coasts Flashcards
compare constructive and destructive waves in terms of physical appearance
constructive: larger wavelength and smaller amplitude
destructive: smaller wavelength and bigger amplitude
compare constructive and destructive waves in terms of swash and backwash
constructive: powerful swash, weak backwash
destructive: powerful backwash, weak swash
how and when do constructive waves form
formed by storms often hundreds of kilometres away
common in summer
how and when do destructive waves form
formed by local storms close to the coast
common in winter
what are the three types of weathering with basic descriptions
mechanical - disintegration of rock
chemical - chemical changes
biological - actions of flora and fauna
description of example of mechanical weathering
freeze thaw
water collects in cracks of rock and expands as it freezes. cracks and collects as scree at foot
description of example of chemical weathering
carbonation
rainwater is slightly acidic because it absorbs co2. contact with alkaline rocks e.g limestone causes slow dissolve
description of example of biological weathering
plant roots and animals burrow into weak rocks/sand
what is mass movement and three examples
downward movement of material under influence of gravity
sliding, slumping, rockfall
what is sliding
rock sliding down the slide plane of a cliff due to rainfall or an earthquake
what is slumping
collapse of saturated/weak rocks along curved slip plane (scarp) due to unstable base
what is rockfall
rocks falling down cliff face due to freeze thaw. collects as scree
what is hydraulic action
power of waves and air that gets trapped by them causes erosion
what is abrasion
sandpapering effect of rocks against rocky platform
what is attrition
rocks knocking against each other and becoming smaller/more rounded.
does not contribute to coastal erosion
what is solution (transportation)
dissolved chemicals from limestone or chalk
what is suspension
particles carried within water
what is traction
large pebbles rolled along sea bed
what is saltation
bouncing motion of particles too heavy to suspend
what geological structure is required for headlands and bays
discordant coastline: bands of stronger and weaker rock perpendicular from the coastline
how do headlands and bays form
on discordant coastline, weaker rock erodes faster (bay). sheltered and low energy waves - deposition.
harder rock sticks out (headland). high energy waves - wcn & no deposition
how do caves form and which erosion/weathering processes occur
weaknesses e.g faults or joints in cliff face start to erode.
ABRASION AND HYDRAULIC ACTION
how do arches form and which erosion/weathering processes occur
back to back caves connect
ABRASION AND HYDRAULIC ACTION
how do stacks form and which erosion/weathering processes occur
roof of arch is weakened and collapses
WEATHERING PROCESSES
how do stumps form and which erosion/weathering processes occur
wave cut notches form at bottom of stack and collapses
HYDRAULIC ACTION
how do faults form in cliffs
hydraulic action
what is a wave cut notch
hydraulic action and abrasion processes between the high and low wave zones erode the base. material removed by destructive waves. notch formed
why do cliffs retreat
once wcn become to large for the overhanging cliff to defy gravity, it falls onto the beach, aided by weathering.
processes repeats
what is a wave cut platform
former base of cliff is left. continuously smoothed by abrasion.