Coasts - EQ1 - Why are coastal landscapes different and what processes cause these differences? Flashcards
Define Littoral Zone
area of shoreline where land is subject to wave action`
What are the 4 parts of the littoral zone
Offshore
Nearshore
Foreshore
Backshore
What is the order of the littoral zone, going inland
Offshore
Nearshore
Foreshore
Backshore
Define Offshore
area of deeper water beyond the point at which waves begin to break
Define Nearshore
- area of shallow water beyond the low tide mark,
- within which friction between the seabed and waves distorts the wave sufficiently,
- to cause it to break (breaker zone)
Define Foreshore
area between the high tide and low tide mark
Define Backshore
area above the high tide mark, affected by wave action only during major storm events
List some natural causes of changes to the littoral zone
- constructive and destructive waves
- sediment input from sea and rivers
- LSD
- tidal range - determines where wave action occurs
List some human changes to the littoral zone
dredging of offshore areas
dredging of rivers
building of coastal rivers
Coastal systems are in a state of D__________ E_________
Dynamic Equilibrium
Coasts are systems driven by ____ energy
wave
3 components of the coastal system
inputs
processes
outputs
What are the inputs to a coastal system
Marine
People
Land
Atmosphere
What are the processes in a coastal system
mass movement
weathering
erosion
deposition
transport
What are the outputs to a coastal system
erosional landforms
depositional landforms
different types of coasts
Coasts can be classified using
short and long term criteria
What are the long term changes which classify coasts
land level rise and fall (isostatic)
sea level rise and fall (eustatic)
geology
word for land level rise and fall
isostatic
word for sea level rise and fall
eustatic
What are the short term changes which classify coasts
erosion
deposition
wave type
wave energy
How are Igneous rocks formed
when hot molten rock crystallizes and solidifies
Features of Igneous rock
crystals, hard rock
Examples of Igneous rock
granite and basalt
How are Sedimentary rocks formed
dead biological matter or eroded weathered matter falls to the bed and are deposited in layers these become compact and cemented
Features of Sedimentary rock
layers
often contain fossils
range from hard to soft rock
Examples of sedimentary rock
sandstone
limestone
chalk
How are Metamorphic rocks formed
existing rocks are put under intense pressure and heat forming layers and bands of crystals
Features of Metamorphic rock
Layers
Crystals
Very hard rock
Examples of Metamorphic rock
schist
slate
What are the conditions to form Rocky Coasts (high relief)
-result from resistant geology to the erosive forces of sea, rain and wind often in a high energy environment
Waves in a low energy coast
less powerful, constructive, short fetches
What are the conditions to form Coast Plain Landscapes (sandy & estuarine coasts)
- found near areas of low relief
- result from the supply of sediment from different terrestrial and offshore sources
- often in low-energy environments
Waves in a high energy coast
more powerful, destructive, long fetches, storm conditions
Processes in a low energy coast
- deposition and transport of sediments from rivers
- LSD and nearshore currents
Processes in a high energy coast
- erosion and transport of sediment from eroded land
- mass movement
- weathering
- offshore currents
Landforms in a low energy coast
beaches, spits, salt marshes, sand dunes, bars
Landforms in a high energy coast
cliffs, wave-cut platforms, arches, caves, stack
General location of a low energy coast
sheltered from large waves
coastal plain landscapes
lowland coasts
General location of a high energy coast
exposed to larger waves
rocky landscapes
high and lowland coasts
example location of a low energy coast
East Anglian Coasts
example location of a high energy coast
Pacific coasts of Alaska and Canada
Features of constructive waves
low energy
occur in calm conditions
material is deposited building up coasts
Features of destructive waves
high energy
backwash stronger than swash which erodes the coast
What are the coastal morphology determiners
- relief & slope
- geology
- lithology
- rock permeability
- resistance / hard or soft rock
Define lithology
the general study of the physical characteristics of rocks e.g colour, texture, type
Define structure
- the study of permanent deformation & rock failure
- created by the changes in stress through geologic time
- e.g jointing, bedding, faulting, angle of dip
Define strata
layers of rock
Define bedding planes
horizontal cracks / natural breaks in the strata
Define joints
- vertical cracks/ fractures
- caused by contraction as sediments dry out or by earth movement
Define folds
formed by pressure during tectonic activity, which makes rocks crumble
Define faults
formed when the stress or pressure to which a rock is subjected, exceeds its internal strength (causing it to fracture)
Define dip
refers to the angle at which rock strata either horizontally or vertically, dips towards the sea or the land
Define coastal morphology
the shape & form of coastal landscapes & their features
resistance of igneous rocks
very resistant
erosion rate of igneous rocks
VERY SLOW – less than 0.1 cm per year.
permeability of igneous rocks
impermeable - very few spaces of joints for water to pass through
Describe the Internal Structure of Sedimentary Rocks
- Most are CLASTIC (composed of sediment particles becoming cemented together).
- Many cements are REACTIVE and easily chemical weathered.
- BEDDING PLANES and JOINTS make them even more vulnerable to recession.
- Geologically young rocks tend to be weaker.
resistance of sedimentary rocks
not very resistant
erosion rate of sedimentary rocks
MODERATE TO FAST – 1-10 cm per year.
permeability of sedimentary rocks
often porous - susceptible to weathering
resistance of metamorphic rocks
very resistant
erosion rate of metamorphic rocks
SLOW – 0.1-0.3 cm per year.
permeability of metamorphic rocks
impermeable - very few spaces of joints for water to pass through
Describe the Internal Structure of Metamorphic Rocks
- Metamorphism can cause the grains to RECRYSTALLIZE into a very solid INTERLOCKING network.
- These rocks are resistant.
- Again, folding and faulting makes them less resistant than igneous rocks.
Describe a discordant coastline
alternating bands of resistant (hard) and less resistant (soft) rock which are perpendicular to the coast
What forms on discordant coastlines
headlands and bays
Describe the Internal Structure of Igneous Rocks
CRYSTALLINE structure - Crystals INTERLOCK making the rock resistant.
FEW JOINTS (micro features) means there are limited weaknesses to exploit.
Describe a concordant coastline
same band of resistant (hard) rock which lies parallel to the coast
What are the two types of concordant coastlines
Haff Coasts & Dalmatian Coasts
Where are Haff coastlines formed
in low-energy environments where there is deposition of muds and sands
Describe how Haff Coastlines are formed
- These form where deposition produces unconsolidated geological structures parallel to the coastline
- During the Devensian glacial the sea level was about 100 m lower than today as water was retained in huge ice sheets
- Meltwater rivers on land beyond the ice front deposited thick layers of sand and gravels onto outwash plains (sandurs)
- In the Holocene Interglacial constructive waves pushed the ride of sands and gravel landwards as sea levels rose
- Sand ridge formed bars across some bays and river mouths, with trapped river water forming a lagoon behind (callled haffs in Poland on the Baltic Sea)
Describe a feature of Haff Coastlines
Large lagoons are found behind the deposits parallel to the shoreline.
Give an example of a Haff Coastline
The Baltic Sea coastline of Poland.
How are Dalmatian coastlines formed
- Formed as a result of a rise in sea level.
- Valleys and ridges run parallel to each other.
- When the valleys flooded because of a rise in sea level, the tops of the ridges remained above the sea surface – as a series of offshore islands that run parallel.
Give an example of a Dalmatian Coastline
Adriatic Sea, Croatia
How are steep seaward dipping cliffs formed
- rock slabs sliding down the cliff along the bedding planes
How are seaward dipping cliffs formed
- joints being opened by weathering & pressure to release slabs
How are steep sided cliffs formed
formed in areas of horizontal layers or bedding planes
How are stable, steep cliffs formed
when bedding planes dip inland
How are side planes formed
when rocks dip inland with well developed joints at right angles to the bedding planes
What is a micro-feature
small scale features which form part of a cliff profile
Give examples of micro features
caves and blowholes
how are micro features formed
form in areas weakened by heavy jointing, which have faster rates of erosion, enlarging the joint to form a sea cave
describe the location of micro features
often controlled by the location of faults and/or strata which have a particularly high density of joints and folds.
Define rate of recession
the speed at which the coastline is moving inland
Coastal recession is caused by ………. factors (……. & …….)
Physical Factors (geological & marine)
Coastal recession is caused by physical factors (geological & marine) but can be influenced by ……… factors (….. & …… )
Human Factors (dredging or coastal management)
what does bedrock lithology consist of
igneous, metamorphic & sedimentary rock
What decides how susceptible a rock is to erosion or weathering
- the bedrock lithology
or - the unconsolidated material geology such as rocks with cracks, joints and bedding planes
Name the 4 coastal ecosystems
mangrove forests
coral reefs
sand dunes
saltmarshes
name 2 low land coastal ecosystems
sand dunes & salt marshes
To survive on coasts plants are often highly ________
specialised
define halophytes
salt tolerant
example of halophytes
Mangroves
define xerophytes
drought tolerant (salt water is drying and sand does not retain water)
example of xerophytes
Marram grass
define psammophytes
- grown in wind blown sand
- can tolerate dry, salty conditions and being buried
example of psammophytes
Sea Holly
Define plant succession
- means the changing structure of a plant community over time as an area of bare sediment is colonised
- each step in this stage is called a seral stage
define zonation
how ecosystems change spatially away from the shoreline
define pioneer species
the first hand species to have colonised areas of exposed sediment
define climax communities
the final stage of succession with the greatest biodiversity
Where are salt marshes found
- In low energy environments, like estuaries or sheltered bays
- they can also be found in creeks & a the edges of estuaries & behind a spit
What is flocculation
- once fine muds and silts are deposited,
- the tiny particles stick together to create thicker mud/ sediment
How does vegetation change the conditions of salt marshes
- Overtime, the plants change the conditions, by trapping more sediment
- which builds the salt marsh up to a higher level,
- so that other plants can colonise.
Vegetation in salt marshes also provides…
ecosystems for wildlife
Describe the lower part of the salt marsh
Its underwater for longer periods of time & only pioneer halophytic plants may grow here
How do salt marshes help to stabilise coastal landscapes
- Found behind estuaries & creeks
- minimal erosion, & more deposition, so an increase in flocculation
- builds saltmarsh up to a higher level so plants can colonise e.g halophytes & green algae
- these absorb wave energy, preventing erosion; & creates habitats for wildlife which will encourage depositional processes via movement
- therefore, halophytes create a self sustaining vegetation cycle, which stabilises the landscape via habitat creation and flocculation
Named location example of a salt marsh
Walton on the Naze
Where can mangrove plants be found
- Along the intertidal zones of coastlines in tropical & subtropical areas,
- which can experience extremely destructive waves, high energy environments
What do mangroves reduce
- the height & energy of wind
- & swell waves passing through them,
- reducing their ability to erode sediments
- & to cause damage to structures such as sea walls
Describe how mangroves reduce the height & energy of wind & swell waves
- During rising tides, as the sea comes in, waves enter the mangrove forests.
- They lose energy as they pass through the tangled above-ground roots & branches, so the waves height is rapidly diminished,
- by between 13 & 66 % over 100m of mangroves.
- As this happens, waves lose their ability to scour the sea-bed & carry away sediments
What type of plants are mangroves
halophytes
Why is it important that mangroves are halophytes
It means they can help to resist erosional processes in many hostile tropical coastal environments, as they have salt-tolerant properties
Give a named historical example of Mangroves stabilising an estuarine environment
- The Boxing Day tsunami of 2004
- Only 2 people were killed in a Sri Lankan village with dense mangrove coverage,
- but up to 6,000 lost their lives in a near by village no longer protected by similar vegetation
What are the characteristics of mangroves
- root systems - allow trees to withstand the ebb & flow of daily tides
- also act as buffers, slowing the flow of tidal waters,
- allowing nutrients to settle & build up as nutrient-rich mud
- provides habitats - valuable shelter & breeding sites for fish
What are the 6 stages of sand dune succession
Berm
Embryo
Fore
Yellow
Grey
Mature
How do sand dunes develop to stabilise estuarine environments
- Bare ground (rock, sand dunes, salt marshes & mud flats) are gradually colonised by plants - pioneer species
- These species begin the process of plant succession,
- during which other species invade & take over until a balance is reached
How do pioneer plants stabilise sand dunes
by binding sand or soil
They modify the environment by undergoing flocculation with their roots and adding nutrients when they die & decay
How do pioneer plants stabilise sand dunes
shade
- Creeping plants, with leaf cover, help the sand/mud retain moisture,
- by providing shade, which reduces evaporation,
- so the land can retain more moisture
- which allows for more species to colonise
What pioneer species can be found in sand dunes
psammophytes & halophytes
Describe the process of plant succession
- Embryo dunes are the first to develop, as sand collects in shelter of rocks/wood
- As embryo dunes develop, they grow into bigger fore-dunes - which are initially yellow in colour,
- but darken to grey as decaying plants add humus
- Depressions between dunes can develop into dune slacks
What is a dune slack
damper areas where the water table is closer to, or at the surface
What is the climatic community
The final community will be adjusted to the climatic conditions of the area
In a sand dune, as the environment changes overtime, different species will colonise it until it becomes_______
stable
Pioneer plants add to the nutrients & organic matter in the sand, which eventually forms a …..
foreshore
In a yellow dune________________ can colonise
marram grass
How can marram grass stabilise sand dunes
- The halophyte has roots that grow up to 3m deep,
- which helps stabilise the sand,
- moreover, their stems allows for sediment accumulation,
- increasing the rate of deposition,
- which helps to build up the sand dune, stabilising the unconsolidated sand prior
In a sand dune, overtime, the percentage of sand exposed will…
- reduce as vegetation adds more humus,
- which creates a self-sustaining cycle,
- allowing for more flocculation to take place,
- so more vegetation can grow
What vegetation forms in fore dunes
sea rocket & couch grass
What vegetation forms in grey dunes
low shrubs (brambles)
What vegetation forms in dune slacks
aquatic plants
Name 2 examples of sand dunes in the UK
Winterton dunes in Eastern England
Studland on the south coast
As the sand dune develops, the ph of the soil ________and the soil nutrients & vegetation coverage ________
decreases
increases
