Coastal Environment 2 Flashcards by Tiff Y

All types of Geomorphic processes

Sub-aerial processes- weathering and mass movement

Aeolian processes- erosion, deposition, and transportation

Fluvial processes- erosion, deposition, weathering and transportation

Marine processes- erosion, transportation and deposition

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Define weathering

Uses energy to break down material from surface rock

Weakens the rock and is later used in erosion

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What are the three types of weathering

Physical
Chemical
Biological

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What are different types of physical weathering

Freeze-thaw- water enters cracks and joints, at night, freezes and expands by 10%, exerts pressure on rock, break them apart

Thermal expansion- expands when heated and contracts when cooled, changing temperature consistently cause outer layer to crack and flake off

Salt crystallisation- sea water get into cracks of rocks, salt remains in the crack, salt expands when heated up, put pressure on the rock, expands and breaks

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What are different types of chemical weathering

Oxidation- oxygen reacts with minerals in the rock (metal)- e.g rust- weakens the rock

Carbonation- rainwater combines with carbon dioxide from atmosphere- weak carbonic acid, reacts with calcium carbonate in rocks e.g (limestone)- produce calcium bicarbonate- which is soluble

Solution- mineral dissolves in water

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What are the different types of biological weathering

Root growth- roots grow into cracks and put pressure on rocks causing them to break

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What is mass movement and what is regolith

Movement of material (regolith) down a slope

Regolith- loose layer of rocky material lying over the bedrock

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What are the different types of mass movement

Soil:
Soil creep- slow movement of soil downslope

Mudflow- fast, heavy rain causes material move downhill

Rock:
Landslide- rock slip down the cliff

Rockfall- fall straight off the cliff

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Different types of marine erosion

Hydraulic action- weight of water hits the rocks

Attrition- wearing down of rock when they rub against each other

Abrasion- rocks carried in waves hits the cliff

Solution- freshwater mixed with salt water, break down the rocks

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Different types of marine transportation

Traction- large boulders rolled along the seabed
Saltation- small stones bounced along the seabed

Solution- dissolved material

Suspension- small particles carried in water

Longshore drift- wave hits the shore at oblique angle, Swash moves sediments up the beach at same direction

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Fluvial processes and landforms

Significant in low energy environments
Erosion, weathering, and mass movement, supply sediment to river channel
Then transported downstream into the sea
Mudflats and salt marshes are formed in sheltered low energy coastlines- large tidal range- powerful waves transporting large quantities of fine sediments

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What is deflation

Wind picks up particles and move them

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Factors influencing formation of erosional landform

Beach Morphology- wide and flat (low energy), narrow and steep (high energy), waves dissipate energy on the beach

Wave types- e.g storm waves

Rock type- less or more resistant

Structure- jointing and faulting, angle of dip, concordant/ discordant coastline

Human activities- removing beach material, building on top of cliff (increase in pressure), construction of sea defences
-distorts equilibrium

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Formation of headlands and bays

Formed where there are bands of different rock with different resistance to erosion

-discordant coastline

Largest erosional landform
70km

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Example of headland and bay

The Foreland- Chalk
Swanage Bay- Clay and limestone
At Purbeck Coast, Dorset

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Formation of cliff and shore platforms

High waves concentrate erosion at base of the cliff
Cliff is undercut, forming wave cut notch
Overtime, cliff collapse and retreats
Wave cut platform is formed
Abrasion cuts the base
Waves break further out to sea, wave energy dissipated, erosion is reduced

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Formation of geos and blowholes

Geo- narrow, steep sided inlet formed where there is line of weakness in the rock, and is exposed to erosion, leading to collapse of cliff face

Blowholes- formed when cave is eroded vertically upward and the top of the cliff collapse
Vertical shaft that reaches the cliff top

Formation of caves, arches, stacks and stumps

Line of weakness in resistant rock
Erosion widens and undercuts the line of weakness, forming a cave
When the cave is further eroded and often meet another cave, forms the arch
Gravity causes the arch to collapse eventually, forming a stack
As the wave cut notch gets undercut and collapsed, forms the stump- visible at low tides

Formation of cove

Concordant coastline
Soft rock sit behind hard rock
Hydraulic action cause cracks and faults in hard rock, expose soft rock behind
Soft rock gets eroded faster and water enter from the inlet
Wave refracts inside and create circular shape of cove

Example of cliff and shore platform

The Foreland
At Purbeck Coast, Dorset

Example of Geo

North side of Sand point
North Somerset Coast

Example of Blowholes

Sand Point (headland north side of Sand Bay)
North Somerset Coast

Example of Cave, Arch, Stack, and Stump

Old Harry’s Rock
At The Foreland
Purbeck Coast, Dorset

Example of Cove

Lulworth Cove
Purbeck Coast, Dorset

Factors influencing erosion

Wave characteristics: High energy waves Long fetch Steepness of beach Structure of rocks (macro)- concordant, discordant Structure of rocks (micro)- jointing, faulting, angle of dip Supply of beach sediments Beach morphology Geology

What are the two high energy coastline case studies

Sand Bay- Somerset Jurassic Coast-Dorset

Two types of beaches

Swash aligned- waves break parallel to the shore, no LSD, Swash and backwash through the same path up and down the beach -form headlands and bays Drift aligned-follow LSD movements,low tidal range (wave action concentrated in narrow zone), hits the coast at an angle -form spit and tombolos

Two different beach profiles

Shingle beaches- longshore movement of sediments, steep and narrow, high percolation rate (water moves faster through sand)- backwash less effective, common in low tidal range (wave energy concentrated in narrow area) -pebbles Sand beaches- longer swash, more powerful backwash, wider and lower slope angled beaches, sand is compacted, low percolation rate- more sand moves down the beach -sand

Formation of beaches

Constructive waves- strong swash and weak backwash- brings sediments up the beach LSD transport sediments along the coast

Example of beach

Sand Bay- sand beach

Formation of spit

Beaches needs to be present LSD present Sudden change in coastline LSD carries sediments along the beach until a sudden change in coastline, leading to spit forming, it may curve at the end due to (recurring laterals (sudden change of wind direction)), eventually may not grow further due to river present, or increase depth of the sea Salt marshes may form behind the spit where it is low energy environment- only low energy waves enter the sheltered area Drift aligned beaches

Define spit

Long narrow ridge of sand and shingle which is attached to the land at one end and finishes with a recurved end in the open sea

Example of Spit

Hurst Castle Spit 2km long Jurassic Coast, Dorset

Formation of tombolo

When a spit is connected to an island

Example of tombolo

Chesil Beach Jurassic Coast, Dorset

Formation of onshore bar

When LSD transports sediments and forms a spit, it grows across a bay and connects two headlands together Behind the bar, lagoon is created, where water is trapped, salt marshes may develop, overtime, lagoon filled up by deposition

Example of onshore bar

Chesil Beach Jurassic Coast, Dorset

Formation of salt marshes

Behind spits or bars, in sheltered areas Carbon Sink Mud and silt accumulate in a sheltered area of a coastline, forming mudflats Pioneer Plants (salt tolerant plants) start to live on mudflats, they have long roots to stabilise themselves in mud As mudflats build up, raising surface further out of the sea Conditions are less harsh when rainwater washes out salt and improves fertility New plant species, increase biodiversity Eventually leads to growth of trees as land rises above sea level

Formation of delta

Largest depositional landform When freshwater meets sea water, flocculation happens where electrical charge is produced causing clay particles to settle Finest materials carried furtherest into the ocean-bottom set beds Top sets nearest to the land

What is a delta

Flat area of land at the mouth of a river extending into the sea

Example of delta

Nile River

Factors influencing deposition

Wave characteristics: low energy waves Swash align beach/ drift align beach Sediment Supply: Sand and shingle from cliff erosion Human Activity: Coastal defences Changes in water depth/ sea level change Beach gradient and profile