The UK's evolving physical landscape - Coasts Topic 4, GCSE Geography

Factors affecting the landscape

Geology

Use carbon dating

As skeletons fall to the sea floor, they form horizontal lines (strata).

Two processes turn the skeletons into solid rock:

As skeletons fall, they crush those beneath, eventually squeezing out water and compacting them into rock

CaCO3 crystallises around the fragments; this cements them together and even preserves some fossils intact

Definitions Coasts

Carbon Dating

Uses radioactive testing to find the age of rocks which contained living material

Erosion

Wearing away the landscape

Tectonic Processes

Example of three processes in the Pennines:

Convection currents beneath the plate uplifted rocks from below the sea - becoming land

During uplift, some rocks snapped and moved along the faults in a series of earthquakes over thousands of years - each movement distributed the strata so they tilted
Sometimes the faults form a steep edge called a fault scarp where uplift has raised some parts more than others

The plate on which the UK sits shifted, away from the tropics!

Fault scarp

When a fault creates a steep edge

Glaciation

When the Pennines were uplifted , rivers like the Wharfe eroded into them causing V-shaped valleys

The most recent Ice Age (10 000 yrs ago) bought huge glaciers

Two effects:

Altering river valleys, making them deeper and widening them into U-shaped troughs

As they melted they left features like Malham Cove with a spectacular waterfall!

Rocks

Types of rocks

Sedimentary

Metamorphic

Igneous

Earth's oldest rocks
Formed from lavas and deep magmas
Once moten, then cooled and crystallised
Most are resistant to erosion

Formed when sediments eroded and deposited by rivers
Some are resistant yet some crumble easily

Sedimentary rocks that were heated and compressed during igneous activity
Heating and compression harden and make them resistant

Tees- Exe Line

To the N and W

To the S and E

Older rocks
More resistant igneous and metamorphic
More faults, where uplands were uplifted by tectonic activity

Younger rocks
Weaker sedimentary rocks - easily eroded

Examples:

Examples:

Examples:

Granite
Formed from magma cooling deep underground
Contains crystals of quartz, feldspar, mica; very resistant

Carboniferous limestone
Created in the Carboniferous period through compression in rock strata
Permeable, with underground rivers, passages and caves; generally resistant

Slate
Formed from heated muds or shale
Very resistant

Basalt
Formed from lavas rich in minerals
Almost black, and heavy; very resistant

Clay
Formed from muds deposited by rivers or at sea
Soft and crumbly; when compacted it becomes shale; generally weak

Sandstone
Formed from sand grains compacted together
Slightly porous; less than 100mya are weak; more than 300mya are resistant

Millstone grit
Sandstone which has been firmly cemented and compacted
Very resistant

Chalk
A purer, younger form of limestone
Very porous; medium resistance - stronger than most clays and younger sands

Schist
Formed by the further metamorphosis of slate, where it partially melted and solidified
Very resistant

Marble
Formed by heated limestone
Very resistant

Scree

Rock fragments which make the ground rough

Weathering

The physical, chemical or biological breakdown of solid rock by the action of weather or plants

Features

Wave-cut platform

Over time the base of the cliff will erode, leaving a wave cut notch

You are left with a wave cut platform

Destructive waves erode the cliff

Fetch

Size of open water the wave has come from

Waves

Factors affect the surf

Wind Speed

Wind Duration

The Fetch

Swash

When the water goes up the beach

Backwash

When the water goes back into the sea

2 types

Constructive

Destructive

Long wavelength - short height

Weak swash

Shallow gradient waves

Weak backwash

Strong swash

Strong backwash

Strong wavelength - tall height

Steep gradient waves

Beach built up by deposition of material bought up by swash

Beach erosion

Unfrequent

Frequent

Wide Gently sloping Beach

Steep Narrow Beach

Less violent

More violent

Coastlines

Concordant

Disconcordant

Rock strata are parallel to the sea

Rock strata are perpendicular to the sea

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Formations: coves

Formations: headlands and bays

Processes

Erosion

Solution

Hydraulic Action

Attrition

The force of water forces the air into the cracks; air eventually causes the rock to expand and explode

Abrasion

Small particles dissolved in river due to chemical reactions between the salt water and rock

Material carried by river smashes into each other and break into smaller, smoother pieces

1⃣ Large crack opened by hydraulic action

2⃣ Crack grows into a cave by H.A. and abrasion

3⃣ Cave becomes larger

4⃣ Cave breaks through the headland forming a natural arch

5⃣ Arch is eroded and collapses

6⃣ Leaves a tall rock stack

7⃣ Stack erodes forming a stump

Sea's load (rocks and sand) is thrown against the base of the cliff eventually eroding it

Transportation

Saltation

Suspension

Traction

Solution

Heavy boulders get carried along the sea/river bed

Bounced along the river or sea bed

Materials carried in suspension along the sea bed

Chemical reaction between rocks and salt water; rocks are dissolved and are now carried in solution

Longshore Drift

Backwash carries sediment back down the beach under gravity

Another wave moves the material up the shore; cycle carries on

When the wave breaks, swash carries sediment up beach following angle of wave

Over time sediment will be carries parallel to the beach because of L.S.D

Waves approach beach at angle, depending on wind direction

By longshore drift

Bars

Tombolos

Spits

When the sediment is deposited by L.S.D

When it hooks around and joins to another place

When the spits connect to another island

Contrasting coasts

Geology/rock types

Hard Rock Coasts consist of resistant rocks ie. granite, limestone. E.g: Lulworth Cave (Devon) & Flamborough Head (East Yorkshire).

Soft Rock Coasts consists of less resistant rocks i.e. clays,shales. E.g: Holderness Coast (East Yorkshire), Christchurch Bay (Dorset/Hampshire) and North Norfolk Coast.

Sand Dunes are formed when strong winds blow sand inland.

Human Activities

Effects of development

Office Devlopment

Housing

People working in London cannot afford housing there

Good place for retirement

Companies in London cannot afford rent cost

Popular with younger workers

Effects of agriculture

Price of farmland

Risen sharply

Climate change and rising sea levels

Effect of industry

Critical to UK Economy

Risks from costal flooding

World at risk

UK - London and Essex: Low lying, so at risk of flooding

Bangladesh: If water rises 1m, 15% of country will become flooded

Pacific/Indian Islands: Could disappear entirely

Flood Risks and Future

If air pressure falls to very low levels a storm surge occurs

Twice a month there are exceptionally high tides (spring tides)

Twice a day, due to moons gravity, high tides occur

Erosion

Cliff Processes

Waves

Geology

Depends on wave energy, in turn affected by fetch

Weak geology - suffer from cliff foot erosion, mass movement, sub-aerial proceses, cliff face erosion

Resistant or non resistant

Case Study: Christchurch Bay

Without management, cliff erodes 2m+ every year, threatening residential areas

Impacts

Rapid cliff collapses are dangerous for those on cliff and beach

Infrastructure gets destroyed

Erosion makes living here unattractive

Houseowners lose their homes to the sea; house values fall with insurance impossible to get

Managing the coast

Hard Engineering

Sea wall w/ steps and bullnose

Revetments

Sea Wall

Gabions

Rock armour (rip-rap)

Groynes

Reflects waves back into sea

Prevents easy access to beach

Suffers wave scour

£2000 per m

£5000 per m

Steps dissipates wave energy; bullnose throws waves back to sea

Breaks up incoming waves

Restricts beach access; looks ugly

£1000 per m

Can be distroyed by big storms

Absorbs wave energy as they are permeable

Cheap type of sea wall

Not very strong

£100 per m

Easy to build

Expensive if built in sea

£300 per m

Dissipates wave energy and looks 'natural'

£2000 per m

Prevents longshore drift, trapping sand/ shingle

Larger beach dissipates wave energy

May increase erosion downdirft

Dissipate

Reduce wave energy, which is absorbed as waves pass through/over sea defenses

Stakeholders

Local people living further inland - Unaffected, fear taxes will rise; want low cost options

Environementalists - Fear that coastal defences will affect environement

Local politicians & council - Want effective coastal protection but not at any cost

Residents/ Buisnesses downdrift - Want integrated approach to management

Coastal residents & buisness owners - Prefer to 'hold the line'

Fisherman/ Boat users - Priority is access to the sea

Holistic Management

Advance the Line

Strategic Realignment/Retreat

Hold the Line

Do nothing

Use sea defenses to stop erosion, so coast stays where it is; expensive

Use sea defenses to move coast further into sea; very expensive

Gradually let the coast erode and move people/buisnesses from risky areas; may include financial compensation when homes are lost

Take no action, let mother nature take her course

Soft Engineering

Beach nourishment

Planting vegetation

Offshore breakwaters

£20-50 per sq m; plants are used to make cliff more stable

£500-£1000 per sq m; sand is pumped onto beach to increase its size

£2000 per m; built using rip-rap, forcing waves to break before the beach

In cliff drainage

Variable; pipes reduce water pressure an prevent saturation