OCTOBER, 2018: ERRATICS
In geology, the term erratic refers to a rock which has been transported a considerable distance from where it was formed. It's basically "a rock which does not belong here."
Let's go way back in time. So far into that past, believe it or not, that I was not even yet born. Back to 15,000 years ago, in fact. Way over in Montana was a 2,000 foot (610 m) tall wall of ice (Donald Trump would have been jealous, I'm sure). Because this wall blocked the flow of water down the Clark Fork River, a lake formed behind it. We now call that historic lake Lake Missoula, and it had a surface area of about 3,000 sq. miles (7,770 sq. km). Now, as the water became deeper, it placed more and more pressure on the bottom of the dam. If you have ever applied pressure to an ice cube (try using a thin wire to do this, if you have never done the experiment, and you can end up with the wire in the middle of the ice cube), you know that pressure tends to melt ice. The dam eventually broke, releasing a deluge of slushy ice-water (called a glacial outburst flood) which probably exceeded 10 times the flow of all current rivers of the world combined. This torrent, gushing at 80 mph (130 km /hr) carried and rolled huge boulders. Even after the flow had reached the area where the photos herein were taken, it was probably at least 1,000 feet deep. Some boulders were actually carried, at least part way, on gigantic ice chunks. Others became rounded as they were rolled along by the torrent like how a strong wind blows tumbleweeds.
Now consider this: Between 15,000 and 12,000 years ago, all this occurred several times! According to some estimates, maybe once every 55 years or so! Each time Lake Missoula drained the ice dam formed again. Lake Missoula filled again. Pressure eventually again caused a catastrophic failure of the dam, and all these rocks rolled further down river.
The rocks have since weathered, and many have split into pieces. However, it's still easy to envision these huge round hunks rolling to their current positions. Keep this in mind as you view these photos and videos.
Read MoreLet's go way back in time. So far into that past, believe it or not, that I was not even yet born. Back to 15,000 years ago, in fact. Way over in Montana was a 2,000 foot (610 m) tall wall of ice (Donald Trump would have been jealous, I'm sure). Because this wall blocked the flow of water down the Clark Fork River, a lake formed behind it. We now call that historic lake Lake Missoula, and it had a surface area of about 3,000 sq. miles (7,770 sq. km). Now, as the water became deeper, it placed more and more pressure on the bottom of the dam. If you have ever applied pressure to an ice cube (try using a thin wire to do this, if you have never done the experiment, and you can end up with the wire in the middle of the ice cube), you know that pressure tends to melt ice. The dam eventually broke, releasing a deluge of slushy ice-water (called a glacial outburst flood) which probably exceeded 10 times the flow of all current rivers of the world combined. This torrent, gushing at 80 mph (130 km /hr) carried and rolled huge boulders. Even after the flow had reached the area where the photos herein were taken, it was probably at least 1,000 feet deep. Some boulders were actually carried, at least part way, on gigantic ice chunks. Others became rounded as they were rolled along by the torrent like how a strong wind blows tumbleweeds.
Now consider this: Between 15,000 and 12,000 years ago, all this occurred several times! According to some estimates, maybe once every 55 years or so! Each time Lake Missoula drained the ice dam formed again. Lake Missoula filled again. Pressure eventually again caused a catastrophic failure of the dam, and all these rocks rolled further down river.
The rocks have since weathered, and many have split into pieces. However, it's still easy to envision these huge round hunks rolling to their current positions. Keep this in mind as you view these photos and videos.
PANORAMA: COLUMBIA RIVER FROM COLUMBIA RIVER BLUFFS ROAD
Curious about where this is taken from? Click on the little "i" in the circle, then click on "Map." You may then maximize the map, zoom in and out, and toggle between map view and satellite view.
The Columbia River is in the bottom of the valley (you can't see it from here, however). If you look at the valley to your extreme left, that is where Lake Chelan is nestled. You can see a few erratics in the foreground / middle ground.
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