Wednesday, January 3, 2018

High Quality Video of Fracture Development at Union Gap Slope Failure

A so far slow moving slope failure has developed just south of Yakima where the Yakima River cuts through Rattlesnake Ridge at Union Gap. I have had numerous emails and linked facebook posts sent my way on this.


This failure is a worrisome event. The orientation and geometry of the fractures suggests that the movement is towards the steep slope of the gap; however, news articles suggest that mush of the slide will be directed towards the quarry. The cracks have formed a graben-like feature. One of the articles by the Yakima Herald noted rock fall onto Thorpe Road. That suggests some deformation may be taking place on the slope below the fractures and on the steep slope.

Maybe a bit more on this later. Travel and now work precludes much time to get into more detailed theory or research or information sharing.  


Upupaepops said...

wow that is a scary looking situation that looks like it has the same potential as the Ohop slide, only impacting a major roadway. I look forward to hearing your further thoughts on this situation and what the river bed below says about previous occurrences.

susan said...

That drone video is so revealing. It ain't ONE crack, it’s a network of cracks/fractures. The piece notes that the potential slide is “slow-moving,” yet also, "Officials say the hillside above the quarry is moving an average of 1.4 feet per week…” 1.4 feet a week??! More than six feet a month?? That doesn’t seem slow-moving to me. In fact, in a geological sense, it is GET THE F@#! OUT NOW!!!

Still, ya know, COOL!

Al Heezen said...

On Google Earth the surface running north of the quarry for a couple thousand feet is much darker than the rest of the ridge. It doesn't look to me like it is just shade from the sun (but if it is, that is one scary steep slope!) Do you know what gives here? [BTW the captchas on this comment form are freaking impossible! This is my third attempt to post.]

Dan McShane said...

Al - Thanks for sticking it out with the comment. Yes, that slope to the west down towards the river is very steep. It is a mix of talus, scree and a few low cliffs.