advanced physical Flashcards
fetch
distance over which the wind blows
wave formations
1) wind moves across surface of water, frictional drag creates small ripples. circular orbital motion of particles
2) Closer to coastline, orbit becomes more elliptical
3) wave height increases, wavelength and velocity decrease
4) water backs up from behind wave until it breaks and surges up beach
swash and backwash
swash - movement of wave onto beach after wave breaks, material deposited
backwash - movement of waves back down the beach. drags material off beach
wave types
constructive - deposit material, creates depositional landforms and ↑ size of beaches
destructive - remove depositional landforms through erosion, ↓ size of beach
high energy coastlines
powerful waves, large fetch, rocky landforms, destructive waves. erosion > Deposition
low energy coastlines
less powerful constructive waves, Deposition > erosion
wave refraction
waves turn and lose energy around headland on uneven coastline. creates erosive features on headlands
why waves break
friction between waves and floor causing wave to slow. Wavelength ↓ wave becomes steeper until can no longer be supported
types of Marine erosion
Hydraulic Action, corrasion, abrasion, solution, attrition
Hydraulic Action
bubbles found within water implode under high pressure, creating tiny jets of water that erode rock over time
Corrasion
sand and pebbles picked up from offshore sink and hurled against cliffs at high tide
Abrasion
sediment moved along coastline, worn down over time by rubbing against coastline
Solution
mildly acidic water dissolves alkaline rocks into solution
Attrition
wave action causes rocks and pebbles to hit against one another, wearing down and becoming smaller and smaller
Sub aerial processes
Physical: freeze thaw, salt crystalisation, wetting & drying
Chemical: Carbonation, Oxidation
Biological: Rock boring, seaweed acids, decaying vegetation
mass movement
soil creep - slowest, particles rise & fall due to wetting and freezing. forms shallow terracettes
mudflow - ↑water content of soil ↓friction, mudflow over underlying bedrock
Rockfall - sloped cliffs over 40° exposed to mechanical weathering. vertical cliffs and earthquakes
landslides and rockslides - heavy rainfall, water enters joints in cliffs
Transportation
Traction: Large, heavy sediment rolled along the seabed
Saltation: Smaller sediment bounces, pushed by currents
susprnsion: smaller sediment carried. higher velocity = ↑size of sediment which can be carried
Solution - dissolved material carried, potentially in chemical form
Gravity setting
water’s velocity decreases so sediment begins to be dropped
flocculation
clay particles group together due to chemical attraction
Sediment sources
Rivers & estuaries, cliff erosion, wind, glaciers, offshore, longshore drift
sediment cells
coasts split into sections. within cells, movement of sediment almost contained & flows act in dynamic equilibrium
cliffs on coastlines
high energy - steep, strong, resistant. absence of beach
low energy - weaker, less resistant rock prone to slumping. low energy waves and short fetch form scree mound at bottom of cliff which reduces angle
wave cut notch
hydraulic action and corrasion from waves create a wave-cut notch. notch gets deeper, cliff falls
caves, arches, stacks, stumps
caves - water enters faults in cracks in headland through HA and Abrasion
Arch - Cave widens due to marine erosion and sub-aerial processes, erodes through to other side
Stack - arch continues to widen until unable to support itself
stump - marine erosion attacks base of stack until it collapses