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Alevel Geography- COASTS > Chapter 2 > Flashcards

Chapter 2 Flashcards

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1
Q

What is physical/ mechanical weathering

A

Breaks the rock down into smaller fragments of the same rock

Increasing the exposed SA of the rock exposes more to physical weathering

In many coastal landscapes the sea prevents temps dropping below O degrees which reduces extent and effectiveness of some physical weathering processes

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2
Q

Types of physical weathering

A

Freeze thaw
Thermal expansion
Pressed release
Salt crystallisation

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3
Q

Freeze thaw

A

Wages enters cracks/ joints and expands by 10% when freezes

In confined space this exerts pressure on the rock causing it to spilt or have sections break off

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4
Q

Thermal expansion

A

Rocks expand when heated and contract when cooled

Frequent cycles of this cause outer layers to crack and break and flake

Doubts unless water is present

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5
Q

Pressure release

A

When overlying rocks are removed by weathering the underlying rock expands and fractures

Exposes subsurface rocks like granite(✅✅)

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6
Q

Salt crystallisation

A

Salt solutions can seep deep into pores in rock and from crystals

Growth creates stress in the rock and can result in disintegration

NaS and NaCO3- can expand by 300%

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7
Q

What is weathering

A

Uses energy to alter the physical or chemical materials on surface rock

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8
Q

Weathering definition

A

Process of weakening and breaking up rocks m

Physical and chemical breakdown of rocks and minredals near the earths surface

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9
Q

Biological weathering

A

Together of plant roots/ chemical actions like organic acids

Categorised separately

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10
Q

Chemical weathering

A

Chemical reactions between moisture and minerals

Chemical weathering creates WEAK residues that are then easily washed away

Higher temp=higher rate

Change in climate= co2 to rainfall and ocean= more acidic

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11
Q

Types of chemical weathering

A 
Carbonation 
Hydrolysis 
Solution 
Oxidation 
Hydration
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12
Q

Carbonation

A

Chemical

Rainwater and dissolved co2, weak carbonic acid, reacts with caco3 in rocks in limestone= calcium bicarbonate

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13
Q

Hydrolysis

A

Chemical

Chemical reactions between rock minerals and water

Silicates combined with h20 to produce secondsry minerals eg clays

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14
Q

Solution

A

Chemical

Minerals dissolved BUT iron- only in acidic water

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15
Q

Oxidation

A

Minerals in rocks react with o2 especially iron

Extremely acidic - original structure is destroyed

Sandstone - bindings destroyed

CHEMICAL

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16
Q

Hydration

A

Chemical

H20 added to rock minerals - new minerals of larger volume

Surface flaking - some minerals expand 0,5% during chemical change

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17
Q

Mass movement

A

When gravity exceeds the force holding material to the cliff eg friction

Once mass movement has occurred, large amounts of sediment added to sediment budget

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18
Q

Regolith

A

Sediment from mass movement

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19
Q

Types of mass movement

A

Rock fall

Slides

Slumps

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20
Q

Rock fall

A

Slopes of 40 degrees or more

Bare cliff face- no vegetation to bind

Gravity, weathering- rocks become detached

Waves may wash it away or it forms a SCREE SLOPE ( gently sloping slope away from the cliff)

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21
Q

Slides

A

Linear movement

Slip, fault or bedding plane present

Or rotational - along a curved bedding plan

Undercutting at base of cliff

Wave cut platform because of MANY slides

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22
Q

slumps

A

Weak rocks

Heavier when wet = greater downward force

Sand above clay - rainwater penetrates sand but not clay

Greater pore pressure in sand

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23
Q

What are the geomorphic processes

A 
Wave processes 
Weathering 
Mass movement 
Flyvial processes 
Aeolian processes
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24
Q

Fluvial processes - erosion

A

Fluvial erosion in the upper catchment is MAIN source of a rivers sediment load

Rivers use similar erosional processes to waves

Sediment also derived from weathering and mass movement

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25
Deposition - fluvial processes
Low energy at river mouth As rivers enter sea, reduction in their velocity as waters enters static sea Energy reduced, rivers sediment deposited Largest particles first Fresh water and salt water = flocculation of clay particles( clump together= HEAVIER) due to electifcal charges between them in saline conditions
26
Aeolian processes- erosion and transportation
Wind is able o pick ups and particles and move them by deflation Surface creep- when sand is moved across surface due to wind Attrition on land very effective, particles carried for greater distances and NOT protected from collisions by film of water around them Except from solution - transported material using same mechanic as a as water
27
Deposition - aeolian processes
Wind speed falls Vegetation traps more sand from air and builds dunes
28
Wave processes - erosion ( what are the 5 processes)
``` Abrasion Attrition Hydraulic action Pounding Solution ```
29
Abrasion
Waves armed with rock particles scour the coastline, rock rubbing against rock
30
Attrition
Rock particles, transported by wave action collide with each other and with coastal rocks, progressively become worn away Become smoother, rounded and smaller ( eventually sand )
31
Hydraulic action
Waves break against the cliff face Air and water trapped in cracks and crevices becomes compressed As the wave recedes, the pressure is released and the air and water suddenly expand The crack is widened the aw pressure of Atlantic breaking wave is 11,000 kg2
32
Pounding
Mass of a breaking wave exerts pressure on the rock causing it to weaken Forces of as much as 30 tonnes per m2 can be exerted by high energy waves
33
Solution
Dissolving minerals like MgCO minerals in coastal rock PH of sea water= 7-8 Process is limited of significant unless h20 is polluted or acidic But even then onlycoastal rocks containing significant amount of soluble minerals are likely to be affected
34
Wave processes - transportation
``` Solution Suspension Saltation Traction Longshore drift ```
35
Solution
Minerals that have been dissolved into mass of moving water This type of load is invisible and the minerals will remain in solution until the water is evaporated and they precipitate out of solution
36
Suspension
Small particles of sand , silts, clays can be carried by currents This accounts for the brown muddy appearance
37
Saltation
Series of irregular movements of material which is too heavy to be carried continuously in solution Hopping motion Turbulent low may enable sand sized particles to be pinched up and carried for a short distance Other particles may be dislodged by impact, allowing h20 to get beneath them and cause entrainment
38
What is entrainment
When sand sized particles get picked up by water
39
Traction
Largest particles in the load may be pushed along the sea floor by the once of the flow Movement is rarely have continuous Large boulders may undertake a partial rotation before coming to rest again
40
Longshore drift
Deposited onshore May move by lsd Waves approach coast at an angle due to direction of dominant wind When waves break, smash carries particles diagonally up the beach - gravity moves them perpendicularly down
41
Deposition - wave processes
When a loss of energy caused by velocity decrease and or water VoLTE Rate of sediment accumulation exceeds removal rate When waves slow down immediately after breaking At the top of swash where water doesn't move During backwash- when water percolates into the beach material In low energy environments- eg sheltered from waves and wind
42
What is settling velocity
Velocity in which sediment particles are deposited
43
How are cliffs and shore platforms formed
Destructive waves break repeatedly on relatively steeply sloping coastlines Undercutting can occur between high and low tide levels ( wave cut notch) Weakens support for the rock strata above- collapses = steep profile and a cliff
44
What happens with cliffs and shore platforms when rock debris is Boulder sized
Accumulates on platform Gets so wide it produces shallow water and Smallwood aves- friction slows approaching waves so undercutting slows and eventually stops
45
How do wave cut platforms occur
When backwash carries away eroded material. Leavin a wave cut platform
46
At what angles do shore platforms slope seawards
Between 0-3 degrees
47
When are water levels constant for longest
High and low tide | Erosio is greater at these points
48
Cliffs and shore platforms - High tide
Ramp
49
Cliffs and shore platforms - low tide
Small cliff
50
Best tidal range for shore platforms developing (tidal range)
<4 If its higher - erosion is spread over a wider area of the platform , water is at its high and low tide positions for a shorter time and so platform is more uniform and steeply sloping Lower - cliff
51
Factors forming shore platforms
Erosion Solution Freeze thaw Salt crystallisation ALGAE - at night they release c02- mixes with sea water=more acidic nd more chemical weathering -
52
Horizontally bedded strata- cliff erosion
Undercutting by wave a to leads to rock fall, the clouds retreat inland - parallel to coast
53
Seaward dipping strata- cliff profiles
Undercutting by wave action removes basal support Rock layers loosened by weathering Slide into sea along bedding planes
54
Landward dipping strata- cliff profiles
Rocks loosened by weathering and wave action Is difficult to dislodge Slope profile lowered by weathering and mass movement
55
Caves arches stacks and stumps
Wave refraction - energy has concentrated on sides of headlands Points of weakness( faults and joints) exploited by erosion all processes , particularly abrasion and hydraulic action CAVE Concentrated wave attack between high and low tide Arch- 2 caves Widen arch ad weakened support- stack- stump
56
Headlands and bays formation
Weaker rocks erode more rapidly More resistant rocks Reve more slowly= headlands (shelter bays) DISCONCORDANT Width of bays = width f band of weaker rock Bay depth - depend on differential rates of erosion between the more resistant and weaker rocks
57
Wave refraction
When waves approach an irregularly shaped coastline become more parallel Waves slow down by friction in shallower water of the headland and the part if the Eva crest n deter water moves faster as there's no fraction waves bend round the headland and the orthography converge
58
Bays - refraction
Orthogal converge and energy is dissipated Deposition As waves break on sides of headland at an angle there's LSD of eroded material in bays
59
Blowholes
Part of a roof of a tunnel like cave collapses along a major joint- may form a vertical shaft that reaches cliff top ( blowhole) In storm conditions- large waves may force white aerate water out Eg trevone, Cornwall
60
Geos
Narrow, steep sided inlets Even on coastlines with resistant geology , may be lines 0[of weakness like joints and faults These are eroded more rapidly by wave action than the rocks around Hydraulic action - force air and water and weaken strate Eg huntsman leap in penbookshire
61
What are deltas
Large areas of sediment formed at mouths of rivers Deltaic sediments are deposited by rivers and tidal currents, form when rivers and tidal currents deposit sediment at a faster rate than the wave and tides can remove it Deltas are crossed crossed by branched network of distributaries
62
What happens when deltas get overloaded with sediment
Deposition in the channel forms bars which cause the channel to split in. 2 This produces 2 channels with reduced energy levels and so more deposition and further dividing occurs Although these channels may be lined with levees i their banks, in times of floor these natural embankments are breached and deposition of lobes of sediment will take place in low lying areas between them
63
Where do deltas form
Low energy environments Tidal ranges low Rivers entering sea are carrying large sediment loads A broad continental shelf margin exists at the river mouth to provide a platform for sediment accumulation
64
Types of delta
Cusp ate Birds food Arcuate
65
Cuspate delta
Pointed extension to the coastline occurs when sediment accumulates , but this is shaped by regular gentle currents from opposite directions
66
BIRDSFOOT delta
Distributaries build out form the coast ina. Branching pattern River sediment supply exceeding some rates of removal by waves oand current
67
Arcuate delta
Sufficient sediment supply is availed for the delta to grow seawards, wave action strong enough but ti smooth leading edge
68
Structure of delta ( 3)
Upper delta plain Submerged delta plain Lower delta plain
69
Upper delta plain
Furthest inland, beyond the reach of tides and composed entirely of river deposits
70
Submerged delta plain
Lies below mean low water mark and is composed mainly of marine deposits Seawards growth of delta
71
Lower delta plain
In the inter-tidal zone regularly submerged and composed of BOTH river and marine depots
72
Tombolos
Beaches that connect mainland to an offshore island Often formed form spits that have continued growing seawards until the hey reach and join an island Eg 30km shingle beach at chesil near Weymouth
73
Beaches
Most common landform. Of depostion | Accumulation of material deposited between lowest tides ad. Higher storm waves
74
Sources of beach material
Cliff erosion - 5% Offshore - Combed From sea bed often during periods of rising sea levels, 5% Rivers- 90% carried onto coastal syste as suspended and bed load though river mouths
75
Sandy beaches
Gentle gradient <5 degrees Small particle size means it becomes compact when wet , allowing LITTLE percolation Material is carried back down the beach rather than being left at top- gentle gradient adn ridges/ tunnels parallel to top of beach
76
Shingle beaches
Steeper gradient Smash stronger than backwash so net movement of shingle on beach Shingle may make up upper part of the beach, where rapid percolation due to larger air spaces mean that little backwash and so material is left at top of beach
77
Spits
Long narrow beaches of sand or shingle attatched to land Extend across bay , estuary or indentation Longshore dritt Strong winds/ tided currents can cause spit to develop curved end ( recurred end) Wave refraction
78
Onshore bars
If a spit. From across an indentation such as a cove or bay in the coastline until it joins land Form a lagoon fo brackish water on the landward Waves approaching a gently sloping coast deposit sediment due to friction with the sea bed The build up of sediment offshore causes waves to break at some distance from coast
79
What happens behind spit
Sheltered area Depostion Silt and mud build up Salt marsh
80
Berms
Smaller ridges tat develop at the position of the mean high tide mark Depostion at top of smash
81
Cusps
Smaller , semi circular depressions Temporary features formed by a collection of waves reaching the same poitn and when the smash adn backwash have similar strengt Sides of cusp channel incoming swash into the centre of the depression - this produces STRONG backwash , which drags material Down the beach from centre of cusp enlarging the depression

Alevel Geography- COASTS (4 decks)

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