waves radiated by the earthquakes, a seismic station need not be on Mauna Loa to record Mauna Loa earthquakes. However, determination of earthquake depth is greatly improved if recording seismic stations lie directly above the earthquake. Mauna Loa stations are critical to precisely calculating depths of Mauna Loa earthquakes. These stations will certainly help in recognizing whether there is a systematic shallowing of earthquake activity that could hint at impending eruption.

Monitoring a volcano's gas emissions also provides insights into its magma system. This includes changes in magma composition, changes in magma supply rate, and changes in the pathways that the emitted gases follow due to magma movement. Continuous and remote monitoring of volcanic gas emissions at Kīlauea have demonstrated the value of such measurements. Gas monitoring sites will be developed on Mauna Loa to afford similar capabilities there.

Beyond this summer, other improvements to our Mauna Loa monitoring networks will continue. Our goal is to have our upgraded monitoring tools in place and mastered well in advance of Mauna Loa's next eruption. This would provide us with a baseline of observations while the volcano is relatively quiet and thus greatly contribute to our observation and understanding of how our volcanoes reawaken.

Volcano Activity Update

Eruptive activity at Pu`u `O`o continues. The Banana flow, which breaks out of the Mother's Day lava tube a short distance above Pulama pali, is entering the ocean off the 2002 Wilipe`a lava delta. The national park has marked a trail to within a short distance of the active lava delta, and thousands have been enjoying the show. In addition, lava has been visible between Pulama pali and Paliuli for the past three weeks, and on occasion lava cascades down Paliuli to the coastal flat. Eruptive activity in Pu`u `O`o's crater is weak, with sporadic minor spattering and small flows.

One earthquake was reported felt on the island during the week ending June 30. Residents of Glenwood, Papa`aloa, and Papa`ikou felt a magnitude 2.8 earthquake at 4:09 p.m. on June 26. The earthquake occurred 3 km (2 miles) east-southeast of Pepe`ekeo at a depth of 29 km (18 miles).

Mauna Loa is not erupting. The summit region continues to inflate slowly. Seismic activity remains low, with only 1 earthquake located in the summit area during the past week.