Types of erosion at coasts
Hydraulic Action,
Abrasion, Corrosion, Attrition
What does the size and energy of a wave depend on?
Fetch, strength of wind and how long wind has been blowing.
Two different types of waves:
Destructive and Constructive
Characteristics of destructive waves
Weak swash and strong backwash. Backlash removes sediment from beach. Good at eroding the beach Steep wave gradient High frequency (10-12 per minute) Short wavelength (<20 metres) High energy
Characteristics of constructive waves
Strong swash and weak backwash
Good at pushing material up and depositing
Shallow wave has a gradient and crests far apart
Low frequency (6-8) per minute
Long wavelength (<100 meters)
Low energy
Describe the formation of a spit.
- Sediment is carried by longshore drift.
- When there is a change in the shape of the coastline, deposition occurs. A long thin ridge of material is deposited. This is the spit.
- A hooked end can form if there is a change in wind direction.
- Waves cannot get past a spit, therefore the water behind a spit is very sheltered. Silts are deposited here to form salt marshes or mud flats.
Describe the order of land forms that are formed in making a stump.
cave, arch, wave cut platform, stack, stump.
What is long-shore drift and how is it countered?
The movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it.
It can be countered through the use of groynes.
Name 3 hard coastal protection methods.
Sea wall, groynes and gabions.
Name 3 soft coastal protection methods.
Beach nourishment, dune regeneration and beach re profiling.
Describe the formation of a bay and headlands
- There are alternating bands of soft and hard rock at a discordant coastline
- The soft rock is eroded backwards creating a bay
- The harder rock isn’t eroded as much, creating a headland
Describe the formation of a wave cut platform
- The sea erodes the base of the cliff
- A wave-cut notch is formed by erosional processes (e.g. abrasion and hydraulic action)
- As the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face.
- The backwash carries away the eroded material, leaving a wave-cut platform.
- The process repeats. The cliff continues to retreat. The wave cut platform is often only visible at low tide
Describe how a cave, arch, stack and stump are formed
- Cracks and fissures are widened in the headland through erosional processes
- The cracks erode through and open up to form a cave.
- The cave becomes larger and eventually breaks through the headland to form an arch.
- The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea.
- This leaves a stack
- The stack is undercut at the base until it collapses to form a stump.
Name 3 coastal landforms made by erosion
- Cave
- Arch
- Stack
- Stump
- Headlands and Bays
- Wave cut Notch
Name 3 coastal landforms made by deposition
- Spit
- Bars
- Tombolos
- Beaches
- Sand Dunes
What are the types of Erosion on coasts?
- Hydraulic Action
- Abrasion
- Attrition
- Solution
What is Managed Retreat?
It is where the land is allowed to flood naturally. This is normally done in areas of low econmic value
give 3 factors that affect waves
- the Length of the fetch
- How strong the wind is
- How long the wind has been blowing
At which type of coastlines do headland and bays form?
Discordant
What are the benefits of living near the coast?
- Port
- Tourism
- Less pollution
- Fishing
What is another name for corrasion
Abrasion
Explain how different erosional processes shape cliffs.
hydraulic action;
air in cracks compressed ;
corrasion/abrasion;
loose materials thrown at cliff by waves
corrosion;
rocks dissolved by chemicals in sea water
undercutting;
slumping/collapse;
as cliff cannot take weight of overhanging section
Main characteristics of mangrove swamps
Salt tolerant/live in brackish water/salty water/live in sea water/are halophytes;
Aerial roots;
Salt filtering roots;
Salt excreting leaves; Prop roots
Conditions required for coral reef growth
Warm water/temperatures between 18–27 degrees C
Shallow water/not more than 60 metres deep;
Water free from sediment/clear/clean/not polluted/sunlight able to penetrate the water;
Plentiful supply of oxygen in water;
Plentiful supply of plankton;
In areas of gentle waves/currents/calm/slow moving water; Neutral/high pH/alkaline water;
Salty water
