Vog (=volcanic fog) at the new eruption in Hawaii

Vog model from University of Hawaii
Source is here

Vog, the noxious mixture of sulfur dioxide and sulfate aerosols that creates a "volcanic fog"=vog, is being emitted at increased levels from the fissure eruption that has developed in Hawaii.  Vog can cause headaches, breathing problems, vulnerability to respiratory ailments, irritated eyes and throat.  So far, the northeast tradewinds are keeping the gas from populated areas, but if they diminish or change direction the vog could move toward populated areas. The March 10 report from HVO says that potentially-lethal concentrations of sulfur dioxide gas are present within 1 km downwind of vent areas.

Scientists at the University of Hawaii developed the concept of a Vog Measurement and Prediction (VMAP). If you click on the picture to the left, it should start a GIF animation. If it doesn't work, go to the site referenced in the caption. In 2008 the Halemaumau vent began emitting elevated sulfur dioxide gases, and the idea arose of trying to do vog forecasting.  Steven Businger and Roy Huff of U.H. developed some preliminary concepts and fortunately, Stimulus Act funding to HVO allowed development of a feasibility study.  Preliminary products are on the WWW site referenced in the figure caption.

The east rift eruption has been called the March 5 Kamoamoa fissure eruption.  The activity diminished through the 9th, and paused at 10:30 p.m.  The sulfur dioxide emission rate was estimated at 5,000 tonnes/day from the east rift sources. At the summit of Kilauea, the lava lake remains deep below the rim of the vent (220 m or 720 feet) in Halemaumau. The sulfur dioxide emission rate from this eruption was 700 tonnes/day on March 9. Detailed information is available on the USGS Hawaiian Volcano Observatory WWW site.

Spectacular event at the Puu Oo eruption in Hawaii

New fissure opening at Puu Oo. Note lava just breaking through
to the surface in the foreground.  USGS photo

(I was going to continue yesterday's blog on Mount St. Helens here, but events in Hawaii are too interesting to ignore!)

Last Saturday at 1:42 p.m. HST, the USGS monitoring network detected the onset of deflation at Puu Oo crater, and increased harmonic tremor (which usually indicates movement of magma).  Puu Oo lies ~15 miles from the summit of Kilauea.  Twenty minutes after Pu u Oo began deflating, the summit of Kilauea also began to deflate.  At 2:16 p.m. the floor of the crater began to collapse with the development of incandescent ring fractures developing a few tens of meters away from the crater wall.  The floor continued to drop, a spatter cone within the crater collapsed, and a large scarp developed on the west side.  Lava cascaded over the scarp toward the center of the crater.  The floor continued to collapse at least through 4:26 p.m. (See previous post on activity in February.)

Map of Kilauea showing Puu Oo, Napau,
and Halemaumau. Photo: USGS

Coincident with the collapse in Pu u Oo, an earthquake swarm began along Kilauea's middle east rift zone, and tiltmeters showed deflation of this area as well.  A pre-existing crater, Napau, then started to erupt, and the eruption continues between Pu u Oo and Napau. Simultaneously, the lava lake level within Halemaumau at the summit of Kilauea is also dropping. The floor of Pu u Oo has dropped at least 115 meters (377 feet).

The volcanoes of Hawaii are rarely dangerous in the style of Mount St. Helens, but they can be. One sequence of events that can cause an explosive eruption is exactly what is going on now:  magma disappears from the summit or craters down into the underground reservoirs, or it moves out of one crater to another, leaving exposed rocks. USGS reference here. If there is groundwater nearby, it can drain into the emptied crater/conduit creating a violent steam-driven eruption. On February 21, 1924 lava in Halemaumau drained, and the floor sank to 115 m below the rim (ironically, the same number as above; this is not a typo!).  Two months later, on April 29, the floor began to sink again, and by May 7, the floor was about 210 m below the rim.  As is being observed today, this withdrawal of magma allows heavy rockfalls from the walls of Halemaumau.  Groundwater flowed into the still-hot conduit, the steam pressure built up, and on the night of May 10-11, 1924, rocks and dust were blown out of the crater.  This activity peaked on May 18, and occurred episodically until May 27. While not exactly similar (because Puu Oo is out on the east rift zone), the withdrawal of magma from both the summit and Puu Oo suggests that there is a potential for an explosive eruption over the next few months.

Footprints in muddy ash from the 1790 eruption.
Photo: USGS

Legend has it that footprints on the southwestern side of Kilauea are those of warriors caught in one of these violent eruptions.  Don Swanson and colleagues have pieced together a picture of the event (2008 AGU abstract).  A group of people, deduced to be women and children from the size of the footprints, were apparently out in the southwest area searching for obsidian for toolmaking.  An initial eruption occurred, during which this group may have taken shelter.  About 1" of muddy ash was deposited. The survivors of that phase of the eruption walked around on wet ash, leaving the footprints.  Meanwhile, warriors and their families were camped out at the summit waiting for the eruption to end, perhaps waiting for 3 days.  When they saw the sky clear the started walking southwestward along the west side of the summit area.  Unfortunately, the most powerful stage of the eruption then began, sending base surges of hot, wet ash-laden steam at them. Many were killed.

Status reports on this eruption can be found at the USGS Hawaii Volcano Observatory website. A webcam here shows the Halemaumau situation, and here shows Puu Oo.

Spectacular videos of crater rim collapse into Kilauea lava lake

The active crater within the caldera of Halemaumau on the
 summit of Kilauea. The rim is about 150 meters across,
and the lava is about 100 m below the rim. USGS.

The U.S. Geological Survey (USGS) has a permanent observatory on the summit of Kilauea volcano in Hawaii, the Hawaii Volcano Observatory (HVO).  For the past 24 years, Kilauea has been active, with 55 "episodes" of activity spread over these years.  Some of the activity has been at the summit, where there is a large crater (small caldera), "Halemaumau", and some activity has been on the flank at a growing cone named Puu Oo (I can't do the Hawaiian symbols for the proper name here).  Between 1983 and 1986, Puu Oo built a massive cone, but in 1986 the activity migrated 3 km east, and lava poured out of the east rift zone all the way to the coast.

Cover image of Krafla from Geology magazine,
March 2011

In 1992, the activity shifted back to Puu Oo, and from then until 2007 lava flows poured out of vents into the ocean, mainly inside the volcano national park. After 2007, activity continued both at Puu Oo and at the summit of Kilauea in the caldera, Halemaumau.  You can explore the USGS HVO site here for more details. Related work is described in the March issue of Geology magazine (Houghton et al., Pigeonholing pyroclasts: insights from the 19 March 2008 explosive eruption of Kilauea volcano, Geology, 39(3), 263-266, 2011.)

A few days ago, the U.S. Geological Survey reported several (?) events in which a section of rock broke off the wall and fell into the lava lake.  One of these "rocks" was about 395 feet long and 16 feet wide. It had been hanging over the pit by about 180 feet and so the USGS was able to forecast the collapse.  There is great videos of these events here and here. In this video you are looking into the throat of a crater on the floor of Halemaumau (same view as on the photo on the upper left on this post).  The walls of the crater form an arch at the top, and you are looking at a lava lake in the bottom of this crater.  The molten lava is in the bottom of the crater, about 100 meters down.  It is "red hot magma", but the surface cools by radiation to the sky and conduction to the cooler air, and so it is covered with a black crust.  Motion of the magma under the crust causes it to crack and move, a miniature version of "plate tectonics."  (The USGS made a movie exploring this analogy back in the 1960's or 1970's.)

Does anyone know if this movie still exists or is available to the public?