Costal landscapes and change eq1 & 2

Why

Littoral zone

Part of a sea, lake or river that is close to the shore

The 4 sub zones in the littoral zone

Offshore, nearshore, foreshore, backshore

characteristics of high energy coastlines

Destructive waves, long fetches, high rates of erosion, caves, stacks, stumps, cliffs, wave- cut platforms

Characteristics of lowEnergy coasts

Constructive waves, shorter fetches, high rates of deposition, beaches, spits, bars

Concordant coastline

Alternating bands of hard and soft rock parallel to the coastline

Discordant coastline

Alternating bands of hard and soft rock perpendicular to the coast.

Erosional landforms more common here cuts erosion happens are different rates along their length

An example of a discordant coastline

Dorset coast, consisting of Portland limestone and greenlands (greenlands less resistant)

Strata

The layers of rock

What are Dalmatian coasts, how they form, an example (concordant example)

Tectonic forces has compressed limestone. Created up fold ridges (anticlines) and down fold ridges (synclines) parallel to the coast. Sea level rise flooded the synclines.

Lines of elongated islands formed from projecting sections of anticlines parallel to coast, separating narrow sea channels parallel to coast (sounds)

E.g. the Croatian Dalmatian coast

What are haff coastlines, how they form, an example (concordat example)

Formed when sea level was 100m lower and water was retained in ice sheets. Meltwater rivers deposited sediment into out wash plains. Waves pushed the ridge of sands and gravel land wards as sea level rose. The sand ridge became a bar. River mouthed trapped forming the lagoon.

What are bays and headlands (discordant example)

Formation of headlands causes a change in the way waves approach the coastline (wave refraction) and causes an increase into he rate of erosion on the headlands

What causes joints, the angle of dip, faulting and folding.

Why are rocks with these more susceptible to erosion and weathering

The deformation and stress placed on them from tectonic processes.

They’re ore susceptible because these processes exert forces on the weaknesses found

What’s dip

the angle of inclination of the rock strata compared to the horizontal

What happens with bedding planes with dip towards the sea

Have a gentler cliff profile but these cliffs are vulnerable to mass movement.

High angle of seaward dip (>45) produces a sloping, low-angled profile with one rock layer facing the sea; vulnerable to rock slides down the dip slope when uppermost strata are attacked by sub-aerial processes. The profile slopes corresponding to that of strata dip. Bedding planes between strata are weakly bonded and readily loosened by weathering.

Low angle of seaward dip (<45) produces a steep profile, that may even exceed 90 degrees, creating areas of overhanging rock; very vulnerable to rock falls. Frequent small-scale mass movement of material weathered from cliff face. Major cliff collapse when undercutting by marine erosion makes overhang unsustainable. 

What happens with bedding planes with dip towards the land

Have a steeper cliff profile but these cliffs are vulnerable to erosional processes.

Landward dipping strata produces steep profiles as downslope gravitational force pulls loosened blocks into place. Very stable profile with few rock falls. 

Lithology

Physical properties of different types of rock

3 rock types in order of strongest to weakest

Igneous, metamorphic, sedimentary

How do igneous rocks form (e.g. granite)

The crystallisation of magma.

It can be intrusive (formed from magma inside Earth) or extrusive (formed when magma escapes earth surface)

What’s the erosion rate of igneous rock and why

Very snow because of interlocking crystals which make it strong and hard.

They have few joints so limited weaknesses to exploit

How does metamorphic rock form (e.g. slate and marble)

The change in structure of sedimentary and igneous rock caused by variation in pressure and temperature

What is the erosion rate of metamorphic rock and why

Slow because crystalline metamorphic rock are resistant to erosion.

Many have folication where crystals are orientated in the same way- creates weakness.

They’re folded and have heavily fractured- weaknesses to exploit

How does sedimentary rock form (e.g. sandstone, limestone)

Form from the build up, compacting and hardening of sediments into layers over time by lithification

What is the erosion rate of sedimentary rock and why

Fast because they’re clastic so erode faster.

Geologically young (would’ve had less time to compress to become harder).

That have many bedding planes and fractures so more weakness to exploit

How do micro features form

A focus of high energy at one particular point in the cliff. Large amounts of pressure and heat can cause microfeatres.

Why are microfeatres significant

They’re providing places where preferential weathering and erosion take place

Weathering definition

The breakdown of rocks at the earths surface by the action of rainwater, extremes of temperature and biological activity

Erosion definition

Material broken down and removed from area by water or wind

3 costal areas where vegetation can act as a stabilising agent

Costal salt marsh, costal sand dunes, costal mangrove swamps (low energy depositional environments)

3 ways the presence of vegetation helps stabilise coastal sediments

The roots bind sediment together so they’re harder to erode.

When submerged or decomposed plants provide a protective layer so surface layer isn’t directly exposed.

Plants protect from erossion by reducing wind speed at surface due to friction with the vegetation

What’s a halophyte

Salt tolerant plants (e.g. cordgrass) which slow tidal flow and step mud and slit

What’s a xerophyte

Dry condition tolerant plants

What’s plant succession

When a place that becomes bare is colonised by plants. When other species invade and take over until balance is reached

What’s pasammosere

Plant succession on plant dunes

What’s halosere

Plant succession in salt water environments

5 sand dune stages

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

What do pioneer species do in the colonisation of embryo dunes (three things)

Stabilise the mobile sand with roots, reduce wind speed at sand surface so more sand can be deposited, add dead organic matter to the sand beginning soil formation

How do fore dunes form

New species colonise the embryo dunes

How do grey dunes from

Environmental modification continues as soil developed so more plants can colonise. The dunes formed grow upwards

How do dune slacks form

Periods of wind erosion creates low areas (dune slacks). Erosion stops when damp sand at the water table is exposed

Sand dune example

Dawlish warren

Why are estuaries a good place for salt marshes to develop (2 reasons)

Sheltered from strong waves so sediment can deposit, rivers transport a supply of sediment to the river mouth which can be added to the sediment flowing into the estuary at high tide

What are the 5 stages of salt marsh development

Algal stage, pioneer stage, establishment stage, stabilisation, climax vegetation

What happens in the algal stage (salt marsh)

E.g. blue green algae, grows on and within bare mud, binding it together

What happens in the pioneer stage (salt marsh)

E.g. cord grass, roots begin to stabilise the mud, allowing further mud accretion

What happens in the establishment stage (salt marsh)

E.g. salt marsh grass, a continuous carpet of vegetation is established and the salt marsh height increases

What happens in stabilisation (salt marsh)

E.g. sea lavender, this area of the salt marsh is rarely submerged

What happens in climax vegetation (salt marsh)

E.g. rise, developed soil profile and only submerged once or twice a year

What are beach profiles like in summer

Less windy. there’s a stronger swash depositing sediment (constructive waves dominate). There’s a berm. Net addition of sediment (steep). Fill cycle.

What’s the beach profile like in the winter

high wind. there’s a stronger backwash removing sediment (destructive waves dominate). The berm goes into making a bar. Shallow water cuz of bar so waves will break earlier. Net loss of sediment (steep). cut cycle.

What causes waves to form

Friction between wind and sea

2 Factors that control wave size

Wind, length of fetch

What happens as a wave enters shallower water

Wave becomes shallower,

circular orbit of water particles changes to an elliptical shape,

wavelength and velocity decreases as height increases, causing water to back up from behind,

Forces push wave whither so steeper before breaking offshore,

Water rushes up beach as swash then back as backwash

What’s fetch how does it affect wave energy

Distance of open water which waves move. the grater the fetch the larger the wave

Features of constructive waves

Low wave height, long wavelength, gentle and flat, strong swash weak backwash

Features of destructive waves

Taller, shorter, strong backwash that arises and carries sediment ofshore

What’s hydraulic action. When’s it most effective

The force of water crashing against the coastline causing material to dislodge and carried away.

Most effective with high energy waves where there’s no debris in cliff to absorb wave energy

What’s abrasion

Material carried by sea picked up and thrown against the coastline

What’s corrosion When’s it most effective

Where water in waves dissolves rock minerals.

Most effective in constructive waves cus they’re slow and prolong contact with water

What’s attrition when’s it most affective

materials eroded through collisions with other materials.

Occurs in foreshore and nearshore where sediment is moved by swash and backwash

4 marine processes of erosion

Hydraulic action, abrasion, attrition, corrosion

3 sub aerial processes

Weathering, mass movement, surface runoff

What’s chemical weathering. Conditions needed

Rain absorbed CO2 to form a weak carbonic acid. Reacts with calcium carbonate in rocks to from calcium bicarbonate which is easily dissolved.

Colder temp of rain = more CO2 absorbed = increased effectiveness of carbonation in Water

Examples of biological weathering

Plant roots widening cracks as they grow.

Water raining through decaying life becomes very acidic.

Animals digging burrows in cliff

3 types of physical weathering

Freeze thraw, salt weathering, wetting and drying

What’s freeze thraw

Water enters crack freezes and expands

What’s salt weathering

Salt water evaporates leaving salt crystals behind. Grow overtime. Salt corrodes rock especially if there’s iron

What’s wetting and drying

Rocks rich in clay expand when wet contract when dry so crack and break

What’s a bay

An inlet of the sea where the e land curves onwards usually with a beach

What’s a headland

An area of land jutting out into the sea

What’s a wave cut notch

Formed by erosional processes eg abrasion and hydraulic action

What’s a wave cut platform

A wide sloping surface found at the foot of a cliff

How do cliffs form

Erosion and weathering. Soft rich breaks of or grainy rocks from hard rock. The lard rock left is the cliff

How do headlands form

When the sea attacks a section of the coast with a discordant coastline and the soft rock erodes first

Example of a wave cut platform

Severn sisters in Sussex

2 landforms or coastal erosion

Headlands & bays, wave cut platforms

6 landforms of coastal deposition

Barrier beaches/ bars, offshore bars, cuspate forelands, tombolos, beaches, spit,

How do barrier beaches/ bars form

when there’s a gap in the coastline with water in it, longshoreman drift carries material across making a spit till it joins the other side. The water behind is called a lagoon

Barrier beach/ bar example

Chesil beach

What is an ofshore bar

Ridges of sand or shingle running parallel to the coast in the offshore zone. They cause waves to break earlier lowering rates of erosion

How do offshore bars form

Form when sediment is eroded and carried backwards by backwash then dropped. Carried by traction and saltation as it doesn’t go far (low energy).

How do cuspate forelands form

Created by longshoreman drift and accretion (increase of layers added to an area). This causes the progradation of sand and shingle causing the material to extend outwards form the shoreline in a triangular shape.

formed by longshoreman drift from both directions making 2 spits thst join and fill with sediment

Cuspate forelands example

Dungeness in the uk

What are tombolos

Linear ridges of sand and shingle connecting an offshore island to the coastline of the mainland

How do tombolos form

longshoreman drift occurring on the coastline and sediment builds up between the beach and an island instead of on the beach. Wave diffraction and refraction happens too as it reaches the shallow water and builds up the tombolo

Tombolo example

St ninian’s tombolo

What is a spit

An extended stretch of sand or shingle jutting out into the sea from land

How do spits form

Sediment carried by longshoreman drift deposited at a change in the shape of the coastline. 3 characteristics of spits are salt marshes, estuaries and hooked ends.

Example of a spit

Dawlish warren and spurm head

What is a tide and how often d othey happen

The regular rise and fall of the ocean waters. There’s 2 high and 2 low tides every 24 hrs and 50 min

What causes tides

The gravitational forces exerted on the earth my the moon and to a lesser extent, the sun

What’s the tidal range

Difference between high and low tide

What’s a spring tide

They occur when the sun moon and earth are lined up. This causes high and low tides to be much higher

Wants a need tide

They occur when the sun moon and earth form a right angle. This causes high snd low tide to be much lower

What do tidal ranges influence

High tidal range = more fast moving water = erosion increases. Currents stronger, more energy

4 ways material is transported at the coastline

(as you go down the lighter the particles get, the less energy needed, the ones first are more likely to happen during high energy storms so not moved very often, the last ones happen continuously)

Traction, saltation, suspension, solution

What is traction

Sediment rolls, pushed by waves and current

What’s saltation

Sediment bounces along due to forces of water or wind

whats suspension

Sediment carried in water column. Sea often muddy brown

What’s solution

Dissolved material carries in water as soliton. Chemical compounds in a solution

What’s negative feedback and an example

Reverses the change brings things back to normal. E.g. summer and winter beach profiles