July 12, 2007
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
?It?s like d?j? vu all over again!?
Many people are watching the filling of Pu`u `O`o crater live via a webcam on the rim (http://hvo.wr.usgs.gov/cam/). Since July 4, traffic to our web site has quadrupled, and we have received several appreciative comments about the availability of the views.
The process of crater filling and lava lake development has been a frequent occurrence at Kilauea volcano. A lava lake existed within Halema`uma`u crater for at least 100 years before it drained prior to an explosive eruption in 1924. Halema`uma`u has hosted lava lakes since, and the most recent in 1967-1968 left the prominent bathtub ring visible in the crater today. Lava lakes occupied craters during the Mauna Ulu eruptions between 1969 and 1974 and during the Kupaianaha phase of the current eruption from 1986 to 1992.
Most relevant to the current activity at Pu`u `O`o is the lava lake that formed in Pu`u `O`o crater in early 1997. The 1997 sequence started on January 29, with swarms of small shallow earthquakes occurring in the upper east rift zone; several of the quakes had magnitudes greater than 3 and were felt in nearby communities. Within hours, the crater at Pu`u `O`o drained completely and collapsed to a depth of over 200 m (650 feet). About five hours later, a 22-hour eruption occurred between Napau crater and Pu`u `O`o that HVO designated episode 54 of the current eruption.
Twenty three days after the collapse, lava re-emerged and began to fill the Pu`u `O`o crater, forming a lava lake. Almost two months later, on March 28, when lava stood about 50 m below the east crater rim, lava emerged outside the crater in one of several collapse pits on the west flank. In May, several brief eruptive pauses occurred. On June 16, the crater filled and overflowed through the west gap. Later overflows went over the east rim.
The only surface lava activity on the flow field in 1997 between the end of January and the end of June was located immediately around Pu`u `O`o; no flows made it as far as Pulama pali in that time. The first flow to reach the ocean did so on July 3, 1997.
The beginnings of the 1997 sequence were very similar to the sequence of events that started on Father?s Day, June 17, 2007, with an earthquake swarm in the upper east rift zone. A small eruption occurred sometime during the night of June 18, at least 40 hours after the swarm started. Incandescence was last seen in a collapsing Pu`u `O`o crater on June 18. Lava re-emerged on July 2 and started filling the crater, which had collapsed to at least 100 m (325 feet) below the rim.
As of this writing on July 12, lava levels continue to rise and are estimated at between 40 and 50 m below the east rim. Over the last few days, the lava has formed levees confining the lake well inside the crater?s walls. The levees continue to be built higher by periodic overflows of the lake.
What will happen next? Based on the history of the events following episode 54, we expect that lava will emerge somewhere on the flanks of Pu`u `O`o cone or continue to fill the crater to a point where overflows are possible. The southwest flank of Pu`u `O`o cone has been undermined by lava for more than a decade and is the most likely location for the next emergence of lava outside the cone. If the level of lava in the lake continues to rise and an underground outlet is not found, the lake may eventually overflow its levees and, ultimately, the crater.
If lava makes it outside the cone, when might lava flows make it down to the coastal plain where visitors can again enjoy them? Again, based on the episode 54 history, this may take months. New flows and tube systems that are capable of transporting the lava to the ocean must form first, and there is no indication that this process has started yet.
But it?s not over. We are, again, guided by Yogi Berra?s words, ?It ain?t over till it?s over.?
This past week, activity levels at the summit of Kilauea Volcano remained low. Seismic tremor levels remain low; earthquakes continue to be concentrated in the upper east rift zone. The summit caldera is again inflating.
Early in the morning on July 2, Pu`u `O`o reawakened and began to intermittently erupt lava from two vents, one vent in the center of the crater floor and the other in rubble below the northeastern wall of Pu`u `O`o crater. Lava continues to erupt from these two vents, and the level of the lava lake is still rising. While the western vent was initially the most active, the eastern vent took over last weekend and is now the dominant vent.
Though much of the crater floor has now been resurfaced by the new lava, the surface of the pond is still about 40-50 meters lower than the crater floor prior to its collapse in mid-June. The lava pond within Pu`u `O`o crater has provided spectacular viewing, especially at night, via the Pu`u `O`o webcam (http://hvo.wr.usgs.gov/cam/). Lava has not yet appeared outside of Pu`u `O`o cone, though, with the rapid rate of refilling, this may not be the case for long.
One earthquake beneath Hawai`i Island was reported felt within the past week. A magnitude-2.3 earthquake occurred at 10:40 a.m. on Friday, July 6, and was located 1 km (1 mile) northeast of Pa`auilo at a depth of 10 km (6 miles).
Mauna Loa is not erupting. No earthquakes were located beneath the summit. Extension between locations spanning the summit, indicating inflation, continues at steady, slow rates, which have slowed further since May 2007.
Updated: July 16, 2007 (pnf)