Flashcards
Systems and processes
Flashcards do conjunto (92)
- 1How does wind influence other processes?It is a primary source of energy for other processes and a vital input for the coastal system
- 2What do spatial varations in energy result from?Variations in wind strength and duration
- 3What is the connection between wave energy and wind speeds?Wave energy is higher when wind speeds are persistently high and uninterrupted
- 4What is prevailing wind?Most coastline have one. It is when the wind generally reaches the coast by one direction
- 5Why is prevailing wind important?Controls the direction of waves approaching the coastline and the direction of transport material
- 6What is fetch?Fetch refers to the distance of open water over which a wind blow uninterrupted by major land obstacles. Length of fetch helps to determine the magnitude and energy of waves reaching the coast
- 7What part does wind play in wave formation?Waves are created by the transfer of energy from the wind blowing over sea surface (fractional drag). The energy acquired by waves depends upon wind strength, wind blowing time and fetch
- 8What part does wind play in erosion?Can firstly pick up and remove sediment from the coast and use it to further erode other features. Most common type of wind erosion is abrasion, where the wind uses carried material to wear away landscape features. wind moves sediment along the coast, inland from the shoreline and beyond the tidal line
- 9What is wave height?Height difference between crest and trough
- 10What is wave length?Distance between successive crests
- 11What is wave frequency?The time for one wave to travel one wavelength, or the time between one crest and the next crest when passing a fixed point
- 12What happens as waves approach shallow water?Friction with the seabed increases and the wave slows down. This increases the height and steepness of the wave. The upper part plunges forward and the wave breaks onto the shore
- 13What is swash?The rush of water up the beach as a wave breaks
- 14What is backwash?Any water running back down the beach towards the sea
- 15What is a constructive wave?Low wave height, long wave length (up to 100m), low frequency (6-8/min). Front steepens slowly so they gently spill onto the beach surface. More powerful backwash than swash = material built up along beaches
- 16What is a destructive wave?High wave height, steep form and high frequency (10-14/min). They approach the beach, rapidly steepen and plunge down when breaking. Powerful backwash and weak swash. Swash remains weak for the next wave. Little material deposited, material pulled back
- 17Describe negative feebdback in beaches.Cycle of constructive and destructive waves. Constructive waves build up the beach, resulting in a steeper beach profile, encouraging destructive waves. Over time these destructive waves move material back towards the sea, reducing the angle and encouraging constructive waves. This should remain in equilibrium except strength and direction are not constant
- 18How are waves refracted?Eg: a bay is separated from another bay by a headland
As the wave approaches the coast, it drags in the shallow water, increasing height and shortening wavelength. The part in deeper water moves forward faster, causing the wave to bend. Wave energy becomes greater concentrated on the headland, causing greater eroision. Low energy waves then spill onto the beach, causing deposition - 19What are longshore currents?Often called littoral drift. Occurs due to most waves not hitting the coast head on, but at an angle. This generates a current running parallel to the shoreline. Water is moved along the surf zone and transports sediment parallel to the shoreline
- 20What are rip currents?Strong currents moving away from the shoreline. They develop when sea water is piled up along the coastline by incoming waves. Initially the current may run parallel to the coast before flowing out through the breaker zone
- 21What is upwelling?The movement of cold water from deep in the ocean upwards towards the surface. The more dense water replaces warm surface water, creating nutrient rich cold ocean currents. These form part of the pattern of global ocean circulation currents
- 22What are tides?The periodic rise and fall of the sea level in response to the gravitational pull of the sun and moon. The moon pulls water towards it, creating a high tide. There is a compensatory bulge on the opposite side of the earth. In the areas of the world between the two bulges are at lowest tide
- 23What is a spring tide?Highest monthly tidal range caused by the sun, earth and moon being in a straight line
- 24What is a neap tide?Lowest monthly tidal range caused by the sun, earth and moon being positioned at 90 degrees
- 25How is the regular pattern of tides modified?Morphology of the seabed, proximity of landmasses and impact of coriolis force
- 26What is tidal range?Difference in height of the seawater at high and low tide. Not fixed due to tide cycles. The tidal range determines the upper and lower limits of erosion and deposition and the amount of time the littoral zone is exposed and open to sub-aerial weathering
- 27What is macrotidal?More than 4m
- 28What is mesotidal?2-4m
- 29What is microtidal?Less than 2m
- 30What is a tidal surge?An occasion when meteorological conditions give rise to strong winds which produce higher water levels than at high tide
- 31Descrube tidal surges in the North Sea.- Depressions produce low pressure conditions which raise sea levels
- Rise = 1cm for every mb drop in pressure
- Water piling up caused by strong winds driving ahead, pushing sea water against the coastline
- Water increase is concentrated into a space that is decreasing in size
-Spring high tides intensify the effect - 32What is a low energy coast>- Low wave energy
- Rate of deposition exceeds that of erosion
- Beaches and spits created
- EG Baltic Sea - 33What is a high energy coast?- Strong, steady prevailing winds, creating high energy waves
- Rate of erosion greater than that of deposition
- Headlands, cliffs, wave cut platforms
- EG north Cornish coast - 34What are the sources of sediment?Streams/rivers
Estuaries
Cliff erosion
Offshore sandbanks
Material from biological origin - 35What are the names of the sediment cells?
- 36What is a sediment cell?A sediment cell is generally thought to be a closed system, which suggests that no sediment is transferred from one cell to another. The boundaries of sediment cells are determined by the topography and shape of the coastline. n reality however, it is unlikely that sediment cells are fully closed. with variations in wind direction, and tidal currents. it is inevitable that some sediment is transferred between cells.
- 37What is the coastal sediment budget?Balance between sediment being added to and removed from the coastal system, that system being defined within each individual
- 38Which analogy is associated with the coastal sediment budget?A bank account - balance between sediment is added and removed from the coastal system
- 39What happens when material is added to the cell?More material is added to the cell than is removed ➡ positive budget (surplus) ➡ shoreline builds towards the sea
- 40What happens when material is removed from the cell?More material is removed from the cell than is added ➡ negative budget (deficit) ➡ shoreline retreats landward
- 41How is the sediment budget calculated?Identification of all the sediment sources and sinks and an estimation of how much is added/ removed annually
- 42What is rock lithology?- Characteristics of rocks esp permeability and resistance to erosion
- Resistance rocks (eg granite and chalk) are eroded less than weak materials (eg clay)
- Some rocks eg limestone are well jointed so the sea can penetrate along lines of weakness making them vulnerable
- Differentiation is the rate at which different rocks wear away - 43What is rock structure?When rocks lie parallel to the coast, they produce a very different coastline than when they lie perpendicular. (COME BACK TO)
- 44What is rock dip?The steepest cliffs tend to form in rocks that have horizontal strata or dip greatly inland, where as rocks that dip towards the coast tend to produce much more gently sloping features
- 45What is eustatic change?A global change in sea levels resulting from an actual rise or fall in the level of the sea itself
- 46What is isostatic change?Local changes in sea level resulting from the land rising/ falling relative to the sea
- 47Describe the relationship between sea levels in the quaternary and sea levels now.Many sea level changes took place during the Quaternary. However, current sea levels reflect changes that have occurred since the last glacial maximum 18,000 years BP, especially in the last 10,000 years
- 48What is the first phase in a typical sequence of sea level rise?Climate gets colder, marking the onset of a new glacial period, increasingly precipitation falls as snow, which eventually turns into glacial ice. Snow and ice store water, slowing the hydrological cycle. Water cycled from the sea does not return to the sea. Sea level falls, effecting the whole planet, this is eustatic change
- 49What is the second phase in a typical sequence of sea level rise?Weight of ice causes land surface to sink, affecting only some coastlines at varying degrees. This is isostatic and moderates eustatic sea level falls in some areas
- 50What is the third phase in a typical sequence of sea level rise?Climate gets warmer. Ice masses on the land begin to melt. This replenishes the main store and sea level rises. In some areas this floods the lower points of land, producing submergent features, eg rias and fjords
- 51What is the final phase in a typical sequence of sea level rise?Ice is removed from some land areas, they move back to their original places - this is isostatic readjustment. If isostatic is faster that eustatic, emergent fatures are produced
- 52How is a ria formed?Submergent feature. Created by rising sea levels drowning river valleys
Floodplain vanishes, only middle and upper course valleys filled with sea water. They have a long section and cross profile and a dentric system of drainage - 53How is a fjord formed?Submergent feature
Drowned glacial valley.
Steep valley sides, fairly straight and narrow, U-shaped cross section. Generally consist of glacial rock basin, with a threshold (shallower section at the end) - 54What is a dalmatian coast?Submergent feature
Where topography runs parallel to the coastline and becomes flooded. Here, valleys run parallel to the coast as opposed to perpendicular. Islands and peninsulars are alligned parallel to but just offshore from the mainland - 55What is a raised beach?Emergent feature
Former wave-cut platforms and their beaches are at a higher level than present sea level.
Often found with wave cut notches, sea caves, arches and stacks - 56What is a marine platform?Emergent feature
Where a greater expanse of gently sloping formerly submerged land has been exposed by uplift. The exposed part is part of a gently sloping continental shelf - 57How has, and will, climate change affected coasts?- Sea level rise predicted bet. 18 and 59cm by 2090
- This is the result of two processes: increase in ocean volume and subsidence of the coast
- Ice released into oceans as it melts
- Thermal expansion of oceans
- Increased flooding and erosion - 58How will climate change affect where sea water mixes with fresh water?The zone where seawater mixes with freshwater is dynamic and a rise in sea levels can cause it to move upstream. If this happens between freshwater contained in rocks, salt water may intrude beneath land
- 59How can coastal processes be broken down into five categories?Mass movement
Weathering
Erosion
Deposition
Transport - 60What are marine processes?Those that operate upon a coastline that are connected with the sea, such as waves, tides and long shore drift
- 61What are sub-aerial processes?Those that operate on the land but affect the shape of the coastline, such as weathering, mass movement and run off. This slowly breaks down the coastline, weakening the underlying rocks and allowing erosion to happen more easily. Material is broken down in situ
- 62What is hydraulic action?Erosional process.
Impact on rocks of the sheer force of the water itself. This can exert enormous pressure upon a rock surface, weakening it. Such activity is also described as pounding - 63What is wave quarrying?Erosional process.
A breaking wave traps air as it hits a cliff face. The force of water compresses this air into any gap in the rock face, creating pressure within the fissure/ joint. As the water pulls back, there is an explosive effect of the air under pressure being released. Over time, this weakens the cliff. Storms may then remove chunks of it - 64What is abrasion (corrasion)?Erosional process
The material the sea has picked up wears away the rock face. Sand, shingle and boulders hurled against the cliff do damage. Also apparent on inter-tidal rock platforms where sediment is drawn back and forth, grinding away the platform - 65What is attrition?Erosional process
Rocks in the sea which carry out abrasion are slowly worn down into smaller, more rounded pieces - 66What is solution?Erosional process/ weathering
Process includes dissolving calcium based rocks. In localised areas where fresh water interacts with seawater, conditions for solution may occour, or carbon-based rocks at the coast may be broken down by water flowing from the land or acidic rain water - 67What increases the rate of erosion?- Steeper waves
- Stronger fetch
- Deeper sea
- Headlands
- Beaches absorb energy
- People removing protective materials - 68What is traction?Transportational process.
Large stones and boulders are are rolled and slid along the seabed and beach by moving sea water. Happens in high energy environments - 69What is saltation?Transportational process.
Small stones bounce along the seabed and beach. Small particles may be thrust up from the seabed. When they land they dislodge other particles causing more bouncing motions. Associated with relatively high energy environments - 70What is suspension?Transportational process.
Small particles of sand/silt are carried by moving water. This material is not only carried but is also picked up through turbulence. This can cause a milky, murky affect - 71What is solution?Dissolved materials transported within the mass of moving water
- 72What is longshore drift?Waves approach the shore at an angle. Swash pushed material up the beach and backwash drags material back perpendicularly
- 73What is marine deposition?Where waves are low energy/ where rapid coastal erosion provides a lot of material. The sea deposits material when there is a reduction in energy due to a decrease in velocity/ volume
- 74In what situations may marine deposition take place?- When sand and shingle accumulate faster than they are removed
- When waves slow after breaking
- Water pauses at the top of swash before backwash
- Water percolates into beach material - 75What is aeolian deposition?Entrainment, tranpostation or deposition by wind. During the day wind is generally from the sea. Air moves in response to pressure differentials set up by the warmer land and colder sea. When there is a larger tidal range, large amounts sand may be exposed at low tide
- 76What is surface creep?Similar to traction, wind rolls or slides sand grains along the surface
- 77What is saltation?Wind is strong enough to temporarily lift the grains into the airflow to heights of 1m and distances of 20-30m
- 78What is sub-aerial weathering?Slowly breaks down the coastline, weakens the underlying rocks and allows sudden movements/ erosion. Material is broken down in situ, remaining in or near original position
- 79What is mechanical weathering?Occurs at coasts depending on the nature of the climate. In latitudes where temperatures fluctuate between freezing, freeze thaw action is common. Water enters cracks in rocks when it is above 0.C and when it freezes it expands 10%, exerting pressure on the rock. This process repeats and eventually the rock breaks up
- 80What is biological weathering>Action of vegetation and coastal organisms. Some organisms have adapted to allow them to drill into rocks, eg the piddock. Seaweed attaches itself to rocks and the action of the sea can be enough to cause prying of rocks from the sea floor. Some animals weaken cliffs by burying underneath them
- 81What is chemical weathering?Occurs when rocks are exposed to air and moisture so chemical processes can breakdown the rocks. Solution is the main chemical process and combines with erosion to produce distinctive features
- 82What is oxidation?Oxidation causes rocks to disintegrate when oxygen reacts with them. This especially effects iron-rich rocks
- 83What is hydration?Makes the rocks more susceptible to further weathering. It involves the physical addition of water to minerals in the rocks. This causes the rock to expand, creating stress which can cause rock disintergration
- 84What is hydrolysis?Mildly acidic water reacts or combines with minerals in rocks to create clays and soluble salts which degrades the rock. Both are weaker than the parent rock, making it more susceptible to further degredation
- 85What is carbonation?Occurs when CO2 dissolved in rainwater makes a weak carbonic acid, H2CO3 which reacts with calcium carbonate in some rocks to create calcium bicarbonate (H2CO3)+(CaCO3)=>(Ca(HCO3)2)
- 86What is mass movement?- Common on coastlines (especially when steep)
- Dependent on four factors: Level of cohesion in sediment, height and angle of slope, grain size of sediment, temperature and level of saturation - 87What are landslides?Occur on cliffs made from softer rock and deposited material. They slip as a result of failure within it when lubricated, normally after heavy rainfall
- 88What are rock falls?Occur from cliffs undercut by the sea, or on slopes affected by mechanical weathering (eg frost action)
- 89What are mud flows?Heavy rain can cause a large amount of material to flow downhill. The soil becomes saturated - if excess water cannot peculate deeper into the ground, surface layers become fluid and flow downhill. Nature of flow depends on saturation, sediment and slope angle
- 90What is rotational slip/ slumping>Softer material overlies more resistant material, leaving cliffs more prone to slumping. With excessive lubrication, whole sections of the cliff may move downwards with a concave slide plane, producing rational movement
- 91What is soil creep?Occurs when there is slow imperceptible, but continuous movement of individual soil particles down slope. Some uncertainty about exact causes, but presence of moisture is important
- 92What is run off?May take the form of a stream emerging in a bay, taking with it large quantities of load during flood times. May be a stream cascading over a cliff excavating a V-shaped groove as it does so. May assist mass movement
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- A level Geography (Coasts) FlashCards sobre Systems and processes, criado por Robin Connolly em 03-03-2017.
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- Robin Connolly
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