As the Memorial Day weekend arrives, many Hawaii residents will head for the beach. Others might use the long break to visit family and friends or go for a reflective hike in the mountains. Some may just set up the
As the Memorial Day weekend arrives, many Hawaii residents will head for the beach. Others might use the long break to visit family and friends or go for a reflective hike in the mountains. Some may just set up the barbecue and fill up the kiddie pool in the backyard.
It seems that Kilauea has also been making plans about what to do as summer unofficially begins. This “planning” process has the staff of Hawaiian Volcano Observatory watching with keen interest, especially during the last several months. To better understand what’s going on right now, let’s recap what the volcano did last summer.
At the beginning of August 2011, the lava lake within the Halemaumau Overlook vent at Kilauea’s summit was at its highest level since March 2011. The surface of the lake was only 250 feet below the Halemaumau Crater floor. Downstream along the east rift, the Puu Oo crater hosted a perched, circulating lava lake that was full to the brim, and the rest of the crater floor was buckling upwards as magma tried to squeeze up from below. The Puu Oo “pool” was so full it overflowed the crater rim to the southwest.
All this changed on Aug. 3, when the west flank of Puu Oo ruptured. This rapid unzipping resulted in a spectacular flood of about 2.5 million cubic meters of lava — equivalent to emptying about 1,000 Olympic-sized swimming pools — most of it in the course of an hour or so. The draining also caused both the floor of Puu Oo and the lake within the Halemaumau vent to drop about 260 feet over the next day. Kilauea’s 2011 pool season had officially closed — at least temporarily.
During the next month-and-a-half, the summit and east rift lava lakes refilled slowly, and Puu Oo began to overflow once again. On Sept. 21, though, a fissure abruptly opened on the east flank of Puu Oo, sending the flow toward the south. This flow progressed seaward in the ensuing several months, temporarily taking some of the pressure off Puu Oo.
By December, lava had cut through the Royal Gardens subdivision on its way to the ocean, but activity slowed by the end of 2011 and retreated upslope. Thus far in 2012, lava has worked its way slowly downslope again, burning forest and destroying the last inhabited house in Royal Gardens, but has not yet reached the ocean.
The reduction of pressure at Puu Oo and diversion of lava by the Sept. 21 flow haven’t quite kept pace with the magma supply rate feeding the eruption. At Kilauea’s summit, the lava lake within the Halemaumau vent has been rising fitfully, already surpassing the high lava mark it held last August. Summit surface deformation measurements show Kilauea continues to inflate as magma enters the system faster than it is able to leave it.
Recent seismicity indicates something might be up, as well. Several small earthquake swarms, focused at locations reaching from the upper east rift zone to just northwest of the summit caldera, have occurred since February. The nature of these earthquakes is commonly associated with subsurface plumbing adjustments, especially for those pathways that transport magma from Kilauea’s summit to the east rift eruption site.
What happens next with Kilauea’s ongoing summit and east rift eruptions is anyone’s guess. The Halemaumau overlook vent lava lake, at its highest measured level as of last week, is now dropping steadily in concert with an ongoing deflation-inflation cycle. Summit seismicity remains elevated. On the east rift, a slowly enlarging lava pond is perched at a level nearly even with Puu Oo’s crater rim.
One thing is clear: Kilauea has filled up the “pool” at Puu Oo. This might foreshadow — as it has several times in the past — an eventual structural failure at the cone that could send lava flows from its flanks. Further increases in upper east rift seismicity, however, might portend an eruptive breakout elsewhere.
Kilauea activity update
A lava lake within the Halemaumau Overlook vent during the past week resulted in nighttime glow visible from the Jaggar Museum overlook. The lake, which is normally about 260 to 380 feet below the floor of Halemaumau Crater and visible by HVO’s webcam, maintained high levels earlier in the week, equivalent to about 200 feet below the crater floor. In the later portion of the past week, the lava level steadily dropped with ongoing summit deflation.
On Kilauea’s east rift zone, surface lava flows were active on the pali and coastal plain over the past week. The flows on the coastal plain have made minor progress toward the ocean over the past week. On Tuesday, the coastal plain lava flows were approximately 0.4 miles from the water. As of Thursday, there was still no active ocean entry.
Visit hvo.wr.usgs.gov for detailed Kilauea and Mauna Loa activity updates, photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to askHVO@usgs.gov.
Volcano Watch is a weekly article and activity update written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.
