2 - temporal variations and impacts Flashcards
what is a tide
tides are movements up and down of water adjacent to the coast
how is a tide controlled and created
controlled by gravitational pull of moon and sun
moon greatest influence - close to earth
attracts and pulls water to side of earth nearest to it and creates bulge of water forming high tide with complementary bulge on opposite side of earth
areas in between have low tide
as moon orbits earth high tide follows
explain diurnal and semi diurnal tides
most coastlines experience 2 high and 2 low tides approx every 24 hours - SEMI DIURNAL
some places including Antarctica receive 1 high, 1 low tide in 24h period - DIURNAL
how can tides determine coastal erosion
active area of erosion within area between points of lowest and highest tides, and main transportation processes also happen between these points
only if high tides reach cliff line, cliffs eroded
what is a tidal range
= height difference between high and low water during monthly tidal cycle
inter tidal zone = area of land between spring high tide and low tide and it receives almost all coastal processes of erosion, transportation and deposition
what is a storm surge
result of extreme meteorological conditions and coastline configuration
water levels exceed high tide levels and can cause property damage and death
what is onshore flow
movement of any weather feature moving towards shore eg hurricanes
offshore current = ANY CURRENT FLOWING TOWARDS THE SHORE
what is a sea breeze
sea breeze happens during afternoon when ocean waters and land at different temperatures
air over land warmer than water, air rises vertically over land and air from ocean moves in to shore filling empty space
what is offshore flow
movement of any weather feature moving away from land to sea eg hurricane most common
offshore current = ANY CURRENT FLOWING AWAY FROM SHORE
what is land breeze
occurs during evening
land gets cooler than water creating air over water to go upwards and cooler air over land moves out over water to fill in space
how is summer different to winter (waves and beach profile)
winter = destructive waves, beach berms and dunes erode lowering beach and sediment pulled offshore onto sandbars which protect beach as waves break further from shore. flatter more concave shape
summer = constructive, sand returns to beach and berms and dunes recover. berm changes most during seasonal cycle
what are characteristics of constructive waves
- flat and gentle waves
- strong swash, weak backwash
- little material returned down to beach
- sand carried up beach to form berm
- smaller longshore bar
- low frequency
- long in length
- surging water movement
characteristics of destructive waves
- high and steep waves
- weak swash, strong backwash
- larger longshore bar
- some large material forms storm beach
- most material carried down beach by backwash
- gradient decreases down beach
- high frequency
- short in length
- plunging water movement
what is a wave
a wave is a transfer of energy from wind to seas surface
it is an elliptical motion of water formed by the friction from tides on oceans surface
what is wave fetch
distance over which wind blows over the sea
larger fetch = more powerful and larger waves
