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eqi2 Flashcards

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1
Q

what factors affect size and formation of waves?

A
  • direction of wind
  • fetch
  • strength of wind
  • how long wind has been blowing
  • seabed
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2
Q

what are the parts of a wave?

A

wave crest = top of the wave
wave length = distance between wave crests
wave height = distance between wave crest and trough
trough = bottom of wave

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3
Q

how do waves form in shallow water?

A

the circular motion of the waves change as the waves are driven by winds and currents into shallow water.
- the circular motion becomes elliptical as the orbit encounters friction from the sea bed
- the crest of the wave rises as it moves forward
- the wave steppens

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4
Q

what is the equation of wave energy?

A

wave energy = wave length X (wave height)2

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5
Q

what are facts on constructive waves?

A

6-8 per minute
stronger swash than backwash
low energy
wide, flat beach
deposition

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5
Q

what are facts on destructive waves?

A

high, steep waves
stronger backwash
shorter wave length
10-14 per minute
erosion
high energy

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6
Q

what are seasonal changes in beach morphology?

A

summer beach = constructive waves in summer creating steeper gradient with berms in the front
winter beach = destructive waves creating a steep cliff in the back

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6
Q

how does sediment size affect the profile of the beach?

A

when the beach is made up of rocks the water will percolate leading to a weaker backwash than swash and cannot remove the sediment.
- on a sandy beach there is little friction as the surface is smooth and little percolation as the particles are close together

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7
Q

what are different marine processes?

A
  • abrasion: hurling of the stones and pebbles by the sea against rock face
  • attrition: the knocking together of pebbles to reduce their size
  • hydraulic action: air compression plus force of water on cliff
  • corrosion: weak acid on sea water corrodes calcium carbonate in rocks. limestone and chalk are susceptible to this type of erosion
  • salt crystillisation: where evaporatoin is potentially high, growth of chloride crystals from sea water attacks a wide variety of rocks
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8
Q

what distinctive landforms are created through erosion?

A
  • wave cut platforms
  • wave cut notches
  • cliffs
  • cave, arch, stack, stump
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9
Q

how is sediment transported through long shore drift?

A

attrition occurs and results in sediment becoming smaller and finer along the beach
- swash occurs in the wind direction and backwash after

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10
Q

what are rip currents?

A

forms when a narrow, fast-moving section of water travels in an offshore direction, channeled through a break in an offshore bar
- it is very dangerous

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11
Q

what are currents?

A

tidal currents also moves sediment and are driven by several factors.
one being the rise and fall of tides which is driven by the gravatational attraction of the sun and moon

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12
Q

where do depositional landforms occur?

A

deposition occurs when the waves loose energy or when there is an increase in sediment size

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13
Q

when is deposition more likely to occur?

A

on drift-aligned coasts (when waves hit at an angle and LSD occurs) rather than swash-aligned coasts (perpendicular waves)

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14
Q

what are the different types of mechanical weathering?

A
  • freeze thaw
  • exfoliation
  • pressure release
  • salt crystallisation
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15
Q

what is freeze thaw?

A
  • daily temps fluctuate around 0c
  • ice occupies 9% volume
  • widens joints in rock and ice
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16
Q

what is exfoliation?

A
  • outer layers of rock warm faster and cool more rapidly
  • outer layers peel like an onion
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17
Q

what is pressure release?

A
  • rocks developed under great pressure
  • later exposure releases pressure and exposire to atmosphere
  • cracks develop and sheeting occurs
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18
Q

what is salt crystallisation?

A
  • slightly saline water enter pore spaces
  • evaporation leaves salt crystals which exert stress on the rock
  • this leads to GRANULAR DISINTERGRATION
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19
Q

what are the types of biological weathering?

A
  • oxidation
  • hydration
  • hydrolysis
  • carbonation
  • solution
  • acid rain
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20
Q

what is oxidation?

A
  • most sedimentary rocks contain iron
  • rocks exposed to oxygen will crumble
  • iron in a ferrous state (lost 2 electrons) is changed by oxygen to a ferric state (lost 3 electrons)
  • rocks change colour from blue grey to reddish brown
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21
Q

what is hydration?

A
  • rocks that include salts absorb water and swell leading to decomposition
  • active following periods of wet and dry weather
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22
Q

what is hydrolysis?

Study These Flashcards
A

hydrogen in water reacts with minerals H+ and OH- ions in water combine with ions in the mineral leading to decomposition

23
what is carbonation?
rainwater contains carbon dioxide which produces carbonic acid - dissolves limestone to calcium bicarbonate
24
what is a solution?
minerals which are soluble dissolve, with increasing acidity in the water
25
what is acid rain?
human activity increasing carbon dioxide, sulpher dioxide and nitrogen dioxide - increases rate of carbonation in limestone
26
what are tombolos?
a depositional landform - a spit or bar that connects an island to the mainland. a single tombolo may connect one island with the mainland however a double tombolo encolses a lagoon which may fill with fine sediment
27
what is needed for tombolos form?
you need: - a mainland - a beach with plenty of sediment - the perfect island - long shore drift
28
how do tombolos form?
whilst the prevailing wind drives waves towards the coast at a certain angle, the presence of an island causes those waves to refract. - this means that you have waves colliding in the stretch of water between the island and the coast and the sediment is deposited in the lee of the island
28
why do tombolos need the distance to be less than 1.5X the islands width?
this allows waves to refract around the island and much of their energy to dissipates. the water then lacks the energy to hold the sediment, so it is deposited. - this continues until a visible bar connects the two landforms - the sheltered environment the island creates protects the deposited sand from all but the most violent storms.
29
what is an example of a tombolo?
St Agnes, UK
30
what threatens tombolos?
climate change - led to more extreme weather events and the violent storms have the energy to transport the sediment. it also leads to rising sea levels which threaten to permanently submerge and destroy tombolos human activities - sand mining and removal of sediment threaten to disrupt the balance. tombolos are dynamic and any disruption can threaten that.
31
how are beaches formed?
they are formed via deposition of sediment and can also be formed via biological activity such as plants stabalising the sediment
32
how does human activity affect beaches?
- forms coastal engineering - management of vegetation - beach replenishment
33
how are beaches eroded?
- wave erosion - human activity - weathering
34
what landforms are associated with beaches?
- cliffs with resistant rocks - spits - headlands and bays
35
what are the characteristics of beaches?
- storm beach at the back - steeper beach with bigger sediment - flatter beach with smaller sediment - berms formed with constructive waves
36
what are cuspate forelands?
low lying triangular shaped headlands, extending out from a shoreline, formed from deposited sediment
37
what is an example of a cuspate foreland?
cape kennedy in US
38
how are cuspate forelands formed?
when a coast is exposed to LSD from both directions, sediment is deposited in the low energy environment where the two sets of LSD collide through gravity
39
what are the dynamics of cuspate forelands?
- losing material through waves, tides and currents - land is stabalised through vegetation
40
what is a spit?
a narrow extenstion of sand or single which has one end attached to the coastline and the other end out in the sea or estuary
41
what is a recurved spit?
the same as a spit but shaped by the effects of tides or changes in wind direction. in the shelter formed by a recurved spit, mudflats and salt marshes can develop and increase the size of the spit.
42
what is a double spit?
where two spits extend in opposite directions from different sides of the bay towards the middle and each other
43
how to spits form?
they form on drift-aligned coasts, where the coastline changes direction (over 30 degrees) - at the turn, LSD continues in the original direction but the energy is dispersed as the wave refracts = deposition on the sea bed - sufficient sediment is deposited to break the surface - process continues until an equilibrium is reached
44
what is the formation of the recurved spit?
a hook forms at the end of the spit - it could be due to wave refraction around the disconnected end, which transports and deposits sediment for a short distance - it could be due to the wind and wave front being at an opposing angle to the prevailing wind - could be due to a strong incoming tidal current
45
how are double spits formed?
1) as LSD is operating in different directions on opposite sides of the bay 2) when rising sea levels drive ridges of material onshore from the offshore zone 3) a barrier beach driven across the bay forms a bar, but a strong exiting river current may breach the bar to form a double spit
46
what causes the dynamic nature of spits?
- wave refraction: the waves will be continually shaping and reshaping spits by depositing and eroding sediment on the shoreline. - LSD: sediment is transported along the coastline by the action of the waves and their currents. the movement of the sediment = growth of spits - wind: can affect the shape of the spit by affecting the distribution of sediment along the shoreline. can cause more erosion and deposition - human activities: coastal development can either accelerate and decelerate the growth of spits
47
what threatens spits?
1) coastal development - construction of marinas, resorts can disrupt the natural flow of sediment and can lead to changes in the natural formation of spits 2) sea level rise - increased erosion 3) invasive species - alter the vegetation composition of spits and destabalise them by reducing the sediment trapped 4) pollution - degrade water quality and harm coastal ecosystems
48
what are the types of mass movement?
slides: - rockfalls - rockslide - slumps/rotational slumping flows: - soil creep - solufluction - earth flows
49
what is mass movement?
movement of soil, regolith and rock under the action of gravity acting on unstable slopes but can be exacerbated by: - weathering - excess water content. the presence of water reduces friction making movement more likely - reduction of vegetation cover
50
what is the speed of movement for slides?
increase water reduces friction between bedding planes allowing slabs of rack to slide over underlying rock - seaward angle of dip
51
what is the speed of movement for slumps?
in saturated conditions - difference between sliding and slumping, it's rotational movement with slumping common where softer rock overlies
52
what is the speed of movement for rockfalls?
slopes over 40 degrees - strong jointed, steep cliffs exposed to mechanical weathering or undermined by marine erosion at the base
53
what is the speed of movement for mudflow?
heavy rain reduces friction causing earth and mud to flow over underlying rock - material becomes mixed/jumbled
54
what is the speed of movement for soil creep?
slowest form and can be continuous, pulled by gravity - repeated expansion and contraction of soil particles during wet and dry conditions
55
what is the speed of movement for solifluction?
5cm-1m per year - tundra areas where ground frozen when top layer thaws in summer it becomes saturatied and flows over the frozen sub soil

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