Estuaries, tidal flats and salt marshes

Overview

How a mudflat forms, difference between a mudflat and a salt marsh and creeks in a salt marsh.

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

   Define an estuary.

   Model answer

   An estuary is the tidal mouth of a river, where fresh water from the land mixes with salt water from the sea.

2. 2

   Why is an estuary a low energy environment?

   Model answer

   It is sheltered from open-sea waves and the tidal flow slows and reverses twice a day, so for much of the cycle the water is almost still.

3. 3

   Describe how a mudflat forms.

   Model answer

   Fine silt and clay carried by the river and the tide flocculate and settle in the slack water, building a level surface exposed at low tide.

4. 4

   What is the difference between a mudflat and a salt marsh?

   Model answer

   A mudflat is bare sediment covered by every tide, while a salt marsh is a vegetated surface higher up that only the highest tides reach.

5. 5

   Name a pioneer plant of a salt marsh and state one adaptation it has.

   Model answer

   Glasswort, which stores water in its fleshy stem so it can tolerate the salt in its surroundings.

6. 6

   How does vegetation accelerate the growth of a salt marsh?

   Model answer

   The stems slow the tidal flow so more sediment settles, and the roots bind that sediment so it is not washed out on the ebb.

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