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