Coasts KQ1 Flashcards
Examples of inputs of energy?
Waves
Wind
Solar sources
Definition of a “system”?
An association of components that are connected to each other and the surrounding environment through flows of material and energy.
Examples of outputs of energy?
Noise and
Heat…
Because material is constantly being moved.
Examples of inputs of material?
Sediments from... Ocean Rivers Cliffs Coastal areas from further along the coast
Examples of outputs of material?
Sediment is moved to other parts of the coast and offshore.
Definition of a “landform”?
A physical feature on the earth surface.
Definition of “erosion”?
The wearing away of material by the action of…
Water
Ice
Wind
Definition of “weathering”?
Disintegration of rocks by the action of... Weather Plants Animals Chemical action
Definition of “marine processes”?
Action of the sea on coastal landforms.
Definition of “sub-aerial processes”?
Processes that are active on the face and the top of cliffs.
Name 2 factors that affect the rate of marine erosion?
Geology
Climate
Definition of “physical weathering”?
The rock is disintegrated into pieces that are normally angular and coarse.
Definition of “chemical weathering”?
Rock is disintegrated because the chemical structure of the rock and its minerals are altered.
Explain salt crystallisation (physical)?
Happens in well jointed, porous rocks.
The sea water evaporates leaving salt crystals behind.
Which then grow in the cracks and pores and prises the rock apart into angular fragments.
Explain “wetting and drying” (physical)?
Occurs in exposed rock surfaces.
The rocks are periodically wetted and dried.
The rocks expand when wetted and contract when cry causing the rock to break up = slaking
When this is repeated it causes disintegration and HONEYCOMB weathering is produced.
Explain “frost shattering / freeze thaw” (physical)?
Well jointed, bedding rocks.
Water enters the cracks/joints in planes.
In fluctuating temp. areas 0-9 degrees the rock expands by 9%.
Exerting pressure on the rocks = residue of angular fragments called SCREE.
Explain “insolation and exfoliation weathering / heating and cooling weathering” (physical)?
Exposed, igneous rocks like granite.
Thermal expansion and contraction during rising and falling temps. between 30-50 degrees.
Stresses are created = explosive failure.
Exposed rock heats up more than cooler rocks below = spall curves sheets called ONION SKIN weathering.
Explain “carbonation” (chemical)?
Well jointed, bedding rocks like limestone.
CO2 gas in atmosphere reacts with rain and pore water in soil to form carbonic acid.
Air in soil from plant decay makes it even more acidic.
Resulting in a residue of insoluble clays and dissolves the cements leading to rock collapse.
Explain “oxidation” (chemical)?
The rocks contain minerals with Fe
Some of the minerals react with O2 dissolved in the water to form oxides and hydroxides.
Fe2+ is changed to Fe3+ = collapse of molecular structure
Resulting in the formation of rust (limonite)
Explain “chelation” (chemical)?
Lichens and decaying matter on any rock
The organic acids enter cracks, joints and pore spaces.
Organic acids attack certain minerals releasing Fe and Al
Leading to the Fe and Al being lost and the rock disintegrating.
The types of geology that affect the rate of erosion are?
Rock cohesion - the stronger the grains in the rock are cemented together the longer it takes for erosion to take place (granite and clay)
Lines of weakness - waves attack the weaknesses and are easily eroded.
Composition - when rocks are made of resistant minerals eg Quartz they are eroded slowly compared to Calcium made rocks that are soluble in water therefore erode quickly.
The types of climate that affect weathering?
Precipitation - increased = increased chemical weathering (especially in hot weather)
Temperatures - warm/hot = increased chemical weathering = evaporation
Cold = increase in mechanical weathering = freeze-thaw.
Name the slow types of mass movements?
Soil creep - individual soil particles are moved to the surface through wetting and freezing (rate is 1mm in UK and 5mm in rainforest p/a)
Rain splash - on flat surfaces rain droplets compact soil and dislodge particles on steep slopes so downwards push increases.
Name the flow types of mass movements?
Surface wash - soil infiltration capacity is exceeded leading to the formation of gullies.
Sheet-wash - un-channeled flow of water over soil and carries material from rain splash.
Throughflow - water moving down through the soil in a natural channel allowing material to be transported at a higher volume.
Name the fast types of mass movement?
Slides - slides of material that maintain their shape until the base of the slope (caused by prolonged rainfall)
Falls - occur on steep edges >70 degrees originally caused by weathering, weakening the rock and causing a fall. If the fall is short it causes a talus/straight scree if long it causes a concave scree.
Slumps - occur with weaker rocks like clay as it absorbs the water, becomes heavy and flows along the slip plane to the base where is will be undercut and further weaken the strength.
Explain hydraulic action?
The pressure of the water moves rock and sand.
This pressure can loosen rocks, cause pneumatic pressure (trapped air in joints) then causing wave quarrying (explosive decompression of air when wave retreats) and swash and backwash remove sediment from swash zone.
The LANDFORMS created are: BLOW HOLES/GEOS/CAVES/CLIFF PROFILE AND RETREAT
Explain abrasion?
Waves use pebbles and sand to wear away rock in the inter-tidal zone.
This is slow in hard rocks creating a smooth area.
Differential erosion is accentuated with more resistant rocks protruding and temporarily protecting the less resistant rocks.
This forms : WAVE CUT NOTCHES/CAVES/INTER-TIDAL PLATFORMS.
Explain corrosion?
Wave action aerates the water allowing more weathering.
In shallow water organisms release CO2 = increasing carbonation
Effects are mostly seen in limestone coasts where rounded hollows are formed and are enlarged by abrasion.
Can also create lapies and visors.
Explain attrition?
Blocks are detached by wave quarrying or transported from elsewhere, they are eroded as they collide with each other in the swash and backwash.
Meaning that the pebbles become smaller and rounder and protect the cliffs from hydraulic action and abrasion.
They eventually become small enough to be taken away from the inter-tidal zone and become SAND.
Name 2 wave processes that are eroding the Holderness coastline?
Hydraulic action
Abrasion
Why is the Holderness coastline more vulnerable to corrosion?
The coastline consists of limestone and chalk cliffs. Which contain calcium carbonate which is dissolved in water.
What is another damaging process that takes place at the Holderness coastline?
The cliffs are lubricated by rainfall and then slump = rotational slumping.
How was Old Harry on the Jurassic Coastline formed?
Cracking and faulting has lead to a notch - cave - arch - stack - stump.
What type of coastline is the Jurassic coastline?
Concordant as it has produced landforms such as Old Harry and Lulworth Cove (no headlands or differential erosion)
How can waves transport sediment?
Suspended load - through suspension
Bed load - saltation (bouncing) and traction (dragging or rolling on bed floor)
Define swash and backswash?
Swash - body of water pushing up a beach after the wave has broke.
Backswash - movement of water back down a beach after the wave has reached its highest point.
Definition of “floculation”?
When a river meets the sea - fresh and salt water mix.
Producing an electric charge that causes clay particles to coagulate and settle on the sea floor.
Explain constructive waves?
There is a ridge of settlement meaning that the water doesn’t reach the foot of the cliff.
Small gentle waves and their energy is absorbed by the beach with limited backswash.
Explain destructive waves?
There is little wave energy absorbed by the beach so huge steep waves plunge over and the upper part of the cliff is attacked by spray and the base of the cliff is attacked by the breaking wave.
A lot of sediment is pulled back by the backswash.
Define “wave refraction”?
The deeper the water the slower the wave and they get higher and steeper as they slow.
Waves get refracted towards the headland - promontory effect.
What 5 things influence wave energy?
Fetch (distance travelled by wind or waves across open water) Wave direction Wind speed Storm surges Swell window
Name other factors that influence the development of landforms?
Wave energy Form of coastline Geology Sediment supply Sea level change Human activity
Explain the lithology of limestone?
Grains of calcium carbonate - soluble in acidic water but if grains are cemented together = strong rock
Explain the lithology of sandstone?
Grains of quartz (very hard mineral) making it a resistant rock, but if the grains are poorly cemented it is weak.
Explain the lithology of clay/mudstone?
Tiny grains of clay mineral and mica often chemically bonded but not cemented = weak rock
Explain the lithology of grainte?
Interlocking crystals of resistant minerals like quartz meaning its a resistant rock.
Explain the lithology of boulder clay?
Mixture of grain sizes that are poorly consolidated making it very weak.
Explain how structure can affect the development of landforms?
Arrangement - weaknesses like joints/bedding planes let water into the rock, increasing the permeability and susceptibility to weathering (faults having a similar effect)
Cement - if the grains are poorly cemented the rock may be porous as well as permeable along the weaknesses - surface area exposed to weathering.
Plan-form (view from above) - if rock outcrops run parallel to the coast, fewer lines of weakness are exposed (concordant) when they are not the weaknesses cause differential erosion (discordant)
How do you describe a cliff profile?
Height? Steep/gentle? estimate angle? Weathering or transport limited? Active or dead?
What happens when the cliff “retreats”?
The cliff gets higher and the wave cut platform gets wider.
What do steep, vertical cliffs suggest?
There are horizontal and gently dipping sedimentary rocks that are over steepened by wave attack at the base. At the base more resistant rocks act as bastions against the powerful waves to minimise the erosion of the less resistant rocks.
What do stepped cliff profiles suggest?
Contributions if mass movements such as slumping.
Where do “slop-over-wall” cliff profiles present?
Where rising sea levels have increased wave attack at the base of the cliff.
What landforms are present at the North Devon Coastline?
Cliffs / Headlands / Bays / Beaches / Stacks / Arches
Hartland Quay / Warren Beach / Morte Point
Sand Dunes @ Braunton Burrows
Shingle Ridge @ Westward Hol
Discordant @ west facing
Concordant @ north facing
How is a rotational slump created?
Heavy rainfall reduces the friction that helps hold the slope.
The wetter it becomes the more fissures (faults)
Mudslides also develop
Rotational slumping happens when the whole mass of rocks moves. When this reaches the base of the cliff this will eventually be eroded away which destabilises the cliff = more mass movements.
What coastal landforms are associated with deposition?
Berms (storm ridges) Sand dunes Tombola Sea stack Bay / beach
Explain beach profiles?
They can depend on... Nature of the sediment (pebble beaches = steeper) Wave energy (storm waves tend to flatten beaches)
Explain beach sediment?
Coarse = steeper angle whereas sand = lower angle of rest and is incapable of maintaining steep angles over more than 1metre of <7degrees whereas pebbles is more like 15+degrees.
Shingle allows more percolation so swash is larger than backswash leading to steeper beaches opposite when it comes to sand.
Explain wave energy?
High energy (plunging waves) = wide and flat beaches Lower energy (surging waves) = steep profile
Seasonal changes means that there cannot be a net annual profile as the seasons change the waves energy.
Name some minor beach features?
Storm beach - semi permanent ridge of coarse shingle
Beach ridges or berms - built up by constructive wave action
Beach cusps - embayments that are small and regular
Ripples - at the lower parts and are formed by reversing currents
Anastomosing channels - water draining out of the shingle onto the sand at low tide
Ridges and runnels - broad and gentle rises and depressions, ,ay be occupied by sea water.
What is a swash aligned beach?
The waves approach the coastline parallel to the beach.
Swash and backswash up and down the beach meaning that there is a straight beach.
What is a drift aligned beach?
Beach is at angle and sediment is moved through longshore drift creates a wider beach at the up drift side.
The differences between swash and drift aligned beaches?
Wave break is less than 1m at D-A and more than 2.5m at S-A
Swash period is 5-10s at D-A and up to 60s at S-A
Beach slope is steeper at D-A and the sediment size coarse like gravel.
What is eustatic sea level change?
Worldwide rise of fall in sea level it is a change in the volume of water stored in the oceans.
What are the causes of eustatic sea level change?
Glaciation = fall Climatic warming (interglacials) = rises
What is the impact of eustatic sea level change?
Rise = rias, river valleys drowned. Fall = exposes continental shelf.
What is isostatic sea level change?
Localised rise or fall in sea level.
It is not a change in the volume but it is a change is the isostatic subsidence/rebound(loading/unloading) during (de)glaciation
What are the impacts of isostatic sea level change?
Fall = leaves beaches and cliffs exposed - more sub-aerial processes occur.
Rise - submerges land and forests will deposit more sediment leading to the creation of salt marshes.
What happened in the Devensian glaciation?
110-12,000 years ago. Average temp at -2.5 to 10 degrees Sea level decreased by 100m Tundra (preglacial) Cliffs were abandoned and degraded and the Bristol channel was dry so you could walk to Wales
What happened during the Ipswichian interglacial?
130,000-110,000 years ago
Average temperature was 3 degrees
Sea level rose by 8m
Temperate mixed with woodland. Cliffs cut and beaches formed at higher sea levels
