One of Montana Department of Transportation's great roadside signs.
FFF stands for “Five Fact Friday”, a creation of Tim Havenith at Notes of Nature. Today being Friday, I’m borrowing it for a post about Glacial Lake Missoula (thanks, Tim). We’ve been driving along the old lake bed for two days now.
This was under many hundreds of feet of water not all that long ago.
Fact 1. During the last glacial advance, a lobe of the continental ice sheet formed an ice dam in the vicinity of Sand Point, Idaho, blocking the Clark Fork River drainage and creating a huge lake -- Glacial Lake Missoula.
Diagram showing ice dam, by MT DOT, Alberton Parking area on I-90 between MP 72 and 73.
Extent of Glacial Lake Missoula (dark purple), with ice sheet to north (white) and floods to southwest (bluish); from the Montana Natural History Center.
Fact 2. Missoula, Montana, sits 900 feet below the highest relic shorelines.
Artist’s rendition of the Missoula area 15,000 years ago, from the Montana Natural History Center.
Relic shorelines on “L” Hill, most notable on slope and edge to right (click photo to view).
Fact 3. Sometime around 15,000 years ago (or maybe 12,000) the ice dam floated and failed, letting loose a jökulhlaup.Fact 4. A mass of water, ice and earth hundreds of feet deep poured downstream at 60 to 80 mph, altering the landscape all the way to the Pacific Ocean.
Fact 5. The Scablands of eastern Washington were the result of this flood and others like it (maybe as many as 14 during the last glacial advance). That’s where we’re headed.
Heading north on Interstate 90 along the bed of Glacial Lake Missoula -- looks like the area could use another episode of scouring and cleaning!
