*_I live on the north side of Ahtanum Ridge and have front row seats when and if it slides catastrophically..._* I can see the slide from my kitchen window, driveway, deck, even front door. I made some marks on my kitchen window where slide was, and where it is now. Slide has slowed down, but used to move 1 foot per week. There is a 'gash' on top 150-200 feet wide. That is the top of the slide and shows how far it's moved. There are a number of different slides, all part of bigger block of moving Basalt Layers and Interbeds between each layer of Basalt. Ridge is an Anticline; upside down U. Basalt layers are tipped 45 degrees on the sides of Anticline. The interbeds are very weak and mass of heavier Basalt is sliding along those layers. There are signs of older land movement on both Rattlesnake and Ahtanum Ridges. Union 'Gap' is where Yakima River cut through a thousand feet of Basalt millions of years ago. Many times, rivers will undercut slopes that run next to the river. This can cause land movement; minor to major impact. *_If it slides catastrophically, I hope it's in the Daytime so I can watch it happen..._*

Great footage and NO music! Thank you.

The line of shipping containers at the bottom of this billion ton sliding mass are funny. Someone has an interesting sense of humor.

could this all be from the activities of the business shown at the end of the video? When I mess with the base of a footer wall..... geeeesh, I mess the whole house up.

echoing one of the other comments, wonder how much cutting the toe of the slope off with that aggregate operation undermined the slope above...?