June 10, 2004
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
Lava meets the sea-Enjoy the park but don't sit on the bench
Lava flowing from Kilauea's ongoing eruption finally made its way to the ocean once again a couple of weeks ago. And for the first time in nearly a year, everyone -- from curious park visitors and staff, to intent photographers, to nerdy (and intent) volcanologists -- have been treated to the enrapturing experience of seeing liquid rock encounter liquid ocean.
While making observations at the coastal entry, those of us in the last group of observers are reminded of the unusual hazards posed by the interaction of hot lava and cool seawater. Nearly a half dozen people have died at the coastal entry in the past 10 years and scores more injured. Being prepared for the hazards can help us all to avoid becoming "statistics." The U.S. Geological Survey, in cooperation with the National Park Service, has prepared a useful Fact Sheet on viewing Hawai`i's lava safely, #152-00, available at the Kilauea Visitor Center in the park. You can also find it on the web at http://geopubs.wr.usgs.gov/fact-sheet/fs152-00/.
There are two types of hazards discussed in the Fact Sheet that are especially important to consider right now as the new coastal entry evolves: collapse of the lava delta or "bench" and hazardous conditions associated with the coastal entry steam plume.
New land begins to form when molten (2,120oF, 1,160oC) lava encounters the comparatively cool seawater and disintegrates into rubble. The rubble piles up at the edge of the sea eventually gets plated over with more lava, and forms a delta. The actively growing part of the delta is a bench. And although this "bench" is located in a park, it is definitely not one you want to sit on -- or go near for that matter! In a cyclic process, part of the unstable bench collapses through ocean-wave erosion and then is rebuilt and extended a bit by the successive addition of fresh lava, thus continuing the build-erode-rebuild cycle. Eventually the active bench may substantially extend the size of the coastal entry delta.
A poignant hazard associated with new land formation involves being on, or near a delta when a bench collapse occurs. These collapses happen without warning and sometimes result in several acres of new land catastrophically breaking off into the sea in a matter of seconds. Literally all hell breaks loose. As the land slides into the ocean, the ocean responds by sending huge waves up over the shoreline that encounter, among other things, molten lava. Depending upon whether the lava is on the surface or in lava tubes, this interaction can produce anything from superheated steam clouds at ground level to explosions that hurl hundred pound rocks tens of meters (yards). Coastal entry visitors are implored to stay inland of the national park's guard rope perimeter. Stay alert, stay off the new delta, and, if you hear unusual sounds, move inland quickly.
A subtler hazard posed by molten lava entering the ocean involves the evaporation of seawater to dryness and the associated series of chemical reactions that produce a dense white "laze" plume comprised of a suspended mixture of hydrochloric acid, concentrated seawater steam, and volcanic glass fragments. Hydrochloric acid (HCl) is toxic and extremely corrosive. It causes skin and eye irritation and can also cause breathing difficulties, as well. The mixture of tiny glass fragments, HCl, and seawater raining out of laze plumes has the stinging and corrosive properties of dilute battery acid.
Several years ago, a pair of visitors who ventured too near the coastal entry was found dead, apparently burned by acid-laced steam on the lava bench. Other people have been severely scalded by being near rogue waves washing over molten lava. Avoid being under, or close to, the coastal entry plume. Wear long pants and shirts, and bring plenty of water and a flashlight for each person. Watch for wind shifts, and if you're caught off guard, put on a hat and raingear and rinse off any precipitation that gets on you as soon as possible.
While the foregoing advice may seem like overkill, it is important for all of us to remember that the coastal part of the park is certainly a wonderland but IS NOT Disneyland. With the right precautions taken, we can all witness this most amazing process of the formation of new land. It is enthralling to see it again for the first time!
Eruptive activity at Pu`u `O`o continues. The Banana flow, which breaks out of the Mother's Day lava tube a short distance above Pulama pali, is entering the ocean in two areas off the 2002 Wilipe`a lava delta. In addition, lava has been visible between Pulama pali and Paliuli for the past week. The national park has marked a trail to within a short distance of the end of the flow, and thousands have been enjoying the show. Eruptive activity in Pu`u `O`o's crater is weak, with sporadic minor spattering and small flows. The upper part of the PKK (Kuhio) flow south of Pu`u `O`o has also been active and creating bright glow most nights.
Four earthquakes were reported felt on the island during the week ending June 9. A magnitude 3.2 earthquake was felt at Hale Pohaku and Kea`au at 2:19 p.m. June 3; it was located 6 km (4 miles) south-southwest of Pu`u `O`o at a depth of 10 km (6 miles). Two earthquakes within 22 seconds of one another were felt at HVO and Volcano Village at 12:33 p.m. June 4. The first had a magnitude of 3.2 and occurred 5 km (3 miles) south of Volcano at a depth of 3 km (2 miles). The second, of magnitude 3.4 took place 4 km (2 miles)southeast of Kilauea's summit at the same depth. The last felt earthquake was the largest of the week, a magnitude 3.6 at 2:06 June 4 located 15 km (10 miles) southeast of Pahala at a depth of 35 km (22 miles); it was felt in Hawaiian Ocean View Estates, Honaunau, and Kona Paradise.
Mauna Loa is not erupting. The summit region continues to inflate slowly. Seismic activity remains low, with only 4 earthquakes located in the summit area during the past week.
Visit our website (hvo.wr.usgs.gov) for daily volcano updates and nearly real-time earthquake information.
Updated: July 15, 2004 (pnf)