Volcano Watch — Murky Crystal Ball Suggests Potential for Voggy Future at Kīlauea

High sulfur dioxide flux can be expected from the summit of Kīlauea any time there is an eruption there. An eruption brings up fresh magma that contains dissolved SO₂. When that magma reaches a shallow depth, the SO₂ boils off and gets into the air. That is what happens during an eruption. There is no way around this.

In early January (the exact date is debated), the SO₂ flux from Halema`uma`u became so high that some of us think an underground eruption began. The pressure on the magma was the same as, or not much greater than, atmospheric pressure, and SO₂ boiled off like mad, just as during any observable eruption at the ground surface. Probably spattering into one or more underground cavities was associated with this gas loss, though we didn't see any direct evidence for spatter until March 23, when some reached the surface. All of the details are debatable among HVO scientists, but the bottom line is that the high SO₂ flux is what we would expect from a summit eruption. While true that the current SO₂ flux is higher than non-eruptive background, it is not higher than eruptive background, which is what we are in now.

So, the question for the future is how long will the current Halema`uma`u eruption last? Of course we don't know, but we can look at the past to see how long previous Halema`uma`u eruptions were. The record for the past 185 years, since William Ellis visited the summit in 1823, is not perfect but is good enough for our purposes.

The summit was almost continuously active for 100 years, from 1823 to early 1924; since then, it has been active for a total duration of about 1.3 years. So, the summit has been erupting for 101.3 years of the past 185 years, about 55 percent of the time. Let's reduce that figure to 50 percent to account for possible brief pauses in the 19th and early 20th centuries.

The time distribution of the activity has been very uneven, nearly 100 percent of the time between 1823 and 1924 and only 1.5 percent of the time afterward. Since 1924, only three Halema`uma`u eruptions have lasted longer than 1 month: 33 days in 1934, 136 days in 1952, and 251 days in 1967-68. The current eruption has lasted, arguably, more than 140 days and, inarguably (since March 23, when spatter arrived at the surface), 60 days. In other words, the current eruption is now the second or third longest Halema`uma`u eruption since 1924.

If you've followed the numbers, you can see that Halema`uma`u's eruptions have either lasted essentially for several decades (1823-1924) or less than a year. Those are the times that the historical record would suggest we would have to put up with high SO₂ flux from the summit. Now you can see why the crystal-ball picture mentioned earlier is not pretty. The current eruption has already surpassed all but the longest eruptions in the past 185 years, and the historical record suggests it could continue for decades. If so, that would mean a voggy future.

Fortunately there are many uncertainties in our crystal-ball gazing. Among them is the question of how long the Pu`u `O`o eruption will continue, because it is a major contributor to the current vog problem. If it ends soon, vog would be lessened. Another uncertainty is that we really don't know why Halema`uma`u eruptions last as long as they do. This is the 21st century, not the 19th, and is there any reason to think that volcanic conditions are as favorable for a long-lasting eruption now as they were then? And there are many more uncertainties that make our crystal ball nearly opaque. The bottom line remains, however, that Halema`um`u once erupted almost continuously for 100 years and must have produced high SO₂ flux and vog. We can't rule out this scenario returning to haunt us, and it has, at least in our thoughts.

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Volcano Activity Update

Kīlauea Volcano continued to be active at two locations: a vent in Halema`uma`u Crater is erupting elevated amounts of sulfur dioxide gas and very small amounts of ash. The resulting high concentrations of sulfur dioxide in downwind air have closed the south part of Kīlauea caldera and produced occasional air quality alerts in more distant areas, such as Pahala, during trade wind cycles and communities adjacent to Hawai`i Volcanoes National Park during kona wind periods. Pu`u `O`o continued to produce sulfur dioxide at even higher rates than the vent in Halema`uma`u Crater. Trade winds tend to pool these emissions along the West Hawai`i coast. Kona winds blow these emissions into communities to the north, such as Mountain View, Volcano and Hilo.

The new gas vent observed last week inside Pu`u `O`o has remained active, with no notable change. Lava from the 2007 Thanksgiving Eve Breakout (TEB) flow, erupting from fissure D of the July 21 eruption, continues to flow through what remains of the Royal Gardens subdivision and across the coastal plain to the ocean within well-established lava tubes. Over the past week, the Waikupanaha ocean entry has remained active, with occasional small explosions and a vigorous plume.

The public should be aware that lava deltas could collapse at any time, potentially generating large explosions in the process. This may be especially true during times of rapidly changing lava supply conditions, as have been seen lately. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves that are suddenly generated during delta collapse; these beaches should be avoided. In addition, the steam plumes rising from the ocean entries are highly acidic and laced with glass particles. Check the County of Hawaii Civil Defense Web site or call 961-8903 for information on public access to the coastal plain and ocean entry.

Mauna Loa is not erupting. Three earthquakes were located beneath the summit. Continuing extension between locations spanning the summit indicates slow inflation of the volcano.

Two earthquakes beneath Hawai`i Island were reported felt within the past week. A magnitude-1.9 earthquake occurred at 7:23 a.m., H.s.t., on Friday, May 30, 2008, and was located 2 km (1 mile) southwest of Pu`ulena Crater in Puna at a depth of 3 km (2 miles). A magnitude-2.6 earthquake occurred at 6:29 p.m. on Tuesday, June 3, and was located 6 km (4 miles) north of Ka`ena Point at a depth of 8 km (5 miles).

Visit our Web site (http://hvo.wr.usgs.gov) for daily Kīlauea eruption updates and nearly real-time Hawai`i earthquake information. Kīlauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov. skip past bottom navigational bar