Vog from Kilauea Volcano Hawaii
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Vog from Kilauea Volcano, Hawaii

October 12, 2010
A dense, light gray haze hangs over the Pacific Ocean and the Hawaiian Islands on October 6, 2010 when the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite passed overhead and captured this true-color image. This haze is volcanic fog, or “vog”, and emanates from the Kilauea volcano, which appears as a bulge on the southeastern flank of Mauna Loa, the huge volcano found on the big Island. In this image, Kilauea is hidden under clouds; it is the cone of Mauna Loa which is visible.

Volcanic gases are emitted during active eruption, such as is occurring on Kilauea, but can also rise during volcanic rest. The gas plume rising from an active vent on Kilauea consists of about 80 percent water vapor with lesser amounts of sulfur dioxide, carbon dioxide, and hydrogen. Small quantities of carbon monoxide, hydrogen sulfide, and hydrogen fluoride are also present.

Sulfur dioxide is potentially harmful to human health and vegetation. When combined with water, it forms sulfuric acid, which can attack skin, cloth, metal, and other materials. When a volcanic plume mixes with atmospheric moisture, as it will do over the ocean, acid rain results. Acid rain can significantly retard the growth of cultivated or natural plant life downwind of a vent that degasses over a long period of time.

On the morning of October 6, the summit gas plume was blowing to the southwest. According to the Hawaiian Volcanic Observatory, the sulfur dioxide emission rate was 970 tonnes/day, elevated from the pre-summit eruption average (2003-2007) of 140 tonnes/day.

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