Vog is a form of air pollution that results when sulfur dioxide and other gases and particles emitted by an erupting volcano react with oxygen and moisture in the presence of sunlight. The word is a portmanteau of the words "volcanic" and "smog". The term is in common use in the Hawaiian islands, where the Kīlauea volcano, on the Island of Hawaii (the "Big Island"), erupted continuously between 1983 and 2018. Based in June 2008 measurements, Kīlauea emits 2,000–4,000 tons of sulfur dioxide (SO2) every day. Description Vog is created when volcanic gases (primarily oxides of sulfur) react with sunlight, oxygen and moisture. The result includes sulfuric acid and other sulfates. Vog is made up of a mixture of gases and aerosols which makes it hard to study and potentially more dangerous than either on their own. Vog, which originates from volcanic vents, differs from laze, created when lava enters the ocean. Vog in Hawaii In Hawaii, the gas plumes of Kīlauea rise up from three locations: Halemaʻumaʻu, Puʻu ʻŌʻō, and from along the coastline where lava flows from the East Rift zone enter the ocean. The plumes create a blanket of vog that can envelop the island. Vog mostly affects the Kona coast on the west side of the Island of Hawaii, where the prevailing trade winds blow the vog to the southwest and southern winds then blow it north up the Kohala coast. Prolonged periods of southerly Kona winds, however, can cause vog to affect the eastern side of the Island on rare occasions, and affect islands across the entire state as well. By the time the vog reaches other islands, the sulfur dioxide has largely dissipated, leaving behind ash, smoke, sulfates, and ammonia. Comparing vog and smog Vog and smog are different. Vog is formed when sulfur oxides emitted by a volcano react with moisture to form an aerosol. The aerosol scatters light, thus making the vog visible. Smog is formed largely from the incomplete combustion of fuel, reacting with nitrogen oxides and ozone produced from carbon monoxide by reactions with sunlight. The result is also a visible aerosol. When smog levels are high, the sky appears yellowish-grey because nitrogen oxides are yellow. In contrast, sulfur oxides are colorless and vog looks grey. Once the vog layer dissipates, grey spots of vog in the sky may, for a time, remain trapped in the inversion layer. Several chemicals