systems and processes Flashcards
how is a wave formed?
-winds move across the surface creating frictional drag and ripples creating a circular orbital motion of water particles
-the sea bead becomes shallower and the orbit becomes more elliptical due to frictional drag
-wave hight increases but the wavelength and velocity decrease
-causes the wave to break and surge up the beach
factors effecting wave energy
-strength of wind
-duration of wind
-size of fetch
constructive wave features
-formed by weather systems that operate in the open ocean
-long wave length
-6-9 per minute
-low waves which surge up the beach
-strong swash weak backwash
-occurs on gently slopped beaches
destructive wave features
-formed by localised storm events with stronger winds operating closer to the beach
-shorter wave length
-11-16 per minute
-high waves which plunge on the beach
-weak swash, strong back wash
-occurs on steeply sloped beaches
where is the backshore
between high water mark and landward limit
where is the inshore
between the low water mark and the where waves have no impact on land
where is the foreshore
between the high water mark and the low water mark, this is where most of the processes and changes are taking place
where is the offshore
where waves have no impact on the sea bead
where is the nearshore
seaward from the low water mark to the end of the foreshore
features of low energy coasts
-low wave energy which causes deposition
-depositional landforms:
sheltered bays
beaches
spits
Features of high energy coastlines
-high energy waves with high erosional power and large fetch
-strong steady prevailing winds
-erosional landforms e.g. wave-cut platforms, headlands
sediment sources
-streams/rivers
-cliff erosion
-offshore sand banks or sinks
-biological from coral fragments and shells
-longshore drift
What are sediment cells
-areas of coastlines separated from each other by well defined boundaries such as headlands
-in theory they are closed systems but in reality silt and clay can be transported across cells
-vary in size
-inputs and outputs are balanced
-11 in England and Wales
what is a coastal sediment budget
-balance between sediment addition and removal of individual cells
-requires identification of sediment sources, sinks, inputs, outputs and transfers
-difficult and complex to model
what’s the difference between marine and sub-aerial processes
marine operate on the coastline via the sea whereas sub-arial operate in land but shape the coastline
what are the 15 factors which effect the rate of erosion
-type of wave
-fetch of wave
-wave-steepness and breaking point
-presence beaches
-supply of beach material
-removal of material from the base of cliff
-gradient of sea bead
-headlands
-rock dip
-structure of rocks
-cliff material
-local hydrology
-vegetational cover
-rising sea levels
-human activity
-subaerial processes
what causes tides
the gravitational pull of the moon
what is tidal range
the difference in hight of hight of the tides
what is a spring tide
the highest high tide and the lowest low tide and the largest tidal range
what causes a spring tide
when the sun and the moon are aligned their gravitational pull is combined to pull the oceans towards them
what is a neap tide
when there is the smallest tidal range
what causes a neap tide
when the sun and the moon are perpendicular to each other, the gravitational forces act against each other, so the overall pull is reduced
