In December 1872, this site on Ribbon Cliff, called Broken Mountain by the Indians, experienced a violent earthquake that split the mountain, formed the cliff to the west, and caused a huge rock slide that stopped the flow of the Columbia River for several hours. The black ribbons of the cliff are lava-filled fissures, and plateau lavas of the region later covered this rock mass. The white volcanic ash in the road excavation is recent enough to have buried undecayed logs, and it was blown from Glacier Peak, a volcanic cone, 50 miles to the northwest.

Photo: Cosmos Mariner

Photo: Cosmos Mariner

Photo: Cosmos Mariner