Columbia River Gorge
From Portland Hikers Field Guide
The Columbia River Gorge is one of the key geographical features in the Pacific Northwest.
The natural history of the Gorge starts over 20 million years ago, when thousands of volcanic eruptions created a huge lava formation now called the Ohanapecosh Formation. Millions of years later, the Eagle Creek Formation was formed when mudflows pouring off volcanoes covered the land with hundreds of feet of loose rock and ash. Later, in the Miocene period (17-12 million years ago) floods of basalt covered large parts of Washington and Oregon, including 21 lava flows in the Gorge area, many of which are visible today in the walls of the Gorge. During the Pleistocene (2,000,000 to 700,000 years ago), the Cascade Mountains were uplifted in the area. As the mountains rose, the river kept pace and a huge valley was formed through the mountains. This valley had sloping walls with much less visible rock than we see today.
During the last age ice (16,000-14,000 years ago) a large arm of the northern ice sheet blocked the valley of the Clark Fork River in Montana. Water backed up behind the dam for a long time, possibly hundreds of years. Years later, one of three things happened. Either the water reached a level over the top of the dam, temporary warming melted part of the dam or the water pressure actually floated the dam. In any event, once the water began flowing around the dam, it rapidly melted and broke the ice dam and the entire volume of "Lake Missoula" rushed down the valley in one of the largest floods in earth's history. The water spread out in eastern Washington creating the coulees and Dry Falls. When the floodwaters reached the Gorge, they rushed through at depths of several hundred feet. The floods scoured the Gorge clean, washing away all of the loose rock and exposed all of the basalt cliffs we see today. Today's waterfalls are formed where creeks formerly flowing down rock slopes now tumble from upper hanging creek valleys directly into the bottom of the Gorge. Much of the rock washed from the Gorge and points east now forms the flat bottom of the Willamette Valley. Recent research has revealed that a number of floods repeated this pattern over several centuries.
The most recent geological cataclysm to happen in the Gorge was a large landslide about 500 years ago. A series of four landslides tumbled from Table Mountain, blocking the Columbia River in a pile of rubble 200 feet high. Indian legends survive of crossing the river on dry land. The Columbia River was backed up as far as the current John Day Dam. In a few months, the river managed to erode away the southern part of the landslide creating a series of rapids, later called the Cascades.
Indians lived in the Gorge for thousands of years. It created a natural path for commerce and trade. Abundant salmon and camas roots made living comparatively easy. The Lewis and Clark party were the first white men to travel the Gorge in 1803. Within a generation, white men were settling in the area and traveling through it on their way to western Oregon.
The Gorge has always formed the easiest transportation corridor through the Cascade Mountains. From Indians in canoes, transportation changed every few years. An early portage road was built in 1840s around the Cascades. This road survives as the Portage Road Trail near Tooth Rock. In the 1851, F. A. Chenoweth created a portage railroad pulled by mules on the north side of the river and a competitor soon opened on the south side. By 1855, steamboats carried traffic on the river from Portland to eastern Washington and Oregon using the mule-powered portage railroads and a 12 mile long wagon road east of The Dalles. The Oregon Steam Navigation Company, formed in 1860, soon owned most of the pieces of the Columbia River transportation puzzle. With a monopoly, they set about improving their facilities and charging what the market would bear.
Transportation changed dramatically in the following years. A poor quality wagon road was completed from The Dalles to the Sandy River in 1870. Some of this road survives on the Shellrock Mountain Hike. In 1882, the Oregon Railway & Navigation Company, a successor of OSN, completed the first railroad through the Gorge. This line, much rebuilt and relocated, survives today as the Union Pacific. A second rail line was built by the competing Spokane, Portland and Seattle on the Washington side in 1908. This line is now the Burlington Northern-Santa Fe. The first really usable road, known today as the Historic Columbia River Highway, was pushed through to Bonneville in 1914 and completed to The Dalles by 1922.
The Cascades were finally tamed in 1937, when Bonneville Dam was completed. The construction of Bonneville Dam and The Dalles Dam in 1960 completely transformed the Gorge. The backwaters from these dams flooded the Gorge the Indians knew, replacing it with a series of long reservoirs. Associated construction projects relocated highways and railroads, as well as creating a new waterborne system of freight transportation.
Today the Gorge is a mix of small urban areas, smaller towns and public lands. Recognizing the conflicting interests in the area, in 1986 Congress created the Columbia River Gorge Commission to oversee the area. The Commission is assigned the job of balancing commercial needs with recreational activities while preserving the natural scenic character of the Gorge.
With over 100 waterfalls and countless river viewpoints, the Gorge provides beautiful hiking at every turn.