Flashcards
What is a coast?
The coast is the narrow zone where the land and sea interact.
It’s affected by terrestrial, human, marine and atmospheric processes and their relationships.
It’s the most varied and rapidly changing of all landforms and ecosystems.
The coastal zone is the interface between the sea and the land.
Facts
50% of the world’s population live within 60km of the coast
2/3 of the world’s cities are within 60km of the seam
Coastal diagram
Backshore - area between high water mark (HWM) and the landward limit of marine activity. Normally only changes in storm activity.
Foreshore - area between HWM and LWM. Most important for marine process in times that are not influenced by storm activity.
Inshore - area between LWM and the area with no waves
Offshore - area beyond the waves
Nearshore - area extending seaward from the HWM to area without waves
Why are coastlines regarded as a system?
Elements - the things that make up the system
Attributes - the perceived characteristics of the elements
Relationships - descriptions of how elements work together
What is dynamic equilibrium?
Balence of inputs and outputs. Stores stay the same.
Inputs. • wave • wind • current • tide
How does a beach remain balanced?
.
. /\
. /\
***————————————-bar————————-
The bar slows waves down. This causes the waves to remove the bar and push it back onto the beach in the summer. Then winter waves pull the sediment back into the bar. The system is maintained. To create an equilibrium
Positive feedback (amplifies problem)
Build sea wall to prevent erosion
Reduces new boulders
Beach sediment is finite
Beach is eroded
Polar ice reflects light from the sun
As ice begins to melt less sunlight is reflected
It is absorbed into the oceans and land
Raising the temperature and fueling futher melting
Negative feedback
A cup of coffee is very hot relative to the surrounding air
Coffee cools and heat is transferd to the surrounding air
As the surrounding air heats up then the rate of cooling slows
Fetch
Fetch is the area of sea that wind can travel across and create a wave.
Waves
Crest - top of a wave
Height - distance from calm water level to crest
Trough - bottom of a wave
Wavelength - crest to crest
Wave velocity - spread from a to b
Wave frequency - how many crests pass a point in a second
When does a wave break?
As a wave approaches the beach friction to the floor slows the bottom of the wave. This shows the trough and peak. The falling backwash will slow the trough further and topple (break) the wave
Destructive wave
Winter, high frequency, tall, strong backwash, creates offshore bar.
What is wave refraction
Another example of an equilibrium process
Headlands that side a bay will have shallower water around them. This will create waves on all 3 sides of the headland. This speads erosion in the headland to restore the straightness of the coast. This is also speed up by waves pushing sediment to the beaches which will further slow down erosion in the beach
What is longshore drift?
Pretty fucking easy just remember to mention swash is parallel to prev wind
Where does beach sediment come from?
Streams
Cliff erosion
Offshore banks
Biological origin (shells)
Clastic - rock weathering and erosion
Biogenic - shells
What is a cell?
A cell needs
• A source
• barriers - can be river estuaries
• a budget - the net amount of sand in said cell
