Menan Buttes

The sign treats the two cones as one event, but they differ in the ways that matter to a visitor. By NASA's reading the north butte rose through the channel of the Henrys Fork itself, as the sign says, while the south one came up through groundwater beside the river. The north butte is public land, a National Natural Landmark since 1980 and a research natural area, with a BLM trail to the rim and around the crater. The south butte is private and posted, and its trailhead on older maps is closed. Both are about 10,000 years old.

What the plaque says

Menan Buttes Two cones of glassy lava are located directly south of here. The largest rises 800 feet above the surrounding plain. Hot molten lava, erupting from great depth, met cold surface water in the wet flood plain of Snake river: the northern butte, in fact, formed in the channel of Henry's fork, which was forced further east. Suddenly chilled into small particles of volcanic glass, the lava exploded up in a great spray of steam and solid fragments which built up into wind-blown cones around large summit craters a half mile long and 200 to 400 feet deep. 301 Text prepared by Idaho State Historical Society and Idaho Geological Survey.

Where it stands

Worth the stop nearby

• Menan Buttes — 2.5 mi
  Two volcanoes built where lava ran into the Snake River, and one of them open to walk around the rim.
• St. Anthony Sand Dunes — 11 mi
  Four hundred feet of white sand, open to machines most of the year and closed to people when the elk come down.
• Teton Dam Site — 22 mi
  Geologists warned that the canyon walls would leak. The warnings were softened, the dam was finished, and it never held a full reservoir.

More markers nearby

• Beaver Dick — 3.1 mi
• Brigham Young University-Idaho — 9.1 mi
• Market Lake — 11 mi
• Fort Henry — 12 mi