C 1.1 - 1.5 Flashcards
Zavodovski Island
- uninhabited active volcanic islands in the south Atlantic
- worlds largest penguin colonies
- 36 hours away from South Georgia islands
- 33ft cliffs with 15ft waves
Coastal plains
- land gradually slopes
- deposited sediment eg, sand dunes/ mudflats/ beaches
- sometimes called alluvial coasts
Primary coasts
- dominated by land based processes eg, deposition from rivers/
- new land formed by volcanic lava
Eg, zavodovski island
Secondary coasts
- dominated by marine erosion/ deposition
Eg, slapton
Wave formation
- initially in open water, as energy transferred from air to water
- seabed increases friction and wave breaks
Wave action
- constructive vs destructive waves
- longshore drift moves material along
Sediment systems
- waves break, but vary between high and low tide points
- but can be exceeded by storm waves
- also sea level can change
Coastal defences
- disrupt physical geography processes (latitudinally) eg, walls, or longitudinally eg, groynes
Rock breakdown
- biological/ chemical / physical
- could lead to erosiom
Sediment systems
- material is eroded
- transported along
- deposited elsewhere
Waves are
- Energy moving through water
- waves move up and down in circular/ elliptical orbit
What constitutes wave ‘size’
- strength
- duration
- depth
- fetch
- direction
Wave formation
Shoreline/ seabed
- friction with seabed means water movement slows, wave length decreases and wave height increases
Swell waves
- windless day after a storm
- still, large waves as earlier waves make their way onshore
Constructive waves
- low height, long wavelength 6-8 per minute
- uninterrupted swash, starts at nearshore
- stronger swash than backwash results in sediment berm
- shingle beach has percolation, so less backwash, so steep beach
Destructive waves
- high height, short wavelength 13-15/min
- slower waves approach steep beach
- still circular motion, so mass of wave goes down onto the beach
- Sandy beach has less percolation, so stronger backwash
Coastal morphology definition
- is the study of natural processes ongoing at the shoreline and of the impact due to human interventions within the coastal zone
How can types of waves change over time?
- seasonally - summer = constructive, winter = destructive
- daily - plunging waves become swell waves
- annually - reduced river sediment - building of dams
- coastal management- restricts supply of onshore sediment
- climate change - storms bring destructive waves
Chesil Beach
- shingle barrier beach
- formed by marine transgression (sea level rise)
- 15 metres high
- exposed to English Channel and North Atlantic Ocean
Percolation
Water infiltrating gaps in sediment
- How water permissible is the sediment
Cork coastlines
- limestone/ sandstone
- 90o parallel geology
- some detached islands
What’s the reality of predicting impact on coasts?
- chaotic determinism
- so many different bits of landscape in terms of statistic likelihood’s
- what happens when statistical likelihood forced to work together
- chances of landscape existing the same elsewhere = very close to 0
What did William Morris Davis believe?
- landscapes are ‘uplifted’ by tectonics
- erosion cuts down into the landscape in a four stage model: youthful, mature, flat peneplain, then uplifted again
Walter Penck theory
- uplift and denudation happen at the same time, but come places have rapid uplift, some lower
Role of tectonic activity
- initially, might push sedimentary rocks up from seabed, eg limestone that makes up the coastline
- it might also fold them (plate collisions), and that creates weak points for waves to exploit
- magma might have risen to the surface, cooled, and left igneous rock; sea removed any layers above it, leaving the igneous rocks exposed and resisting wave erosion
Textual explanation of Dalmatia’s formation 1/2
A Dalmatian coast was formed in Croatia where tectonics has compressed and folded layers to form peaks (anticlines) and troughs (synclines). Sub aerial weathering and river erosion has begun to wear down layers in places of weakness, river will have eroded it over time and sea level has risen since last ice age so synclines are now flooded by the Adriatic Sea. Sweater find its way into synclines channels
Role of geological structure
- strata - rocks are arranged in layers
- deformation - how these layers are folded by tectonics
- faulting - fractures that happen when rocks are folded
Geology at concordant coasts
Same rock type along its length, can form anticlines or synclines like at Dalmatia
Geological structure influencing morphology
Dalmatia type
- river eroded, sea level rises, synclines are drowned
- long narrow islands are left
Geological structure influencing morphology
Haff type
- long sediment ridges
- topped by sand dunes
- run parallel to the coast offshore
- results in a series of lagoons (haffs) between the ridges and the shore
New Zealand
- NZ on convergent plate boundary
- Tongue point, New Zealand, in the cook strait, many steep clips with complex seabed
- kaikoura: experienced 7.8 EQ in nov ‘16, 4 different faults broke at once, sea bed is now 2m higher
Isostatic change
- heavy ice pushes land downwards
- melting ice means that land rebounds back
Isostatic readjustment
- because of soft viscous mantle, other parts of the crust also respond to changes
Eg, rubber duck UK
Tectonic influences
- plate convergence/ subduction causes sudden thrust up or down movements of sea bef
Emergent coast
- characterised by raised beaches / fossil cliffs
- Emergent coastlines being produced by post glacial adjustment, a fall in SL has exposed land once part of the seabed.
Raised beach
- a relict beach now above high tide level, a flat land covered by sand or rounded pebbles
- reflects a series of stages of uplift
- smaller particles are removed by waves, leaving rounded pebbles and boulders
Fossil cliffs
a steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion, but now above high tide levels, like Isle of Arran has raised beach 5m above SL
Littoral zone consists of
Backshore, nearshore, offshore zones
Off-> near-> fore-> back
Coastal plains
- Low energy environments where deposition> erosion, so there is a net accumulation of sediment, form through a net accumulation of sediment from both offshore and terrestrial sources
- Can be sandy or estuarine coasts
- Sandy coasts - composed of sands, shingles and cobbles
- Estuarine coasts composed of mud, clay and silts
Discordant coastlines
Different rock types along its length - so differing rates of erosion
Haff coastlines
Haff coastlines are formed where deposition produces unconsolidated geological structures parallel to coastlines. Meltwater rivers on land beyond ice front deposited thick layers of sand and gravels onto outwash plains, as times changed and SLR, waves push ride of sands and gravel land wards. Sand ridge formed bars across many bays and river mouths, with trapped river water forming a lagoon behind - a haff
Bays and headlands at discordant coastlines
In discordant coastlines, less resistance rock types erode first, to form indented bays, and more resistant don’t, to form headlands
Morphology of discordant coasts alters the
distribution of wave energy and rate of erosion throng wave refraction, waves refract around headlands and thus increase rate of erosion at headlands and reduce at bays - decreasing the degree of indentation.
Can be seen in swanage bay, where inn east forest, less resistant Wealden Clays eroded in wards, but more resistant Jurassic Portland limestone forms peveril point headland to the south, projecting out by 1km
Wave breaks when
wave reaches shore, touches sea bed so friction between sea bed begins to distort the wave particle orbit and slows it down, topples
Constructive waves encouraged by _ while destructive encouraged by _
long shallow nearshore, so. Friction slows down the wave and releases energy
short, steep nearshore zone, so little energy loss through friction
Beach sediment profile is
Pattern of distribution of different sized or shaped deposited material
- Constructive cause net movement of sediment up the breach, weaker backwash means little pebbles close to sea, but big ones up north.
- Destructive waves reduce beach gradient.
Rocky coasts
high energy environments where erosion> deposition, erosion continuously moves transported and deposited sediment as well as slowly eroding the cliff
