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
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
Mount Hood