Category Archive 'Rattlesnake Ridge'

08 Jan 2018

There’s Something Happening Here

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The Landslide Blog has an imminent winner:

Rattlesnake Ridge is a large hillside located above the I-82 highway to the south of the town of Yakima in Washington State, NW USA. The Google Earth image below shows the location of the site (at 46.524, -120.467), taken in May 2017. The image is looking towards the east – note the large active quarry on the south side of the ridge, and other signs of earlier (and smaller scale) excavation on the slope. Note also the proximity of the slope to I-82.

In October 2017 a major fissure started to develop through Rattlesnake Ridge. Over the last three months this apparent tension crack has widened to encompass a volume of about 3 million cubic metres.

The latest reports suggest that the crack is widening at a rate of about 30 cm per week at present. Interestingly KIMA TV reports that the expectation is that the slope will self-stabilise:

    Senior Emergency Planner Horace Ward said they have not determined a cause yet and said it’s just nature. Ward said the ridge is being monitored and they think the slide will stop itself.

    “It could continue to move slowly enough to where it kind of just keeps spilling a little bit of material into the quarry until it creates a toe for itself to stop and stabilize the hillside,” he said.

The implication of this is that it is a rotational slip. However, the tension crack has quite a complex structure, with some evidence of the development of a graben structure.

RTWT


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