MASS MOVEMENT AND WEATHERINH Flashcards
mass moovement landofrms
rotational scars, talus scree slopes, terraced cliff profiles)
types of mass movement
blockfall, rotational slumping, landslides
what is mass movement
Mass movement is the downslope movement of material (rock and soil) under the force of gravity
mass movemnt type depends on
lithology:
unconsolidated material (like boulder clay) - slumping
consolidated rock (like carboniferous limestone and granite) - sliding
explainn blockfalln
The angular blockfall debris accumulates at the cliff foot to form a talus scree slope, a fan shaped mound of material.
Undercutting of cliffs by the creation of wave-cut notches can lead to large falls and talus scree slopes at their base.
A talus scree slope has a slope angle of 34-40’ (larger fragments maintain a steeper angle of rest)
what causes block fall
By mechanical weathering
freeze-thaw
salt crystal growth
By marine erosion
what is rotationl slumpng
Rotational slumping exposes a rotational scar
A rotational scar is a fresh, curved, unweathered and unvegetated rock surface on the cliff face.
The detached slope section, often with vegetation intact on top of the slump, forms a beach or terraced cliff profile.
what causse rotational slumping
Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction
what is a landslide
A landslide is the downslope movement of discrete blocks of rock down a flat/linear slip plane, maintaining contact with the cliff surface throughout.
causes of landslide s
marine erosion of a cliff foot undercutting blocks weakened by jointing. The removal of support allows gravity to release the block, resulting in sliding.
Rainstorm events can encourage a landslide, lubricating the slip plane, reducing the resistance.
Landslides occur in consolidated rocks with joints or bedding planes sloping seawards.
