Missoula Floods and the Ice Age: versed in Cataclysmic and Catastrophe Praises
If I were a stranger to the Pacific Northwest, I would probably wonder why there’s such a diversity in the geography between the western and eastern regions of the Cascades Mountain range. In my story I’m sharing today, I represent 70 years of wonderful discoveries and adventures in regards to all forms of rocks, cliffs, river beds, dry channels, hills, canyons, cliffs and all forms of geological oddities created by the Ice Age floods that occurred when the massive glaciers melted from about 16,000 to 11,000 years ago. The first 5 years of my childhood didn’t have much marvel beyond sand box play, backyard trees and the adventures of digging holes—everywhere holes. That was fine enough for those early years; and then geology discoveries took off and haven’t quit one bit, even though I’m somewhat slower at 75 and definitely not gifted with gazelle knees and legs.
But what does the title mean when we talk about Missoula Floods and the unimaginable masses of glacier deposits in the northern hemisphere? The timelines for the ice age era do differ between the opinionated experts. I’ll not go there, but—instead—just be content to stop just about anywhere in the geology moonscapes of the old floods basins and encounter what is there now. The nature shows will give you great documentaries; research there and have good informative ideas of the eons and ages. My best advice for understanding the “mechanism” of the melt floods and their impact on ancient terrains would be this website: “hugefloods.com” from the geology department at Central Washington University. I’m content with understanding the last 16,000 or so years. What happened with the millions of years ago lava floods and other opinions about land mass migrations is another story.
To understand the “now” evident land forms we have on the eastside with mountain ranges going east/west and then crumpled up in other places like massive uplifts of the earth crust, you need to imagine the lava floods that created a very—originally—flat geology plain in our parts. In time—those millions of years—the earth crust in these parts squeezed and crumpled some regions of the lava flows into those rising ridges and slopes we see everywhere now. When the ice masses started to move into valleys and go around the mountain masses, they eventually created huge lakes when river melt channels were blocked. Now, it’s time to put on your imagination hats and think ’cataclysm’. The giant lakes backed up behind the ice dams have certain names for very good reasons. The main lake was called “Missoula” because of the lake level marks on the hillsides still visible today in and around Missoula, Montana. The amount of water held in this lake has been estimated to be maybe 2,400 cubic miles. When the ice dam failed, the water was released suddenly in a torrent of correctly described cataclysmic proportions. The entire volume—2,400 CUBIC miles—gushed out in 1 day, a reasonable guess. Now comes the imagination for catastrophe. The flat basalt that “used” to be our eastside was raked and gouged by the turbidity energy of gigantic water terror. The basalt was ripped out of the flat plains like we might play in my sandbox with a trowel, creating pretend coulees. Granite bedrock everywhere from the northern parts of the Okanogan region and into British Columbia were tossed along like just pieces of pea gravel. That’s the best way to describe the geology debris because the water energy created by speeds of 90 mph plus and walls of flood waves hundreds of feet high could rip and move anything. Hmmm, well, there are plenty of movie examples of how this would have looked like.
Meanwhile, I leave some photo examples (at right) of the Saddle Mountain range that goes from the Beverly area of the Columbia River to Othello as a perfect placed to explore for those fine weekends. Amongst these cliffs and talus slopes of eroding debris, you’ll find wonderful samples of agatized rock resembling the often enjoyed “petrified wood”. The coulees, canyons and many other mountain ranges will all do the same: fantastic embracement and majesty of our terrain forms. Be sure to understand correct permissions for your rock samples to keep. AND remember that the canvas bag seems invincibly strong when going up the slopes and cliffs, but it’s sure a heavy thing hours later with the treasures of gorgeous rocks.
May the joy of too many rocks be with you,
About the Author: Bruce Whitmore is an Arboretum Board Member, retired educator, naturalist, Salmon-in-the-Classroom enthusiast and rockhound.