National Park Service officials said air conditions had worsened since Tuesday, when 2,000 people were evacuated from the Big Island park. Volcanic activity at Hawaii Volcanoes National Park is a source of the gaseous air pollutant sulfur dioxide (SO2).
Hawaii Volcanoes National Park closed while officials wait for a change in wind direction to blow away sulfur dioxide belching from Kilauea volcano. The Hawaii County Civil Defense warned residents in communities outside the park that conditions could worsen before improving. The volcano, which has been erupting since 1983, began venting elevated levels of sulfur dioxide from Halemaumau Crater, located atop the volcano, in mid-March.
Vog, or volcanic fog, forms when sulfur dioxide gas reacts with sunlight, oxygen, dust particles, and water in the air. Tiny droplets known as sulfate aerosols are created, along with sulfuric acid and other substances.
This gas can pose a threat to human health, animal health, and plant life. High levels of SO2 can cause breathing difficulty and respiratory illness and aggravate existing heart disease in sensitive groups. This gas can also react with other chemicals in the air and convert to a small particle that can lodge in the lungs and cause similar health effects. These sulfate particles can also create haze and reduce visibility in national parks. Sulfur dioxide can chemically convert to acids in the atmosphere and deposit out in rain, snow, fog or as dry particles. Such atmospheric deposition can damage vegetation, affect soils, acidify lakes and streams, and ruin memorials, buildings, and statues at our national cultural monuments.
Animation credit : Barbara Schoeberl, Aura science team