Knowt
Coasts
Coastal Processes
Coastal regions
The coast is the area where land and sea meet
The shoreline is the boundary of the land defined by the high water mark on a low-lying coast or the base of a steeply sloping coast
The shore is the area between the highest and lowest tide points
Tides are usually twice a day but vary from coast to coast and with the time of the year
The difference between low and high tide is known as the tidal range
The tide determines the waves' height and depth
The movement of waves and currents affects coastal features
Waves
Winds blowing across the sea's surface create waves, which are marine processes that erode, move, and deposit material
The size of a wave depends on:
The speed of the wind
The fetch (distance the wind travels)
The amount of time the wind blows (in the same direction)
The wave size increases with wind speed, strength, and fetch
Friction from the seabed pushes a wave forward as it gets closer to the coast and into shallower water, where it will finally crest and crash onto the beach
The movement of water up the beach is called the swash, and the return movement is the backwash
There are two types of waves:
Destructive waves erode the beach and have:
a steep wave gradient
a short wavelength with high height
a high frequency wave rate of 10-12 per minute
high energy
a strong, abrasive backwash that drags material out to sea and forms shingle beaches
Constructive waves are beach builders and have:
a long wavelength with low height
a low-frequency wave rate of 6-8 per minute
a shallow wave gradient
low energy
a stronger swash that carries material up onto the beach and deposits a sandy beach
Comparison of Wave Type
Marine erosion
Destructive waves are responsible for the majority of erosion that happens along a coast
They cut into the coastline in four ways:
Hydraulic Action
Attrition
Corrosion
Abrasion
A large, rough boulder is gradually reduced into round sand grains (quartz) the longer it remains in the ocean and the farther it travels along the shore
The effects of attrition are amplified when the waves carry material farther and longer
Rounded pebbles on a beach are known as shingle
Marine Transportation
The sea transports sediment that it gets from erosion in the same way rivers do
Material in the sea arrives from many sources:
eroded from cliffs
transported by longshore drift along the coastline
brought inland from offshore by constructive waves
carried to the coastline by a river
Once in the water, the material is moved in different ways:
Traction
Saltation
Suspension
Solution
Longshore drift (LSD)
Longshore drift (LSD) is the main process of transportation along the coast
Waves approach the beach at an angle due to the prevailing wind
As the waves break, the swash carries material up the beach at the same angle
As the swash dies away, the backwash carries the material down the beach at right angles (90°)
The process repeats, transporting material along the beach in a zig-zag movement
Process of Longshore Drift
Process of longshore drift
Beach sediment is carried farther down the coast on coasts where longshore drift is one way; if it is blocked, sediment cannot move and the area farther down the coast is deprived of sediment. This results in two problems:
Smaller beaches are less attractive to tourists, causing a loss of income
Removes natural coastal protection
Marine Deposition
The waves carry sand or shingle as they travel
Backwash carries it away, while swash carries it onto a shore
The largest material is deposited along the upper reach of the swash when a constructive wave carries sediment up the beach
The backwash loses water and energy as it travels because of the sand's porosity, resulting in smaller and smaller deposits.
When a constructive wave carries sediment up the beach, the largest material is deposited along the upper reach of the swash
During a storm, large shingle is thrown above the usual high tide level to form a ridge at the top of the beach called a berm
Coasts
Coastal Processes
Coastal regions
The coast is the area where land and sea meet
The shoreline is the boundary of the land defined by the high water mark on a low-lying coast or the base of a steeply sloping coast
The shore is the area between the highest and lowest tide points
Tides are usually twice a day but vary from coast to coast and with the time of the year
The difference between low and high tide is known as the tidal range
The tide determines the waves' height and depth
The movement of waves and currents affects coastal features
Waves
Winds blowing across the sea's surface create waves, which are marine processes that erode, move, and deposit material
The size of a wave depends on:
The speed of the wind
The fetch (distance the wind travels)
The amount of time the wind blows (in the same direction)
The wave size increases with wind speed, strength, and fetch
Friction from the seabed pushes a wave forward as it gets closer to the coast and into shallower water, where it will finally crest and crash onto the beach
The movement of water up the beach is called the swash, and the return movement is the backwash
There are two types of waves:
Destructive waves erode the beach and have:
a steep wave gradient
a short wavelength with high height
a high frequency wave rate of 10-12 per minute
high energy
a strong, abrasive backwash that drags material out to sea and forms shingle beaches
Constructive waves are beach builders and have:
a long wavelength with low height
a low-frequency wave rate of 6-8 per minute
a shallow wave gradient
low energy
a stronger swash that carries material up onto the beach and deposits a sandy beach
Comparison of Wave Type
Marine erosion
Destructive waves are responsible for the majority of erosion that happens along a coast
They cut into the coastline in four ways:
Hydraulic Action
Attrition
Corrosion
Abrasion
A large, rough boulder is gradually reduced into round sand grains (quartz) the longer it remains in the ocean and the farther it travels along the shore
The effects of attrition are amplified when the waves carry material farther and longer
Rounded pebbles on a beach are known as shingle
Marine Transportation
The sea transports sediment that it gets from erosion in the same way rivers do
Material in the sea arrives from many sources:
eroded from cliffs
transported by longshore drift along the coastline
brought inland from offshore by constructive waves
carried to the coastline by a river
Once in the water, the material is moved in different ways:
Traction
Saltation
Suspension
Solution
Longshore drift (LSD)
Longshore drift (LSD) is the main process of transportation along the coast
Waves approach the beach at an angle due to the prevailing wind
As the waves break, the swash carries material up the beach at the same angle
As the swash dies away, the backwash carries the material down the beach at right angles (90°)
The process repeats, transporting material along the beach in a zig-zag movement
Process of Longshore Drift
Process of longshore drift
Beach sediment is carried farther down the coast on coasts where longshore drift is one way; if it is blocked, sediment cannot move and the area farther down the coast is deprived of sediment. This results in two problems:
Smaller beaches are less attractive to tourists, causing a loss of income
Removes natural coastal protection
Marine Deposition
The waves carry sand or shingle as they travel
Backwash carries it away, while swash carries it onto a shore
The largest material is deposited along the upper reach of the swash when a constructive wave carries sediment up the beach
The backwash loses water and energy as it travels because of the sand's porosity, resulting in smaller and smaller deposits.
When a constructive wave carries sediment up the beach, the largest material is deposited along the upper reach of the swash
During a storm, large shingle is thrown above the usual high tide level to form a ridge at the top of the beach called a berm
