Lower Grand Coulee Chapter

Lower Grand Coulee Chapter

As the combined flood waters from Glacial Lakes Missoula and Columbia surged westward on the path of the Columbia River the rampaging floods were deflected south by the eastern margin of the Okanogan Lobe of the Cordilleran Ice Sheet.

As the concentrated flood waters spilled over a monoclinal fold at the southern end of the present day Upper Grand Coulee, they tore away at the underlying basalt bedrock creating a recessional cataract that eventually extended 20 miles northward to the older path of the Columbia River.

As the flood waters continued streaming south they hugged the south-trending edge of the monocline and began creating another recessional cataract at the present day location of Soap Lake. The resulting Lower Grand Coulee eventually extended 20 miles northward until the cataract recession ended at the site of Dry Falls when the last of the major floods ended.

These spectacular coulees and their boulder strewn expansion bars mutely but exquisitely testify to the awesome power of the Ice Age Floods.

Lower Grand Coulee Chapter

Lower Grand Coulee Chapter

IAFI’s Lower Grand Coulee Chapter serves the greater Soap Lake and Ephrata region. The Chapter meets at 6 PM the Third Thursday of each month. Meetings and programs are held at the Soap Lake Senior Center, 121 2nd Avenue SE, Soap Lake WA.

Occasionally, on the Third Saturday of the month at 11 AM, Chapter members and friends drive and hike to a selected site to see and learn about an aspect of the ice-age floods and geology. Past hikes have taken members to various caves and molds, ripples, holes carved by kolks, erratics and Coyote Rock, so bring a lunch and join us. If you forget a lunch, there will be time to grab a bite at a local eatery.

For more information about the chapter contact Denis Felton by e-mail or at 509-638-9994.
Please see the Upcoming Events or the General Events Calendar for a listing of all chapter meetings and events.Occasionally, on the Third Saturday of the month at 11 AM,

  • Treasurer – Dee Caputo
Lower Grand Coulee Chapter News

Lower Grand Coulee Chapter News

Map & Events

Upcoming IAFI Events

November 2024
Nov 09
November 09, 2024
Soap Lake Senior Center, 121 2nd Ave SE
Soap Lake, 98851 United States
Nov 11

Chapter Location

Upcoming Chapter Events

November 2024
Nov 09
November 09, 2024
Soap Lake Senior Center, 121 2nd Ave SE
Soap Lake, 98851 United States