Depositional landforms Flashcards
what does deposition form?
beaches
where are depositional landforms most common?
lowland coasts, beaches are the most common depositional landform
what are beaches?
beaches are accumulations of sand and shingle deposited by waves and currents
where does the sediment on a beach come from?
cliff erosion but most is brought down to the coast by rivers
what are the two different types of beaches?
-swash aligned
-drift aligned
swash aligned
beaches where waves approach parallel to the shore and break with swash moving directly up the beach and the backwash returning directly back, these form wide beaches with an even shoreline
how do you identify a swash aligned beach on a photograph?
the lines are parallel to the coastline (berms)
what’s an example of a swash aligned beach?
chesil beach
drift aligned
form when waves approach the beach at an angle resulting n swash moving diagonally up the beach and the backwash returning though gravity, these beaches have an uneven profile especially when groynes have been used to slow the long short drift
how do you identify a drift aligned beach on a photograph?
most likely a straight coastline
what is an example of a drift aligned beach?
west wittering
why are pebble beaches steep?
A strong swash and a weak backwash causes deposition, on a pebble beach the water goes through the gaps in the rocks and goes back to the sea under/through the rocks. This means lots of material is put into the beach but very little is pulled back into the sea which causes it to be very steep.
nearshore
the breaker zone where waves break
backshore
an area that is not usually affected by waves, so the sand is usually dry
foreshore
the inter-tidal zone repeatedly covered, then uncovered by changing tides
offshore
fairly far out to sea where the waves do not break
beach profile`
shows the gradient from the back of the beach to the sea
what kind of bay is a sandy beach formed in?
a sheltered bay as low-energy constructive waves transport material onto the shore
what is the main type of transportation used to form sand dunes?
saltation
how are sand dunes formed?
- wind pushes sand grains along by saltation
- sand grains start piling up as something has trapped the sand at the back of the beach (e.g. seaweed or driftwood)
- more sand piles up
4.the dune stops growing at the high water mark, this is where the highest tide reaches - the dune becomes stabilised by grasses such as Marram or Lyme growing on the new dune
- as the dune is growing another embryo dune is forming in front of it (closer to the sea) over time the new dunes get closer and closer to the sea
what conditions are needed for a sand dune to form?
-large flat beach
-good supply of sand from the seabed that gets deposited on the beach
-a large tidal range
-a regular onshore wind
-an obstacle
why is a large flat beach important for sand dunes to form?
have enough room for the dunes to form without being swept away by waves/tides
why is a good supply of sand from the seabed important for sand dunes to form?
to create dunes at the back of the beach
why is a large tidal range important for sand dunes to form?
to expose large amounts of sand at low tide
why is a regular onshore wind important for sand dunes to form?
to move the sand to the back of the beach
why is an obstacle important for sand dunes to form?
to trap the sand
embryo dune
a newly formed sand dune closest to the sea
marram grass
a plant found in sand dunes that has long, binding roots
crest
top of a sand dune
windward slope
slope that faces the wind
leeward slope
the slope that faces away from the wind
dune slack
where there is a trough or low point in a line of dunes
water table
the upper horizontal limit of wet sand
describe a spit
-beaches joined to the coast at one end
-at their seaward end, shingle ridges form a series of recurves or hooks
where do spits often develop?
across river mouths or where the direction of the coastline changes abruptly
what process causes spits to form?
longshore drift
what’s tucked away behind spits?
quiet backwaters that waves cannot reach, where tidal currents deposit fine silt and build up mudflats and salt marshes
name some depositional landforms
-spits
-bars
-beach
-sand dunes
describe bars
-bars are extended spits that join up to another headland
how do bars form?
due to the lack of a strong river current that would wash the sediment away like in the tidal race of a spit
give an example of a bar
Slapton Sands in Devon
what is a tombolo?
when a spit extends and joins with an island
what’s the difference between a barrier bar and a submerged bar?
a barrier bar touches the land and has a salt lagoon behind it whereas the submerged bar doesn’t
what are the different types of coastal management?
-hard engineering
-soft engineering
what are the different types of hard engineering?
-sea walls
-groynes
-rock armour
-gabions
describe sea walls
a wall made out of a hard material like concrete that reflects waves back to the sea, placed at the top of the beach or the foot of the cliffs
describe groynes
timber or rock structures built out to sea from the coast (at right angles), they trap sediment being moved along by longshore drift
describe rock armour
pieces of large boulders dumped at the foot of the cliff, rocks force waves to break, absorbing their energy and protecting the cliffs
describe gabions
wire cages filled with rocks that can be built up to support a cliff or provide a buffer against the sea
what are the benefits of sea walls?
-effective against erosion
-gives a sense of security against flooding
-often has walkway or promenade for people to walk along
what are the benefits of groynes?
-creates a wider beach which slows the waves, giving more protection which is beneficial for the tourists
-not too expensive
-useful structures for fishing
