Physical factors influencing Flashcards
How does wind influence the coast? How significant is it?
=air moving from an area of high -> low pressure, stronger winds are caused by a larger pressure difference
-increase wind speed= increase fetch -> larger waves that poses more energy
-source of energy in transportation and terrestrial erosion
- longer duration of wind= larger build up of waves
- if blows at oblique angle towards coastline, waves at same angle -> LSD
SIGNIFICANCE= determines severity, strength + direction of waves
-larger factor in more EXPOSED places
-TEMPORARY (varies daily)
How do waves break? What is a wave?
= Kinetic energy caused by the motion of water particles in a wave
1. oscillation wave due to wind blowing over water surface
2. circular motion molecules touch sea floor
3. friction slows water down
4. waves bunch up and decrease wavelength
5. crest toppled over base as there is a SIGNIFICANT FORWARD MOVEMENT OF ENERGY
-height depends on depth of water, strength of wind + length of fetch
How do waves influence the coast?
SWELL WAVES= long wavelength, travel far from point of generation, smooth
STORM WAVES= generated locally from high wind energy, short wavelength
CONSTRUCTIVE= dominating summer months, create a ‘summer profile’, spilling process, strong swash to increase the gradient of the beach pull sediment onshore
DESTRUCTIVE= plunging process little forward movement, moves sediment off beach to nearshore area to decrease gradient of beach
How do tides influence the coast?
=periodic rise and fall of the sea surface
- form gravitational effects of the sun and moon eg neap spring tide = highest tide when moon, earth + sun all align
- low in enclosed areas of sea as wave/wind action is restricted
- low tidal range results in more erosion being focused on one area for longer-> wave-cut platform
- high tidal range when coast is funelled eg Seven Estuary
INFLUENCES WEATHERING + WHERE WAVE ACTION OCCURS
How does geology affect the coast? 2 main things?? SIGNIFICANCE?
LITHOLOGY= physical + chemical composition of rocks
- strong lithology= crystal-like features (cliffs+headlands) as strong bonds between particles, high resistance to erosion, eg basalt
-weak lithology= weak bonds, mass movement events, eg clay
STRUCTURE= properties of rock types (permeability/joints/bedding)
limestone + chalk= soluble in weak acids=> vulnerable to CHEMICAL weathering processes + CARBONATION. Many joints + cracks so eroded fast when waves exploit weakest points
-primary permeability= in porous rocks eg chalk where tiny air spaces separate mineral particles to store water
-secondary permeability= water seeps into joints + is enlarged by solution
MOST significant as a PERMANENT FACTOR => control RATE at which coastal processes happen (varies from place to place though)
Concordant/discordant? Angle of dip?
Concordant= strata parallel to coastline
Discordant=At right angles to coastline => alternating patterns of indented bays + projecting headlands due to bands of hard + soft rock
Horizontal dip-> wave-cut platform
Seaward dip-> landslides
Landward dip-> stable profile and little rock falls
What are ocean currents? How do they influence a coastline?
= large scale flows of ocean water due to convection from earths rotation and driven by offshore winds
- warm currents transfer heat energy at low latitudes-> poles, cold currents do the opposite
-change the temperature of ocean => affects air temp. => affects weathering processes + inputs of sediment into a system
GLOBAL SCALE, more LT SMALL impacts though
