1.1.8 Variations in coastal processes, coastal landforms and landscapes over different timescales Flashcards
Which coastal processes take decades to occur?
erosion and accretion cycles
coastal process response to defenc e
Which coastal processes take centuries to occur?
loss of towns and villages to the sea , historic coastal developments
Which coastal process takes a millenia to occur?
sea level changes in repsonse to glaciers ,tectonics etc
Which coastal processes take seconds, minutes,
hours, days, weeks, months and years to occur?
seconds- sediment movement by wind or wate r
mins -cliffs falls from mass movements
hours - storm surgees - break of defeces n
days - shore profile adjsutment
weeks - tidal cycles
months - coastal accretion erosion
years - longshore drift
What process and landform changes occur in
seconds?
process and landforms wchanges in sec high energy storm events and rapid mas movemnets processess causing changes in cliff profiles
high energy storm events and the resulting erosion of beaches and dunes and the rapid mass movement processes in cliffs can take place over a short time span , from sec to hours and certainty over a day
r.g cliff collapses captured , saturated rocls leads to rock a nore near hasting
How did storm generated erosion affect the town
of Towyn in 1990 (physical and human factors)?
Storm generated erosion can occur on very short timescales.
At midday on Monday 26th February 1990, a violent storm
breached the sea wall at Towyn, North Wales, flooding 10km of
lowlying land, damaging 2800 houses and 6000 caravans.
what human factors are their of toweyn ?
built toweyn on a coastal land in flood risk area
lack of maintenance of the seaway
little natural barrier
wjat physical factors to why this storm breahced the sea walls of towyn ?
toweyn low gradient flood plain
spring tide wuth a 1.5m surge led to extreme wave s
westerly storm force wind
combo of low atmosphere prssure
How do seasonal changes in constructive and
destructive waves affect beach profiles?
There is a strong relationship between wave steepness and
the angle of the beach profile.
Wave steepness is the ratio of wave height to wave length –
the higher the value, the greater the energy brought by the
wave onto the beach.
what are constructive wave ?
Constructive waves tend to occur during the
summer. Constructive waves are low, flat and
gentle, with wavelengths up to 100m and a low
frequency of 6–8 waves per minute. They are
characterised by a relatively more powerful
swash, which carries sand and shingle up the
beach, and a relatively weaker backwash.
Constructive waves contribute to the formation
of beach ridges and berms.
what are destructive wave ?
Destructive waves tend to occur during storms
and in winter. Destructive waves are steep in form
and break at a high frequency, at 13–15 waves per
minute. They have a plunging motion that
generates little swash and a relatively more
powerful backwash; this transports sediment
down the beach face, resulting in a net loss of
material.
what happens in the winter for destructive wave and summer for constructive wave ?
In winter the waves tend to have more energy (generally stronger winds) so they erode and transport sediment offshore, possibly forming an offshore bar/sand bar.
During summer, the waves are generally less energetic, so they move material onshore, building up the beach.
what is thre process and landform and how id thta affect the sea level ?
Sea level is continuously changing. Globally, all coasts have
undergone considerable variations in sea level over geological time
and especially since the Quaternary period, beginning about 2 million
years ago.
Some coastlines have experienced more ‘recent’ sea level change
than others. Since the last extensive glaciation/ice age, sea levels
have risen by about 120m.
Changes in sea level alter energy inputs and outputs and are therefore
important for the development of landforms.
What occurs in an eustatic change and what does
it mean by an ‘absolute’ effect?
Eustatic change is when the sea level changes due to an alteration in the volume of water in the oceans
a change in the shape of an ocean basin and hence a
change in the amount of water the sea can hold.
always a global effect – in this instance we would call it absolute.
At the beginning of an ice age, the temperature falls and water is frozen and stored in glaciers inland,
suspending the hydrological cycle.- results in water being taken out of the sea but not being put back in leading to an overall fall in sea level.
contemporary :
as an ice age ends, the temperature begins to rise
so the water stored in the glaciers will re-enter the hydrological cycle - and the sea will be replenished, increasing the sea levels.
Increases in temperature outside of an ice age will also effect the sea level since an increasing temperature will cause the ice sheets to melt, putting more water in the sea.
What occurs in an isostatic change and what does
it mean by ‘regional’ change?
Isostatic sea level change is the result of an increase or decrease in the height of the land.
When the height of the land increases, the sea level falls
Isostatic change is a local regional sea level change
During an ice age, isostatic change is caused by the build up of ice on the land.
water is stored on the land in glaciers, the weight of the land increases and the land sinks slightly, causing the sea level to rise slightly. - sl rises refered to as compression
When the ice melts at the end of an ice age, the land begins to
rise up again and the sea level falls. This is referred to decompression or isostatic rebound.
Isostatic rebound takes place incredibly slowly and to this day,
isostatic rebounding is still taking place from the last ice age.
Isostatic sea level change can also be caused by tectonic uplift or depression.
