Mass Movement Processes Flashcards
the freefall of individual rocks or a mass of rocks from a steep cliff or slope, usually due to weathering or erosion
falls (rock falls)
____ is at the base of the cliff – it will naturally end up at the same angle (because of the angle of repose)
talus slope
a type of mass wasting where a block of rock or soil tilts forward and falls due to gravity, often rotating around a pivot point near its base
Topples - usually triggered by erosion, undercutting or weathering that weakens the base of the material
rock, soil or debris moves downslope along a relatively flat or planar surface - keeps the material moving as a more or less intact block
translational slide
moves along a curved surface, usually involves a more localized movement with a distinctive stair-step or terraced appearance
slump
broader term for mass movements that occur along a curved failure surface - material ____s backwards as it moves downslope
rotational slide
the slow, gradual movement of soil or rock, often caused by freeze-thaw cycles or the expansion and contraction of materials
creep
a fast-moving mixture of water, soil, rock and organic material. high proportion of coarse material (gravel/boulders), common in mountainous areas after heavy rain or volcanic eruptions, contrails larger rocks and has more water than other types…
debris flow
slower-moving mass of saturated soil and fine-grained sediment (like clay and silt) - usually forms lobed shapes. occurs on hillsides after rainfall
earthflow
like is like a debris flow but with higher water content and finer material. can be extremely fast moving, especially in arid or semi-arid regions where heavy rain causes flash floods
mudflow - mud/silt/clay
a slow, water-saturated flow of soil over frozen or impermeable ground (common in permafrost regions)
solifluction
of the three flows, which is the FASTEST
debris flows and mudflows. earth flows and solifluction are slower
which flow has the largest material size?
debris flows (rocks and boulders) - mudflows and earth flows have finer material
which flow has the most water content?
mudflows - debris flows are water-rich but chunky, and earth flows are less fluid
After a period of intense rainfall, a thick, muddy slurry surges rapidly down a narrow canyon in a desert region. It travels fast, sweeping up cars and small structures in its path. The material is mostly fine-grained with high water content.
What process is this?
A. Debris flow
B. Earthflow
C. Mudflow
D. Slump
C
In a permafrost region, during the short summer, the top layer of soil becomes saturated and slowly oozes downhill over a still-frozen layer. The movement is very slow and creates a rippled pattern in the tundra landscape.
What process is this?
A. Solifluction
B. Creep
C. Earthflow
D. Topple
A
At the edge of a steep cliff, repeated freeze-thaw cycles cause chunks of weathered rock to break off and fall freely to the base, where they pile up at a consistent angle.
What process is this?
A. Slump
B. Rockfall
C. Topple
D. Translational Slide
B
On a steep slope, a large block of soil tilts forward and rotates around a point near its base, eventually falling. It was triggered after the base was eroded by a nearby stream.
What process is this?
A. Rotational slide
B. Topple
C. Landslide
D. Slump
B
Following heavy rain in a hilly area, saturated soil and fine sediment slowly slide downhill in a lobe-shaped form. The movement is visible but not rapid.
What process is this?
A. Earthflow
B. Debris flow
C. Mudflow
D. Avalanche
A
Over decades, utility poles on a hillside tilt ever so slightly downhill. No sudden events have occurred, but seasonal moisture and freeze-thaw cycles are to blame.
What process is this?
A. Creep
B. Earthflow
C. Slump
D. Translational Slide
A
A massive section of mountainside breaks loose after a volcanic eruption and crashes downslope with incredible speed, pulverizing everything in its path, including forest and structures. It contains a mix of rocks, soil, and snow.
What process is this?
A. Avalanche (Debris avalanche)
B. Debris flow
C. Landslide
D. Mudflow
A
During a seasonal glacier melt, a large outburst flood undercuts the valley sides, leading to entire sections of hillslope failing and sliding into the river.
What process is this?
A. Slump
B. Landslide
C. Topple
D. Translational slide
B
A section of slope breaks loose and slides downhill as a single, coherent block along a flat bedding plane. The movement is fast, but the material remains relatively intact.
What process is this?
A. Translational Slide
B. Rotational Slide
C. Creep
D. Earthflow
A
Heavy rain triggers a chaotic mixture of water, rocks, tree debris, and boulders to rush down a mountain stream channel at high speed. It’s not as fine as mud, but it’s faster and chunkier than an earthflow.
What process is this?
A. Earthflow
B. Debris flow
C. Mudflow
D. Solifluction
B
