coasts Flashcards
what is the definition of lithospsphere?
the crust and the uppermost mantle;this consitutes the hard and ridgid outer layer of the earth. this layer is split into a number of tectonic roles
what is the definition of hydrosphere?
a discontinous layer of water at or near the earths surface. it includes all liquid and frozen surface waters, groundwater held in soil and rock and atmospheric water vapour
what is the definition of biosphere?
the total sum of all living matter. the biological component of the earths systems
what is the definition of the atmosphere?
the air that surrounds the earth, made up of gases and water vapour
what is a systems approach?
is a model used to help explain phenomena such as coastal environment. the system is a way of analysising relationships within a unit and consists of a number of components between which there are linkages
what 3 ways can a system be described as?
-isolated
-closed
-open
what does it mean when a system is isolated?
there is no input or output of energy or matter
what does it mean when a system is closed?
there is input, transfer and output of energy but not of matter
what does it mean when a system is open?
there are inputs and outputs of both energy and matter
what is dynamic equilibrium?
this is when the inputs and the outputs in a system are balanced and the stores remain the same
what is negative feedback?
when a system acts by lessening the effect of the original change and ultimatly reversing it
what is positive feedback?
occurs within a system where a change causes a further, or snowball, effect, continuing or even accelerating the original change; the effects are amplified
what is wind?
within the atmosphere, areas of high and low pressure form. in a low pressure area the air is rising, which draws air in from higher pressure areas. this movement of air from higher to lower pressure is wind
how are waves formed?
as air moves across the water, frictional drag disturbs the surface and forms ripples or waves. in the open sea, there is little horizontal movement of water. instead there is an orbital motion of the water particles. close to the coast, horizontal movement does occur as waves are driven onshore to break on the beach
constructive waves:
-distant weather systems generate these waves in the open ocean
-low surging waves-with a long wavelength
-strong swash and weak backwash
-beach gain (constructive)
-usually associated with a gentle beach profile- although over time they will build up the beach and make it steeper
destructive waves:
-local storms are responsible for these waves
-high, plunging waves-with a short wavelength
-weak swash, strong backwash
-beach loss (destructive)
-usually associated with a steeper beach profile- although, over time they will flatten the beach
what is wave refraction?
the change in direction of a wave as a result of travelling at different speeds at different points along the wave front. refraction causes the wave energy to become concentrated on the headland which leads to greater erosion
what is a storm surge?
is an abnormal rise of water generated by a storm, over and above the astronomical tide.
-its the change in water level that is due to the presence of the storm
-since storm surge is a difference between water levels, it does not have a reference level
what is a storm tide?
is the water level rise during a storm due to the combination of storm surge and the astronomical tide.
-since storm tide is the combination of surge and tide, it does require a reference level
-a 15ft. storm surge on top of a high tide that is 2ft. above mean sea level produces a 17ft. storm tide
what is a current?
refers to the permanent or seasonal movement of surface water in the seas and the oceans
what are lonshore currents?
waves that do not hit the coastline ‘head on’ but approach at an angle to the shoreline. this generates a flow of water running parralell to the shoreline. this not only moves water along the surf zone but also transports sediment to the shoreline
what are rip currents?
strong currents moving away from the shoreline. they drop when seawater 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, possibly at a headland or where the coast change direction
what is upwelling?
is the movement of cold water from deep in the ocean towards the surface. the more dense cold water replaces the warmer surface water and creates nutrient rich cold ocean nutrients. these currents form part of the patern of global ocean circulation currents
low energy coasts:
-coastlines where wave energy is low
-the rate of deposition often exceeds the rate of erosion sediment
-typical landforms include beaches and spits
-e.g. the baltic sea
high energy coasts:
-coastlines where strong, steady prevailing winds create high energy waves
-the rate of erosion is greater than the rate of deposition
-typical landforms include headlands, cliffs and wave-cut platforms
-e.g exposed atlantic coasts of northern europe and north america
what is sediment?
any naturally occuring material that has been broken down by the processes of erosion and weathering and has then been transported and sebsequently deposited by the action of ice, wind and water
what are the sources of sediment?
-rivers
-cliff erosion
-longshore drift
-glaciers
-offshore
what is a sediment budget?
the balance between changes in the volume of sediment held within the system and the volume of sediment entering or leaving the system
what is a positive budget?
is when there are more inputs than outputs to the system and a negative budget is when outputs are higher than inputs
what can alter sediment budgets?
-input changes
-coastal defences
-sea level rises
-output changes
what is geomorphology?
is the study or landforms, their processes, form and sediments at the surface of the earth (and sometimes other planets). study includes looking at landscapes to work out how the earth surface processes can mould the landscape
what is the definition of marine processes?
operate upon a coastline and are connected with the sea, such as waves, tides and lonshore drift
what are sub-aerial processes?
includes processes that slowly (usually) break down the coastline, weaken the underlying rocks and allow sudden movements or erosion to happen more easily. material is broken down in situ, remaning in or near its original position. these may affect the shape of the coastline, and include weathering, mass movement and run off
what is weathering?
the breakdown and/or decay of rock at or near the earths surface creating regolith that remains in situ until it is moved by later erosional processes. weathering can be mechanical, biological/organic or chemical
what is run off?
all the water that enters a river channel and eventually flows out the drainage basin
what is erosion?
the wearing away of the earths surface by the mechanical action of process of glaciers, wind, rivers, marine waves and wind
what is transportation?
the processes that move material from the site where erosion took place to the site of deposition
what is marine deposition?
often takes place where the waves are low energy or where rapid coastal erosion provides an abundent supply of material. the sea lays down material when there is a reduction in energy resulting from a decrease in velocity or volume of water
what is aeolian deposition?
refer to the entertainment, transport and deposition of sediment by wind. wind plays an important role in shaping many coastlines and is an almost constant feature of most, not just because of the general pattern of prevaling winds that drives the waves. during the day, the wind on the coastal fringe is generally from the sea. air moves in response to small pressure differentials
what are the processes of marine trasportation?
-traction
-saltation
-suspension
what is traction?
large stones and boulders are rolled and slid along the seabed and beach by moving seawater
what is saltation?
small stones bounce or leapfrog along the seabed and beach. this process is associated with realtivley high energy conditions. small particles may be thrust up from the seabed only to fall back to the bottom again. as these particles land they in turn dislodge other particles upwards, causing more such bouncing movements to take place
what is suspension?
very small particles of sand and silt are carried along by the moving water. such material is not only carried along by the moving water. such material is not only carried but it is also picked up, mainly through turbulence that exists in the water.large amounts of suspended load, especially near estuaries, can cause a milky or murky appearance of the sea
what is solution?
dissolved materials are transported within the mass of moving water
what is cliff profile?
the shape of cliff viewed from the side on
what is strata?
layers of rocks
what are bedding planes?
horizontal, natural breaks in the strata, caused by gaps in time during periods of rock formation
what are joints?
vertical fractures caused either by contraction as sediments dry out, or by earths movements during uplift
what are folds?
formed by pressure during tectonic activity, which makes rocks buckle and crumple
what are faults?
formed when the stress or pressure to which a rock is subjected, exceeds its internal strength. the faults then slip or move along the fault planes
what is a dip?
refers to the angle at which the rock strata lie
what is lithology?
the physcial characteristics of rock. e.g. resistance, permeability, physcial make up and chemical composition
what is coastal development?
means the processes of weathering/transportation/deposition that have occured to make the area look the way it does
what are the 3 ways of classifying coastlines?
-concordant or discordant
-a cliffed coast, flat coast or graded shoreline
- emergent or submergent coastlines
what are t he factor which govern the characteristics of coastal landscapes are:
-high versus low energy coastlines
-erosion versus deopsition
-more or less intensley managed
-geology
how do headlands and bays form?
these develop where there are alternating bands of resistant and less resistant rocks. the softer rocks are eroded more rapidly creating indentations along the coastline (bays), with the more resistant harder rocks remaining as headlands
what is a concordant coastline?
where the rock bands run parallel to the coastline
what is a discordant coastline?
where the rock bands run at right angles to the coastline
