Maar craters and tuff rings occur in several parts of the plain. The largest, Menan Buttes , may have formed by interaction of magma with surface water, possibly the ancestral Snake River. Others, such as Sand Crater and Split Butte , are young maar craters that apparently have involved groundwater. They consist of tephra deposits around central craters 500-800 meters in diameter that developed in lava flows. They appear to have formed by an early phreatomagmatic phase followed by an effusive phase that emplaced a lava lake, which then subsided to form the craters.
Rhyolitic hills occur in several places in the eastern Snake River Plain .
One of the most prominent is Big Southern Butte . Big Southern Butte Rhyolitic hills occur in several places in the eastern Snake River Plain . One of the most prominent is Big Southern Butte . Craters of the Moon lava field lies along the northern border of the Snake River Plain , midway between Arco and Carey, Idaho. It consists of Holocene to Pleistocene lava flows, cinder cones, spatter cones, lava tubes, and other features typical of basaltic volcanism.