Systems And Feedback Loops

Question 1

Sediments cells

Answer 1

Coasts can be split into sections called sediment cells. These are typically considered a closed - system in terms of sediment.

Question 2

Sources
Through flows
Sinks

Answer 2

Sources - where the sediment originates from
Through flows - movement of sediment along the shore through LSD
Sinks - locations where deposition of sediment dominates (beach,spit)

Question 3

What is dynamic equilibrium

Answer 3

Dynamic equilibrium in a sediment cell is where input and outputs of sediment are in a constant state of change but remain in balance

Question 4

What can change dynamic equilibrium?

Answer 4

Physical and human action can change this equilibrium.

Question 5

What is a Negative feedback loop?

Answer 5

This lessens any change which has occurred within a system.
For example, a storm could erode a large amount of beach (taking it out of dynamic equilibrium as there is a larger input of sediment into the system than output).

Question 6

What is an example of negative feedback loop

Answer 6

• When the destructive waves from the storm lose their energy, excess sediment is deposited as an offshore bar.
• The bar dissipates the waves energy which protects the beach from further erosion.
• Over time the bar gets eroded instead of the beach.
• Once the bar has gone normal conditions ensue and the system goes back to dynamic
  equilibrium.

Question 7

What is positive feedback?

Answer 7

It exaggerates the change making the system more unstable and taking it even further away from dynamic equilibrium

Question 8

What is an example of positive feedback?

Answer 8

• People walking over sand dunes destroys vegetation growing there and causes erosion.
• As the roots from the vegetation have been holding the sand dunes together, damaging the vegetation makes the sand dunes more susceptible to erosion. This increases the rate of erosion.
• Eventually the sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from dynamic equilibrium.