Six years is a blink of an eye in geologic time, but it can fly by for people, too. In a way, it doesn’t seem very long ago that the summit eruption began, with a small explosion that threw blocks around the Halemaumau Crater rim. On the other hand, so much has happened at the new vent that it is getting harder to remember what it was like when Kilauea Caldera was open to traffic and Halemaumau was quiet.
The summit eruption began March 19, 2008, following several months of increasing seismic tremor and gas emissions. A new crater, about 115 feet wide, formed that day on the wall of Halemaumau Crater. We informally call the new crater the “overlook” crater, as it formed directly below the closed visitor overlook. Over the next two years, the overlook crater enlarged dramatically because of frequent collapses of the overhanging crater walls. A handful of small explosions threw blocks and fresh spatter around the Halemaumau Crater rim. Lava was sporadically observed in the new crater during 2008 and 2009, but was very deep — about 656 feet below the floor of Halemaumau Crater.
The eruption changed in February 2010, when a more persistent lava lake appeared in the crater and slowly rose to higher levels. The lake disappeared only once, when it drained for a week during the Kamoamoa eruption in March 2011.
The lake today is quite large, about 660 feet long by 525 feet wide, making it one of the largest lava lakes on Earth. The lava level has been fairly shallow over the past year, about 100 to 200 feet below the floor of Halemaumau. Normally, lava upwells at the north margin of the lake and quietly migrates toward the south margin, where it sinks back into the magmatic system. A persistent spattering source is often present in the southeast portion of the lake, throwing spatter up to 65 feet. The gas plume is normally carried toward the southwest in the tradewinds, but can drift toward other parts of the island when winds shift.
By closely monitoring the eruption, we have learned a number of interesting things. For instance, geophysical data indicate that the lake has a very low density, close to that of water, because of abundant gas bubbles in the lava. We also know that the lava level fluctuates nearly perfectly in tune with the pressure of the summit magma chamber, meaning that the lava lake acts as a kind of liquid pressure gauge. Moreover, a number of indicators measured over the past few years — including lava level, gas emissions and lava chemistry — reaffirm that an efficient magmatic connection exists between the summit and east rift zone vent at Puu Oo.
The eruption has also been a draw for National Park visitors, who can view the strong glow from Jaggar Museum. For residents of the Big Island, the glow is another reminder of how close we all live to volcanic activity.
But as much as the eruption has enhanced scientific understanding, or boosted tourism, this is little consolation for those adversely affected by the persistent vog. The primary hazard of this eruption has been the long-term elevated gas emissions that are carried downwind into residential and agricultural areas. Vog is a respiratory irritant and can aggravate existing respiratory problems, such as asthma. Farming and ranching, particularly in the Ka‘u district, have been hit hard. The increased amount of sulfur dioxide can cause chemical burning of cultivated plants and faster corrosion of metal fencing that is essential for ranching.
When will the eruption end? There are no signs of any imminent change in the eruption, and recent activity has been remarkably steady. We have to look at Halemaumau’s history to gain longer-term insight into the future. There was lava lake activity at the summit from at least 1823 to 1924, with most of it focused around Halemaumau. This history shows that Halemaumau has the potential for eruptive activity lasting decades. Now entering its seventh year, the current eruption may turn out to be a repeat performance of Halemaumau’s sustained lava lake.
More details on the summit eruption can be found online in a new fact sheet at pubs.usgs.gov/fs/2013/3116.
Kilauea activity update
A lava lake within Halemaumau produced nighttime glow visible via HVO’s webcam during the past week. The lava level was fairly steady over the past week, and was between 130 and 150 feet below the rim of the overlook crater.
On Kilauea’s east rift zone, the Kahaualea 2 flow continued to be active northeast of Puu Oo. This week the active flow front was 5 miles northeast of the vent on Puu Oo. Webcam images indicate that small forest fires are continuing.
One earthquake was reported felt on Hawaii Island in the past week. A magnitude 3.5 earthquake occurred March 9, and was located 3 miles southwest of Volcano Village at a depth of 1.7 miles.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.