Volcanoes Along the Snake

Distant hills called buttes are shield volcanoes formed when lava flowed from cracks, or vents, in the earth's crust. Over the past seven million years, these lava flows repeatedly blocked the Snake River and forced it southward. Erosion often exposes remains of past lava flows as dark layers of basalt rock along the canyon walls. Volcanic eruptions in this region ended about 50,000 years ago. Successive layers of porous basalt rock hold and channel the Snake River Aquifer, one of the largest underground fresh water systems in America.

Hagerman, Idaho · United States