Jackass Butte erosional remnant from Bonneville flood

Bonneville flood

The Bonneville flood was a catastrophic flooding event in the last ice age, which involved massive amounts of water inundating parts of southern Idaho and eastern Washington along the course of the Snake River. Unlike the Missoula Floods, which also occurred during the same period in the Pacific Northwest, the Bonneville flood only happened once. The flood is believed to be the second largest in known geologic history.

• http://en.wikipedia.org/wiki/Bonneville flood
• Page 113 - Bonnichsen, B., et al. 2016, From land to Lake: Basalt and rhyolite volcanism in the western Snake River Plain, Idaho: Geol. Soc. Amer., Field Guide 41