how can coastal landscapes be viewed as systems 1 Flashcards
components of an open system
- INPUTS - kinetic energy from wind and wave, thermal energy from sun, potential energy from material on slopes
- OUTPUTS - marine and wind erosion from baches and rock surfaces - evaporation
- PROCESSES - which are stores: beach and nearshore sediment accumulation. flows and transfers like movement of sediment along a beach by LSD
whats an open system
energy and matter can be transferred from neighboring systems as an input and also transferred to neighbouring systems as an output
example of negative feedback and equilibrium in a coastal system
- EQUILIBRIUM
- inputs and outputs are equal
- eg rate sediment is added is same rate as sediment removed so beach remains same size - NEGATIVE FEEDBACK
- equilibrium disturbed and system changes to restore equilibrium
- this turns it to a dynamic equilibrium == example of negative feedback
whats a sediment cell
- stretch of coastline where movement of sediment, sand and shingle is largely self-contained
- closed system - no sediment transferred from one cell to another - but not completely due to wind and tides
- has sub cells - smaller scale cells existing in major sediment cell
list of PHYSICAL FACTORS that affect coastal landscapes
wind
wave
tide
geology
currents
winds - PF affect coastal landscapes
- wind is the source of energy for coastal erosion and sediment transportation
- this ENERGY generated by frictional drag of winds across ocean surface
- higher wind speeds and long fetch = larger waves and more energy created
- waves at an angle = LDS
- wind is an aeolian process
how do waves generate energy
- potential energy bc of its position above the wave trough
- kinetic energy bc of motion of water within the wave
- waves don’t move water forward but create a circular motion to individual wave molecules (like if you put a ball on waves it would rise and fall not just move horizontally across the sea surface)
4 parts of a wave - wave anatomy
- fetch - distance wave travels over the sea
- waveheight - distance between crest and trough (highest and lowest points on a wave)
- wavelength - distance between crests
- frequency - number of waves per minute
the process of how a wave breaks
- in shallow water - circling molecules hit seafloor - FRICTION
- friction slows wave bc of drag at bottom
- wavelength decreases and waves bunch up
- then deepest part of wave slows more than the top
- this steepens the crest which then causes wave to eventually topple over and break
constructive waves
- low waveheight
- long wavelength
- low frequency (6-8 per min)
- they break spilling forwards: strong swash travel long way up gently sloping beach
- long wavelength means backwash returns to sea before swash on next wave so swash is uninterrupted and energy is carried up beach
destructive waves
- high waveheight
- short wavelength
- high frequency (12-14 per min)
- they break plunging downwards so little energy carried forwards up the beach
- friction from steep beach slows swash so it doesnt travel far before coming back as backwash
- short wave length also means swash is interrupted and meets the backwash of previous wave therefore energy of backwash exeeds swash
high energy and low energy waves
HIGH ENERGY
- winter months
- remove material from top of beach and transfer to off-shore zones REDUCING BEACH GRADIENT
LOW ENERGY WAVES
- summer months
- build up beach and steepen profile
what are tides
- the periodic rise and fall of sea surface due to gravitational pull of moon and a bit the sun
- moon pulls water towards it (high tide). this makes compensatory bulge on opposite side of earth. then at places between the bulges is low tide
tidal ranges
- enclosed seas (Mediterranean) LOW tidal ranges so wave action restricted
- tidal ranges influence where wave action occurs and therefore the development of coastal landscapes
what does geology consist of
lithology - physical and chemical composition of rocks
Structure - properties of rock types like jointing, bedding, faulting
lithology
- physical and chemical composition of rocks
- WEAK lithology: clay bc bonds are weak therefore less resistant to erosion, weathering and mass movement.
- STRONG lithology: basalt bc made of dense interlocking crystals highly resistant - form coastal features like headlands and bays
- chalk and limestone - vulnerable to chemical weathering - carbonation -= bc soluble in weak acids
structure
- properties of rock types like jointing, bedding, faulting
- permeability of rocks
- porous rocks like chalk - tiny pores absorb and store water = primary permeable
- water seeps into limestone bc of joints = secondary permeable
- also includes angle of dips
concordant and discordant coastline
CONCORDANT - rocks parallel to coast and produce straight coastlines
DISCORDANT - rocks at right angles to the coats. more resistant rocks form headlands and weaker rocks for bays
rip currents
- caused by waves breaking at right angles to the shore
- a cellular circulation is created by differing wave heights parallel to shore
- water from top of break waves with large height travels further up shore and then returns through the adjacent area where the lower height waves have broken
- create features like cusps
ocean currents
- large scale - created by earths rotation and convection
- set in motion by movement of winds across water surface
- warm ocean currents transfer heat energy from low latitudes towards the poles
- cold ocean currents move cold water from polar regions to equator
- the transfer of heat affects coastal landscapes.
3 ways coastal sediment is supplied - inputs
- Terrestrial - rivers, wave and cliff erosion, LDS
- Offshore - constructive waves, tides, currents, wind
- Human - beach nourishment
