Landforms of glaciofluvial deposition - Sandur (outwash plain)

Question 1

What is a sandur?

Answer 1

A sandur is a flat expanse of rounded, sorted and stratified sands and gravels characterised by braided channel systems.

Question 2

How is a sandur formed?

Answer 2

Rapid melting of the ice results in meltwater moving over the morainic material, transporting and sorting it. As velocities fall, the material is deposited and sorted, leaving the coarse cobbles, gravel and sand spread in distinct zones (proximal, medial and distal) in front of the moraine.

Question 3

What is the impact of glaciofluvial material being deposited beyond the ice margin?

Answer 3

As glaciofluvial material is deposited beyond the ice margin, there is a loss of pressure and therefore velocity. As a result, only finer materials can be transported far from the glacier snout as energy levels fall.

Question 4

Which type of material can be transported far from the glacier snout as energy levels fall?

Answer 4

Only finer materia

Question 5

What are braided streams?

Answer 5

Braided streams - When glacial ice melts, the water moves away from the glacial snout in fast flowing streams and rivers. The water transports vast quantities of sediment and larger debris.

Question 6

Why does braiding occur?

Answer 6

The high load and seasonal variations in discharge lead to braiding.

Question 7

How thick are some outwash plains?

Answer 7

Some outwash plains can be in excess of 50m thick.