Volcano Watch — HVO scientists are closely watching Kīlauea—and Mauna Loa

The USGS Hawaiian Volcano Observatory (HVO) is closely tracking the Kīlauea lava flow, which is threatening residential areas in the Puna District of the island. We are also maintaining situational awareness of the far-away eruptions while other scientists within the U.S. Geological Survey's Volcano Hazards Programs provide assistance to Icelandic and New Guinea colleagues.

HVO scientists also continue to monitor the five other potentially active volcanoes on and around the Islands of Hawai‘i and Maui—Mauna Loa, Hualālai, Mauna Kea, Haleakalā, and the submarine volcano Lō‘ihi. With the exception of Mauna Loa, all of these volcanoes have been quiet over the past several years.

Mauna Loa, the most voluminous active volcano on Earth, has erupted twice in the past 40 years—in 1975 and 1984—and a large intrusion of magma swelled its summit (but did not erupt) in 2002–2009. During the "quiet" period after that intrusion, HVO took the opportunity to increase the sensitivity of our monitoring instruments on Mauna Loa.

Starting in 2009, HVO's monitoring networks on Hawaiian volcanoes were significantly upgraded with funding from the American Reinvestment and Recovery Act. As of 2012, our monitoring networks are capable of detecting changes in volcanic processes that are much smaller than could be detected by networks installed during the past two eruptions of Mauna Loa in 1975 and 1984.

That upgrade has already paid off. Beginning in March 2013, and continuing into 2014, HVO's networks have detected small sporadic swarms of earthquakes deep beneath the west flank and summit of Mauna Loa. These swarms are located in the same general area as earthquake swarms that preceded the 1975 and 1984 eruptions, but the 2013–2014 earthquakes have been significantly weaker than those recorded in 1975 and 1984. Many of the most recent swarms were followed by shallower earthquakes at the summit of Mauna Loa and can be seen on HVO's interactive earthquake pages (http://hvo.wr.usgs.gov/seismic).

Prior to the 1975 and 1984 eruptions of Mauna Loa, HVO detected dozens of magnitude-3 earthquakes and a handful of magnitude-4 earthquakes 1.5 or more years before the eruptions started. The strongest earthquakes detected beneath the west flank of Mauna Loa in 2013–2014 have been weaker than magnitude-3. While the current activity is smaller in magnitude, it is clear that some of the same volcanic processes may be at work.

Since 2009, the southeast flank of Mauna Loa has been slowly moving southeastward and there have been no signs of magma intrusion beneath the summit. Subtle changes in the deformation pattern began in the spring of 2014. HVO's GPS network started to detect weak inflation beneath the summit, the same area that inflated during the period 2002–2009. The amount of inflation detected so far in 2014 is very small compared to previous inflations.

While we can definitely detect and monitor these weak signals within Mauna Loa, they do not yet indicate that an eruption is necessarily coming. The recent changes are not yet equivalent to those observed before the 1975 and 1984 eruptions, but because we are able to better resolve these early signals, we are closely watching them. Should they increase in intensity or start to change at a more rapid rate, HVO will elevate the Alert Level Code for Mauna Loa to indicate its relative state of unrest and whether or not it may be headed toward an eruption.

Given its current level of activity, updates for Mauna Loa are posted monthly on the HVO website and can be viewed at http://hvo.wr.usgs.gov/activity/maunaloastatus.php. Should Mauna Loa activity increase, updates will be posted more frequently.

An important reminder about Kīlauea Volcano's ongoing eruption: You can track the current lava flow activity through HVO's website. Daily eruption updates are posted every morning, and new maps and photos are posted after every HVO overflight of the lava flow. You can also call 808-967-8862 to hear the eruption update.

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Volcano Activity Update

The summit lava lake within Halema‘uma‘u Crater produced nighttime glow that was visible via HVO's webcam over the past week. The lava lake level ranged from 50 to 65 m (165–215 ft) below the rim of the Overlook crater.

On Kīlauea Volcano's East Rift Zone, the June 27th lava flow from Pu‘u ‘Ō‘ō remained active. The tip of the flow was 13.3 km (8.3 mi) from the vent and 1.2 km (0.7 mi) from the east boundary of the Wao Kele o Puna Forest Reserve as of September 4 (the time of this writing). Within the Pu‘u ‘Ō‘ō crater, glow was visible above several small lava ponds and outgassing openings in the crater floor.

No earthquakes were reported felt during the past week on the Island of Hawai‘i.