coastal systems -landscape development (depositional landforms -beaches) Flashcards
(23 cards)
what are the 6 depositional landforms?
.beaches
.simple and compound spits
.tombolos
.offshore bars
.barrier beaches and islands
.sand dunes
where do depositional landforms occur?
.at low energy coastlines
what are the characteristics of low energy coastlines?
.rate of deposition exceeds rate of erosion
.less powerful construct waves
.sheltered parts of the coast
why does deposition take place?
.when the velocity of the water or wind falls below a critical value for a particular size of particle and can no longer be transported
.large supply of sediment
when might deposition happen?
.currents weaken or prevailing winds may lighten in strength altering the energy source
.when waves move over the seabed or shore land features, friction occurs which slows the waves and results in deposition of heavier particles
.when rivers or landslips add additional sediment to the sea because energy is insufficient to transport the additional load
how is a beach formed?
.when sediment accumulates
.they form between the highest tide and lowest tide
.formed of either sand or shingle and are formed of material from:
-rivers (largest source of sediment)
-longshore drift
-wind-blown (aeolian) sand
-mass movement and erosion of cliffs
what is the structure of a beach?
.backshore -level reached by the sea at high tide
.foreshore -the level reached by the sea at low tide
.nearshore -point where waves no longer have an effect on the land
.offshore -area beyond the point where waves impact the seabed
what are beach profiles?
.many beaches are a combination of both sand and shingle with the larger sediment tends to be at the top of the beach because it takes high energy storm waves to deposit this material
what are the 2 types of beaches?
.sand
.shingle
what is a sand beach like?
.gently sloping
.form in low energy environments because only low energy waves can transport small sediment
what are shingle beaches like?
.steeper
.form in high energy environments because the waves have enough energy to transport larger sediment
what are the 2 ways beaches can be created
.swash aligned
.drift aligned
what are swash beaches associated with?
.swash beaches are associated with large beach profiles, sand dunes and berms
what are drift aligned beaches associated with?
.drift aligned coastlines are associated with spits, tombolos and barrier beaches
what are the 3 main features of beaches?
.storm berm
.cusps
.ridges, runnels and ripples
what is a storm berm?
.raised, wide and flat area of sediment at the backshore
.deposited by a strong swash during high tides and remains largely in tact as normal waves don’t reach that far up the beach
.they mark different tide levels
.highest berm is called the spring tide berm and is made up of large and most course sediment
what are cusps?
.cresent-shaped indentations that form on beaches of mixed sand and shingle
how is a cusp formed?
.waves hit the horn of a beach cusp and split into two directions
.the breaking of a wave into the cusps slows its velocity, causing coarser sediment to be deposited on the horns
.waves then flow along the embayments, pick up finer sediment, and run into one another in the middle -waves flow back out to sea, taking the finer sediment with them
what happens when a cusp is established?
.coarser sediment is constantly being deposited on the horn and finer sediment is being eroded away from the embayments
where do ridges, runnels and ripples form?
.form on low gradient, sand beaches
.form parallel to coast
.form due to the interaction of tides, currents, sediments and the beach topography
what are ridges?
.raised areas of sand
what are runnels?
.depressions behind ridges that water gets trapped in when the tide goes out
what are ripples?
.smaller versions of ridges and runnels
