Depositional Landforms

Question 1

Formation of beaches

Answer 1

• large sediment is found towards the top of the beach where it has been left from storms
• backwash is often weaker than the Swash as the water quickly percolates into the sand
• as backwash isn’t as powerful, larger sediment remain at the top of the beach
• scree near the cliff as a result of mass movement + weathering means that angularity increases towards the cliff

Question 2

Formation of a storm beach

Answer 2

• formed during storms - material deposited above high water mark
• semi-permanent, can become vegetated

Question 3

Formation of cusps

Answer 3

• semi-circular depressions formed by a collection of waves reaching the same point
• once the curving shape is created, Swash is concentrated in the small bay that forms in the centre of the cusp
• this creates a stronger backwash that removes material down the beach
• act like headlands + bays once formed
• few cms high, few metres across (up to 60m)

Question 4

Formation of anastomosing drainage basins

Answer 4

• mini drainage basins formed by water flowing down the beach often from runnels

Question 5

Formation of runnels (ripples)

Answer 5

• formed by turbulence + wave action
• the spreading out of wave energy across a wide area of beach creating ridges + intervening depressions
• common on sandy, shallow beaches

Question 6

Formation of breached ridge

Answer 6

• raised area on beach
• cause water pools to form (runnels) which drain over time by breaching the ridge

Question 7

Formation of Swash-aligned beaches

Answer 7

• form in low energy environments e.g. bays
• waves approach parallel to the shore, so there is limited LSD
• sediment doesn’t travel far along the beach where it
• wave refraction may reduce the speed of high energy waves, leading to the formation of a shingle beach with larger sediment

Question 8

Formation of drift-aligned beaches

Answer 8

• forms when waves approach at an angle
• so LSD causes sediment to travel far along the beach = may lead to the formation of a spit at the end of a beach
• generally larger sediment is found at the start of the beach + weathered sediment moves further down the breach through LSD (smaller sediment at the end)

Question 9

What is a spit?

Answer 9

A long narrow strip of land which is formed when LSD causes the beach to extend out to search due to changes in direction of coastline

Question 10

Spit formation

Answer 10

• LSD transfer material along the coastline following the direction of prevailing winds as Swash
• if a chnage in direction of coastline occurs, material continues to be transported following the direction of LSD
• deposition of sediment occurs when there is a drop in velocity, commonly at estuaries as the flow into the sea is stronger than the LSD
• this causes the build up of sediment + therefore the extension of land out to search due forming a spit

Question 11

What can influence the shape of a spit?

Answer 11

• changes in direction of prevailing winds will influence wave direction + therefore cause the change in direction of transported material
• wave refraction can also create a recurved tip as material is carried round into the more sheltered water behind the spit

Question 12

How may a spit change over time?

Answer 12

• the recurved end may be abandoned as a new spit will be formed on the old recurved end + so on
• this creates a spit with multiple recurved ends = compound spit

Question 13

Formation of offshore bars

Answer 13

• also known as sand bars
• submerged or partly exposed ridges of sand created by waves offshore
• destructive waves erode sand from the beach with their strong backwash + deposit it offshore
• offshore bars act as both sediment sinks + input stores
• they can absorb wave energy thereby reducing the impacts of waves on the coastline

Question 14

Formation of a tombolo

Answer 14

• a beach or ridge of sand + shingle that has been formed between a small island + mainland
• deposition occurs where waves lose energy due to wave refraction off the island + the tombolo begins to build up

Question 15

Formation of barrier beaches

Answer 15

• where a beach or spit extends across a bay to join two headlands
• this traps water behind it leading to the formation of a lagoon which is separated from the sea
• some barrier beaches may have been formed due to rising sea level after the last glacial period = meltwater from glaciers deposited sedimentary in the coastal zone

Question 16

Sand dune formation

Answer 16

• occur when prevailing winds blow sediment to the back of the beach
• the formation of dunes therefore require large quantities of sand + large tidal range
• this allows the sand to dry, so it is light enough to be picked up + carried by the wind to the back of the beach
• dunes develop as a process of a vegetation succession

Question 17

Vegetation succession for sand dunes

Answer 17

• pioneer species such as sea rocket are resistant to+ able to survive in the salty sand, with it’s roots helping to bind the dunes together
• decaying organic matter adds nutrients + humus to the soil allowing marram grass to grow

Question 18

Dune structure

Answer 18

• embryo dunes = upper beach area where sands starts to accumulate around a small obstacle
• yellow dunes = more sand accumulates + dune grows - vegetation may develop to stabilise the dune - tallest of succession
• grey dunes = sand develops into soil with lots of moisture + nutrients, as vegetation dies enabling more varied plant growth
• dune slack = water table rises closer to surface allowing the development of moisture loving plants
• mature dunes = sandy soils develop due to greater nutrient content, trees will grow (willow, oak etc.) = woodland area becomes windbreak to mainland behind

Question 19

Formation of salt marshes

Answer 19

• in sheltered bays or behind spits, salt + minerals will build up
• vegetation may establish, further stabilising the salt marsh
• like sand dunes, salt marshes can stabilise through vegetation succession

Question 20

Formation of mangroves

Answer 20

• trees that are adapted to grow in saline, low oxygen conditions
• they develop in coastal swamp areas
• they can stabilise shorelines with roots + protect areas from erosion as well as providing an environment for wildlife

Question 21

Tidal sedimentation in estuaries

Answer 21

• estuary = point where river meets sea
• when the flow of water from the river meets the incoming tides + waves from the sea, the water flow ceases so sediment is deposited
• flocculations also causes rapid deposition
• pioneer plants colonise the area leading to more sediment being trapped
• mudflats + salt marshes may develop as a result

Question 22

Embryo Dunes

Answer 22

• sand couch grass
• pH 8-8.5
• humus <1%
• 20-50m inland

Question 23

Fore Dunes

Answer 23

• marram grass colonises = binding soil together + provides organic matter
• pH 8
• humus 1-2 %
• 50 + years
• 50-80m inland

Question 24

Yellow dunes

Answer 24

• marram/ sea sedge = more organic material
• pH 7-7.5
• humus 2.5%
• 100+ years
• 150m inland

Question 25

Grey dunes

Answer 25

• creeping willow
• pH 6.5
• humus 5%+
• 150 years old
• 300m inland

Question 26

Dune Slack

Answer 26

• orchids
• 6.5 pH
• humus 10%

Question 27

Mature Dunes

Answer 27

• trees = eventually pine trees
• 4.5 pH
• humus 10%+
• 2000m inland