Compared to a Suburban
"I was very fortunate to get access to the Snake River landslide today (Wednesday, May 18). Wow, is an understatement. It is huge and is going to be there for awhile." - Dave Bell
|
|
Simply Incredible—The Power of Nature
Dave Bell photos of the Snake River mud slide
by Dave Bell
May 18, 2011
Its size is staggering—and even attempting to calculate the enormity of the earth which has sloughed off and slid down the hill will require an engineer who is very good with a slide-rule.
I had a real treat today, quite by coincidence and good luck. With business meetings in Jackson, I concluded early and headed back home to Pinedale, but detoured down towards the Snake River landslide. As the roads are officially closed with flashing signs and gates, I felt I’d be in trouble any minute for running the gates, and didn’t figure my Pinedale Online Reporter story was going to cut much mustard with a State Trooper. But, I made it to the slide and shot off a dozen or so shots and was just preparing to leave when a WyDOT vehicle rolled up, with a flasher going and with some tough looking characters in it who demanded to know what I was doing in the slide zone.
Well, as luck would have it, Pete Hallstrom and Bob Maxam were among the five WyDOT officials investigating the mess.
So, on went a hard-hat and orange vest and the tour started.
Imagine standing at the banks of the Snake River looking up at the highway—some 300 vertical feet above you. The slide has come all the way to the river and then some—however the swift water of the river has washed most of the in-river debris away. The slide is shaped like a large dog-leg which continues up the hill beyond the highway, into steeper terrain and then dog-legs to the right.
It probably continues 400 yards up the hill from the highway and another couple hundred vertical feet. So it must be at least 800 yards long and 500 vertical feet. At its thickest visible point, the highway crossing, it must be 35-40 feet thick, at least, and at least 200 feet wide or more. The dimensions are very difficult to calculate.
The ground has literally sloughed away and turned to a jello-like goo. The banks on both sides of the slough are stripped smooth as the rock, mud, goo, trees, bushes and debris were swept by in the initial surge.
In some places trees were literally split in half—up the trunk. Not broken in half, but torn in half as if you’d split a piece of firewood. One root gave way and another was firmly entrenched in bedrock so, the tree was split in half.
Whole trees are embedded in the flow, some still standing upright and others toppled and going every which way in a jumbled pick-up-sticks configuration.
The head escarpment is a vertical wall probably 30-40 feet tall. The earth broke at this point, but to the untrained eye it is hard to figure why here! On one side of the slide is bedrock and on the other is more soil and rock—kind of that gumbo looking stuff which our Wyoming Range is famous for when it is wet. Very slippery and gooey.
Huge earthen chunks of ground moved in unison as the slide was coming down the hill. The earth is ripped and torn in huge chunks—many feet thick with cracks visible on the surface. It looks like an earthen tile pattern—with no grout between the tiles. When you step on them they quiver because there is gooey mud beneath them.
It was not apparent that a stream was running down the valley at the head escarpment, but towards the center of the dog leg a sizable snowmelt stream is running into the slide providing ongoing lubrication the earthen mass.
As I hiked (which is a loose term), more like stumbled up the slide, hopping from rock to earthen chunk back to mud then to rock, climbing the several hundred feet towards the head escarpment, it dawned on me it was very quiet.
Certainly there is no traffic. The wind wasn’t blowing, in fact it was very pleasant. But, I kept hearing noises underfoot. Rocks were falling, things were clicking, grinding and moving underfoot. It was not visible to the naked eye, but the whole mass was still moving. I would stand still and listen and small rocks were falling, pieces were moving—I could tell by the grinding and clicking. A rock would fall here, a small earthen slide in another spot, a tree would shake, and a bush would rustle. It was a very eerie sensation.
The WyDOT geologists had set up linear stakes across the slide, basically at the center point of the slides highway crossing. Yesterday the slide was moving very rapidly, but today is was moving about 18-24 inches an hour. So, the mass is slowing and beginning to settle out. It has spent most of its energy at this point.
We talked on the rock pile which is the highpoint above the highway (or in the center of the highway) about the volumes of earth and rock which have moved. An engineer somewhere in WyDOT will calculate this amount and it will be amazing. But to the untrained eye it is a whole unbelievable lot of stuff which moved down that mountain on Saturday night and early Sunday.
Click on this link for his pictures: Snake River Landslide--May 18, 2011 (23 photos)
|
