The glaciers on the mountain's upper slopes may be a source of potentially dangerous lahars when the mountain next erupts. There are vents near the summit that are known for emitting gases such as carbon dioxide and sulfur dioxide. Prior to the 1980 eruption of Mount St. Helens, the only known fatality related to volcanic activity in the Cascades occurred in 1934, when a climber suffocated in oxygen-poor air while exploring ice caves melted by fumaroles in Coalman Glacier on Mount Hood.