EQ1 Flashcards
Littoral zone
Breakwater area
Or area nearest the coastline where high + low tides occur
Offshore
Area of deeper water beyond the point at which waves begin to break
Friction b/ the waves + the sea bed may cause some distortion of the wave shape
Nearshore
Area of shallow water beyond the low tide mark w/i which friction b/ the seabed + waves distorts the wave sufficiently to cause it to break (breaker zone)
May be a breakpoint bar b/ the offshore + nearshore zones
Foreshore
Area b/ the high tide + low tide mark
Backshore
Area above the high tide mark affected by wave action only during major storm events
Different types of coastlines formed by the littoral zone
Rocky/cliffed coast
Sandy coastline
Estuarine coastline
Rocky/cliffed coast
Areas of high relief
Usually resistant rock areas
High energy environments where erosion is greater than deposition
Destructive waves
Sandy coastline
Low relief areas
Generally flat
Soft rock areas
Low energy environments with deposition being greater than erosion
Estuarine coastline
Low relief areas w/ salt marshes + mudflats
River mouths deposition greater than erosion in a low energy environment w/ soft rock
Dynamic equilibrium
Balance b/ inputs, flows, outputs of energy + material
Long term changes = sea level rise
High + low tide
Weather conditions
Varyingwave energy
Classifying coasts
ST classification criteria
Energy inputs:
Tides ebb + flow over a 12.5 hour period + currents, rivers, precipitation, gravity + tectonics create high + low energy coastlines
Sediment inputs:
Deposition + erosion rates - deposition is higher meaning expanding coastline
Erosion = higher meaning erosive coastline
Advancing + retreating:
Happens due 2 erosion + deposition as well as = emergent + submergent coasts linked with sea level
Classifying coasts
LT Classification criteria
Geology:
The lithology (rock type) + structure (arrangement of those rocks) Used 2 determine whether a coast = rocky, sandy, estuarine + Concordant (parallel) / discordant (perpendicular)
Sea level Change:
Used 2 classify emergent + Submergent coasts. Tectonic plate movement can lift or submerge sections of land. Climate change causing sea level rise can cause a coast to become submergent
Submergent coastline
Coasts occur where se level rise relative to land
Features of Submergent coastline
Rias
Fjords
Dalmatian coastline
Rias
River valley at the coast that has been inundated by the sea as relative sea levels have risen
Resukting in a ‘drowned valley’
Fjord
A glaciated valley at the coast that has been inundated by the sea. Has steeper rising walls a straighter long profile + deeper than a ria due to glaciers over deepening the valley
Dalmation coastline
A series of longitudinal river valleys next 2 the coast that have been in inundated leaving parallel ranges of watershed ridges as islands
Rocky coastline
1,000km of the UKs coastline - mainly N + W
Cliffs vary in height (Scotland) to low relief (Cornwall)
Geology is resistant + they erode v slowly
Little deposition + high energy erosion
Sandy plains
Flat, low relief, often containing wetlands + salt marshes
Low energy environment
Deposition is high
Can be sand, shingle, cobble
Most of the UKs S+Ecoastlines
Concordant coasts
Most of the south coast (Dorset)
One continuous layer of hard rock protecting the other layers behind it
Discordant coasts
Most of the E coast (Holderness)
Differing layers of resistant + soft rock in bands
Softer rock will erode faster than harder rock
Concordant e.g. Dalmation coast = Croatia
Concordant coastline produced by the geological structure of folds parallel 2 the coast
Tectonic forces produced by the collision of African + Eurasian plates
Created up folded ridges (anticlines) + down folded valleys (synclines) aligned parallel 2 the coast
Sea levels rise - overtopped the low points = anticlines + sea flooded synclines
Lines of islands separated by narrow sea channels parallel 2 the coast
Influence of coastal dip on strata
Dip is the angle of inclination of the rock strata from the horizontal
Tectonic feature
Sedimentary rocks are deposited horizontally but can be tilted by folding + faulting by tectonic forces
Dramatic effect on cliff profiles
Horizontal dip
Produces vertical / near vertical profile
Notches reflecting weathering + small scale mass movement of strata that are more easily eroded
High angle of seaward dip
Produces a sloping low-angled profile with 1 rock layer facing the sea
Vulnerable 2 rock slides down the dip slope when uppermost strata are attacked by sub-aerial processes
Profile slopes correspond 2 that of strata dip
Bedding planes b/ strata are weakly bonded + readily loosened by weathering
Low angle of seaward dip
Produces a steep profile may exceed 90 degrees
Creates areas = overhand rock
V vulnerable to rock falls
Frequent small-scale mass movement of material weathered from cliff face
Major cliff collapse when undercutting by marine erosion makes overhang unsustainable
Landward dropping strata
Produces steep profiles = 70-80degrees as downslope gravitational force pulls loosened blocks into place
V stable profile w/ few rock falls
Faults
Major fractures created by tectonic plates
Create a fault line
Increases the rate of erosion
Large forces involved leading 2 these rocks being easily eroded
Joints
Fractures created w/o the rock being moved
Occur in most rocks + can be seen as blocks of rock
Igneous rock - form during magma cooling
Sedimentary rock - form through compression + stretching from overlying rock
Folding
Bends in the rock
Produced by sedimentary rock layering
Main types: anticlines + synclines
Bedrock lithology
Rate of coastal recession/retreat is influenced by the type of bedrock
Influenced by how reactive the rock is to chemicals
Wither it’s clastic (less resistant) + crystalline (more resistant) + whether it has cracks, fissures, fractures
Igneous
Granite, basalt
Erode + weather v slowly because they have interlocking crystals - resistant
Contain few joints + weaknesses
Metamorphic
Marble, slate, schist
Recrystallised rock through heat + pressure
Crystalline rock = resistant BUT LESS THAN SEDIMENTARY ROCK because the crystals form in the same direction (not interlocking)
Sedimentary
Sandstone, limestone, clay
Formed by compaction least resistant type of rock because they’re heavily jointed - weak structures
Moderate erosion rates
Unconsolidated sediment
Not yet solid rock
Not yet cemented + compacted
Drifts due 2 deposition + usually overlays bedrock
V easily eroded = 2-10 meters per yr
Complex cliff profiles
Produced where there are differing types = lithology
Less resistant strata erode + weather quickly producing wave cut notches
Resistant strata erode + weather slowly retreating less rapidly
Complex cliff profiles can be produced when there are
Alternating permeable + non-permeable strata
Permeable rock
Allow water to flow through them because
Porous (chalk)
Numerous joints (Carboniferous limestone)
E.g. sandstone + limestone
Permeable rock = less resistant to weathering because
Water percolating comes into contact w/ large surface area that can be chemically weathered
Limestone weathered by carbonation converting calcium carbonate to soluble calcium bicarbonate
Pioneer plants
1st to colonise at a coastline
Modify the environment by stabilising sediment, adding nutrients to the soil + reduce evaporation rates
Create plant succession which is the process of different plant communities occupying an area of the coast overtime
