June 5, 2008
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
What to worry about in Kilauea volcanic emissions?
First, let's review why we worry about SO2. Kilauea is currently producing up to 4,000 tonnes/day of SO2, resulting in concentrations in air greater than 5 parts per million (ppm) in downwind communities within 50 km (31 miles). Sustained concentrations greater than 0.3 ppm are considered unhealthy. During its journey through the air, the SO2 reacts with oxygen, sunlight, and water to form vog, a mixture of gas and tiny sulfuric acid aerosol droplets. This aerosol mixture appears as a dense haze that obscures Hawaiian scenery and ocean views. The acidic droplets in vog are small enough that they can be inhaled deep in the lung and can pose health problems. In addition to the effects on living creatures, the acid mist can acidify rain and burn the leaves of plants, including many agricultural crops, such as protea, roses, fruits, and vegetables.
The most abundant constituent of eruptive emissions is water, but that's nothing to worry about. We can always use more water, and Kilauea adds more than 4,000 gallons per minute in the form of water vapor to the Earth's water supply. Carbon dioxide (CO2) is the second most abundant constituent in Kilauea emissions. Current CO2 emission rates are about 10,000 tonnes/day. We already have CO2 in concentrations of 0.04 percent and more in the air that we breathe, thanks to human-generated emissions. Fortunately, plants photosynthesize some of this to make oxygen. CO2 is heavier than air and can be a problem in low-lying areas immediately downslope of a volcanic vent when its concentrations exceed 5 percent. Worldwide, human activities produce more than 100 times the amount of CO2 emitted by volcanoes. So although Al Gore is worried about CO2 he isn't blaming volcanoes.
Water, SO2, and CO2 comprise about 99 percent of Kilauea's emissions. All the other constituents together account for the remaining 1 percent and there are many of them. Hydrogen (H2), Hydrogen Chloride (HCl), Hydrogen Fluoride (HF), and Carbon Monoxide (CO) are the principal minor constituents. Of these, H2 and CO are already in the atmosphere at trace levels.
Hydrogen chloride combines with moisture in the air to acidify rain and burn vegetation. HCl is also produced by a chemical reaction where lava enters the sea.
Gaseous hydrogen fluoride (HF) is emitted at rates between 7 to 12 tonnes/day from Kilauea and is therefore generally not a direct problem; however, fluoride is deposited on the leaves of downwind vegetation and is not metabolized by the plants. Animals grazing on the tainted forage can get fluorosis and ultimately die if the fluoride amounts are high enough. Very few studies have been done on the fluoride content in Hawai`i vegetation around Kilauea. Fortunately, no fluorosis symptoms have been reported in Hawaiian grazers recently.
But wait, there's more. About one tonne/day, combined, of various metals, such as lead, copper, gold, silver, zinc, bismuth, and mercury are emitted by Kilauea. There are many more components present in trace amounts - in fact, it's probably easier to name elements that are not present in Kilauea emissions than to list all the ones that are.
Taken all together, much of the Earth's metallic ores, oceans, and atmosphere owe their presence to volcanic emissions. We have many things for which to thank volcanoes; we just don't want all of them right in our neighborhood airspace.
Hawaiian volcanoes have always emitted these gases and metals in varying amounts. The emissions are currently high, but probably not higher than during the 251 days of the 1967-68 Halema`uma`u eruption or from the lava lake that existed throughout much of the 19th and early 20th centuries. However, the island population has increased, and land uses have changed substantially since these past long-lived summit eruptions. More people and diverse crops are exposed than ever before. Most of the exposed individuals are unaware of this long history.
HVO continues to watch the summit activity closely and to track the rate of emission of sulfur dioxide, the main gas hazard - and public concern.
[note: the hydrogen fluoride emission rate was updated in late 2009 based on more recent information than was available at the time this article was originally written.]
Kilauea 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 Kilauea 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 (http://www.lavainfo.us) 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 Kilauea eruption updates and nearly real-time Hawai`i earthquake information. Kilauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov.
Updated: June 12, 2008 (pnf)