Kolk
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/* Examples */ Oswego Lake is also mentioned in this book
A '''kolk''' (also known as ''colc'') is an underwater [[vortex]] that is created when rapidly rushing water passes an underwater obstacle in boundary areas of high shear. High velocity gradients produce a violently rotating column of water, similar to a [[tornado]]. Kolks are capable of plucking multi-ton blocks of rock and transporting them in suspension for some thousands of meters. <ref name="Alt"> {{cite book|first=David|last=Alt|id=ISBN 0-87842-415-6|location= |title=Glacial Lake Missoula & its Humongous Floods|publisher=Mountain Press Publishing Company}} </ref><ref name="Bjornstad">{{cite book|author=Bjornstad, Bruce|title=On the Trail of the Ice Age Floods: A Geological Guide to the Mid-Columbia Basin |publisher=Keokee Books; San Point, Idaho |year=2006|id=ISBN 978-1-879628-27-4}}</ref>
Kolks leave clear evidence in the form of plucked-bedrock pits, called [[Rock-cut basin]]s or lakes and downstream deposits of gravel-supported blocks that show percussion but no rounding.<ref name="Alt" />
==Examples==
Kolks were first identified by the Dutch, who observed kolks hoist several ton blocks of [[riprap]] from dikes and transport them away suspended above the bottom.<ref name="Alt" />
Kolks are credited with creating the pothole-type geographical features in the highly jointed basalts in the [[channeled scablands]] of the [[Columbia Basin]] region in eastern [[Washington]]. Depressions were scoured out within the scablands that resemble virtually circular steep sided potholes.<ref name="Bjornstad" /> Examples from the [[Missoula Flood]]s in this area include<ref name="Alt" />:
* The region below [[Dry Falls]] includes a number of lakes scoured out by kolks.
* [[Sprague Lake]] is a kolk-formed basin created by a flow estimated to be 8 miles wide and 200 feet deep.
* The Alberton Narrows on the [[Clark Fork River]] shows evidence that kolks plucked boulders from the canyon and deposited them in a rock and gravel bar immediately downstream of the canyon.
* The south wall of [[Hellgate Canyon]] in [[Montana]] shows the rough plucked surface characteristic of kolk eroded rock.
* Both the walls of the [[Wallula Gap]] and the [[Columbia River Gorge]] also show the rough plucked surfaces characteristic of kolk eroded rock.
* [[Oswego Lake]], in the middle of [[Lake Oswego, Oregon]] (a [[Portland, Oregon|Portland]] suburb), was an abandoned channel of the [[Tualatin River]] that was scoured by a kolk
==References==
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[[Category:Oceanography]]
[[Category:Geomorphology]]
[[de:Kolk]]
[[nl:Kolk (water)]]