How Sulfur Is Born main content.

How Sulfur Is Born

by AMNH on

News Posts

Stand in the Gottesman Hall of Planet Earth in front of the topographical bronze globe of Earth, and you can’t miss the two bright yellow forms a short distance just beyond and to the left. A quick scan of the display text reveals they are samples of sulfur from the Kawah Ijen volcano on the island of Java in Indonesia.


Large bronze model of planet earth is displayed in the middle of a Museum hall which contains geological specimens.
The sulfur column and slab, and a video of Dr. Webster on expedition at Kawah Ijen, on view in the Gottesman Hall of Planet Earth.
© AMNH/ D. Finnin, C. Chesek

The sulfur column and slab were collected on June 8, 1998—the very day the sulfur solidified on the volcano—by a team led by geologist James Webster, curator in the Museum’s Department of Earth and Planetary Sciences. The trip was one of dozens of reconnaissance and acquisition expeditions undertaken from 1996 through 1999 in preparation for the opening of the hall on June 12, 1999. Museum teams worked with experts around the world to identify geologically significant specimens to show the dynamic nature of Earth’s formation and ongoing existence.


Steam billows from a high mountain lake; sulfur deposits dot the mountainside.
The crater lake is beautiful but scalding.
© AMNH/D. Finnin

The yellow sulfur forms after volatile gases—in this case, sulfur dioxide and hydrogen sulfide—are driven up by a volcano’s solidifying magma, flow to the surface, and escape from vents or fumaroles. It’s perhaps the best-known mineral to form in this way, although volcanic gases sometimes result in other minerals forming, such as silica and native gold.


Miner carries baskets of sulfur across his shoulders as he walks up the mountain.
Miners at Kawah Ijen hand-harvest the mineral, then trek out of the crater carrying their own weight—or more—in what is considered one of the most difficult and dangerous jobs in the world. 
© AMNH/D. Finnin

Kawah Ijen is distinguished by a crater lake so intensely acidic, the water would eat through clothing and human flesh. Foul-smelling gases—think rotten eggs—vent from beneath the surface of the water, sometimes explosively in what’s called a phreatic eruption. But there are moments when the lake’s deep turquoise beauty can be enjoyed free and clear.

Says Webster, “It depends on how the wind blows.”


Steam rises from large pile of sulfur.
A large sulfur deposit at Kawah Ijen.
© AMNH/D. Finnin


A version of this story originally appeared in the Fall 2017 issue of Rotunda, the Member magazine.