Lesson 10-What are the depositional landforms at the coast? (PART 2) Sand Dunes:

Question 1

Sand Dunes

Answer 1

• Small ridges or hills of sand found at the top of a beach, above the usual maximum reach of the waves

Question 2

Plant succession

Answer 2

A directional change in the types of plant species that occupy a given area through time. It involves the process of colonisation, establishment and extinction

Question 3

Psammarse

Answer 3

An ecological succession that began life on newly exposed coastal sand. Most common psammoseres and sand dune systems

Question 4

Climax Vegetation

Answer 4

• The dominant mix of vegetation species that characterise an environment given time for colonisation to occur and reach stability

Question 5

Coasts as systems-What processes are important in the development of sand dunes?

Answer 5

• Inputs-cliff erosion rivers (90%)
• Outputs-Storms, destructive waves
• Stoes, beach, sand dunes
• Transfers, wind, LSD

Question 6

Where do sand dunes develop?

Answer 6

• Largely sand beaches
• Shallow beach gradient providing good conditions for sediment transport
• Large tidal zone exposing a large beach (source material)
• Persistant onshore winds to dry and move the sand particles by saltation in land.

Question 7

Example of a sand dune

Answer 7

• Gibraltar Point
• 400-800m of erosion in 500 years which has led to these dunes
• 7m tidal range across a wide beach

Question 8

Order of dune formation

Answer 8

• Embryo dune- prickly salt wart=pioneer plant
• Fore dunes-Cyme grass
• Yellow dunes-Marram grass
• Gray dunes-Sea bachman

In order from youngest to oldest and from the least vegetation to most vegetation

Question 9

Why are tides important when considering sand dunes?

Answer 9

• At low tide, the sand dries out allowing the prevailing winds to move the loose sand up the beach.
• Most moves by saltation in a series of short hops but strong winds may be powerful enough to carry the finer sand grains for longer distances.

Question 10

Detail process of dune formation-Embryo Dune

Answer 10

• Sand accumulates when it meets an obstruction on the beach.
• Seaweed, dead seabirds, driftwood and other detritus may all serve this purpose.
• Conditions here are very extreme, with high pH values (over 8), rapid drainage, no humus, high wind speed and lots of salt spray.
  -These young dunes may reach no more than 1 metre in height.

Question 11

Detailed process of dune formation-Fore Dune

Answer 11

• The first plants to colonise the foredunes are lyme grass, sea couch grass and marram grass.
• These plants are drought-resistant and capable of withstanding burial by the shifting sand.
• As they grow up through the sand, they help trap more sand and so the dunes increase in height.
  -Here the dunes may typically reach up to 5 metres.

Question 12

Detail process of dune formation-Yellow Dune

Answer 12

• Begin to show a greater diversity of plants due to better conditions
• Humus layer builds up and this traps water and nutrients.
• The pH is only slightly alkaline (about 7.5), there is less salt spray.
• The dunes by this stage reach 5-10 metres in height.
• Up to 80% of the sand surface may now be vegetated.

Question 13

Detail process of dune formation-Grey Dune

Answer 13

• The grey dunes are more stable and mosses fill the few remaining spaces between plants so that vegetation cover may reach 100%.
• Small shrubs (brambles, gorse, buckthorn) appear for the first time.
• Environmental conditions 50-100 metres from the sea are much more friendly.
• These large dunes are commonly 10 metres in height and wider than those dunes nearer the shore.

Question 14

Detail process of dune formation-Dune Slack

Answer 14

• The dune slacks are found in between the more mature dunes where the water table reaches the surface causing seasonal or even permanent waterlogging and surface water.
  -Plants which are well adapted to these damp, sheltered hollows include rushes, edges, cotton grass and creeping willow.

Question 15

Detail process of dune formation-Mature Dunes

Answer 15

• The most mature dunes are found several hundred metres from the shore.
• These dunes develop a soil which can support shrubs and trees including hawthorn, ash and birch.
• Humans may plant fast-growing conifers which flourish in the sandy soil.
• Eventually an oak climax vegetation may develop.

Question 16

Case study of Sand Dunes

Answer 16

• Camber Sands is situated to the east of the ancient town of Rye
  -It is a popular sandy beach, with picturesque dunes and interesting wildlife
  -The village of Camber is very close to the beach

Question 17

Is Camber Sands anthropogenic?

Answer 17

• Dune seeding and installation of fencing to lower wind speeds and promote the dune formation-1967
• Sand mining of beach material to build Dungeness Power Station-1967
• Tourism-25,000 tourists vistit per day during summer months and this means footpath erosion occurs and leads to ‘blowouts’ forming

Question 18

Is Camber Sands a natural landscape?

Answer 18

• Sand dunes first develped here 350 years ago due to increased amount of fluvial input of sand to the coast
• The orientation of the coast means that prevailing south-westerly wind casuses aeolian processes such as saltation to move sediment up the beach during low tide
• Sand tranported by longshore drift

Question 19

Which factors are most important in sand dune development?

Answer 19

• Strong onshore winds
• An initial obstacle
• Vegetation
• Flat gradient
• Large beach exposed at high tide
• Fine sand particles

Question 20

Evaluate importance of these factors?

Answer 20

• Most significant is onshore winds as this is the force that deloveres the energy for the sand to be transported to the dune
• Least significant is large exposed area of wet sand as event though it provides a steady supply of wet sand other factors are more important

Question 21

What is a bar/barrier beach?

Answer 21

• A bar is another coastal landform created by deposition
  -It is similar to a spit, but instead of projecting out into the sea, it runs parallel to the coast, connecting two headlands and enclosing a body of water behind it, forming a lagoon or bay

Question 22

What is a tombolo?

Answer 22

• A tombolo is a spit connecting an island to the mainland or another island
  -due to sediment deposition, it is formed when a spit extends from the mainland to an island or between two islands.

Question 23

What are barrier islands and offshore bars?

Answer 23

• An offshore bar is a submerged ridge or sandbar that is located offshore, beyond the nearshore zone. It is typically formed by the action of waves and currents on the coastline, and it can shift and change in size and shape over time.
• A barrier island is a long, narrow island that runs parallel to the coastline and is separated from the mainland by a lagoon or estuary. Barrier islands are typically formed by the accumulation of sand and sediment