EQ2 Flashcards
Sediment cell
A linked system of sources of material transfers of that material + the sink along a coast
It’s an example = dynamic equilibrium system - balance between the material being added, moved + removed in the cell
E.g. E coast = England:
Source: Flamborough head
Transfer: Holderness coast
Sink: Spurn head
Inputs
Cliff erosion River transport
Wind blown sediment
Subaerial processes
Marine organisms
Onshore currents
Transfers
Longshore drift
Swash
Backwash
Tidal currents
Ocean currents
Wind
Sink
Backshore landforms (sand dunes)
Foreshore landforms (beaches)
Nearshore landforms (bars)
Offshore landforms (barrier island)
Negative feedback
When the change produced creates effects that operate 2 reduce or work against the OG changes
E.g. major erosion of sand dunes may lead 2 deposition offshore, creating an offshore bar which reduced wave energy
Therefore protecting the sand dunes + allowing them time 2 recover (build back up)
Positive feedback
When the change produces an effect that operates 2 increase the OG change
E.g. when wind erodes sand dunes + removed the stabilising vegetation further wind erosion later will increase the depletion of the sand dune
Types of mass movement depend = lithology
Unconsolidated material- slumping
Consolidated rock - sliding
Rotational slumping
Involves rock failure + movement along a curved rock plane
Slower than rockfall - can take years for large masses 2 move
Occurs in:
- weaker rocks e.g. clays + shales
- Unconsolidated material- boulder clay
- complex rocks - e.gl where permeable rock strata overlie impermeable beds
Rock moves in a rotational manner
Rockfall
Angular block fall debris accumulates at the cliff foot 2 form a talus scree slope (fan shaped mound of material)
Undercutting of cliffs by the creation of wave-cut notches can lead 2 a large fall + talus scree slopes at their base
Talus scree slope has a slope angle = 34-40 degrees
April 2013= large block fall in St Oswald’s Bay on the South Dorset Coast where an 80m section of chalk cliff was detached overnight
A large talus scree slope was created = slope foot extending 30m into the sea that will protect the cliff from further erosion for a decade or more
Rotational slumping
Exposes a rotational scar
Rotational scar = fresh curved un weathered + unvegetated rick surface on the cliff face
Detached slope section often w/ vegetation intact on top of the slump forms a beach/terraced cliff profile
