Columbia National Wildlife Refuge

Columnar basalt cliff

The Columbia National Wildlife Refuge reveals a dynamic geologic story. The Refuge is located in the southwest part of the Columbia Basin in an area known as the Channeled Scablands. Each butte, coulee and lake tells of a chapter in the geologic history of this unique landscape. A series of forceful geologic events shaped the area over the past million years and even through the last century. Today it is characterized by isolated cliffs and hills, surrounded by braided channels or coulees.

Lava Flows

Top view of columnar basalt columns

The foundation of the Columbia Basin, including the area of the Refuge, primarily formed 17 million to 6 million years ago. During this time, more than 300 flows of basalt lava erupted form long wide fissures in the earth’s surface. These flows formed a broad plateau of basalt, eventually covering 63,000 square miles and accumulating to a thickness of 6,000 feet in various areas. As some flows cooled, the lava cracked in the formation of hexagonal columns, known as columnar basalt.

Ice Age Floods

A series of events that significantly defined the geology of the Refuge and surrounding area occurred in the last Ice Age, between 18,000 and 12,000 thousand years ago. During numerous cooling periods, glaciers advanced southward into the Idaho panhandle, damming the Clark Fork River and creating Glacial Lake Missoula. This lake often covered 3,000 square miles and could reach a depth of 2,000 feet deep at the ice dam.

Cliffs and coulees of the Drumheller Channeled Scablands

Periodic warming phases would cause the ice dam to weaken and suddenly fail, sending the lake waters rushing through the Columbia Basin and towards the Pacific Ocean at a rate of 15 cubic miles per hour, over 10 times the combined flow of all the rivers on earth. Repeated dozens of times, these massive floods cut deep canyons and created buttes and cliffs in the basalt bedrock forming the Channeled Scabland terrain of the Refuge.

Irrigation Project

Not all of the events shaping the landscape of the Refuge occurred thousands of years ago. Just last century the Columbia Irrigation Project was constructed, altering the landscape of the Refuge once again. Prior to this project there were only a few shallow lakes and wetlands on the Refuge. The raised water table from the irrigation project and seepage from O’Sullivan Dam created over 3,800 acres of lakes and wetlands throughout the Refuge. Read more about the Columbia Basin Irrigation Project and its influence on Refuge History.

Mount St. Helens

By 11:30 am ash from the eruption had obscured the sun soon causing total darkness.

The most recent event to dramatically shape the geology and landscape of the Refuge occurred just a few decades ago on May 18, 1980. On this day Mount St. Helens, located 150 miles southwest of the Refuge, erupted violently sending a cloud of volcanic ash over eastern Washington turning day into night. On the Refuge a heavy layer of powdery ash varied in depth from 1 inch on the southern portions to 2 inches near the north. The ash flattened vegetation and suffocated many terrestrial insects creating food shortages for other wildlife. Over the years the ash layer has eroded and incorporated into the soil but is sill evident throughout the Refuge.