With a diameter exceeding 1 kilometer and a depth of approximately 300 meters, the Ijen volcano crater has formed the Ijen Volcano Lake due to the presence of abundant sulfur salts and volcanic magma activity at the bottom. The lakebed is rich in sulfur deposits.
Every year, local residents and workers climb the volcano and then collect sulfur from the lakebed. This is a strenuous and hazardous occupation, as workers labor in an environment saturated with toxic gases, traversing the steep slopes. The sulfur mined by them is primarily used in the production of fertilizers and industrial products such as chemicals.