We went on a tour through Hawaii Volcanos National Park. We were led on a short hike by Park Ranger Kuokomo McDaniels. This is the rain forest surrounding the mountain of Kiluea. In the background is the caldera. Another view of the caldera There were many steam vents like this one near the caldera.
Rain seeps down through the porous lava till it gets to rock that is still very hot.
The water then boils off and the hot steam forces its way through fissures and cracks to the surface. Sometimes the steam brings dissolved minerals with it. This place is called Sulfur Banks. The yellow stain on the bank is sulfur crystals that have been deposited as the steam evaporates. Here's another steam vent spewing sulfur dioxide.