Coastal landscape and change Flashcards
The littoral zone and the processes in each section
Coastal zones develop between winds waves and currents. the littoral zone consists of 4 sub-categories which include backshore, foreshore, nearshore and offshore.
Backshore- the part of the beach that lies between the beach face and the coastline, often characterised by berms, and is only exposed to waves in extreme events
Foreshore- the zone between high tide levels and low tide levels, long shore drift happens here.
Nearshore- the area of shallow water beyond the low tide mark, this is where waves break and deposition occurs as the waves drop the sediment.
Offshore- the area of deeper water beyond the point at which waves begin to break, offshore bars occur here.
Coastal classification and coastal systems and the factors that influence them.
2 main types of coastal classification which include rocky cliffs and coastal plains
Rocky cliffs- characterised by erosional features
- high energy zone
- rock falls occur here because the cliffs are made from hard rock like chalk or limestone.
Coastal plains- flat, low lying land that is adjacent to the coast
- sandy
- low erosion
- open area
Sediment from rocky cliffs are transported to the coastal plains and deposited there to create a beach or other physical features
Geological structure and how it influences coastal features
Strata- layers of rock
Bedding planes-horizontal cracks, or natural breaks in the strata created during the formation.
Joints-vertical cracks, fractures caused as sediment dries out or during earth movement.
Folds-formed by the pressure during tectonic activity
Faults-when stress and pressure on the rock exceeds the internal strength(faults can slip)
Dips-the angle at which strata lies(horizontally,vertically, dipping towards/away from the sea
Geological structure- how do they influence cliff profiles
The two aspects of geology that influence the coastal landscape are lithology and structure
Lithology- the chemical and physical characteristics of rock types.
Structure- the physical characteristics of rocks, including their jointing, bedding, faulting, angle of dip ect.
Coastal recession- influenced by lithology
- Bedrock is made of indigenous, sedimentary and metamorphic rocks which determines the erosion rates. Harder rocks are more impermeable which lowers the rate of erosion.
- Erosion occurs at the foot of the cliff, creating a notch. the material above the notch becomes too heavy and collapses and its washed away. This cycle repeats and causes the cliff to retreat
- Vegetation stabilise sandy coastlines, provides habitats and flood defences. This is because the roots hold the sand together and stop it from blowing/washing away.
vegetation is important for stabilising the coastlines
- Roots hold the sediment together
- Bind the soil/sand which helps to stabilise the area
- Over time more sediment is deposited
- There is a mild up of sediment which in hand with other things, protects the coastline
- Examples can consist of sand dunes, salt marshes and mud flats
wave types influence beach morphology
Constructive waves
- Swash, going up the beach, is bigger than backwash, going down the beach
- Adds sediment to the area
- Low energy environment
- Shallow beach gradient
Destructive waves
- Backwash, going down the beach, is bigger than the swash, going up the beach
- Takes away sediment from the area
- High energy
- Steep beach gradient
erosional processes lead to different landforms
Hydraulic action-waves hit the front of the cliff and some water gets into the cracks, the pressure then makes the crack expand, this process repeats until the crack gets bigger and turns into caves.
Corrasion- the chemicals in the water dissolve the minerals in the rock and washes it away
Abrasion-rocks rub against the sea bed, which removes small pieces of the rock
Attrition- rocks bash against each other in the water and become smaller and more rounded.
Sediment transfer and deposition lead to different coastal landscapes
Gravity settling- this is when waves are carrying sediment, they become too weak to carry so the large sediments drop first.
Flocculation- small particles like clay being carried by the water. they clump together due to electrical or chemical attraction. they then become very dense and the wave doesn’t have enough energy to carry it so it drops.
The sediment cell and the coastal system
The sediment cell is the complete cycle of sedimentation including source, transport and sinks
Weathering and the coastal system
Biological weathering
-weeds growing through cracks
Mechanical weathering
-Freeze thaw
mass movement and coastal landscapes
Sliding
-Large chunks of rock sliding down a cliff(hard rock)
Slumping
-permiable rock(soft) fills with water and becomes dense and slides down the cliff-clay
Sea level change and landscapes
Eustatic change
- ice caps melting back into the sea and causing sea level to rise
isostatic change
- relates to land rise or downfall
- in the uk, an ice cap used to be in the north which caused the land in Scotland to sink. however now because the ice cap has melted, the land is beginning to rise again which is causing the land in the south to sink.
contemporary sea level change and the risks to coastlines
Kiribati case study
- a group of small islands between the north and South Pacific oceans, practically on the equator
- most land is less that 1 metre above sea level
Coastal recession causes both physical and human
Physical
- ice caps melting
- extreme weather events
human
-part of the reason for climate change
holderness coastline erodes around 2-7 metres each year, due to the easily erodible rock that stretches across the coastline.
-since the roman times, 29 villages have been lost due to coastal recession.