Glass Mountain (Tachylites) are Unusual and Unique The Menan Buttes are extinct volcanoes formed by violent eruptions 10,000 years ago.  Unusual because they erupted through the cold waters of the Snake River that flowed where the buttes stand today. When molten magma met the cold river water, it cooled so quickly crystals were unable to form and the lava solidified into glass called tachylite.  The heat of the magma flashed the river water to steam, shattering the magma into tiny fragments that welded together as the hot ash settled to the ground into glassy rocks.  North Menan Butte is a National Natural Landmark because the buttes are the only volcanoes in the United States to erupt through freshwater.   Spaces left by gas bubbles in hot lava as it surfaced, cooled and solidified from the vent of the North Menan volcano. Photography: BLM

Animals

• Wildlife 
• Raptors 

Geology

• Wind Bowl 
• Strange Rocks 
• Glass Mountains 

Views from the Top

• Snake River Plain 
• Deer Parks Wildlife
• Henry's Fork Habitat
• Faulty Mountains
• St. Anthony Sand Dunes

Maps

• Area Map
• Trail Map

Brochure

• Download the pdf (1240 kb.)

Area Recreation Sites

• Big Southern Butte
• Birch Creek Campground
• Cress Creek Nature Trail
• Hell's Half Acre
• Henry's Fork- Snake River
• Henry's Lake
• Kelly Island Campground
• North Menan Butte
• South Fork of Snake River
• St. Anthony Sand Dunes
• Stinking Springs
• Wolf Flat