Sunday, February 9, 2020

Landslide Split Tree Stump

I assess a lot of slopes for potential landslide hazards as part of my work. The bluff slope of this inspection was obviously not stable. There was recent slope movement on the steep slope. And the top edge was failing along much of the bluff.

Fracture along outer edge of steep bluff from slope movement expanding into the upland above the older slides on the slope.

Given the wet weather over the past two months, slope failures on steep glacial drift soils is not surprising. Landslides can rip roots apart and twist trees. Indeed we observed roots that had been broken by the soil moving away down the slope.

Broken roots hanging above dropped down slide block

But, the tree stump pictured below is the first time I have seen a split stump ( I have seen split and splintered trees on landslides)  

Split and offset stump on landslide

The slide was taking place within glacial marine drift. While the definitive shells were not present, the marine drift was over consolidated by past wetting and drying and has distinctive vertical fracturing from the consolidation. The vertical fractures can lead to blocks of the upper hard drift breaking and sliding down steep slopes.

Fractured drift underlying upper slope

Hard silt/clay drift

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