North Menan Butte, the middle landform in the photo above, lies at the confluence of the Henry's Fork and main stem of the Snake River.
The butte is one of the world's only examples of a glassy tuff cone, a geologic formation resulting from hot lava chilling suddenly as it erupted through alluvium saturated with much cooler water. This prominent evidence of basaltic volcanism is the primary reason for the butte's ACEC designation and its designation as a National Natural Landmark.
Hiking trails allow up-close experiences of the butte's natural features and ascend to panoramic views of the eastern Snake River Plain from the summit rim.
A 346-acre research natural area lies within the ACEC. The butte's greatly varied vegetation accents the unique geology. Basin big sagebrush, black sagebrush and threetip sagebrush are the dominant shrubs, with bluebunch wheatgrass, Sandberg bluegrass and needle-and-thread grass in the understory. In places, scattered Utah juniper combines with big sagebrush and bluebunch to form small woodlands.