[ VOLCANO WATCH ]
A few days before the long Labor Day weekend, Hawaii County officials closed the newly opened lava-viewing road because a surface lava flow threatened to cross it. Fortunately, the lava flow stopped just after it crossed the road, and the road reopened a few days later. Lava covering viewing roads
often comes from ruptured tubesERUPTION UPDATE
For some it was a revelation that this could happen so soon. Others realized it was business as usual.
Highway 130 and later roads laid along its course have been covered many times in the last 15 years. The previous version of the road was carved out of 1986-1991 vintage lavas to allow residents of Royal Gardens access to their properties.
Over the last several years, more and more of that road has been covered by progressive eastward expansion of the Episode 55 flow field. The most recent surge of activity ended in May 2001, with the establishment of an ocean entry and the lava tube that feeds it.
Of course, viewing the spectacle of lava entering the ocean is the whole reason that the road was improved and reopened. That entry is made possible by an established lava tube bringing a relatively constant supply of lava from Pu'u 'O'o to the ocean.
Surface lava flows almost always originate from a rupture or blockage of a lava tube. With the ocean-entry tube only 2,300 feet from the end of the access road and the start of the trail to the viewing area, some might expect frequent surface flows to threaten the road and trail.
The Labor Day surface flow was not the first to break out so close to the road in the last few months, but it was easily the biggest. For a few days prior to closure of the viewing area, the flow was advancing more than 820 feet a day. The area was closed by Hawaii County Civil Defense when the flow was less than 820 feet from the road.
The Labor Day flow started in a portion of the lava tube, almost 1.2 miles up-tube of the ocean entry, from where several small flows started in the last four months. Most last for a few days before stagnating.
The Labor Day flow was active for about two weeks. Since then, there were other small surface flows and another large one that flowed west and away from the lava-viewing road.
What makes some sections of a lava tube more prone to ruptures that produce surface flows? In some tube systems, the tube is weakest at sharp bends or abrupt changes in width.
In the case of the ocean-entry tube, we believe that the tube roof is thin in the areas of persistent ruptures. We know that because that same portion of the tube was unusually visible in our aerial infrared scans conducted in May right after the tube formed.
Infrared scanning is a method of visualizing heat; if the tube roof were thin, it would allow lava heat to be conducted more easily to the surface than in an area where the tube roof is thicker.
How much lava pressure would need to be exerted to break through the tube roof? That is unknown. However, local construction industry students know that some ancient tube roofs have buckled when a 54-ton D-9 bulldozer rolls over them.
Yet many tubes survive. We will not be surprised if surface flows threaten the viewing area a few times a year. In fact, such occurrences should be viewed as another kind of lava-viewing opportunity rather than a threat, especially in light of the real threats we were all recently forced to acknowledge.
Eruptive activity of Kilauea Volcano continued unabated at the Pu'u 'O'o vent during the past week. Lava moves away from the vent toward the ocean in a network of tubes and descends Pulama pali in several separate tubes. [ERUPTION UPDATE]
Pu‘u ‘O‘o vent offers
visitors visual treatsThe two surface flows reported on the pali last week are now crusted over. Many surface flows are active on the coastal flats, and one is within 0.3 miles of the ocean in the area west of Kamokuna. Lava also continues to enter the ocean in the area east of Kupapau and provides visitors to the viewing area a great show.
The public is reminded that the bench of the ocean entry is very hazardous, with possible collapses of the new land. The steam cloud is extremely hot, highly acidic and laced with glass particles.
Swimming at the black-sand beach of the bench can be a blistering or deadly venture.
There were no earthquakes reported felt during the week ending on Sept. 27.
The Star-Bulletin introduces "Volcano Watch," a weekly column written by scientists at the U.S. Geological Survey's Hawaiian Volcano Observatory. The writers will address the science and history of volcanos in Hawaii and elsewhere. It also will include a short, separate update on eruption activity on the Big Island. VOLCANO WATCH