Irrigation canal operators stand ready to open dams and take water from the river if it is blocked by a rock slide. “It’s a unique thing.”CANADA Spokane Seattle WASHINGTON Pacific Ocean Union Gap OREGON Portland 100 Miles BIRCHFIELD RD. Union Gap 82 Yakima River Area of landslide 97 THORP RD. 1 mileIn the last few weeks, the main mass of rock has been moving toward a gravel quarry at the base of the ridge. Over time, the layers have folded upward, forming the ridge, and the topmost basalt layer is now sliding over the sedimentary layer beneath it.

Source: New York Times January 22, 2018 01:40 UTC