Coasts (Definitions) Flashcards
What is a coast?
The interface between land and sea, can be viewed as a system, with inputs, processes and outputs.
What are the 4 inputs for a coastal system?
Wave energy
Geological structure
Sub-aerial activity
Human activity
What is the fetch of a wave?
The distance over which the wind blows in a constant direction across the surface of the water
What are the 4 processes at a coastal system?
Wave erosion
Mass movement
Hard/soft engineering
Transport
What are the 2 outputs at a coastal system?
- Landforms of erosion
- Landforms of deposition
The 7 processes of coastal erosion:
Abrasion - Waves throw loose material at cliffs
Attrition - Movement sandpapers rocks into smoother and rounded rocks
Solution - Carbonic acid in sea water reacts, and spray corrodes rocks, so they disintegrate
Biological activity - Secretions from algae attack rocks, or some molluscs can bore holes in them
Wave pounding - Wave impact can loosen cliff face rock.
Hydraulic pressure -Waves enter tiny crevice/crack and air is trapped
Sub aerial weathering - Rain leading to saturation of cliff material and the failure of cliff by mass movement
What determines the amount of energy waves have?
Higher wind speeds impart more energy to the waters surface, creating larger and more powerful waves
A longer fetch allows the wind to transfer more energy to the water, resulting in larger waves
What is meant by wave pounding?
The forceful impact of large and powerful waves on a cliff face or coastal structure, pounding or battering effect is pronounced during storms or periods of high winds, with intensified waves.
What are two examples of mass movement?
Landslides involve the rapid downslope movement of rock, soil, and debris along a defined surface, triggered by many diff factors or activities that disturb the stability of a slope
Mudflows are fast-moving mixtures of water, mud, rocks, and debris that flow downslope. They are similar to landslides but involve a higher proportion of water, giving them a fluid-like consistency.
Sub aerial activity triggers this movement when soils are more saturated.
What do all rocks have and why is this important?
Minerals, are fundamental to the composition, classification, and understanding of rocks
What does lithification mean?
The process by which loose sediments are transformed into solid rock, critical in formation of sedimentary rocks
What happens to waves in bays?
The behaviour of waves in bays is influenced by the bay’s specific characteristics, including its shape, depth, and the presence of coastal features
What is threatening the Holderness Coast?
Rapid coastal erosion due to soft geological formation, lack of coastal defences, high erosion rate due to strong waves from the north sea, and sea level rise.
What are the three major inputs influencing cliff formation?
Geological structure - Different types of rocks have varying resistance to weathering and erosion.
Folding and faulting -As a result of earth movements all rocks exhibit some degree of folding which can become weaknesses, creates lines of weakness which can be exploited.
Coastal morphology - On an indented coastline, headland sand the offshore topography concentrate wave attack on the headland by the process of wave refraction.
Abandon the line
the strategic withdrawal of human occupation in areas of high risk
Accretion
the accumulation of marine sediments
Advance the line
Active intervention to produce a defence line that is seaward of the existing line
Arch
A raised area when two caves erode back to back on a headland
e.g. Durdle Door
Backwash
movement of water back towards the sea after a wave has been broken
Bar
Coarse grained deposit of sediment extending across the mouth of the bay
Berm
Low hill of sand or gravel that forms at the upper limit of the swash
Beach nourishment
sand and shingle brought from elsewhere are added to beaches to maintain depth to protect from erosion in a natural way
Char
An island formed from silt deposit in a delta, the land is about at sea level and is very fertile, however easily washed away
Constructive waves
Low frequency 6-8 per minute waves with elliptical water motion, powerful swash and weak backwash
Concordant geology
The alignment of bands of alternate geology that run parallel to the coastline
Corrasion
Erosion by friction in load of contact with banks and bed
Deltas
Form when the amount of sediment delivered at the mouth of a river exceeds the amount removed by waves
Destructive waves
High frequency 13-15 per minute waves with circular water motion, with weak swash and strong backwash
Differential erosion
Varying rates of erosion relating to geology
Discordant geology
Coasts which cut across the rock structure
Diurnal range
The difference between the lowest temperature and the highest temp in a 24 hour period
Eustatic
Changes in sea level caused by variations in water levels in the ocean
Fiord
Very deep U shaped estuaries formed by drowning of glaciated valleys
Gabion
cages enclosing rocks to defend the coast
Geo
Steep sided narrow inlet
Groyne
Posts with boards which run at right angles to the coastline which trap sediment drifting along the shore
Hard engineering
Structures developed to protect the foot of cliffs and prevent erosion
High energy coast
Coasts in which wave power is strong for a significant part of the year
Hold the line
taking action to maintain the current defence line
Isostatic
Change in sea level resulting from the rise and fall of land masses
Isthmus
A narrow piece of land connecting two larger pieces of land
Littoral zone
Extends from the high water mark to shoreline areas that are permanently submerged
Low energy coasts
coasts in which wave power is weaker, low fetch, few gales enclosed and therefore sheltered
Plagioclimax
where succession is stunted by human interference
Psammosere
Succession of stages of plant growth forming colonisation of bare sand to climax vegetation
Return period
average time between occurrences of a given event
Saltation
Sand bounces across the surface of the beach blown by wind
Slumping
Triggered by undercutting at the base of cliffs with rotation in the slip plane
Spit
Long ridges of sand and shingle attached to land at one end
Spring tide
Particularly high or low tides caused when the sun, moon and earth all lie in a straight line, happens twice a month
Stack
A residual post of rock resulting from the continued erosion of arches
Surges
Changes in water level as a result of meteorological forcing
Swell
a circular motion caused by wind in sea as a wave reaches the shore
tidal bore
in narrow estuaries the effect of tides can be more pronounced
Tombolo
Shingle ridge linking the mainland to an island
What can you say about low energy environments and deposition
Deposition occurs when there is insufficent energy to push the sediments further
- In low energy environments, factors such as wave and wind direction, the supply of sediment and the depth of water are often significant.
What is the maximum tidal range for large depositional landforms?
3 meters
What is a “swash aligned” beach? (Deposition)
Forms when waves break parallel to the coast. Creates bay beaches (Dorset coast) and barrier beaches, like Start Bay (Devon)
What is a “Drift aligned” beach? (Deposition)
When LSD moves material down the coast producing a range of partly detached features. Such as spits.
How are sand dunes formed? (Deposition)
When dry material from flat, open beaches is blown inland. Dunes migrate and a succession of plants colonise and adapt to this environment forming a dune or psammosere ecosystem.
How are mudflats and salt marshes formed? (Deposition)
Formed of finer material which flocculates (sticks together) in the shallow water of estuaries. Plants here adapt to salt water and tidal conditions
What is beach drift?
Swash processes caused by longshore currents may move material laterally along the shoreline
What are beach susps?
Material at the top of the beach is of a larger calibre and supports steeper concave slopes, beach cusps occur where this coarser material is absorbing wave swash.
How are bay head beaches developed (Deposition)
They build up in the sheltered, low energy environments of coves.Wave refraction focuses erosion on the surrounding headlands and so encourages deposition in the bay.
why are drift aligned beaches more of an open system?
Sediment enters at one end, passes along the length of the beach due to LSD and then leaves the beach at the other end. the predominant angle of wave approach brings with it enough energy to keep the sediment moving
What are the 4 criteria for a spit to form?
- Ready supply of sediment, particularly sand and shingle
- LSD is active
- The coast has an abrupt change in direction, such as at an estruary or bay
- Tidal range is limited (<3 metres)
