Sand dunes and aeolian processes

Overview

How wind moves sand on a beach, embryo dune and change in soil conditions across a dune succession.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What conditions are needed for coastal sand dunes to form?

   Model answer

   A large supply of dry sand, a wide beach exposed at low tide, a strong onshore wind, and an obstacle such as driftwood or vegetation to trap the sand.

2. 2

   Explain how wind moves sand on a beach.

   Model answer

   Grains are rolled along the surface by surface creep and bounced in short hops by saltation, with the bouncing grains dislodging others as they land.

3. 3

   What is an embryo dune?

   Model answer

   The first, lowest dune to form, where sand accumulates around an obstacle just above the high tide line.

4. 4

   Name the pioneer species that colonise an embryo dune.

   Model answer

   Sea rocket and sea couch grass, which tolerate salt spray and occasional inundation.

5. 5

   Why is marram grass so important in dune development?

   Model answer

   Its long roots bind the sand and its stiff leaves slow the wind at ground level, so more sand is trapped and the dune grows taller.

6. 6

   Describe the change in a dune's height and shape from the beach inland.

   Model answer

   Dunes rise from low embryo and fore dunes to the tallest yellow dunes, then fall away through grey dunes to lower, flatter mature dunes and heath.

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