Photoglossary

Sulfur   Sulfur is a nonmetallic element which is common throughout the solar system. It is pale yellow as a solid, but when it is in liquid form, it changes color as its temperature changes. It is dark brown at the highest temperatures, changing to red, then orange, and finally to yellow as it cools. Sulfur has long been associated with volcanic activity and was known to the ancients as "brimstone", or the "fuel of hell". Earth possesses its share of sulfur, but scientists believe that much of it migrated to the center of the Earth with iron to form the core. The sulfur that does exist in the mantle often makes its way to the Earth's surface through volcanic activity. As sulfurous gases escape at the surface, they cool and crystallize to form yellow deposits around the volcanic vent. Two common gases associated with volcanic activity are hydrogen sulfide and sulfur dioxide. Both have a foul odor, much like that of rotten eggs.   Photo Credit: R.L. Christensen, USGS        Io Home Page Photoglossary Home Page