8 - variations of coastal processes over timescales Flashcards
what is a storm surge
result of extreme meteorological conditions and the configuration of coastline
water levels rise higher than predicted at high tide
can result in property damage and death
what is the most recent disastrous storm surge in england
in 2013 , december 5-7, North Sea Storm Surge
intense rain, stormy seas, spring tide, low pressure system and low lying coastline and shallow sea lead to high storm surge
what strong relationship can be seen regarding waves and the beach
WAVES (particularly steepness) and ANGLE of the beach
steepness = ratio from height to length. higher the value, greater energy brought to beach
differences between winter and summer beaches
WINTER - waves have more energy due to stronger depressions. erode and transport material off beach and out to sea in powerful backwash. lower beach profile and less mass
SUMMER - waves have less energy - increased anticyclonic activity. deposit material in swash so built up profile. some beaches sandy in summer rocky in winter
how can tides influence beach profiles
(LUNAR monthly cycle - spring high tide, neap high tide, neap low tide and spring low tide)
4 marks are made during the cycle
how can seasonal variations influence beach profile
areas of monsoon activity or seasonal rainfall patterns
wet or dry seasons impact beach profile
how does beach steepness influence other factors
steepness changes seasonally - type of beach may change
STEEP beaches have plunging waves - REFLECTIVE beach
SHALLOW beaches have breaking/spilling waves - DISSIPATIVE beach
what are two main causes of long term change
EUSTATIC
ISOSTATIC
what is eustatic changes
EUSTATIC = changes in absolute global sea levels, all seas/oceans interconnected
2 main causes:
- thermal expansion (warmer water expands with global warming)
- glacio-eustatic changes (melting ice caps/sheets release water locked up for long)
what are isostatic changes
ISOSTATIC - regional changes of sea level
earths crust (lithosphere) floating on asthenosphere below
isostatic balance changed by increase/decrease in relative weight or changing meeting point of land and sea
what is ISOSTATIC readjustment/rebound
in ice age, weight of glacier depressing land and sea levels raised
ice melts = land ‘rebounds’ slowly to original position increasing height relative to sea
still occurs in NW britain today, land rebounding since pleistocene epoch
what is isostasy
GLACIO-ISOSTASY = occurs when weight of glaciers depresses land relative to sea
HYDRO-ISOSTASY = increased weight of water depresses ocean basins relative to land
fall in sea level = negative changes and EMERGENCE occurs
positive changes = SUBMERGENCE
what can cause sea level to rise relatively
- sea level falls + land rises, remains the same or falls at slower pace
- sea level remains fixed while land level rises
- sea level rises, land rises at faster pace
what can also affect landforms as well as sea level change
- discordant/concordant coastline
- relief of land
- special local factors (eg was coast glaciated before sea level change)
what are the landforms of submergence?
- ria
- fjord
- dalmation coast
what are landforms of emergence
- raised beach
what is a RIA and how is it formed (example?)
- former river valley floods and opens into sea
- caused by eustatic reasons of sea level rise, isostatic reason of land sinking below sea level
- Pourtsmouth Harbour in Hampshire, submergent coastline
what is a FJORD and named example
- a fjord is a drowned glacial valley
- formed when glacier retreats
- has steep rising walls, straighter long profile and is deeper than a ria due to glaciers over deepening valley
- west coast of Norway
what is a DALMATION coast and how is it formed (example)
- concordant coastline produced by geological structure of folds parallel to coast
- series of longitudinal river valleys next to the coast that have been flooded (synclines) leaving parallel ranges of watershed ridges as islands
- tectonic forces produced by african/eurasian collision compressed limestone causing anticlines and synclines
what is a RAISED beach
- beach above shoreline not reachable by waters at high tide
- sometimes called marine terrace
- formed by wave action when close to waterline
- Ballyhillin Beach in mainland Ireland
what is a RELICT CLIFF
a cliff that has been abandoned by sea level fall displaying CASS
emergent landform
what is an ELEVATED MARINE PLATFORM
wave cut platform which now exists as extensive flat area in front of relict cliff above wave action
what is the main positive impact of the coast on humans
attracts human activities - fishing, tourism, port development, settlement
what physical resources make people travel to the coast
- scenery (eg cliffs)
- ecosystems (eg coral reefs)
- sandy beaches
- sunny climates
- high quality seawater free from strong currents and rip tides
what human resources make people travel to the coast
- cultural attractions
- heritage resources
- quality provision of services
- leisure facilities
- watersports
