Coastal Landscapes Flashcards
What are the zones that the littoral zone can be divided into
-name them in order
-coast
-backshore
-foreshore
-nearshore
-offshore
What is the backshore zone found in the littoral zone
-what is it
-area between the high tide mark
-affected by wave action during major storms
What is the foreshore zone found in the littoral zone
-what is it
-area between high tide and low tide mark
-seen as most important area for marine activity
What is the nearshore zone found in the littoral zone
-what is it
-area of shallow water where friction occurs between seabed and waves- causing waves to break
What is the offshore zone found in the littoral zone
-what is it
-area of deeper water beyond the point where waves begin to break
-friction occurs between seabed and waves- could cause distortion in wave shape
Name the 2 main types of coastlines formed by the littoral zone
-Rocky/ Cliffed coastlines
-Coastal plain landscapes
What are rocky coastlines
-areas of high and low relief
-resistant rock areas- resistant to erosive power of sea, wind, rain
-high energy environments
rock types: igneous, sedimentary and metamorphic rocks- granite, slate, limestone
-erosion is greater than deposition
-destructive waves
What are Coastal plain landscapes
-low, flat relief areas
-soft rock areas
-low energy environment
-rock types: weaker, younger sedimentary rocks- chalks, clays, sandstones
-deposition is greater than erosion
what is the littoral zone
-boundary between land and sea
Why does the littoral zone vary
-due to:
-short-term factors- daily tides, seasonal storms, individual waves
-long-term factors- changes to sea levels, climate change
Name the 4 ways
-geology
-sea level change
-energy inputs
-sediment inputs
-advancing/ retreating
How can coasts be classified because of geology
lithology (rock type) and structure of rocks
-used to determine if coast rocky, sandy or estuarine and concordant / discordant
How can coasts be classified because of sea level change
-used to classify coasts as emergent/ submergent
-can be caused by:
-tectonic processes- lift/ subside land- effects sea levels
-climate change- seal levels rise and fall
How can coasts be classified because of energy inputs
-receive energy inputs form waves, tides, currents, rivers, atmospheric processes, gravity tectonics
-classify coasts as high/ low energy
How can coasts be classified because of sediment inputs
-Coasts receive sediment inputs from waves, wind, tides, currents, mass movements, tectonic processes
-sediment added to coastline through deposition
-removed by erosion
-erosion > deposition- loss of sediment- coastline retreats- eroding coastline
-deposition > erosion- gain sediment- coastline advances- building coastline
What are concordant coasts
- have geological strata that runs parallel to the coast
-outer hard rocks acts as a protective barrier to erosion of the softer rocks further inland
- Sometimes outer hard rock is punctured- allowing sea to erode the softer rocks
-cove is produced (a circular area of water with a relatively narrow entrance from the sea)
-dalmatian
-haff
What are discordant coasts
-form when different rock strata intersect the coast at an angle
- differing erosion leads to
formation of headlands and bays - Less resistant rocks are eroded to form
bays
-more resistant geology
remains as headlands
-swanage bay
-bantry bay
What produces concordant and discordant coasts
geological structure
Definition of coastal morphology
shape and form of coastal landscapes and their features
Definition of coastal recession
another term for coastal erosion
Definition of strata
layers of rock
Definition of bedding planes (horizontal cracks)
natural breaks in strata caused by gaps in time during periods of rock formation
Definition of joints (vertical cracks)
fractures caused by contraction as sediments dry out/ earth movement during uplift
Definition of folds
formed by pressure during tectonic activity
-makes rocks buckle and crumple
Definition of faults
major fractures in rock produced by tectonic forces
-faults then move along fault planes
Definition of dip
the angle at which rock strata is
Definitoon of lithology
physical characteristics of particular rocks
What affects the speed at which the coast erodes
-geology
-lithology
Name 3 characteristics of igneous rocks
-is erosion rate fast/ slow
-give examples of igneous rocks
-crystalline
-resistant
-impermeable
-VERY SLOW erosion rate
-granite
-basalt
-dolerite
Name 3 characteristics of metamorphic rock
-is erosion rate fast/ slow
-give examples of metamorphic rocks
-very hard
-resistant
-impermeable
-SLOW
-slate
-schist
-marble
Name 3 characteristics of sedimentary rock
-is erosion rate fast/ slow
-give examples of sedimentary rocks
-formed in strata
-jointed sedimentary rocks (sandstone and limestone)- permeable and resistant
-other sedimentary rocks (chalk)- air spaces between particles- porous
What are Haff Coasts
-type of concordant coastline
-long spits of sand and lagoons- parallel to coast
Where is the Haff Coastline named after
Haffs/ Lagoons of the Baltic Sea
What is differential erosion
When different types of rocks are eroded at different rates
Name 2 characteristics that influenece cliff profiles
-rocks resistance to erosion
-dip of rock strata in relation to coastline
What type of cliff profile does horizontal dip produce
-vertical/ near vertical profile
with notches reflecting strata that are more easily eroded
What type of cliff profile does seaward dip, high angle produce
-sloping, low angle profile
-with one rock layer facing sea
-vulnerable to rock slides down sea
What type of cliff profile does seaward dip, low angle produce
-profile may exceed 90 degrees
-producing overhanging rock
-very vulnerable to rock falls
What type of cliff profile does seaward dip, landward dip produce
-steep profiles of 70-80 degrees
-producing very stable cliff with reduced rock falls
Definition of a cliff profile
the height and angle of a cliff face
What 3 geological features influence cliff profiles
-faults
-joints
-fissures
What controls the location of microfeatures
the location of faults and/ or strata which have a high density of joints and fissures
What are microfeatures in cliffs
caves, wave-cut notches
What are sub-aerial peocesses
processes of weathering and mass movement
What are the three factors involved with sub-aerial processes
-Weathering
-Mass movement
-Surface run-off
What is weathering
-chemical, biological and mechanical breakdown of rocks into smaller fragments and new minerals
What is mass movement
landslides slumps and rocks falls, which move material downslope under influence of gravity.
What is surface run-off
water, usually during heavy rain, flowing down the cliff face and causing erosion of it
What factors can determine a rocks resistance to erosion and weathering
-How reactive minerals in the rock are when exposed to chemical weathering- e.g. calcite (found in limestone) can be weathered by solution, whereas quartz (found in sandstone) is not subject to chemical weathering
-if rocks are clastic/ crystalline- igneous rocks are crystalline and are more resistant, sedimentary rocks are clastic (made of cemented sediment particles
-if rocks have cracks, fractures and fissures, which are weaknesses exploited by the forces of weathering and erosion
Give 2 examples of concordant coastlines
-Coast of Dalmatia, Croatia, Adriatic Sea
-Lulworth Cove, Dorset
How did the Dalmatian coast become a concordant coastline
- Geology is limestone
- folded by tectonic activity into series of anticlines and synclines- parallel to coastline
- drowned by rising sea levels creating
concordant coastline
How did Lulworth Cove become a concordant coastline
- The outer hard rock is limestone
- sea has broken through this barrier and eroded clays behind it
- A chalk cliff face at the back of the cove
slows further erosion - This has allowed the formation of a cove
Why is there little erosion at discordant coastlines?
- In deep water wave crests are parallel
As waves approach the shallow water offshore of a headland they slow down and wave height increases
In bays, wave crests curve to fill the bay and wave height decreases
The straight wave crests refract, becoming curved, spreading into out in bays and concentrating on headlands
The overall effect of wave refraction is to concentrate powerful waves at headlands (meaning greater erosion) and create lower, diverging wave crests at bays, reducing erosion
Give two examples of discordant coastlines
-Dorset Coastline
-West Cork coast of Ireland
How did Dorset Coastline become a discordant coastline
The limestone is resistant to erosion; then
to the north at Swanage bay the rock
type is softer greensand
- North of Swanage, the chalk outcrop
creates the headland which includes Old
Harry Rocks
How did West Cork coast of Ireland become a discordant coastline
- Rock strata that include: Limestone,
Mudstone and sandstone meet the
coastline 90 degrees in parallel bands - Weak rocks have been eroded, creating
elongated, narrow bays, whereas more-
resistant rocks for headlands - Especially resistant areas remain as
detached islands
Explain how faulting influences the features of a Cliff profile
- Represents major weaknesses within rock
layers (cracks in crust) - Either side of a fault line, rocks are often
heavily fractured and broken and these
weaknesses are exploited by marine
erosion
Explain how jointing influences the features of a Cliff profile
- Occur in most rocks, often in regular
patterns, dividing rock strata up into
blocks with a regular shape
Explain how Folding influences the features of a Cliff profile
- Folding occurs due to crust compression
- Horizontal strata can be folded into a
series anticlines and synclines
What is pore water pressure and how can it weaken the structures of rocks
The pressure water experiences at a particular point below the water table due to the weight of water above it
Permeable rocks allow water to flow through them – which can weaken rocks by removing the sediment that binds the rock together
– it can also create high pore water pressure within cliffs, which can affect their stability.
What are the three types of coastal vegetation that can protect a coastline from erosion
-Coastal sand dunes
-Coastal salt marshes, found in many river estuaries
-Coastal mangrove swamps
What are Halophytes
Plants that can tolerate salt water, either around their roots, being submerged at high tide or salt spray from the sea
What are Xerophytes
Plants that can tolerate very dry conditions, such as those found on coastal sand dunes where the sandy soil retains very little water due to drainage
What is the importance of Embryo dunes in protecting the coastline
- Embryo dunes pioneer plants
- They stabilise the mobile sand – reduce
wind speeds at the sand surface allowing
more to be deposited – add dead organic
matter to the sand, beginning the process
of soil formation - They alter the environmental conditions
from harsh, salty, mobile sand to an
environment that other plants can
tolerate - They lead to the development of plant
colonisation - Grey dunes were once embryo dunes, but
due to plant colonisation, have grown
upwards
What is the importance of Marram grass in dune succession
- Sand dune succession relies on
specialised plants such as marram grass - Marram grass has tough, long and flexible
wavy leaves that are designed to limit
water transpiration - Marram grass has roots up to 3m long that
can tap water far below the surface and
can tolerate temperatures of up to 60
degrees centigrade
What is the importance of salt marsh succession in reducing flooding
- Bare mud, hosts species of algae
- Pioneer plants which colonise mud flats
- Taller plant species from later serel stages
can be seen - The salt marshes form and gradually
slopes towards the shore, because plants
trap sediment on incoming tides, which is
deposited
How does the wave react at the shore?
When they reach the shore, forward movement starts to occur, which, as the depth is less than the wavelength - the base of the wave is slowed down by friction against the sea floor and the wave crest topples over and breaks onto the shore.
Describe constructive waves
- Have a low wave height and a long wave
length - They are gentle, flat waves with a string
swash but weak backwash - The strong swash pushes sediment up
the beach, depositing it as a (berm/ridge
of sediment) at the top of the beach
Describe destructive waves
- Have a very high wave height and a short
wavelength - Common during storms
- Have a strong backwash that erodes the
beach material and carries it offshore,
creating an offshore ridge
What is beach morphology
shape of the beach- width, slope, features, such as berms, ridges and runnels. It also includes the type of sediment found at different locations
What are the four different types of wave type that influences beach morphology
-Hydraulic Action
-Corrosion
-Abrasion
-Attrition
What is hydraulic action
Waves crash against rocks and compress air in the cracks, adding pressure. Repeated compression widens the cracks and causes rocks to shatter
What is corrosion
Water dissolves minerals in the rocks (particularly limestone) and washes it away
What is abrasion
Sediment picked up by breaking waves is thrown against the cliff face
The sediment acts like a tool on the cliff – chiselling away at the surface and gradually wearing it down
What is attrition
Eroded particles in the water collide with each other and break into smaller fragments
What influences how sediment is transported
- Sediment is transported along the
coastlines by currents - Sediment transformation is influenced by
angle of attacks depending on wind
direction, tides and longshore drift
(current flowing at angles to the coast,
transporting material through the actions
of swash and backwash)
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What are the four different processes of sediment transport
Traction: Sediment rolls along
What are the four different processes of sediment transport
Traction: Sediment rolls along, pushed by waves and currents
Saltation: Sediment bounces along, either due to the force of water or wind
Suspension: Sediment is carried in water columns
Solution: Dissolved material is carried in the water as a solution
What depositional landforms are formed as a result of sediment transport deposition
- Beaches
- Spits
- Bars
- Barrier beaches
- Tombolo
- Cuspate Foreland
Describe the formation of a beach
Found on coasts between the high-water mark and the low water mark. They form due to constructive waves depositing sand and shingle
Describe the formation of a spit
Beaches which stick out at sea.
They form at sharp bends on coastlines where longshore drift transports sand and shingle past the bend and deposits it in the sea.
Strong winds can curve the spit (called a recurved spit) and plants can grow bashing the spit where waves cannot reach.
Describe the formation of a Bar
Form when a spit joins two headlands together, cutting of the sea from the water trapped between the bar and coastline. This forms a lagoon.
What are sediment cells
largely self-contained stretch of coastline.
- closed systems as sediment is not usually transferred from one to the other.
- they operate as a system with
inputs, transfers and outputs of sediment.
operate in a state of dynamic equilibrium
with sediment inputs balancing outputs to
sinks.
Name the 3 types of coastal landscape the littoral zone forms
-Rocky, cliffed coastline- areas of high relief- resistant geology- high energy environment- erosion > deposition
-Sandy coastline- areas of low relief- less resistant geology- low energy environment- deposition > erosion
-estuarine- areas of low relief- less resistant geology- low energy environment- deposition > erosion
How can coasts be classified because of advancing/ retreating
classified as advancing or retreating due to long-term processes (emergent/submergent) and short term (outbuilding/eroding).
Describe coastal plains
-contain wetlands and marshes- just above sea level- poorly drained- flat landscape
- formed in two ways: fall in sea level, coastal accretion
– maintained in dynamic equilibrium by deposition of sediment from river systems and the erosion by marine action at the coast
What is coastal accretion
deposition of sediment at coast, seaward growth of coastline, creating new land.
-often involves sediment deposition being stabilised by vegetation
What is Dynamic equilibrium
The balanced state of a system when inputs and outputs balance over time If one element of the system changes because of an outside influence, the internal equilibrium of the system is upset and other components of the system change
definition of plant succession
the changing structure of a plant community over time as an area of initially bare sediment is colonised by plants
How does vegetation stabilise sediment
-roots of plants bind sediment particles together- harder to erode
-when submerged- plants growing in sediment provide protective layer- surafce of sediment not exposed
-friction with vegetation slows wind speed- protects sediment from wind erosion
How does the wave react at the shore?
When they reach the shore, forward movement starts to occur, which, as the depth is less than the wavelength - the base of the wave is slowed down by friction against the sea floor and the wave crest topples over and breaks onto the shore.
What effects the size of the wave
- The size of a wave depends on a number
of factors including: Strength of the wind,
duration the wind blows for, water depth
and wave fetch
Describe the formation of a barrier beach
Sand or shingle bar above high tide, parallel to the coastline and separated from it by a lagoon
Describe the formation of a tombolo
A spit connected to the mainland, an example being Chesil Beach
Describe the formation of a Cuspate Foreland
Created by longshore drift where sand and shingle deposits extend outward from the shoreline in a triangular shape
What are the three different types of weathering
Weathering can either be mechanical,
chemical or biological
- Weathering contributes to rates of coastal
recession in a number of ways
- Weathering weakens rocks, making them
more vulnerable to erosion or mass
movement processes.
Describe two types of Mechanical weathering
Freeze Thaw
Water expands by 9% in volume when freezing, exerting a force within cracks and fissures; repeated cycles force cracks open and loosen rocks.
Salt Crystallisation
The growth of salt crystals in cracks and pore spaces can exert a breaking force, although less than for freeze-thaw.
Describe the three different types of Chemical weathering
Carbonation
The slow dissolution of limestone due to rainfall
Hydrolysis
The breakdown of minerals to form new clay minerals, plus materials in solution, due to the effect of water and dissolved CO2
Oxidation
The addition of oxygen to minerals, especially iron compounds, which produces iron oxides and increases volume contributing to mechanical breakdown
Describe the two different types of Biological weathering
Plant roots
Trees and plant roots growing in cracks, forcing rocks apart
Rock boring
hen species (clams) bore holes into rocks
Explain mass movement
the process responsible for downslope movement of weathered material under influence of gravity
types: Rockfall, rotational slides, landslide
What landscapes are formed as a result of mass movement
Rotational scars: Material deposited from rotational slumping
Talus scree slopes: The loose debris accumulated at the foot of the cliff
Terraced Cliff Profiles: Eroded rocks create ridges within the cliff
What is Eustatic sea level change
Occurs when ice on land melts and returns to the ocean, increasing the volume of the water present in the sea.
What are the main factors that cause rapid coastal retreat
Long wave fetch and large, destructive
ocean waves
Soft geology
Cliffs with structural weaknesses such as
seaward rock dip and faults
Cliffs that are vulnerable to mass
movement and weathering, as well as
marine erosion
What is a sand dune ecosystem known as
psammosere
What is a wave-cut notch
Marine erosion attacks the base of a cliff, creating a notch of eroded material between high tide and low tide height.
notch becomes deeper due to sub-aerial weathering weakening cliff, cliff face becomes unstable and falls due to mass movement. Leaves behind a wave-cut platform
Explain the process of Caves, Arches, Stacks & Stumps
occurs on pinnacle headlands.
Marine erosion widens faults in the base of the headland, widening creating a cave.
Cave widens due to marine erosion and sub-aerial processes, eroding through to the other side of headland, creating arch.
The arch continue to widen until it is unable to support itself leaving a stack marine erosion attacking
the base of the stack,
eventually the stack will collapse into a
stump.
Explain what occurs in the process of retreating Cliffs
Through the process of repeat wave-cut notches and platforms, new cliff
faces are created, whilst the land retreats.
What is Blowhole - A Blowhole is a combination of two features: a pot hole on top of a cliff, created
by chemical weathering, and a cave, formed by marine erosion. As the cave erodes deeper into
the cliff face and the pothole deepens, they may meet. In this case, a channel is created for
incoming waves to travel into and up the cliff face (occasionally water splashes out of the top of
the blowhole when energetic waves hit the cliff face).
A Blowhole is a combination of two features: a pot hole on top of a cliff, created
by chemical weathering, and a cave, formed by marine erosion. As the cave erodes deeper into
the cliff face and the pothole deepens, they may meet. In this case, a channel is created for
incoming waves to travel into and up the cliff face
How are waves formed
-friction between wind and water
-force of wind blowing onto surface of water generates ripples which grow into waves
