I was just in Oahu, Hawaii and the meterologists kept talking about "vog". It was foggy but it wasn't like our "fog." What exactly is "vog?"

MIKE MOSS SAYS:      Rhonda,      They were referring to "volcanic smog" that forms due to gas and aerosol plumes emitted rather steadily from the Kilauea volcano on the Big Island since 1986, with a recent new vent that has increased its output. The vog often takes the form of sulfuric acid aerosols that can restrict visibility, cause respiratory health issues and damage vegetation, especially near the Kona Coast. Prevailing winds across the island chain mean that most of the time, the other Islands, including Oahu, are not affected as the downwind plume passes well south of them, but on occasion wind shifts will carry some of the material the 200 miles or so northwest required to affect Oahu as well.

The attached photo is a NASA image snapped by astronauts aboard the International Space Station, and you can see three plumes from the volcano along the left side of the Big island. From what I read, the most inland vent near the crater (marked "A" in the photo) recently opened and doubles the emissions from the volcano, as well as more frequently keeping parts of the plume over land in the Kona area.

The US Geological Survey has a very informative fact sheet about volcanic air pollution that you may find interesting. It is located at http://pubs.usgs.gov/fs/fs169-97/.