# How voggy is it?

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How do we measure vog? Hawaii Island and the State are getting a good dose of it so far this December. Vog is a combination of pollutants measured by monitoring its most important components-sulfur dioxide gas (SO2) and respirable particulates or aerosol (PM2.5).

How voggy is it?

(Public domain.)

The Hawaii State Department of Health (DOH) and the Hawaii Volcanoes National Park (HVNP) currently operate highly accurate air-quality sensor networks on Hawaii Island. HVNP started monitoring sulfur dioxide (SO2) within the park with one sensor in 1986 expanding to two in 1999. DOH had two SO2 sensors in Captain Cook and in Hilo by 2000 and added Mountain View and Pahala in 2007. Particulate (PM2.5) monitoring at those sites began in earnest in early 2008 after testing in Captain Cook in late 2007.

In response to changes in air quality brought on by the 2008 Halemaumau eruption, Hawaii County Fire Department deployed SO2 sensors in several locations, including Kulani Prison. These sensors are less accurate than those in the DOH and HVNP networks but are ideal for quickly tracking high concentrations.

In addition to these networks of continuously operating monitors, several studies have been made over shorter periods of time to characterize vog produced by Kīlauea Volcano. Beyond long-term concerns about volcanic gasses, air quality was a critical aspect of assessing the environmental impact of geothermal development along Kīlauea's east rift zone in the early 1980s. In fact, DOH installed air quality monitoring sites around the geothermal development area of Kīlauea's lower east rift zone.

We have heard many stories about how much worse the vog is in Kau and Kona since the Halemaumau vent opened up in March. Using data from all of these sources, can we estimate how much worse vog has become in 2008?

The data kindly provided by DOH and downloaded from the National Park Service data site tell an interesting story. For this analysis, we determine the long-term average SO2 and PM2.5 concentrations evident in the DOH data, not the short-term high-concentration events mentioned in an earlier Volcano Watch. Although the several-hour-long periods of exceptionally poor air quality are easy to remember, it's the steady low-level conditions that are key to evaluating exposure.

According to the DOH data, SO2 concentrations tripled and PM2.5 concentrations doubled at Captain Cook since the Halemaumau vent fired up in early 2008. SO2 concentrations in Pahala nearly quadrupled. These communities are downwind of both Puu Ō ō and Halemaumau during trade-wind conditions that blow as much as 85 percent of the year. They are experiencing the direct effects of increased gas emissions from Kīlauea Volcano.

On the other hand, the long-term conditions at Hilo and Mountain View changed little. These locations only get vog during kona conditions. Under most kona-wind conditions, only Puu Ō ō fume gets to Hilo and Mountain View, and its emission rate didn't change in 2008 during kona-wind conditions. Unfortunately, continuous PM2.5 data acquisition started after the Halemaumau eruption began, so no before-and-after comparison can be made.

We can also use these long-term conditions to rank which monitoring sites are more affected by vog. Since March, 2008, long-term average SO2 concentrations have been highest in Pahala, followed in order by the HVNP sites, Kona, Mountain View and Hilo. Long-term average PM2.5 concentrations have been highest in Kona followed by Pahala with Hilo and Mountain View in a tie for least affected community.

Conclusions about long-term air quality within communities near HVNP and Kulani Prison will await further analysis. HVO continues to monitor volcanic gas emissions from Halemaumau and Puu Ō ō and will be looking at these downwind air quality data for any patterns that might prove useful.

Mahalo to the DOH, HVNP, the Hawaii County Fire Department, and Hawaii County Civil Defense for their efforts in providing information about this unique hazard.

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### Volcano Activity Update

Kīlauea Volcano continues to be active. A vent in Halemaumau Crater is erupting elevated amounts of sulfur dioxide gas and very small amounts of ash. 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 and communities adjacent to Hawaii Volcanoes National Park, during kona-wind periods. There have been several small ash-emission events from the vent, lasting only minutes, in the last week.

Puu Ōō continues to produce sulfur dioxide at even higher rates than the vent in Halemaumau Crater. Trade winds tend to pool these emissions along the West Hawaii coast, while Kona winds blow these emissions into communities to the north, such as Mountain View, Volcano, and Hilo.

Lava continues to erupt from the Thanksgiving Eve Breakout (TEB) vent and flows toward the ocean through a well-established lava tube. Lava breakouts in the Royal Gardens subdivision and adjacent coastal plain have been active throughout the past week. As of Tuesday, December 9, these active flows had crept approximately 40 yards into the National Park. Activity at the Waikupanaha ocean entry continues, with occasional small explosions. A deflation-inflation cycle began at the summit early on December 11 and was still ongoing at the time of this writing (afternoon of December 11). These cycles normally cause short-term fluctuations in lava supply to the flow field.

Be aware that active lava deltas can collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves generated during delta collapse; avoid these beaches. In addition, steam plumes rising from ocean entries are highly acidic and laced with glass particles. Check Civil Defense Web site or call 961-8093 for viewing hours.

Mauna Loa is not erupting. Five earthquakes were located beneath the summit this past week. Continuing extension between locations spanning the summit indicates slow inflation of the volcano, combined with slow eastward slippage of its east flank.

Two earthquakes beneath Hawaii Island were reported felt within the past week. A magnitude-3.5 earthquake occurred at 4:53 p.m., H.s.t., on Saturday, December 6, 2008, and was located 9 km (6 miles) southeast of Captain Cook at a depth of 10 km (6 miles). A magnitude-2.0 earthquake occurred at 6:25 p.m. on the same day, and was located 4 km (2 miles) northwest of Honaunau at a depth of 17 km (11 miles).

Visit our Web site for daily Kīlauea eruption updates, a summary of volcanic events over the past year, and nearly real-time Hawaii 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