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The Geology of the Columbia River Gorge:

Washington Side


DESCRIPTION OF FIELD TRIP:  The tour explores the unique geology on the Washington side of the Columbia River Gorge.  Some of the stops are:  1) a river-level view of Beacon Rock, named by Lewis & Clark in 1805, but called Castle Rock until 1915 when it was officially named Beacon Rock.  It is over 800 feet of basalt lava that once was the core of a volcano.  Its sides were cut away by the Lake Missoula Floods.  2) Coyote Wall, a 200 foot high cliff that dips down to the Columbia River as part of a over 1,600 feet geo-syncline.  It was formed from a basalt flow from a fissure that spread hundreds of miles at least partly under water.  A short hike will let you discover the evidence for this.  3) Underwood gravels, part of the deposits that filled the Portland Basin where they are called Troutdale Formation.  

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Geology of the Columbia River Gorge: Oregon Side


See the beauty of the Columbia River Gorge and learn how the unique geologic layers and up-lifts were exposed and reshaped by the Lake Missoula Flood to create the vivid scenery we see today.  


This tour explores the unique geology in the Columbia River Gorge and features related to a remarkable history of cataclysmic Lake Missoula Ice Age Floods which resculpted the Gorge into the stunning beauty we see today. Stops include Columbia Park where huge basalt boulders rest which were torn from the Gorge; Troutdale Formation which shows the rapid deposition of these layers; Latourell Falls in an alcove carved by the Lake Missoula Flood; Multnomah Falls; The Mosier eddy bar and erratic boulder; and Rowena Crest with its mima mounds.

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Discovering the Lake Missoula Flood  In Clackamas County 


The Lower Columbia Chapter of the Ice Age Floods Institute took an all-day bus tour of Lake Missoula Floods evidence in Clackamas County. Lead by  Lake Missoula Floods (LMF) expert Rick Thompson who has extensively studied and mapped features in the area left by the cataclysmic Missoula Ice Age Floods.


Highlights of the trip included:  Being the first to see a newly discovered spillway between the Clackamas Valley and the Willamette Valley.   Baker Cabin where the Lake Missoula Flood created a short-lived waterfall and carved holes in the basalt which the Native Americans later used for grinding stones.  A bird’s eye view of the Carver Gap and flood channel.  The reputed second largest glacial erratic in Oregon.  Canemah - a scabland on the east side of the Willamette River.  Willamette Falls which is a receding waterfall created by the ice age floods.  .

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Tualatin / Sherwood Ice Age History:

Mega-floods & Mega-fauna


     Tour of the Tualatin area of northwest Oregon emphasizing the ice age topography as well as the remains of ice age animals found there.  This area is known to have had mastodons, giant ground sloths, ancient bison and saber-tooth cats.  Research is still being done on evidence of the animals within and around Lake Missoula Flood deposits.


     The central figure in this story is the mastodon found just south of where the Tualatin Fred Meyer parking lot is today.  The field trip visits the Tualatin Public Library where most of the mastodon bones are and the Tualatin Heritage Center where the tusk and molar are as well as a vertebra from a giant ground sloth found near the Tualatin River.


     Most of this field trip concerns itself with evidences for the ice age flooding that totally reshaped the area into what J Harlan Bretz called a “Channeled Scabland.” Geologists have identified 14 flood channels in a complex called the “Tonquin Scablands” or the "Tonquin Geological Area"  and this trip includes 10 of them.  

GigaFlood Field Trips

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We offer the following tours and can tailor it to your interests.