Chapter 15 Mass wasting

What is permafrost, and what can result from disturbing it?

Permafrost is permanently frozen ground. If the thermal balance of permafrost is disturbed, ice within the permafrost may melt, causing the ground to slide, slump, or subside.

Rapid mass-wasting events do not always need a trigger.

True

What causes creep, and how can it be recognized?

Creep is caused by the repeated expansion and contraction of the regolith, which may be caused by repeated freezing and thawing or wetting and drying. Creep can be recognized by tilted trees, tilted fences, and displaced retaining walls.

What is the difference between an earthflow and a debris flow?

Debris(mudflow): -consists of soil & egolith w/ large amount of water -confined to channels -hazard in dry areas w/ heavy rains (alluvial fans) Earthflow: -forms on hillsides in humid regions -water saturates soil; involves clay/silt rich materials -large range in size -relatively slow movement; active days to years

slide

A mass movement in which a cohesive block of earth or rock slips downhill relatively quickly in one piece along a zone of weakness

slump

A type of mass movement that occurs when a mass of material moves down a curved slope

Why can rock avalanches move at such great speeds?

Air becomes trapped and compressed beneath the falling mass of debris, which allows the debris to move as a flexible sheet across the surface of the slope.

In a river valley, mass-wasting processes can ______. CHOOSE ALL THAT APPLY.

Less steep, and wider

What is mass wasting, and how does it differ from other erosional processes (e.g., streams, glaciers, wind)?

Mass wasting is the downslope movement of rock material driven by the force of gravity. It differs from other erosional processes in that mass wasting does not require a transporting medium.

What landscape feature indicates that mass wasting has helped shaped a river valley?

Much wider than deep

During which season does solifluction occur in the Arctic, and why?

Solifluction occurs during the Arctic's summer, when the top meter or so of the active layer thaws. Because the resulting meltwater has nowhere to go, it saturates the active layer, causing it to slowly flow.

Creep

very gradual mass movements in which the whole slope moves downhill slowly.