Coasts Flashcards
Littoral?
Coastal zone
What are the 4 main zones between the land and sea boundary?
Backshore
Foreshore
Nearshore
Offshore
What are the 4 input processes operating at the coast?
Marine- waves and tides
Atmospheric- climate change
Land- rock type
People- human activity
What are the 3 main processes operating at the coast?
Weathering
Erosion
Transport
What are the 3 main outputs operating at the coast?
Erosional landforms
Depositional landforms
Different types of coasts
What 4 ways can coasts be classified?
Via:
Geology- is the geology resistant to the erosive forces of the sea, wind and rain or not?
Energy- is the coast exposed to powerful waves or sheltered?
Balance- does erosion exceed deposition or vice versa? Is the coast retreating or advancing?
Sea level- does the coast have emergent or submergent features?
What are the main features of a high energy coastline?
Destructive waves
Storm conditions
Longer fetches
What are the main features of a low energy coastline?
Constructive waves, calmer, short fetches, sheltered
Why might it be difficult to classify some coasts?
Changes in space
Seasonality change
Local geology can produce rocky areas within coastal plain landscapes
Along fetches + destructive waves in bays
Geological structure?
The arrangement of rocks in layers, or folds and joints + bedding planes within them
Lithology?
Rock type and their general characteristics
Bedding planes?
Horizontal breaks in the strata, causes by gaps in time during periods of rock formation
Dips?
The angle at which the rock strata lie. Can be horizontal. vertical, towards the sea or inland
Faults?
Formed when the stress or pressure to which a rock is subjected exceeds its internal strength causing it to fracture
Folds?
Formed by pressure during tectonic activity, which makes rock buckle and crumble
Joints?
Vertical cracks caused by contraction (shrinking) as sediments dry out, or by earth movements during tectonic uplift
Strata?
Layers of rock
Coastal morphology?
Shape
What type of coastline to caves form on?
Concordant coastline- waves exploit weaknesses or faults
What type of coastline to headlands and bays form?
Discordant coastline
What is a concordant coastline?
Where rock is eroded at the same rate
What is a discordant coast?
Rock is eroded at different rates due to the different layers of softer vs harder rock
Cliff profile?
Height and angle of cliff face
What does horizontal strata of a cliff produce?
Steep cliffs
What does strata of a cliff that dips seaward produce?
Unstable cliffs- gravity causes mass movement ie rock fall
What does strata of cliff that has a landward dip produce?
Steep, stable cliffs
Igneous rock?
Formed from cooling of lava eg basalt + granite
Sedimentary?
Formed when layers of sediment deposited in lakes and sea are cemented together
Metamorphic?
Formed from other rocks that are chemically changed by intense pressure from surrounding rock, or by heat from near magma
What is glacial till?
A type of unconsolidated rock found in much of eastern england: it’s a mixture of sand clay and stones left behind by glaciers as they retreated at end of ice age
Prosity of igneous rocks?
Non-porous
Tightly fit together
Permeability of igneous rocks?
No water can be absorbed. No bedding planes of joints.
Resistance of igneous rock?
Very resistant to erosion and weathering
Prosity of sedimentary rocks?
Very porous due to rounded crystals
Permeability of sedimentary rocks?
Able to absorb water- permeable
Resistance of sedimentary rocks?
Less resistant to marine erosion and chemical weathering
Prosity of of metamorphic rock?
Non-porous- heat and pressure flatten rounded crystals in sedimentary rocks
Permeability of metamorphic rock?
Impermeable- no bedding planes or joints
Resistance of metamorphic rock?
Hard but some rocks are prone to mass movement
Example of sedimentary rock
Chalk
Example of metamorphic rock
Slate
Example of Igneous rock
Granite
What are the 4 coastal ecosystems?
Salt marsh
Coral reef
Sand dune
Mangrove forest
Why are salt marshes and sand dunes important?
They stabilise soft sediment (mud and sand) which is deposited in low energy coastal environments
Plant succession?
Evolution of plant communities at a site over time
Coastal plain?
Low land
What do sand dunes need?
A plentiful supply of land
Large area for the sand to dry out
Onshore winds to blow sand towards the land
Sand dunes?
Known as psammosere where drought-tolerant or xerophytic plants can survive with little fresh water
Porous?
Sedimentary rocks often contain small holes called pores which can contain water or other fluids. If the holes are connected, then the rock is permeable and fluids can flow through the rock.
Dune slack?
Area of the dunes which is lower than the water table
Water table?
Level of the soil that is saturated with water
What type of dunes tend to be the highest?
Yellow dunes
What type of grass is found on yellow dunes?
Marram grass
What type of plant is located on grey dunes?
Gorse
Salt marshes?
Are known as haloseres where salt tolerant or halophytic plants can survive in brackish (salty) conditions. Are common in the low energy environments of estuaries and sheltered bays
Where are salt matches commonly located?
Low energy environments of estuaries and sheltered bays
Why is coastal vegetation important?
Stabilises sediment in low energy coastlines allowing coasts to advance
In also provides a buffer between the land and the sea acting as long term flood and storm defence
Wave period?
The time interval from crest to crest in seconds. Sea waves have intervals of 1 and 20 seconds
5 key features of constructive waves
Strong swash Weak backwash Forward spilling breaker 6-8 mins frequency Deposition
ie build up beaches
5 key features of destructive waves
Weak swash Strong back wash Downwards plunging breaker 15per min frequency Erosive
How are beaches formed?
By deposition of rounded sand and shingle
What do beach profiles (gradient) have a close relationship with?
The dominant wave type
What are the features of a beach that have constructive waves as a dominant wave type?
Strong swash and weak backwash pushes material up the beach. The main feature is a large berm near the high water mark
What are the features of a beach that have destructive waves as a dominant wave type?
When backwash is stronger than swash it removes material from the beach and creates large bars. The beach is steeper at the very back above the high water mark
SWELL waves?
Waves generated during storms in the middle of oceans and maintain their energy for thousands of miles.
What is the distance of open water swell waves move travel called?
The fetch- the longer the more destructive the wave
What is the main form of transport at the coast?
Long shore drift or litoral drift
Long shore drift?
The offshore movement of sediment along the coast
What pulls sediments back off of a beach?
The backwash
When is long shore drift strongest?
When waves approach the coast at an angle of 30 degrees to the beach
What is the sediment cell concept?
The idea that sediments move along the coast in sediment cells.
What do sediment cells act as?
Closed systems with inputs, outputs and transfers
What is the main transfer of sediment cells?
Long shore drift