Factors affecting coastal recession and stability 1.3

What is coastal recession and what may it be caused by

It’s the retreat of coastline inland

• Erosion, sea level rise

Characteristics of Sedimentary rocks

• Erode the fastest

• Have weak bedding planes

• Have many fractures

Example of sedimentary rock

Sandstone, limestone

Characteristics of metamorphic rocks

• Erode slowly

• Have a crystalline structure

• Are folded and faulted

Example of metamorphic rock

Marble, slate

Characteristics of Igneous rock

• Erode and weather very slowly

• Has fewer joints and weaknesses

What is differential erosion and what does it lead to

Changing rates of erosion of different rock types

• Leads to complex cliff profiles

• Influences rates of recession

How does permeability impact rate of erosion

Permeable rock is vulnerable to mass movement as lubrication of water leads to instability

How does differences in geology affect landforms

• On discordant coastlines, differential erosion leads to headlands and bays

How does vegetation help stabilise coastlines

• Plant roots help bind sand together, reducing impact of erosion

• Wind speeds reduced which decreases erosion

What are pioneer species

First plants to grow in harsh coastal environment, paving way for other plants that are less able to survive

What are Halophytes (pioneer species)

Can tolerate salt water around their roots, being submerged at high tides

What are Xerophytes (pioneer species)

• Can tolerate very dry conditions

• On sandunes where sandy soil retains little water

What is succession

Changing structure of plant community as area is colonised by plants

What is psammosere

Succession in a sand environment

Order of Formation of a sand dunes

Embryo dune, fore dune, yellow dunes, grey dune, dune, mature dune

Embryo dunes

Wind blown sand is trapped in debris

Pioneer species like Lyme grass colonise (halophytic plants)- tolerate high salt levels

Little soil and high Ph levels

Embryo dunes are fragile, reach max height of 1m

Fore dunes

Embryo dunes give protection against wind allowing other plants like marram grass to grow

Marram grass stabilises prune with its root

They add organic matter to dunes enabling plants to grow

Max height reached is 5m

Yellow dunes

Marram grass domaines vegetation but other plants found

Max height of 8m

Grey dunes

More stable and good range of biodiversity

Soil is less alkaline and more water retentive

Shrubs and bushes apple

Height between 8-10m

Mature dunes

Oldest and most stable dunes

Found far away from shoreline

Soil supports oak trees

What is a halosere

Succession in salty water

Why do salt marshes develop in estuarine areas

Shelter from strong winds

Steady supply of sediment from river

1st stage of salt marsh succession- clay particles mixing

In estuarine environment, fresh water and sea water mix

Causes clay particles to stick together and sink, sediment builds up

2nd stage of salt marsh succession- algae

Deposited sediment colonised by algae which

• Binds sediment together

• Increases organic matter

3rd stage of salt marsh succession- sediment covered by tide

Sediment builds up and covered by tide allowing cord grass to colonise

Height of sediment increases until it’s covered by highest tide

More plants colonise like sea lavander and climax community is achieved