Notice anything unusual about last summer’s sunsets and sunrises?
The colors were slightly different. While they didn’t change enough to grab the world’s attention, as Krakatoa did when it lit up London’s skyline in 1883, they were still very pretty:
I think the paintings of brilliant sunsets shown here are actually from that Krakatoa eruption, not Tambora’s in 1815.
Anyway, here is one of the two paintbrushes that Nature used for those artistic effects:
— Dan Lindsey (@DanLindsey77) August 3, 2019
That’s from Ulawun volcano, in Papua New Guinea, during a three-month-long eruption that began with a subplinian blast that lofted ash more than eight miles into the sky on June 26, 2019.
It does resemble a paintbrush a little. But that’s not shattered volcanic glass and pulverized igneous rock. It’s gas — this satellite can “see” the emission of sulfur from Ulawun.
Unusual colors in a volcanic sunset develop from a plume’s sulfur content.
And like many volcanoes in the Bismarck Archipelago, Ulawun has a lot of this element in its magma.
Ulawun’s 2019 eruption seeded the stratosphere to produce sulfate aerosols. But so did that of another high-sulfur volcano: Raikoke, much farther to the north.
Raikoke went off just four days before Ulawun did. Its VEI 4 eruption is probably the one responsible for light effects in the Northern Hemisphere during the summer and fall of 2019. Ulawun is closer to the Equator and therefore is the more likely culprit behind colorful changes in twilight and dawn skies over the tropics and Southern Hemisphere. (Kloss et al)
Fortunately neither eruption seems to have affected the stratosphere very much. (Vernier et al)
But Ulawun, not Raikoke, is a Decade Volcano.
Look at the volcano’s shape in the image at the top of the page.
While a different volcano rises in the background, everything we see in the foreground is Ulawun, including that jagged edge on the left (the south flank).
Such a feature usually means that a flank collapse happened in the past, sort of like the one at Mount St. Helens in 1980.
This is not a good thing to see on such an explosive, steep-sided volcano, especially one that’s well over a mile high and sits close to the shore so its debris can hit the sea at high speed.
Japan’s worst volcanic disaster was a tsunami caused by a collapse event like this at Unzen in the 18th century.
And the dome that collapsed there wasn’t anywhere near the size of Ulawun volcano!
Indeed, while volcanologists were holding a Decade Volcano workshop about Ulawun in 1998, a big earthquake struck nearby, causing 13-foot-high tsunami waves that killed more than 1600 people and devastated the area. (IAVCEI Workshop)
That was a seismic event, unrelated to any eruption. However, a cone collapse like the ancient one that scarred Ulawun could trigger a similar tragedy in the region.
In addition, local people face other dangers from the volcano’s frequent eruptions.
While Brown et al. list no fatalities at Ulawun in their comprehensive database, it causes much social and economic disruption, as this 2019 news video shows:
NASA issued a disaster report on the 2019 eruption; the accompanying picture, from Reuters, looks terrifying!
Volcanologists also report that, since the 1970s, Ulawun’s frequent eruptions have become much more intense than those during the previous 100 years.
The largest ones have even reshaped Ulawun’s summit through lava flows and pyroclastic density currents.
There’s obviously a potential for big trouble from Ulawun. It could happen at any time.
To make matters worse, experts know very little about this remote Melanesian volcano.
Ulawun therefore was an ideal Decade Volcano candidate.
Unfortunately, this didn’t lead to hoped-for breakthroughs, though monitoring of Ulawun has continued through the Rabaul Volcano Observatory as well as with satellite surveillance.
This monitoring did help authorities call an evacuation of thousands of local residents in late 2000, just before Ulawun had its first VEI 4 eruption (as listed by the Global Volcanism Program).
It was the only time in 75 years that volcano monitoring had contributed to an evacuation anywhere in Near Oceania. (Johnson and Ripepe)
However, Decade Volcano project plans were hindered by two major events (European Volcanological Society; Michigan Tech):
- A double eruption at another volcano on the island. This destroyed Rabaul, the provincial capital of East New Britain Province. Ulawun is in West New Britain Province, but the huge disaster affected everyone.
- Civil service reforms and cutbacks in the late 1990s limited the development of hazard maps and a Ulawun monitoring network.
5.05° S, 151.33° E, on Kimbe Bay in West New Britain Province, Papua New Guinea. The GVP Volcano Number is 252120.
Per the Global Volcanism Program website:
- Within 5 km (3 miles): 30
- Within 10 km (6 miles): 1,801
- Within 30 km (19 miles): 10,577
- Within 100 km (62 miles): 61,018
Stage 1 alert, per the Rabaul Volcano Observatory via the Global Vocanism Program bulletin for January 19 to February 4, 2020.
- Eruption styles: Per Michigan Tech, Ulawun erupts in a variety of ways, including purely explosive (McCormick et al. describe recent ones as violent Strombolian eruptions); explosive with lava flows; magma-water (phreatomagmatic) explosions; lava flows from either the summit or a flank vent; and pyroclastic flows, which may be the biggest hazard to people near the volcano. Lahars (mud flows) are a problem here, as well.
- Biggest recorded event: Ulawun had a VEI 4 eruption in September 2000; the Global Volcanism Program doesn’t list a VEI number for the 2019 eruption, but that might have been a VEI 4, too, based on the height of the eruptive column and the event’s duration.
- Most recent eruption: 2019.
- Past history: See the GVP for details. Since Europeans came to the area in the 1700s, Ulawun has had more than 20 eruptions.
The Rabaul Volcano Observatory, though I cannot find a working online link to this other than Facebook.
It is part of the Geological Survey of Papua New Guinea and associated with the Department of Mineral Resources. (IAVCEI Workshop)
Featured image: Wally Johnson (Australia Bureau of Mineral Resources) via the Global Volcanism Program.
Brown, S.K.; Jenkins, S.F.; Sparks, R.S.J.; Odbert, H.; and Auker, M. R. 2017. Volcanic fatalities database: analysis of volcanic threat with distance and victim classification. Journal of Applied Volcanology, 6: 15.
Cas, R. A. 2019. IAVCEI: from small beginnings to a vibrant international association. History of Geo-and Space Sciences, 10(1): 181-191.
European Volcanological Society (SVE). n. d. Decade volcano program 1990/2000. http://www.sveurop.org/gb/program/program.htm
Global Volcanism Program. 2000. Report on Ulawun (Papua New Guinea) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 25:8. Smithsonian Institution. https://volcano.si.edu/showreport.cfm?doi=10.5479/si.GVP.BGVN200008-252120
___. 2000. Report on Ulawun (Papua New Guinea) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 25:11. Smithsonian Institution. https://volcano.si.edu/showreport.cfm?doi=10.5479/si.GVP.BGVN200011-252120
___. 2020. Ulawun. https://volcano.si.edu/volcano.cfm?vn=252120 Last accessed April 21, 2020.
IAVCEI Workshop on Ulawun Decade Volcano, Papua New Guinea. 1998. Volcanic Cone Collapses and Tsunamis: Issues for Emergency Management in the Southwest Pacific Region. https://www.adrc.asia/management/PNG/Ulawun%20Decade%20Volcano.html
Johnson, J. B., and Ripepe, M. 2011. Volcano infrasound: A review. Journal of Volcanology and Geothermal Research, 206(3-4): 61-69.
McCormick, B. T.; Edmonds, M.; Mather, T. A.; and Carn, S. A. 2012. First synoptic analysis of volcanic degassing in Papua New Guinea. Geochemistry, Geophysics, Geosystems, 13(3).
Michigan Tech. 1996. Ulawun Decade Volcano, Papua New Guinea. http://www.geo.mtu.edu/volcanoes/boris/mirror/mirrored_html/ULAWUN.html
Newhall, C. 1996. IAVCEI/International Council of Scientific Unions Decade Volcano projects: Reducing volcanic disaster. status report. US Geological Survey, Washington, DC. Retrieved from https://web.archive.org/web/20041115133227/http://www.iavcei.org/decade.htm
Oregon State University: 2020. Volcano World. Ulawun. http://volcano.oregonstate.edu/ulawun. Last accessed April 20, 2020.
Papua New Guinea, Minerals page (archived):
2005. Ulawun. https://web.archive.org/web/20050322025513/http://www.mineral.gov.pg/volcObs/ulawun.htm
Silver, E.; Day, S.; Ward, S.; Hoffmann, G.; and others. 2009. Volcano collapse and tsunami generation in the Bismarck volcanic arc, Papua New Guinea. Journal of Volcanology and Geothermal Research, 186(3-4): 210-222.
Vernier, J. P.; Thomason, L. W.; Pommereau, J. P.; Bourassa, A.; and others. 2011. Major influence of tropical volcanic eruptions on the stratospheric aerosol layer during the last decade. Geophysical Research Letters: 38(12).