Coasts Flashcards
three components of a sediment cell
sources - where sediment originates
flows - movement longshore drift
sinks - where deposition dominates
negative feedback loop
lessens any change that occurred in the system
positive feedback loop
exaggerated changes - making more unstable
e.g. people walking over sand dunes - erosion
littoral zone components
backshore
foreshore
nearshore
offshore
abrasion
moved along the shoreline causing it to wear away
hydraulic action
the wave crashes onto rocks, air forced into cracks causing high pressure, forces rock to break open (cavitation)
corrosion/solution
acidic water erodes alkaline rock
attrition
rocks and pebbles collide, wearing down
what causes high erosion rates (physical)
- long fetch
- perpendicular waves to the cliff
- heavy rainfall - percolation makes rocks weaker
- destructive waves - strong backwash
which type of rock is the most vulnerable to erosion and which one is the least (examples)
sedimentary - limestone (weakest)
igneous - granite (strongest)
explain the formation of cave, arch, stack, stump
- headlands attacked by marine erosion at the base, widens to become a CAVE
- cave widens to another side of the headland due to erosion, causing an ARCH
- This arch is then eroded until its unable to support its own mass, it collapses and leaves a STACK on the other side
- This stack is then attacked at the base until it also collapses, leaving a stump
how does a wave-cut notch form
- marine erosion attacks the base of the cliff, creating a notch of eroded material
- as the notch becomes deeper, the cliff eventually collapses due to a lack of stability
- there is then a platform left behind under the notch that didn’t collapse
traction
large heavy sediment rolled along the sea bed
saltation
smaller sediment bounces along the seabed
suspension
small sediment carried within the water column
solution
dissolved material carried with the water
swash-aligned transportation
parallel waves - limited longshore drift
drift-aligned transportation
perpendicular waves - longshore drift occurs the most
what is deposition
when waves lose energy and the sediment becomes too heavy to carry so it’s dropped
DP landform - spit
- long narrow strip of land formed by longshore drift depositing sediment along a straight line. If prevailing winds change, a hook is created
DP landform - bars
- overtime a spit crosses a bay and links two sections of the coast.
DP landform - tombolo
- bar/beach that connects an offshore island to mainland due to wave refraction
DP landforms - cuspate forelands
- triangular shaped headlands - longshore drift creates a beach on each side that connects and creates a cuspate foreland
DP landforms - offshore bars
- sand deposited early at a region offshore
DP landforms - sand dunes
- prevailing winds blow sediment to the back of the beach, causing the sand to dry
sand dune succession processes
embryo dunes
- upper beach - sand accumulates around an object
yellow dunes
- vegetation develops and stabilises dunes
grey dunes
- sand develops in soil with lots of moisture and nutrients - when vegetation dies, plants evolve and become more evolved/varied
weathering
breakdown of rocks over time then transferred to littoral zone as an input into a sediment cell
freeze-thaw (Mechanical)
- water enters cracks of water and then freezes (water expands) increasing pressure, leading to faults and weaknesses
salt crystallisation (mechanical)
- seawater evaporates leaving water behind, salt crystals grow over time exerting pressure and causing the rock to widen
wetting and drying (mechanical)
- rocks like clay expand when wet and contract when drying, frequent cycles of this lead to breaks
Acid rain (chemical)
- reacts with limestone to form calcium bicarbonate which is easily dissolved, allowing for erosion
oxidisation (chemical)
- minerals become exposed to oxygen e.g. iron minerals into iron oxide
What is biological weathering
breakdown of rocks due to actions of plants, animals, and bacteria
how do plant roots and birds contribute to biological weathering?
plant roots grow into cracks of rocks
birds dig burrows into cliffs weakening them
what factors determine the severity of mass movement?
angle of slope
geology
saturation of ground
what is soil creep and mudflows
soil creep
slow, continuous mass movement
mudflows
increase in water content in the soil
concordant coastlines
rock strata run parallel to the coast, consisting of rocks with alternating resistances e.g. limestone and clays/sands
what landforms do concordant include
Dalmatian coasts
- rise in sea levels - flooded river valleys
Haff coasts
- large bays crossed by spits, creating lagoons
discordant coastlines
strata are perpendicular to the coast
creating headlands and bays due to different levels of resistance
wave refraction
waves lose energy when approaching a headland or uneven coastlines, therefore the energy is concentrated on the headland. This creates erosional features
how does vegetation stabilise coastline sediment
- roots of plants bind the soil together reducing erosion
- plants reduce wind speed
difference between xerophytes and halophytes
xerophytes - tolerant of dry conditions
halophytes - tolerant of salty conditions
outline the process of plant succession
long term change in a plant community
- pioneer plants grow in mud and sand
- limited plant growth due to salty soil conditions
- as these plants die they release nutrients that reduce the saltiness allowing for the growth of others
- continuous process allowing new plants to colonise
how is marram grass adapted
- tough and flexible
- adapted to reduce water loss; evapotranspiration
- roots are deep
- survive high temperatures
high energy coastline
- powerful waves / destructive - due to large fetch
- erosion exceeds deposition - erosional landforms
- rocky headlands
low energy coastline
- less powerful waves (constructive) - sheltered area
- depositions exceeds erosion
- sandy beaches
destructive waves
- erosional
- high height
- high frequency
- strong backwash
constructive waves
- depositional - strong swash
- low height
- low frequency
short term sea-level change causes
- atmospheric pressure - low pressure, higher sea level
- high or low tide - time of day
- wind strength / direction
isostatic sea level change causes
local scale sea-level rise
- post-glacial adjustment
- tectonic activity
eustatic sea-level change causes
global rise in sea-level
- thermal expansion - as the water heats up it expands and therefore increases in volume
- global warming e.g. melting glaciers
what is coastalisation and why does it occur
movement of people towards the coast
- tourism
- agricultural productivity
- housing pressure
what is a storm surge?
short term change in sea level
maybe due to low pressure e.g. tropical cyclone
what factors exacerbate storm surges
- subsidence of land
- removing natural vegetation e.g. mangroves
- global warming
ICZM - integrated coastal zone management
- managing the coast as a whole rather than segments
- different UK councils working together
- sustainability and the best long term choice
- all stakeholders must be considered
Hard Eng - groynes
rock protrusions that trap sediment \+ builds up the beach - good for tourism \+ cost-effective - unappealing - exacerbates erosion elsewhere
Hard Eng - sea walls
concrete structures that absorb wave energy \+ effective \+ tourism promenade maintenance - unappealing - wave energy refracted elsewhere
Soft Eng - beach nourishment
+ looks natural
+ increases the size of beach
- needs regular maintenance
Soft Eng - dune stabilisation
marram grass planted
+ cost-effective
- time-consuming
Soft Eng - marsh creation
allows low-lying areas to flood
+ wildlife habitat creation
- farmers may lose land as a result
