. Ian Madin Rocks Geology – Points of Interest, Day One | Cycle Oregon

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Ian Madin Rocks Geology – Points of Interest, Day One

IMGP1106 copy-fixedIan Madin is the chief scientist at the Oregon Department of Geology, and he will be providing us with information about the areas we’ll be visiting each day. As it turns out, Mother Nature has dished out some particularly fascinating fury on this region over the years, and knowing a bit about it is going to make the ride even more enjoyable. Best of all, Ian will be on the ride and is more than happy to share his expertise with his fellow riders. Many thanks, Ian.

We start Day One by riding across the Columbia River and down the Columbia River Gorge.  The Gorge started as a valley about 6 million years ago as the Columbia River carved a path through the rising Cascade Range, but it owes it current scenic form to ice-age floods that happened about 15,000 years ago. The ice-age floods occurred repeatedly as glacier-dammed lakes filled over decades and then emptied catastrophically.

Dozens of these floods, among the largest known to have occurred on Earth, swept down the Columbia River, carving the Gorge down to bare rock. At The Dalles, the largest floods were almost 1,000 feet deep, and moved fast enough to remove any and all loose rock or soil. As we pedal across the river and turn west on Highway 14, we’ll pass numerous “scabs,” bare-rock outcrops left behind when the last flood stripped everything else away.

As we head down the Gorge and then turn up the Klickitat River, we’ll spend most of the day riding through the remnants of yet another catastrophic flood – but one of lava rather than rock. The Columbia River Basalt is a series of gigantic lava flows that erupted 16 million years ago from a series of fissures extending from modern-day Enterprise, Oregon, nearly to Spokane, Washington. Dozens of massive flows spread across eastern Oregon and Washington, eventually finding their way west along an ancient course of the Columbia, which passed through Portland and Salem, and in some cases reached as far as Newport, Oregon, having traveled over 400 miles. Many of the lava flows we ride through on the first day will show pronounced columnar structure, the result of cracks that formed as the lava cooled.

At day’s end we’ll be treated to spectacular views of Mt. Adams, one of a dozen active volcanoes in the Cascade ranges of Oregon, Washington and California. Mt. Adams is not the tallest at 12,277 feet, but it is one of the largest. Over the last million years, Mt. Adams has built up 70 cubic miles of volcanic ash, rubble and lava, which is enough to cover the entire state of Oregon with a layer four feet thick. Mt Adams has erupted almost two dozen times in the last 15,000 years, most recently about 1,000 years ago.



  1. Ken Wilson says:

    “Bretz’s Flood” is an amazing book about J Harlen Bretz, the geologist who first identified the giant “Glacial Lake Missoula” floods, was roundly denounced, and lived to be proven correct. A wonderful read.

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