Sulfur dioxide from the eruption of Kasatochi Volcano in the Aleutian Islands on August 8 continued to spread eastward on August 12 and was observed by the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite. Winds were moving the gas in a large counter clockwise loop over the Pacific Ocean and back toward Alaska, but also spreading streamers over the Arctic and eastward across the United States and Canada.
The scale shows values as the natural logarithm of Dobson Units of sulfur dioxide. A logarithmic scale is one in which the values represented by the colors increase exponentially, not linearly. A Dobson Unit is a measure of the concentration of the gas in a 15-kilometer tall column of the atmosphere. If you could compress all the sulfur dioxide in that column of the atmosphere into a flat layer at the Earth’s surface (at 0 degrees Celsius), one Dobson Unit of the gas would be 0.01 millimeters thick, and it would contain 0.0285 grams of sulfur dioxide per square meter.
Additional images showing the spread of the sulfur dioxide plume from this eruption are featured in an Image of the Day.
NASA OMI image courtesy Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC). Caption by Rebecca Lindsey.