Russian Academy of Science, Anton Yakushev photos (fair use policy)
Kudriavy is a small volcano inside a large caldera on Iturup island, in the Kuril Archipelago north of Japan. One of the world's most remote locations, Kudriavy made news a few years ago when a unique deposit of rheniite, rhenium sulfide, was found around the steaming fumaroles at its top. The Kurils are, like the Aleutian chain farther around the Pacific rim, subduction-related volcanic arc islands.
The field of fumaroles is particularly hot, and this photo shows the extensive sulfur deposits around the steam vents. Russian researchers had to wear metallized, acid-resistant outerwear and beware of the wind direction to approach this deadly zone.
Anton Yakushev, the Russian scientist who discovered rheniite, said of his dangerous research, "Acid gases is a reason why I became blond during field work."