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Geology

Rock SpiresWhat caused the incredible cliffs and valleys on Columbia National Wildlife Refuge?

Most geology does not happen fast, but it can be very dramatic. However, in the case of the formation of the channeled scablands, it was both. Multiple catastrophic events, going back millions of years, help explain the origin of this puzzling landscape of high cliffs, rock columns, buttes and chaotic "valleys."  But some of the most violent happenings occurred while early Native Americans occupied this area, and some, in total awe and terror, probably witnessed the destruction. But to go back closer to the beginning . . .

A long, long time ago, about 50 million years ago to be inexact, a great upheaval began in what was to become the western portion of the North American continent, eventually giving rise to the Rocky Mountains. Much later, great fissures in the crust of the earth spewed molten lava over the land, flowing from Idaho all the way to the Columbia Basin and beyond. This occurred multiple times over millions of years, from 17 million years ago to 6 million years ago, the rivers of lava solidifying into the rock called basalt and piling up in layers eventually reaching over a mile in depth in many places. Later, wind-blown silt covered the rock, permitting the growth of plants.

More recently, beginning with the last ice age, which brought man to North America, the pace of geologic activity in the Columbia Basin accelerated. About 2 million to 12,000 years ago, as the global climate cooled, glaciers pushed out from the North Pole, sometimes following previously existing valleys or creating entirely new ones. These mammoth blocks of ice could be thousands of feet deep and many miles in width. At the height of the glacial advance, about 15,000 years ago, many lobes extended into northern Washington, Idaho and Montana. One large lobe of ice blocked the path of the Clark Fork River in western Montana, resulting in the formation of an immense lake, Glacial Lake Missoula. Many glacial lakes were created during the ice age, but this one was truly exceptional in size. At its maximum it was 1.3 million acres in size and up to 2,000 feet deep. It held 500 cubic miles of water, half the volume of present-day Lake Michigan. So what does a big lake in Montana have to do with the rocky scablands in Washington? Well . . . everything!

 

Let's find out about Ice Age Floods on the next page.

Ice Age Floods

Ice Age Floods

As the ice dam slowly melted, or the lake became too large to hold back, the dam suddenly gave way. The effect was about like hitting someone in the back with a water-balloon, only on a scale millions of times greater! A torrent hundreds of feet deep and unlike anything else recorded in the history of the earth rushed down the Clark Fork River Valley, destroying everything that wasn't tied down, and everything that was tied down. The turbulent maelstrom was quickly filled with silt, trees, rocks as big as cars, and blocks of ice as big as houses. The amount of water gushing from the lake was ten times the combined flow of all the rivers on earth today. And this cataclysm did not happen only once, but perhaps dozens of times, perhaps hundreds, because the ice dams re-formed as the glaciers continued their slow push down the valleys.

As the lake emptied, existing drainage ways could not accommodate the massive volume of water, and it spread out over Washington from present-day Spokane to the Tri-Cities.  Further west another ice dam formed at times and blocked the course of the Columbia River, diverting it south, creating Dry Falls and other massive canyons en route to the Moses Lake area. Today's diminutive Crab Creek drainage once held the roaring Columbia River. Both the Frenchman Hills and the Saddle Mountains became islands in the flood as water spilled around their west and east ends.

 

So what was the result of these floods? That's the next page.

Columbia Cliffs

A New Landscape

The velocity, depth and duration of the floodwaters formed a powerful erosive force. First, the soil and silt was stripped away by the flood, then the underlying basalt layers began to go. While the silt could only be stripped away one grain at a time, large blocks of cracked and fractured basalt were picked up whole by the great force of the water, thus rock could be eroded more quickly than silt. Massive vortices formed in the turbulent flood and drilled deep holes into the basalt. One can be seen just 2.5 miles north of the refuge office, on the east side of the Morgan Lake Road. Many basalt boulders were left scattered miles below their original position, but many were carried all the way to the Pacific Ocean!

But first, the re-united floodwaters had to negotiate the narrow confines of Wallula Gap, south of where the Tri-Cities are today. There was simply way too much water, so it began backing up, forming another large lake. It eventually became hundreds of feet deep and expansive enough to include where Othello stands today. This lake that re-formed with each breach of Glacial Lake Missoula contained hundreds of glacial fragments, or icebergs. Some giant icebergs carried within them granite boulders from Canada weighing several tons. Each time the floodwaters subsided, and the lake slowly drained through the Wallula Gap, some of these icebergs became stranded on the shoreline. The granite boulders, left behind by the melting ice, are now "miraculously" perched on hills hundreds of feet above the Tri-Cities. Other granite boulders, carried by ice or the force of the floodwater itself, are also perched high on the sidehills of Columbia NWR. They are usually pale, and pinkish in color, and not as fine-grained as the native basalt, which is dark in color.

With each successive mega-flood a new landscape emerged from beneath the water. Where the silt was deep, distinctly-shaped hills—long, narrow and bevel-shaped—were left by the flood waters. Where the overlying silt and some of the basalt were carried away, a complex pattern of canyons and buttes were left behind. Fortunately, after the last flood, wind-blown silt was deposited over the rock, providing a thin soil for plant growth. Today, standing on the west side of Othello and looking north-west, a person can easily see the line of demarcation between the higher, gently rounded slopes and hills and the lower area scoured by the floods, a deep, rocky gash in the earth.

Because of this fractured land, early settlers referred to this area as the "scablands," an area mostly unsuitable for cultivation. However, with the coming of the Columbia Basin Irrigation Project and completion of the O'Sullivan Dam, the scablands west of Othello begin to receive water once again, albeit on a much more modest and beneficial scale. The deep holes in the bottom of the flood channels filled with water seeping through the dam and small creeks appeared. These new "pothole" lakes were the impetus for designation of Columbia NWR. The lakes attracted birds by the thousands; thus, Columbia NWR was established to provide habitat for migratory birds, particularly the waterfowl. Being one of the best examples of channeled scabland topography, the Drumheller Channels was designated a national natural landmark by the National Park Service in 1986. Most of the refuge falls within the Drumheller Channels National Natural Landmark and owes its existence to the fascinating geologic events that shaped this area.

 

Who figured all this out? Read on.

J. Harlan Bretz

J. Harlan Bretz

No story of the ice-age floods should end without mention of J. Harlan Bretz. In the 1920's, he was the first to propose the outlandish idea of a mega-flood to explain the bizarre, rocky landscapes of eastern Washington. But he was not of the elite geological establishment, and his ideas were scoffed at for decades. His contemporaries were blinded by the dogma of the time that suggested that geologic events happen very slowly and gradually, not as dramatically as a mega-flood of a scale heretofore unknown in the history of the earth. And Bretz had no explanation for the origin of the vast quantity of water that was a prerequisite for his theory. Only after years of debate and acrimony, and with the advent of aerial photography, did Bretz begin to win his case. In photographs taken high over western Montana, another geologist recognized giant ripple marks, such as those that form on lake beds subject to wave action. The scale of the ripples, like almost every other physical feature of the floods, was unprecedented; as seen from ground level they were taken as simple hills or ridges. These mega-ripples had formed at the bottom of Glacial Lake Missoula. With this and other evidence to come, the geologic community eventually accepted the mega-flood theory and Bretz was vindicated. Speaking of the Drumheller Channels, Bretz wrote: "Drumheller is the most spectacular tract of butte-and basin scabland on the plateau. It is an almost unbelievable labyrinth of anastomosing channels, rock basins, and small abandoned cataracts."

Page Photo Credits — Rock Spires - Gordon Warrick, Columbia Cliffs - Gordon Warrick
Last Updated: Mar 04, 2014
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