Geography coasts

Discordant coastline can also be referred to as?

atlantic coastlines

Concordant coastline can become what types of coastlines?

Haff and Dalmatian coasts

Example of a concordant coastline in UK

Lulworth cove on the Jurassic coast

Harder rock in Lulworth cove

Portland limestone

Softer rock in Lulworth cove

Wealden clay

How was the Dalmatian coast in Croatia formed

through tectonic forces and sea level rise

(that caused the submergence of land and the formation of a series of islands and coastal inlets.)

(folding of the plate caused anticlines and syclines (when it folds the land upwards and downwards, respectively —— to ~~~ the up hump is anticline and down dip is sycline)

on the adriatic sea

from the collision of the African and eurasian plates 50 million years ago

where is a haff coastline?

southern baltic coast

deposition produces unconsolidated (loosely arranged not cemented together like sand etc) geological structures parallel to the coastline

Nerman Haff - from Russia to Lithuania

(just a spit turning into a bar on a large scale really)

what type of coastline is the Jurassic coast?

East = discordant

south = concordant

Name coastal erosion processes

1. Hydraulic action

2. Abrasion

3. Attrition

4. Corrasion

Name the transportational processes

1. Traction (rolling rocks along the bottom)

2. Saltation (skipping rocks along bottom)

3. Suspension

4. Solution

strata

layers of rock also known as beds

bedding planes

horizontal cracks/lines between the different strata

(surface that separates one strata and another)

created by the pauses in rock formation

joints

vertical cracks in the rock caused by tectonic movement or contraction

Folds

the result of pressure during tectonic movement causing the rock strata to fold

Faults

the result of stress or pressure on the rock causing to fracture

Dip

The angle of the rock strata

Sub-aerial processes

• weathering

  • mechanical (physical)

  • chemical

  • biological

• mass movement

  • sliding (mudslide or landslide)

  • slumping

  • rockfall

Mechanical (physical) weathering examples

• Thermal expansion(heating and cooling of the rock in general)

• frost weathering/wedging (water seeps into cracks then expands when it turns into ice over night)

• Salt weathering. (salt water gets in rock, water evaporates leaving salt crystals behind (accumulates adding more pressure))

• exfoliation (curved plates of rock are stripped from rock below)

By how much does water expand when frozen/turned to ice?

by 10%

Chemical weathering

• bodily fluids from animals (feces and urine)

• solution/carbonation (slightly acidic carbonic rain it reacts with the calcium carbonate - affects rocks like limestone and chalk)

• Oxidation (when rocks are broken down by oxygen and water.)

• Hydrolisis (chemical breakdown of a substance when combined with water)

Biological weathering examples

• animals burrowing in the ground

• Plant roots weakening the rock

• humans eroding it by walking all over it

mass movement

when rocks and loose material shift down slopes. This happens when gravity overcomes the force supporting the material.

Where permeable rock over lies impermeable rock, the permeable rock is vulnerable to mass movement because the additional weight and lubrication the water creates leads to instability

Difference between sliding, slumping and rockfall

• Slides - rock moves in a straight line

  

• Slumps are when material moves down a slope with a rotation. (cliff gets saturated with water and base is eroding (maybe wave cut notch)and slumps

• Rock falls are when material breaks apart because of erosion and weathering and then rolls down a slope.

Wave refraction and how it affects the coastline

waves bend as they hit the coastline at an angle, causing uneven distribution of energy and significantly influencing coastal shaping through erosion and deposition

How can mineral composition affect erosion?

Some minerals are more reactive than others which affects the rate of chemical weathering

Examples:

• Quartz (inert) not reactive so chemical erosion is slower

• Calcite is very reactive so erodes much quicker

How are sedimentary rocks formed?

formed from compaction and cementation of sediment called lithification

Examples of sedimentary rock

shales, sandstone and limestone

Properties of sedimentary rocks

• erode and weather more rapidly

• form in layers

• have weak bedding planes

• they are clastic

  • meaning they are made of clasts (sediment particles)

• heavily jointed

• often have many bedding planes and fractures

How are metamorphic rocks formed?

Sedimentary and igneous rocks are altered through heat and pressure but do not melt in the process

Examples of metamorphic rocks

slate and marble

Properties of metamorphic rocks

• crystalline structure

• often folded and faulted

• more resistant the sedimentary

• crystals have parallel arrangement (foliation) which means they are weaker than igneous

How are igneous rocks formed

molten rock from volcanoes cools and hardens

Examples of igneous rocks

granite and basalt

properties of igneous rocks

• most resistant

• can be categorized into 2 types

  • intrusive - form within the ground, cool slowly and have large course crystals

  • extrusive - form on the earths surface, cools quickly, forms smaller crystals

• has interlocking crystals

  • making it harder than metamorphic

• fewer joints and weaknesses than other rocks

what is differential erosion?

changing/differing rates of erosion along a coastline

the whole coastline doesn’t erode at the same rate

• headlands and bays are an example

• bay erodes quicker than the headland

How can differential erosion affect coasts lines?

• leads to headlands and bays on discordant coastlines

• alternating strata can create a cliff profile where they more resistant rock juts out

• alternating permeability

  • permeable is on the top can be at risk of mass movement because of added weight and lubrication

role of vegetation in coastal stability

• plant roots bind sand/soil together reducing the impact of erosion

• reduces wind speeds (which reduces erosion)

• dead plant life left on sand can eventually lead to the formation of soil

why is vegetation often sparse in coastal environments?

• saline water

• evaporation of water causes increase in salinity

• high wind speeds

• lack of shade

• lack of nutrients

• “free draining sediment” - water is not retained

what are pioneer species?

the first plants to grow in the harsh coastal conditions, paving the way for other plants which are less able to survive in these conditions

• help stabilize sediment

• add organic matter

• increase shade

• trap more sediment

what are common pioneer species?

marram grass, sea rocket, and glassworts

What is dynamic equilibrium in coasts

balance between inputs and outputs of energy and material

also be thought of as longer term changes such as sea level - affects the balances

you could factor in more local changes such as low and high tide, weather conditions vary wave energy etc

rate of sea level rise according to NASA and satellite technology

3.4 mm a year

How does dip of strata affect erosion?

Horizontal -

• near perfect vertical cliff profile

• notches reflecting weathering

• small scale mass movement of strata that are jointed or more easily eroded

High angle seaward dip \\~

• sloping low angled profile

• vulnerable to rock slides

Low angle seaward dip |\~

• steep profile

• may create overhanging rock

• frequent small scale mass movement

• major cliff collapse when overhanging is unsustainable from undercutting

landward dip

• steep profile

• gravity pulls loosened blocks into place

• very stable

• few rockfalls

Fancy name for plant succession in a sandy environment

psammosere

Fancy words to describe plants that colonize sand dunes

xerophytic (can withstand dry/arid and sandy conditions)

halophytic (can withstand high salinity)

Maximum height of a embryo dune

1m

fore dunes

• embryo dunes in front of it protect from winds

• allows other species to grow like marram grass

• the grass then stabilizes the dune with its root system

• the organic matter from the plants make it more hospitable for future plants

• micro climate forms in dune slack (dip between dunes)

  • “ small-scale variation in weather conditions, like temperature or wind”

Maximum height for fore dunes

5m

yellow dunes

• initially yellow (sand) but slowly darken as organic material is added to soil

• marram still dominates vegetation but more delicate flowers and bugs can be found in the dune slacks around it

• 20% of the dune is exposed

  • in earlier stages 80% of it is exposed so significant difference in coverage

Maximum height of a yellow dune

8m

grey dunes

• more stable

• good range of biodiversity

• only 10% of sand exposed

• soil acidity increases (good thing as salt is alkaline) and water content due to humus (type of good soil from decomposed organisms) being added

• shrubs and bushes appear eg gorse

Height of grey dune

8-10m

mature dunes

• oldest and most stable

• several hundred meters from the shoreline

• soil can support a variety of flora eg oak trees

• climax vegetation and climax community stage

  • the final, relatively stable stage of ecological succession in a particular environment

fancy word for succession in salt

halosere

what is succession?

the process by which the mix of species and habitat in an area changes over time

why do salt marshes often develop by estuarine areas

• steady supply of sediment from the river

• shelter from strong waves

what happens when salt water and fresh water in estuarine environments mix

• causes flocculation where clay particles stick together

• these clay particles then sink causing sediment to build up

Salt marsh succession

• sediment builds up and is covered less and less by the tide at a time

• this allows other plants such as cord grass to colonise

• the height of sediment increases until it is only covered by the highest tides

• more plants colonize such as

  • sea lavender

  • sea thrift

• saline levels decrease allowing more and different plants to colonise

• this continues until the climax community is achieved

EXAMPLE - Dawlish warren

what happens in estuarine areas when algae colonises the sediment

• binds sediment together

• increases organic matter

• traps more sediment

what is a climax community

the final, stable stage of ecological succession in a particular area, reached when the ecosystem has reached its full potential in terms of species diversity and complexity

what is the main source of energy on coasts

waves

(friction between wind and surface of water transfers energy from the wind to the water)

why does wind occur?

rotation of the earth

differences in atmospheric pressure (when different parcels of air are heated by the sun)

factors that affect how much energy a wave has

Fetch

• the distance of open water the wind blows over

Strength

• How forceful the wind is

  • determined by the pressure difference in the air

Duration

• how long the wind has been blowing

wave height

height from peak to trough

wave length

distance from crest to crest

wave frequency

number of waves which pass a specific point over a given time

what is beach morphology

the geological structure, shape or form of a feature

what % of the population live within 100km of the coast? (about 2.5 billion people)

40%

How do waves affect beach morphology?

• steeper profile in the summer

  • because there are more constructive waves

• gentler in winter

  • destructive waves more often so even out the profile

• storm berms may appear in the winter

  • destructive storm waves carry larger sediment further up the beach than normal

• Winter beaches may have more variation in sizes of sediment

what is terminal groyne syndrome

Beyond the last groyne the beach is starved of sediment so is more vulnerable to erosion.

Holderness coast

• soft boulder clay (deposited 18,000 years ago) is one of the fastest eroding coastlines in europe

  • 2m of erosion a year!

• 23 towns/villages have already been lost

• 61km from Flamborough to spurn point

• strong prevailing winds

• narrow beaches offer little protection from strong destructive waves

• Yorkshire - east england

Management

overall - do nothing approach/ managed retreat

• sea defences can further erode the coast further down

• Terminal groyne syndrome - groynes are trapping sediment and leading areas down drift deprived of sediment eg Hornsea is depriving Mappleton of sediment and Mappleton is depriving Great Cowden of sediment with their groynes leading to increased erosion

what is lithology

study of properties of rock

what is geology

study of how rocks are arranged

Longshore drift

main process of deposition and transportation along the coast

influenced by prevailing wind making waves approach at an angle

backwash carries sediment down the beach at a 90 degree angle T

Currents

surface currents are formed mainly by wind

deep water currents are caused in differences in densities between hot and cold water (also called thermohaline circulation)

salinity differences as well

Happisburgh

• North Norfolk

• 1,400 residents

• 600 properties

• sands and gravels and laminated silts and clays. (softer)

• average rate of erosion 1.7m a year

• groynes in 1959 and rock armor throughout the years

• 2002 4,000 tonnes armor

• 2007 1000 tonnes more

• then In 2015 9000 tonnes of rock armor were re-aligned

• Problem with rock armor is its susceptible to mass movement

• 1996 managed retreat was chosen

  • it would cost £15 million to protect Happisburgh but it is not worth the land its protecting

  • would have an impact on the wider coastal management plan.

  • Happisburgh would end up as a promontory (headland), blocking longshore drift and causing further erosion downdrift.

• council was given £3 million to buy 'unsellable' houses near cliffs at 40% price to create a buffer zone, relocate public toilets and emergency rock armor

• Locals Not happy at all created a group in 1998 called the "Coastal Concern Action Group"

Why does Happisburgh and Holderness have such strong destructive waves?

The north sea is narrowing closer to the English channel so there is lots of energy in such a small corner, more swell, as it turns from north sea to the Atlantic

long fetch

Bangladesh flood risk

• convergence of three major rivers

• 50% of the country has an elevation of 10m or less above sea level

• 20 million people live less than 1 m above sea level

• Cyclones regularly cause storm surges

• monsoon rains increase amount of flood water

• bay of bengal there are hundreds of small islands made from unconsolidated material

  • highly unstable and susceptible to flooding

• 8,000 Km³ will be lost if sea level rises by 0.3 m from its current level

• more at risk as are removing mangrove forests for farmland

• 40% of all recorded storm surges have occurred in Bangladesh

• shortages of rice and vegetables causing malnutrition

  • Farmland has been contaminated with salt water

human interference mangroves

• The Sundarbans Reserve Forest (SRF) - largest mangrove forest in the world

• Natural coastal defence

• They are now at risk of disappearing entirely within the next 100 years

• pond shrimp aquaculture, one of the main causes of mangrove loss

  • inked to as much as 38% of global mangrove deforestation

• mangrove forests can store up to 4 times the amount of carbon as tropical forests

• 71% of bangladesh’s mangrove forest coastline is now retreating by as mush as 200m a year

• Globally ½ of the mangrove trees have been lost since the mid twentieth century

Name of the largest mangrove forest

The Sundarbans Reserve Forest (SRF)

Chittagong Bangladesh management

• 2012 created “ Coastal Climate Resilient Infrastructure Project”

  • make coastal areas more resilient

  • funding from asian development bank

  • US$154.1 million

  • aims to help people, economy and environment (multi-pronged approach)

  • Locally organised and run projects, ensuring greater local engagement

• building coastal embankments lined with halophytic vegetation

• raising the levels of the roads and making them more durable

• upgrade 25 cyclone shelters and improve acces

• upgrade 37 boat landing stages

  • designed to cope with flood water

  • fishermen’s boats and livelihoods aren’t too damaged by storms

• education programs

• improving water supply pipelines

• creating sewage and sanitation networks that are protected from floodwater

Erosion bangladesh coastline

• Bangladesh average erosion 17-22 meters per year some areas its up to 120m a year!