U.S. Geological Survey - Hawaiian Volcano Observatory
Kilauea - Eruption Summary - Hazards - History
The update below is current as of May 13, 1999. This extended update is changed about every 4 to 6 weeks; more frequent updates will be made when there are drastic changes in activity or when residential areas are threatened by lava flows.
The eruption of Pu`u `O`o continues to generate a variety of activity on the pali and coastal plain as lava travels from the vent through a lava-tube system to the ocean. Periodically, the supply of magma to the vent is cut off for short periods of time. The 23rd such interruption in the current eruptive episode 55 lasted for only about 33 hours beginning on May 4, but it was long enough for the steam plume at the entry area to stop and for a sluggish 6-week-old pahoehoe flow on the coastal plain to stagnate. When lava began flowing again through the tube system late on May 5, several small surface flows poured anew onto the pali and coastal plain. Lava finally reached the ocean through the preexisting tube system on May 7.
No significant changes have occurred recently at Pu`u `O`o. At the coastal entry area, however, the lava bench changes constantly as new land is created and then collapses into the ocean. Frequent explosions of varying intensity also hurl lava fragments onto the bench and atop the sea cliff.
This most recent pause in the eruption was very brief, beginning at about 1 p.m. on May 4 and ending at about 10 p.m. on May 5. The eruption resumed slowly, and as lava moved through the tube system, only a few sluggish flows broke out onto the pali and coastal plain.
Caption for photographs: The photographs above were taken about 12 hours after pause #23 had ended. Lava traveling from Pu`u `O`o through the tube system had not yet reached the ocean as indicated by the absence of a steam plume at the edge of the lava bench.
Caption for photographs: The photographs above show the leading edge of a slow-moving pahoehoe flow that broke out from the lava tube on May 6 about 1.8 km from the coast. Typical of pahoehoe flows, this one moved forward as lava spread across the ground in budding toes and small sheets. The flow inflated as lava continued to move through the main body of the flow. In the left-hand image, note the crack at the top of the flow in (to see this more clearly, see the med- or large-sized image). This crack formed when the top crust of the flow fractured because the molten interior of the flow was swelling or inflating with new lava.
Observations into the deep crater of Pu`u O`o` are not possible most of the time because of the thick plume of steam and sulfur dioxide gas rising into the atmosphere. The vent continues to release an average of about 2,000 tons of sulfur dioxide gas each day. Lava is sometimes visible in the northernmost pit on the crater floor (photograph above). When viewed on May 6, a small spatter cone was visible in this pit.
A series of strong explosions from the active lava bench on April 13 were likely related to the progressive collapse of the leading edge of the delta into the ocean. As the lava tubes were sheared off by the collapses, seawater gained access to the remaining tube system and a much larger than usual volume of lava was suddenly exposed to seawater. Both processes led to strong steam-driven explosions that hurled lava bombs and hot rocks into the air as high as 80 m and inland nearly 100 m from the bench's edge. These ballistics did not land behind the warning signs posted by the National Park Service, however, located about 90 m from the sea cliff above the bench.
USGS eyewitness account of the explosions. "When we arrived at the ocean entry at about 2 p.m., two plumes were rising from the edge of the active bench. The widest part of the bench was about 40-45 m in width (a few hours earlier, it was about 80 m wide). Starting just before 4 p.m. the western plume area began venting mainly steam from a hole (probably a skylight) just inland from the outer edge of the bench. The venting sounded like a jet engine. Then just after 4 p.m. explosions from this new vent hurled spatter into the air and formed bubble fountains as large as 10-15 m in diameter."
"This activity turned highly explosive within a few minutes, hurling spatter and rocks as high as 80 m (average height of spatter was between 50 and 60 m). Spatter and hot rocks from the explosions fell to the ground atop the sea cliff more than 75 m from the source. The explosive activity continued for about 90 minutes and then intermittently for the next few hours. One explosive episode caused lightning in the plume. When we arrived at our car parked 5 km away at the end of the Chain of Craters road, we found a thin layer of tiny brown flakes of glass from the exposions on the windshield."
This series of explosions and the continued collapse of new land at the ocean entry area clearly demonstrate the danger that results when lava enters the sea. Visitors to the entry area are advised to remain behind the warning signs posted by the National Park Service. Learn more about explosions, collapses, and hot water.
Lava broke out from the tube system on March 26 about 2 km from the ocean. The breakout fed a wide, slow-moving pahoehoe flow for the next 5 weeks. The flow had advanced to within about 700 m of the ocean when the supply of lava in the tube system was shut off by the pause on May 4. In the photograph above, the surface of the new pahoehoe flow is about 2 m below the top of the rise at its source.
Map showing area covered by lava flows emplaced during the Pu`u `O`o - Kupaianaha eruption between 1983 and February 8, 1999. Flows active between February 7 and February 8, 1999, are shown in pink. The tube delivers lava to the ocean a few hundred meters west of a prominent littoral cone (star) at Kamokuna (click map for a larger view of the map).