Coasts Flashcards
Crest
Top of a wave
Trough
Low areas between waves
Swah
Movement of water and load UP the beach
Backwash
movement of water and load DOWN the beach
Velocity
Speed a wave is travelling
Wavelength
Distance between two crests or troughs
Wave height
Distance between the crest and trough
Wave frequency
Number of waves per minute
The size and energy of a wave is influenced by
How long the wind had been blowing
The strength of the wind
How far the wave has travelled (the fetch)
Why coastlines are under threat
Polluting
Rising sea levels
Destroying wildlife
Importance of coastlines
Sustains community Vacation/tourism Transportation Property value Eco-tourism Oil and gas extractor
What causes tides
changes in how much the moon’s gravity pulls on different parts of Earth
Spring Tides
Spring tides occur twice a month, at new moon and full moon. The combined force of the moon on one side of the earth and the sun on the other, produces a tide with the greatest difference between consecutive high and low tides
Neap tides
Produced at the moons first and third quarter, when the line between the moon and sun is at 90 degrees to the angle between the earth and moon. They occur twice a month
Process of forming tides
The force of gravity pulls the sun and moon toward each other. The moon’s gravity pulls Earth, leaving water behind an additional high tide. Low tides occur between high tides. There are two low tides and two high tides per day.
Constructive waves
Associated with calm weather Less powerful Break on shore depositing material Responsible for transporting material Swash is stronger than backwash
Destructive waves
Associated with storm conditions
Created when a wave energy is higher with a large fetch
Associated with erosion
Backwash is stronger than swash
The process of longshore drift
Waves hit the beach at an angle and then pulls the material straight back. Then repeats and sends them back to the beach at an angle to deposit it again. This action can erode away beaches or completely take them away
In the process of longshore drift, why does beach material get washed up the beach at an angle?
Due to the prevailing winds pushing the waves at an angle to the beach
In the process of longshore drift, why does beach material wash back down the beach at right angles to the coastline?
Because the force of gravity pulls the material straight back
Beach grading: (sorting)
Higher wave energy carries the largest particles.
Energy is lost in the backwash due to percolation
Over time, wave action will “sort” the beach materials from coarse to fine
Backwash has more friction than swash, therefore swash is stronger
Explain why the coastline changes due to erosion
The coastline is made up of hard and soft rock. The constant energy of the waves against the soft rock works to erode bays out of the coastline, Whereas the hard rock does not erode as easily and makes up the headland
How cliff erosion creates wave cut platforms
Formed due to the constant sub-aerial processes of erosion undercutting the rock. Over time, the wave cut notch doesn’t have enough support at the base to stay up, so it collapses, leaving at the bottom where the notch used to be, a wave cut platform that is slightly inclined
Salt marsh
coastal eco system in the upper tidal zone, which during high tides can be flooded with salt water
Eustatic
and uniformly global change in sea level that may reflect a change in the quantity of water in the ocean
Isostatic
The state of gravitational equilibrium between the earth’s crust and mantle which “floats” at an elevation that depends on its thickness and density
Estauries
A partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, with a free connection to the open sea
Tidal currents
occur in conjunction with the rise and fall of the tides. The vertical motion of the tides near the shore causes the water to move horizontally, creating currents. “flooding” and “ebbing”
Fjords
a deep, narrow and elongated sea with steep land on three sides
Raised beach
A former beach now lying above water level owing to geological changes since its formation
Coastal Protection Methods
Sea wall Gabions Rip Rap or Rock Armour Groynes Wooden Revetment Beach nourishment Do nothing Dune Regeneration Managed Retreat
Sea wall
Reflects waves back to sea preventing erosion of the coast. It acts as a barrier to prevent flooding. Needs replacing every 25 years
Gabions
Rock filled cages. Usually built at the foot of cliffs. Absorb energy and reduce erosion. Lasts 10 years.
Rip Rap
Boulders piled up along the coast. They absorb wave energy and reduce erosion. Looks natural so it doesn’t spoil the landscape.
Groynes
Fences built at right angles to the coast. Trap beach material transported by longshore drift. They can cause increased erosion down the coast. Lasts 30 years.
Wooden revetment
These are similar to groynes and sea walls. They break the force of the wave and trap beach material behind it.
Beach nourishment
Sand and shingles are added to the beach from elsewhere to create wider beaches. Lasts 6 months.
Do nothing
Just wait for nature to take its course. Land will be lost due to erosion.
Dune regeneration
Sand dunes are good buffers to the sea but they are easily damaged, especially by walkers.
Managed retreat
This involves allowing low-lying coastal areas to be flooded by the sea to become salt marshes. Cheap but it creates a new habitat for wildlife.
Wave formations
Mainly the product of wind
Tides also play a part
Types of sand dunes
Embryo Fore Yellow Grey Mature
Embryo
Smallest
closest to shoreline
Not stable, plant presence helps to maintain them
Fore
Made up of sand shifted by the wind
minimal plant life such as lyme grass
constant state of change due to proximity to the ocean
Yellow
Develops after embyro and fore dunes
usually around 5m in depth and have barely any sand bare due to being covered in vegetation
Grey
More stable than fore
completely covered by vegetation
Get their name from their top layer of lichen and humus
Mature
Oldest and biggest
Found far from shoreline
Covered in a few different kinds of plants, not just grasses
moderately higher pH, points to having more stable soils
Hard vs Soft Corals
hard corals: Hard, calcium based skeletons. consist of numerous single polyps living together in a colony
Soft corals: contain structures within their tissues called spiracles that support their body.
Coral bleaching
warm waters can cause coral bleaching
corals expel the algae living in their tissues causing the coral to turn completely white
Ocean Acidification
Increased CO2 in atmosphere is absorbed into ocean waters
Corals structure of calcium carbonate disintegrates when it comes into contact with acidic solutions
Over fishing
When more fish are caught than can be replaced through natural reproduction
Careless tourism
Touching reefs, polluting, dropping anchors all substantially damage reefs
Rising Temperatures
Coral bleaching also occurs when the water temperature is too warm
This can make coral reefs subjected to large scale die-offs
