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Coastal landscapes as systems - Coggle Diagram
Coastal landscapes as systems
Coastal landscapes systems
High energy coasts
those that are exposed to strong, steady winds & fronts with high wave energies
unprotected by shallow offshore topography receive highest energy
large fetch waves for most of year
erosion rate > deposition rate
Factors control geomorphic processes (rates, location, extent)
Geomorphic processes
continually shape the Earth's surface, and generate the sediments that circulate in the Rock Cycle
the physical and chemical interactions between the Earth's surface and natural forces acting upon it to produce landforms
Exogenetic
- driven by slow energy which heats the surface, creates winds (and waves) and drives the hydrological cycle
Endogenetic
- driven by the geothermal energy from the earth's interior, it drives plate tectonics, raises relief & elevates the land
Landscapes and landforms of Norfolk
North West Norfolk
NW Cliffs, shore platforms, beaches
The Wash
King's Lynn
Hunstanton (steep 2 tone cliffs)
Central North Norfolk, Western section
islands, sandy beaches, marshes, mudflats & sand dunes
Wells
Holme (sandy beach, greenery behind)
Central North Norfolk Eastern section
shingle ridges & beaches, marshes, estuary mudflats & cliffs
Sherringham
Blakely (spits in ocean)
North East Norfolk
NE cliffs, beaches, lowlands, Norfolk broads
Cromer
Happisburg
Overstrand
Hunstanton
Mass movements
, Hunstanton has rock fall and block fall
In North West Norfolk
Hunstanton Cliffs
Three different rocks, stripes, strata:
ferriby chalk
red chalk
carstone
Greenery
increased weathering
Cliff retreat, shore platform
Beach
covered in rocks
seaweed covered stones
Rock fall
mainly of terribly chalk (weak rock, easily weathered)
cliffs collapsing
rock fall slightly protecting cliffs
some fallen rocks transported elsewhere
Geological features of cliff:
joints & faults
chalk
redchalk
carstone (sandstone)
vertical joints (dip)
eroded rock
rock strata
bedding planes
sub-ariel processes
oxidation of carstone
carbonation of chalk
exposure of shore platform, rocks subject to hydration, salt crystallisation, oxidation & biochemical activity causing spheroidal weathering
differential weathering along structures lead to block separation & scree (gravity driven)
block fall & rock fall
marine erosion processes
Mean erosion rate 2005-2015 = 10.0973 m/yr
Erosional landforms:
cave created by erosion of cliff (hydraulic action & abrasion), beginning to turn into an arch via erosion, has a pillar already
wave cut notch & wave cut platform (cliff retreat)
rock fall (caused by wave cut notches, mainly weathering, hydraulic action & abrasion), some rockfall is polished
micro geos
cracks in cliff widening, bringing of caues
cracks from hydraulic pressure & abrasion + smooth worn down surfaces
left over rocks that are harder to erode
Mass movements
Definition
The transport down slope of material under the force of gravity
occurs when forces acting on cliffs exceeds the forces holding rocks together
Slope failure is caused by:
1) reduction in internal resistance or sheer strength in a slope e.g. erosion/weathering on a cliff, change in water table, earthquakes etc
2) an increase in sheer stress, that is the forces acting on a slope e.g. undercutting the cliff, plant growth (weight onto of cliff), human activity
Rock types and structures in relation to weathering
The importance of rock type:
chemical composition (minerals) and physical arrangement (porosity & permeability) effect how easily a rock is weathered - differential weathering due to rates
Rocks increasing in resistance for mineral weathering -> olivine, propane, amphibole, mica, feldspar, quartz
Rocks increasing in resistance for rock weathering -> gabby, diorite, granite
Rock structure
Definition
structures are the arrangements of grains, lines, planes, surfaces and rock bodies
a plane of weakness in sedimentary rock are called bedding planes
Joint
- a fracture in which there is no displacement across layers
Fault
- a join with displacement
Lithology
- juxtaposition of resistance & less resistant rocks
Joints & faults with weathering
bedding planes & joints are lines of weakness which water can penetrate
weathering enlarges these structures & increases surface areas exposed to weathering and leads to
block seperation
on a small scale break up of grains is called
granular disaggregation
shared (laminations) and cleavage have the same effect and weather quickly
porosity allows water to penetrate into pores
Jointing
, the edges and corners are weathered rapidly leading to spheroidal weathering (exfoliation / onion skin weathering)
During compression and folding, rocks are subjected to stressed leading to joints
Or, joints can be caused by expansion cracks when igneous rocks have overlying rocks gradually removed by erosion
Weathering
Physical:
freeze-thaw
pressure release
thermal expansion (heating & cooling)
salt crystallisation
Chemical:
carbonation
oxidisation
hydrolosis
organic acids
solution
hydration
Biological:
root action
Types of weathering
Physical
Freeze-thaw:
water enters cracks / joints, expanding by 9% when freezes
in confined spaces this exerts pressure on the rock, causing it to split or pieces to break off, even in vert resistant rocks
Salt crystallisation:
solutions of salt seep into pore spaces of porous rock, salt precipitates here forming crystals
crystal growth causes stress on these rocks making them disintegrate
Thermal expansion:
rocks expand when heated and contract when cooled
frequent cycles of temperature change cause outer layers to crack & flake off
also called insolation weathering, but experiments cast doubt on effectiveness without water resent
Definition
the disintregation of rock without any signifiant change in the chemical or mineral composition of the rock
Pressure release:
overlying rocks removed by weathering and erosion, underlying rocks expands and fractures parallel to the surface
significant in sub-surface rocks such as granite and is also known as dilation
parallel fractures sometimes known as pseudo-bedding planes
sometimes huge sheets peel off line onion layers (onion skin weathering / exfoliation)
Biological
Root action
plant roots can force open cracks as they grow and expand lichens (associations of an alga and a fungi) decompose rock by selectively absorbing materials, and many bacteria are capable of oxidising or reducing certain materials during their nutrition
Chemical
Definition
breakdown of rocks an minerals as a result of the activities of plants, animals and micro-organisms
Hydration:
addition of water to mineral lattice
often classes as physical process since disintegration of rock or mineral is due to volume change which occurs when water molecules ar aerobes into crystal matrix of the rock
Hydrolysis:
chemical reaction between rock minerals and water
silicates combine with water, producing secondary minerals such as clays
feldspar in granites react with hydrogen in water produce kaloin, china clay
Oxidation:
some minerals in rocks react with oxygen, in air or water
iron is susceptible as it becomes soluble under extremely acid conditions and original structure destroyed, often attacks iron-rich cements that bind sand grains together in sandstone
Carbonation:
rainwater combines with dissolved carbon dioxide from the atmosphere to produce a weak carbonic acid
this reacts with calcium carbonate in rocks such as limestone to produce calcium carbonate, which is soluable
this process is referable and precipitation of calcite happens during evaporation of calcium carbonate to form satalcities & stalagmites
Solution:
some salts are soluable in water
other minerals, like iron, are soluable in very acidic water, with pH at about 3
any process where a mineral dissolves in water is solution, although specific mineral processes like carbonation can be identified
Definition of weathering:
the insitu decomposition by chemical processes and disintegration by mechanical processes of rocks
the interaction of mechanical / physical and chemical weathering processes affect landforms
5 factors influencing rate of weathering:
1) rock composition and minerals stability (solubility)
2) rock structure
3) climate (amount of precipitation)
4) temprature
5) length of exposure
Why does weathering happen?
most rocks formed below surface at elevated pressures & temps, they are stable at these conditions (minerals in chemical & physical equilibrium)
the process of adjustment is called weathering
at the surface, temp is less, pressure lower, more water available, free oxygen for chemical & biological processes, plant & animals cause biochemical activity, uplift gives rocks potential gravitational activity
minerals that form nearer to the surface area more stable
Rock cycle & Types of rock
The rock cycle
weathering, erosion & transport -> deposition in the sea
deposition in the sea -> burial
burial -> lifification -> sedimentary rock
sedimentary rock -> metamorphism -> metamorphic rock
metamorphic rock -> melting -> igneous rock
sedimentary, metamorphic & igneous rock -> uplift
Igneous-> intrusion
extrusion (crystallisation)
Igneous rocks: crystallisation
orgininating as molten magma on cooling form interlocking crystals e.g. Granite
these range from very fine (e.g. glass) to corse >3mm in size
makes landscape features that stick out, hard rock
some material weathered different to others
Granite = K-feldspar, quartz, mica
Metamorphic rocks
rocks formed by burial and heating of any pre-existing rock (igneous, sedimentary or metamorphic)
two processes occur to transform the rocks:
1) rocks deformed (squeezed) by increasing pressure (tectonic or burial)
2) and heated as a result of burial and new material grow and ones are recrystalisaed
rocks obtain new fabrics and materials
as a result of compression and parallel alignment of new mineral the rock develop planar structures called foliations
Porosity
= how much water it can hold
Permeability
= how much water can pass through = flow
Sedimentary rocks
composted of class (fragments) of pre-existing rocks (igneous, sedimentary and metamorphic) and lithified (turned into rock) by the processes of burial and diagenesis (compacted into rock)
Clastic:
rock & mineral fragments
1) breakdown of rock to made sediment e.g. sandstone
2) transportation moves sediment
3) lithification (compacted, cemented)
Biochemical:
remains of organisms e.g. coal
Chemical:
precipitated from solution e.g. limestone
sedimentation -> compaction
What's a landscape?
Definition
A landscape is an area, as perceived by people, whose character is the result of the action & interaction of nature and/or human factors
Components that form a coastal landscape:
1) climate
2) geology & structure
3) wind
4) waves
5) tide & currents
6) human activity
7) time
Inputs, processes, outputs and stores
Inputs:
waves
tides
currents
sunshine
offshore sediment
river sediment
estuary & land sediment
Processes:
erosion
transport
deposition
sedimentation
weathering
mass movements
Outputs:
silt & clay
sand
organic matter
dredged sediment
noise & heat
Stores:
salt marshes
mudflats
sand banks
sand, shingle & gravel beaches
spits & bars ( wind blow sand & shingle)
estuaries & deltas