Depositional Landforms

Question 1

What is a beach?

Answer 1

• a depositional landform that stretches from the low to high tide line

Question 2

How is a beach formed?

Answer 2

• created when sediment is deposited near coastline, when waves lose their energy
• larger sediment, left behind from winter storms, is found near top of beach bc backwash is often weaker than swash bc water quickly percolates into sand

Question 3

What is a shingle beach?

Answer 3

• beach w steep gradient bc waves easily percolate into sand, dec. effect of backwash erosion + inc formation of sediment into a steep sloping back

Question 4

What is a sandy beach?

Answer 4

• flatter + wider beach, bc smaller particles are evenly distributed + water takes longer to percolate into sand so more sand is removed w backwash

Question 5

What are the diff beach profile features?

Answer 5

• ridges + runnels
• storm beaches
• cusps
• ripples

Question 6

What are ridges + runnels?

Answer 6

• raised areas (ridges) + intervening depressions (runnels) on shallow, sandy beaches, formed by interaction of tides, currents, sediments + shallow beach topography

Question 7

What are storm beaches?

Answer 7

• ridge of boulders + shingle thrown to back of beach by largest waves at high tide

Question 8

What are cusps?

Answer 8

• self sustaining, semicircular depressions formed by waves breaking directly onto beach w a strong swash + backwash

Question 9

What are ripples?

Answer 9

• ridges + intervening depressions that develop on sandy beaches as a result of wave + tidal movements

Question 10

What are the 2 diff types of beach?

Answer 10

• swash-aligned beaches
• drift-aligned beaches

Question 11

How are swash-aligned beaches formed?

Answer 11

• when prevailing winds cause waves to break parallel to coast, LSD is limited, causing swash + backwash to move material up + down beach so sediment doesn’t travel far along beach
• this creates smoothly curved, concave beaches
• wave refraction May dec speed of high energy waves, forming a shingle beach

Question 12

How are drift-aligned beaches formed?

Answer 12

• when prevailing winds cause waves to break at an oblique angle to coast, swash occurs at an angle + backwash runs perpendicular to beach, causing LSD to transport material far along beach
• this may lead to formation of a spit at end of beach

Question 13

What is a spit?

Answer 13

• a long narrow strip of land formed when LSD causes beach to extend out to sea, bc of a change in direction of coastline
• sediment projection can create a salt marsh bc of sheltered, saline envi w a lower speed of water flow, allowing deposition of finer sediments to occur
• length of spit depends on changing currents or rivers, which prevent deposition of sediment so a spit can’t extend across an estuary
• a recurved end can form from a change in wind/wave direction

Question 14

What is a compound spit?

Answer 14

• a spit w multiple recurved ends formed over time when recurved end is abandoned + a new spit is formed on old recurved end

Question 15

What is a tombolo?

Answer 15

• a spit connecting mainland to an offshore island, formed by wave refraction off coastal island, dec wave velocity + leading to deposition of sediments
• if low lying, it may be covered at high tide

Question 16

What are offshore bars/sandbars?

Answer 16

• an offshore region where sand is deposited, formed when waves break bc don’t have enough energy to carry sediment to shore
• can also form when backwash from destructive waves remove sediment from a beach
• they may absorb wave energy, dec erosion in some areas

Question 17

What are barrier beaches?

Answer 17

• a beach/spit extending across a bay to join 2 headlands, which traps water behind it to form a lagoon separated from sea
• some may have formed from rising sea lvls after last glacial period, when meltwater from glaciers deposited sediment in coastal zone
• if it becomes separated from mainland, it forms a barrier island

Question 18

How are sand dunes formed?

Answer 18

• prevailing winds blow sediment to back of beach which requires large quantities of sand + a large tidal range
• this allows sand to dry, so is light enough to be picked up + carried by frequent onshore winds to back of beach
• sand dunes can be stabilised + developed through vegetation succession

Question 19

Describe how sand dunes stabilise + develop by vegetation succession.

Answer 19

• sand deposited above high tide mark forms a embryo dune where pioneer species (e.g. sea rocket), which are resistant + able to survive in salty sand, w its roots helping to bind dunes together, grow
• a fore dune is formed once sand dune becomes bigger + is yellow in colour
• over time, decaying organic matter adds nutrients + humus to soil, turning dune grey + allowing marramgrass to grow which has long roots to seek water + stabilise dune
• dune slacks form when water table rises towards surface + water is trapped in depressions between dunes
• mature dunes form when larger plants can colonise area + climatic climax occurs when trees can colonise area

Question 20

How does tidal sedimentation in estuaries occur?

Answer 20

• deposition occurs in river estuaries (where river meets ocean) bc of change in velocity from a river to an ocean
• when waterflow from river meets w incoming tides + waves from sea, flow virtually stops so water can’t carry small, fine sediment in suspension + forms mud that builds up until it’s above water lvl
• more sediment is trapped by colonising pioneer plants +.mudflats + saltmarshes May develop due to sedimentation

Question 21

What are salt marshes?

Answer 21

• build up of salt + minerals in sheltered bays or behind spits, which can be further stabilised + developed by vegetation succession

Question 22

Describe how salt marshes can be stabilised + developed by vegetation succession.

Answer 22

• gut weed + blue green algae grows on mud, in which their roots help to bind together
• during pioneer stage cordgrass + glasswort grow + their roots start stabilising mud allowing estuarine to grow
• causes height of salt marsh to inc + plants no longer need to be adapted for salty conditions
• this means a wider range of plants can grow (e.g. rush) which improves soil conditions to form a meadow
• eventually, succession reaches its climate climax when shrubs + trees can colonise area bc saltmarsh is only submerged 1/2 times per yr

Question 23

What are mangroves?

Answer 23

• trees adapted to grow in saline, low O2 conditions that develop in coastal swamps in tropical regions, meaning envi around them is constantly changing w tides
• can stabilise shorelines w roots, protect areas from erosion + provide envi for wildlife

Question 24

How is a spit formed?

Question 25

How is a compound spit formed?

Question 26

How is a tombolo formed?

Question 27

How are barrier beaches formed?

Question 28

How are salt marshes formed?

Question 29

How are mangroves formed?