coastal landforms Flashcards
what are examples of EROSIONAL LANDFORMS?
bays, headlands, cliffs, caves. arches, stacks, wave- cut notches and platforms, geos, blowholes.
what are the four erosion processes and what do they do?
HYDRAULIC ABRASION- force of wave- air gets trapped in cliff rocks causing pressure.
ABRASION- large material hits against the cliff.
ATTRITION- rocks hit against each other and break into smaller parts.
SOLUTION- dissolved rocks transported in water e.g. calcium carbonate in limestone and chalk.
how are bays and headlands formed and what processed occur?
DISCORDANT coastlines- layers of soft and hard rock perpendicular to shoreline, resulting in different rates of erosion.
hard rock juts out to sea whereas less resistant rock bays are further retreated inland
WAVE REFRACTION- wave energy concentrated on headland so calmer waves hit beach , encouraging deposition so beaches build up in bays.
what is an example of a soft rock and an example of a hard rock?
clay
limestone
how are caves, arches, stacks, and stumps formed?
what is an example?
headland erodes into a stack/ stump by processed of weathering+ erosion.
weaknesses in rocks are exposed to hydraulic action+ abrasion which widens cracks into cervices.
wave- cut notches then formed by further erosional processes; overtime they are deepened, forming caves.
wave refraction- concentrated wave energy from destructive waves on headland- deepens cave more into an arch.
top of arch can be weathered- e.g. carbonation due to calcium carbonate makeup of limestone; arch becomes unstable so collapses into a stack.
further erosional processes such as sub-aerial processes continue to weather+ weaken rock from above, causing wave- cut notches in stack.
exposed stack will collapse- forms stump. broken material further eroded by attrition- this load can become ammunition to further erode the headlands by deposition.
OLD HARRY- Dorset, South Coast; chalk+ clay coastline. headland called ‘foreland’
what factors may effect how long it takes for an arch to collapse? (rates of erosion)
*geology (more/ less resistant)
*lithology (fractures susceptible to hydraulic action)
*location (prevailing wind+ wave direction; fetch; any human intervention?)
*morphology (how is wave refraction a factor?)
*weathering (amount of rain/ temp- contribute to mass movement (mainly rockfall as hard rock)
how are wave- cut platforms formed?
what is an example?
found on hard rock coastline
destructive waves hit cliff face- cause undercutting between high+ low water marks, creating wave- cut notch.
enlarges into a cave
continued erosion until roof of cave becomes unstable due to pressure+ sub- aerial processes - collapses so cliff retreats landwards.
repeated process of this forms wave- cut platform as cliff remains not eroded way below the tidal range.
Flamborough Head, Yorkshire- chalk headland.
what are blowholes?
what are geos?
joint between sea cave+ land surface above cave becomes enlarged and air can pass through it. water flows into cave- air expelled through pipe-like joint. most likely to cause spray during storm conditions.
can sometimes change topography (relief) near them- can eventually erode surrounding area to form larger sea caves.
sometimes the cave may collapse.
How are DEPOSITIONAL LANDFORMS formed?
due to the transportation of sediment; from sources such as:
*beach nourishment
*eroded/ weathered cliff material
*aeolian transport
*offshore
*longshore drift
what are the four processed of TRANSPORTATION?
SOLUTION (material dissolves)
SALTATION (material bounces along sea bed)
TRACTION (larger sediment rolled along seabed)
SUSPENSION (material is carried/ suspended)
what is LONGSHIRE/ LITTORAL DRIFT?
transport of sediment in one direction caused by PREVAILING WIND DIRECTION
e.g. dom. wind direction in Holderness Coast is north- easterly.
leads to a net shift of sediment along the coastline in a particular direction; may lead to formation of spits.
what are the two types of deposition?
GRAVITY SETTLING (energy of transporting water decreases and cannot carry sediment; large sediment deposited first, followed by smaller material e.g. pebbles, then sand, then silt)
FLOCCULATION (very small particles such as clay; so small they remain suspended in water. clay particles clump together due to electrical/ chemical attraction+ become heavy enough to sink.
CHESIL BEACH TOMBOLO CASE STUDY
18 mile long, 200m wide, 18 metre high shingle tombolo
Dorset- Southern England
West- East longshore drift
Had a secondary prevailing wind
Beach is part of Jurassic Coast World Heritage Site.
What is unusual about the pattern of sediment at Chesil beach, and what is the theory behind this?
Takes more energy to move larger material- so usually as move along spit, sediment would BECOME SMALLER, as heavier sediment is deposited first- however this is the OPPOSITE.
FLANDRIAN TRANSGRESSION- rapid sea level rise 12,000 years ago at end of last glacial period. Allowed waves to move sediment onshore to form Chesil beach.
Why would you expect DEPOSITIONAL LANDFORMS to be UNSTABLE?
*can be easily eroded away by STORMS/ SPRING TIDES (but long term can regenerate)
*LOCATIONS influence stability - e.g. sand more stable inland as more compact+ vegetation- plants protects against alliance processes.
*PLANT SUCCESSION- sand dunes+ salt marshes- plants bind loose sediment together and encourage further deposition e.g MARRAM GRASS.
*STORMS may damage vegetation- more vulnerable and exposed
*consist of UNCONSOLIDATED MATERIAL- vulnerable to change (DYNAMIC environments)
*sea level rise due to climate change threat in future- low lying landforms will be inundated.
*DEPOSITIONAL FEATURES rely on continual supply of sediment+ continual deposition to balance erosion that occurs (equilibrium) - esp. true of spits as distal end in constantly being eroded.
*MATERIAL- pebbles are less easily erode away than sand ad more energy is required.
Where do salt marshes form?
Behind spits and at estuaries (where river meets sea)
*salt marshes in estuarine areas can be known as HALOSERES.
What are HALOPHYTES?
salt- tolerant plants.
What are characteristic of a HIGH ENERGY ENVIRONMENT?
An example?
*destructive waves
*tall waves
*strong prevailing wind
*long fetch
*cliffs/ rocky coastline
*erosional landforms e.g. waves cut notches/ platforms, cliffs, stacks.
Flamborough Head
What are characteristics of a LOW ENERGY ENVIRONMENT?
An example?
*low wave energy/ constructive waves
*low frequency waves
*low wave height
*deposition rate higher than erosion rate
*depositional landforms e.g. spits, beaches, deltas.
The Nile Delta
