Lava Breakout Breakdown (Pahoa Meeting – Nov. 13)

USGS Hawaiian Volcano Observatory on Nov. 13

The past several weeks have been full of suspense and emotion for residents of the lower Puna District of the Island of Hawai‘i. Rather than being restful, recent weekends have been busy with notable events. On October 25, lava crossed Cemetery Road/Apa‘a Street on the outskirts of Pāhoa. Last Sunday, November 9, a new lobe widened the flow along the road, entered private property, and threatened an evacuated home. Just before noon the next day, the house was consumed by fire, the first residential structure taken by the June 27th lava flow.

The Pāhoa community has been in a heightened state of alert for months, following a USGS news release on August 22 that announced the potential hazards posed by the advancing lava flow. Emergency proclamations by the Hawai‘i County Mayor and State Governor followed in early September, paving the way for a Federal disaster declaration by President Obama in early November. This declaration allows local government and qualified nonprofit organizations to access federal funds to help address emergency protective measures and hazard mitigation.

The most obvious hazard is flowing lava. The loss of property and services, associated fires, and threat to community safety by the flow are primary concerns for emergency managers. The lava advance rate has been variable, ranging from negligible to nearly a quarter mile in a day. Planning for evacuations, alternate roads, and continuity of utilities and services becomes more difficult with the inconsistent timing of the lava’s progress.

Currently, the June 27th lava flow is encroaching on residential areas and burning forests, pastures, roads, and other man-made structures and debris. The dense plume, which is frequently visible, is a mixture of volcanic and non-volcanic gases and particles. Although a less overt hazard, poor air quality downwind of the active lava flow can present challenges for some individuals.

Sulfur dioxide gas, the main contributor to Hawaii’s volcanic air pollution, or vog, is primarily released from actively degassing vents at Kīlauea Volcano’s summit (Halema‘uma‘u) and East Rift Zone (Puʻu ʻŌʻō). However, a small amount of this pungent gas is also released from flowing lava. Individuals with preexisting respiratory conditions, such as asthma, could be impacted by the low levels of sulfur dioxide if they are immediately adjacent to an active lava flow.

When lava comes into contact with vegetation, burning plant material produces a complex mixture that includes carbon dioxide and carbon monoxide gas, as well as various particulates. Vegetation can decompose in the hot environment beneath the surface of the lava, generating gases that can ignite and explode when confined in underground pockets. These explosions occur frequently around the June 27th lava flow.

The burning of manmade features, such as paved roads, creates toxic fumes. In the short-term, molten asphalt fumes can cause eye and respiratory tract irritation. The Occupational Safety and Health Administration notes that workers exposed to asphalt fumes are at risk of developing headaches, rashes, cough, and possibly cancer.

If the June 27th flow continues its forward progress, lava could eventually reach the Pacific Ocean. If this happens, molten lava will react vigorously with the cold seawater, creating a large steam plume laden with hydrochloric acid. A 1990 study by the National Institute of Occupational Safety and Health showed that near-shore hydrochloric acid concentration decreased tenfold over a distance of less than half a mile, so areas immediately downwind of an ocean entry would likely be most impacted.

The hazards associated with gases and particles generated by flowing lava depend on the flow’s proximity, the items burned, and how the wind directs and disperses the resulting pollutants. Individuals with pre-existing respiratory conditions are the most impacted by air quality hazards, and are advised to limit their exposures and monitor their responses closely.

Information on air quality impacts and health recommendations are available through the County of Hawai‘i (http://www.hawaiicounty.gov/lava-related), the Hawaii State Department of Health (health.hawaii.gov), and the American Lung Association’s free helpline (1-800-LungUSA). A wildfire smoke guide is available at www.arb.ca.gov. Information on local wind conditions is posted at weather.hawaii.edu and under “local graphics” at www.prh.noaa.gov/hnl/pages.

Puna residents are encouraged to stay informed about the progress of the June 27th lava flow. Daily updates are posted by the Hawaiian Volcano Observatory and Hawai‘i County Civil Defense at http://hvo.wr.usgs.gov and http://www.hawaiicounty.gov/active-alerts/.