Sand Dunes

Question 1

What is a sand dune?

Answer 1

An accumulation of sand blown into mounds by the wind

Question 2

How are sand dunes formed?

Answer 2

1) sand accumulates on the beach from wave deposition
2) at low tide, the sand dries out allowing the prevailing winds to move the loose sand up the beach
3) larger inter tidal zone for sand to be dried
4) sand is transported by process of saltation
5) debris on the beach traps land sand (this is called a strand line)
6) grass (e.g. Lyme grass) grows which stabilises the dunes

Question 3

How can you determine the age of a sand dune?

Answer 3

By the size of it, how much sand has been accumulated
How far away dunes are from shore line
Types of vegetation growing within them
The soil type (dead plants/animals)

Question 4

What are the different types of dunes?

Answer 4

Embryo dune
Fore dune
Yellow dune
Grey dune
Dune slack
Dune heath mature dune

Question 5

Features of embryo dunes?

Answer 5

• sand continuously moving, needs obstruction to break the force of the wind e.g. driftwood
• high ph (over 8)
• high wind speed
• lots of salt spray
• no more than one meter high
• 80% of sand exposed

Question 6

Features of a fore dune?

Answer 6

• drought resistant plants colonise e.g. Lyme grass and marran grass
• as they grow, more sand is trapped and dunes increase in height (up to 5mm)
• 20% of sand exposed

Question 7

Features of yellow dunes?

Answer 7

• greater diversity of plants
• humus layer builds up
• ph slightly alkaline
• more shelter, less salt spray
• marrow grass dominates other vegetation (such as moss, heather, sea holly)
• dunes are 5-10m high
• 80% of sand vegetated

Question 8

Features of grey dunes?

Answer 8

• stable
• 100% vegetation, less marrow grass, more sea spurge and small shrubs
• 50-100 m from the sea
• sheltered from winds
  Humus darkens allowing soil to form
• ph more acidic
• water content low (plants search for water)
• 10 m high and wider

Question 9

Features of dune slack?

Answer 9

• found between mature dunes and where the water tables reaches the surface
• plants adapted to damp and shelter rushes, cotton grass, creeping willow
• can get peaty soil

Question 10

Features of mature dunes?

Answer 10

• found 100m from shore
• if undisturbed can support shrubs, tress (ash, birch)
• humans may plant fast growing conifers