Coastal Sand Dunes

Question 1

Define sand dune

Answer 1

Accumulations of Sand shaped into mounds by the wind ( saltation )

Dynamic landform

Fragile

Question 2

Important inputs to create sand dune

Answer 2

Plentiful supply of sand

Strong onshore winds

Large tidal range

Obstacle

Vegetation to encourage growth

Question 3

Why does deposition occur ?

Answer 3

Shallow water
Weak currents reduce waters energy and velocity.

Increase in friction with seabed so more energy used to over come that friction as water is shallow.

^combined with large amounts of sediment / constructive waves

Question 4

Why does there need to be a large tidal range ?

Answer 4

Exposes sand which can be entrained by the wind and therefore transported to back of beach

Question 5

STEP 1

🥤💨

Answer 5

Sand is transported by saltation to back of the beach and in turn becomes trapped by obstacles - litter/ seaweed because it doesn’t have enough energy to transport sand over it so it becomes deposited.

Question 6

STEP 2

🌿

Answer 6

Embryo dunes develop first.

Alkaline / windy / cold conditions and lack of soil moisture as water table is low down mean not much vegetation.

Pioneer species like marram grass adapted here and they help Stabilise dunes with long root system and add organic matter to dunes.

Pioneer species helps trap more sediment and reduce wind energy.

Question 7

STEP 3

🌼

Answer 7

When plants die they add organic matter to soil and increase nutrient content to further promote plant growth.

This leads to yellow dunes which are initially yellow as they contain little organic matter but as vegetation cover increases humus is added to sand.

As a result they look more get leading to grey dunes.

Question 8

STEP 4

💦💧

Answer 8

Dune slacks develop

Depressions within the dunes where water table is on or near surface conditions / damp

Question 9

STEP 5

🌷🌻🌲

Answer 9

As move inland conditions improve
Reduced wind speed
More soil nutrients through decomposing
Acidic soil

Leads to more and more vegetation

Leading to wasting dune

Question 10

STEP 5

🛑

Answer 10

Climatic climax is reached when vegetation growth is stable and no more plants being added - equilibrium

This is at deciduous woodland

Question 11

(STEP 6)

🌬🌬

Answer 11

Within system you can find blowouts

Wind has funnelled through areas and removed sand .

Wildlife / humans can cause this

Question 12

Size of 
Embryo,
Yellow ,
Grey ,
Wasting dunes ???

Answer 12

Embryo - 1m

Yellow - 5m

Grey - 8-10m

Wasting - 6-8m

Question 13

How much sand is exposed on 
Embryo 
Yellow 
Grey 
Wasting dunes ???

Answer 13

Embryo - 80% sand exposed.

Yellow - 20% exposed.

Grey - less than 10% exposed.