Kolk (vortex)

One of many kolk-formed depressions or "potholes" in the channeled scablands in eastern Washington at 46°54′21.40″N 119°16′47″W / 46.9059444°N 119.27972°W / 46.9059444; -119.27972.

A kolk is an underwater vortex causing hydrodynamic scour by rapidly rushing water past an underwater obstacle. High-velocity gradients produce a high-shear rotating column of water, similar to a tornado. Kolks can pluck multiple-ton blocks of rock and transport them in suspension for kilometres.[1][2]

Kolks leave clear evidence in the form of kolk lakes, a kind of plucked-bedrock pits or rock-cut basin. Kolks also leave downstream deposits of gravel-supported blocks that show percussion but no rounding.[1]

  1. ^ a b Alt, David (2001). Glacial Lake Missoula & its Humongous Floods. Mountain Press Publishing Company. ISBN 0-87842-415-6.
  2. ^ Bjornstad, Bruce (2006). On the Trail of the Ice Age Floods: A Geological Guide to the Mid-Columbia Basin. San Point, Idaho: Keokee Books. ISBN 978-1-879628-27-4.