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Hawaii Volcanic Gases and Ash FAQs - 22 Found

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Where and how do SO2 and volcanic gases (vog) affect air quality in Hawai`i?

The most critical factors that determine how much vog impacts an area are wind direction and speed. Where and how bad the vog is ultimately depends on several additional factors including air temperature, humidity, and rainfall as well as the location of the source and the amount of SObeing emitted. 

There are currently two main sources of SO2 emissions on Kīlauea: Pu`u `Ō `ō (east rift) and the active vent in Halema`uma`u Crater (atKīlauea's summit). The amount of SO2 emitted by Kīlauea began to increase in mid-2007 and has been particularly high since the new gas vent in Halema`uma`u opened in March 2008.

During prevailing northeasterly tradewinds, emissions from Kīlauea are blown to the leeward side of the island, creating a chronic pollution problem along the Kona coast.  During wind reversals, shown by the red arrows, emissions are blown to the east side of the island impacting windward population centers.During prevailing trade (from northeast) wind conditions, much of the SO2 from Pu`u `Ō `ō is blown out to sea, while SO2 from the summit vent often creates vog in Ka`u communities from Pahala to Ocean View. Unfortunately, both plumes eventually reach the west side of Hawai`i Island in a "double-whammy" of combined effects, resulting in an especially dense and nearly constant haze of vog along the Kona coast.

When the winds become light and variable or blow from the south, communities in East Hawai`i and along the entire Hawaiian Island chain can also suffer the effects of vog. Under these conditions, people living in the path of Pu`u `Ō `ō gas emissions continue to experience vog levels similar to those that have beset them for two decades. Communities in the path of summit SO2 emissions, particularly those nearest the source vent, can be subjected to an unusually acrid haze that contains both gas and acidic particles because the emissions have had little time to disperse and dilute before reaching them. 

Learn more: 

  • Vog Measurement and Prediction (VMAP): A feasibility study to determine if vog forecasts are achievable and useful—a collaboration of researchers at the University of Hawai'i at Monoa, USGS, and NOAA. Includes forecast discussions, vog model predictions, and model validation graphics for sulfur dioxide gas and sulfate aerosol.

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