EQ2 2B.6 Flashcards
(15 cards)
What is weathering
breakdown of rock in situ at or near the surface of the Earth
What is mechanical weathering
application of force to physically fragment rock into smaller pieces called clasts
Examples of mechanical weathering
Freeze-thaw
Salt crystal growth : seawater penetrates gaps in rocks at high tides and evaporates at low tides leaving salt crystals, repeats causing pressure
Wetting and drying : Rocks containing clay minerals soaked at high tide and expand in volume, shrink at low tide
What is chemical weathering
chemical reactions attack individual minerals in the rock, breaking bonds and producing new chemical compounds
Examples of chemical weathering
Carbonation - rainwater mixed w CO2, forms soluble calcium bicarbonate solution, limestone rock dissolves
Hydrolysis - breakdown of minerals to form new clay minerals due to effect of water and dissolved CO2
Oxidation - addition of oxygen to minerals inc volume causing mechanical breakdown
What is biological weathering
Break down of rock in situ by living or once-living organisms
Examples of biological weathering
Tree roots - seeds falling into cracks germinate, roots expand and thicken, exert force to widen crack in rock
Rock boring - clams and mollusc drill depressions into rocks using their shell where they live
Seaweed acid - kelp contains sulfuric acid that attacks rock minerals
What is mass movement
Downslope movement of material under the force of gravity
-landslide, rotational slumping, blockfall
When does slumping and when does sliding occur
Unconsolidated material e.g. boulder clay - slumping
Consolidated rock e.g. carboniferous limestone - sliding
What is blockfall
occurs on slopes >40’ where a rock fragment breaks away and drops vertically or bounces downslope
freeze that, salt crystal, hydraulic, abrasion , unercutting
What is rotational slumping
Rock failure and movement along a curved rock plane
Slower than block fall
Facilitated by the presence of water, adds weigh and lubricates it, reducing friction
What are landslides?
Downslope movement of discrete blocks of rock down a flat/linear slip plane, maintaining contact with the cliff surface throughout - consolidated rock
Mechanical weathering, marine erosion, rainstorm
What is a rotational scar
Exposed by rotational slumping
Is a fresh, curved, unweathered and unvegetated rock surface on the cliff face
What is a talus scree slope
Blockfall debris accumulates at bottom of cliff
What is a terraced cliff profile
Debris fallen from rotational slumping forms detached slop by bottom of cliff
Forms terraced cliff profile
