Coastal landforms and SL changes Flashcards
1
Q
Backshore
A
Between high-water mark and limit of wave activity
Sand dunes are formed here
Change only usually takes place here during storms
2
Q
Foreshore
A
Between high-water mark and low-water mark
Most important zone for marine processes
Visible at low tide
3
Q
Offshore
A
Beyond point where waves cease to impact upon the seabed
Deposition of sediment mainly occurs here
4
Q
Nearshore
A
Between the low-water mark and the point off the coast where waves no longer have any effect on the land beneath them
5
Q
3 inputs of coastal systems
A
Coastal geology
Climate
Nature of waves
6
Q
5 processes in coastal systems
A
Erosion
Weathering
Deposition
Wave refraction
Sea level change
7
Q
2 outputs of coastal systems
A
Sediment
Landforms
8
Q
3 types of cliffs
A
Horizontal beds
Seaward
Landward
9
Q
Horizontal bed
A
Near vertical beds
Produce steep cliffs
10
Q
Seaward cliff
A
Loose material slides down the bedding planes
Makes it unstable and dangerous
11
Q
Landward cliff
A
Bedding planes sloping towards land
Relatively steep but stable
12
Q
5 steps of how a wave-cut platform is formed
A
- Destructive waves break at the foot of the cliff
- Erosion, hydraulic action and corrasion in particular
- Cliff becomes undercut forming a wave-cut notch
- Cliff above is weathered and put under stress, eventually collapses
- After a series of collapses, a wave-cut platform begins to develop between the high and low water marks
13
Q
3 steps of how a cave is formed
A
- Weakness in the rock of a headland
- Hydraulic action exploits the rock
- Cliff is undercut and a cave is formed
14
Q
3 steps of how a blow-hole is formed
A
- Cave facing oncoming waves is exposed to full force of the waves applied to the back of the cave
- Weathering can erode the top of the cliff
- Overlying rocks can be sufficiently weakened and collapse forming a blow-hole
15
Q
2 steps of how an arch is formed
A
- A cave is eroded on either side of a headland
- Can erode right through the headland to form an arch
16
Q
2 steps of how a stack is formed
A
- Roof of an arch is eroded by sub-ariel processes and chemical weathering
- Roof becomes unstable and eventually collapses creating a stack
17
Q
2 steps of how a stump is formed
A
- A stack is subject to erosion, upper part of the stack is weathered, base of the stack is eroded
- Over time the whole stack collapses creating a stump
18
Q
Beach
A
Accumulation of sediment to create a depositional landform
19
Q
Swash-aligned beach
A
Waves approach perpendicular to the coast
Limited longshore drift
20
Q
Drift-aligned beaches
A
Waves approach at an angle
Sediment travels along the beach
Longshore drift
21
Q
2 types of spits
A
Simple
Compound
22
Q
Simple spit
A
Straight or recurved but do not have minor spits along their landward edge
23
Q
Compound spit
A
Have a series of minor spits or recurved ridges along their landward side
24
Q
4 steps of how a spit is formed
A
- Occurs when there’s a sudden change in coast direction (estuary/river mouth)
- Longshore drift continues to deposit sediment in line with the coast but at sea
- Changes in wind/wave refraction leads to a curved spit
- Multiple curved ends cause a compound spit
25
Example of a simple spit
Spurn Head, Humberside
26
Example of a compound spit
Hearst Castle, Hampshire
27
2 steps of how a tombolo is formed
1. Longshore drift causes a spit to grow out and connect to an island from the mainland
2. Waves moves around the island, when waves meet at the other side of the island, energy falls and material is deposited
28
2 ways a tombolo can be formed
Longshore drift
Wave refraction
29
Barrier beach
Where a spit extends across a bay and joins two headlands together
30
Tombolo
Island connected to the mainland by a mound or ridge of sediment
31
Spit
Long, narrow ridge of deposited sediment which are joined to the mainland at one end and stick out to sea at the other end
32
2 steps of how a barrier beach is formed
1. Longshore drift continues to deposit sediment across a bay
2. Deposited material joins two headlands together
33
Lagoon
Store of water behind a barrier beach
34
2 steps of how a barrier island is formed
1. Formation of a barrier beach between two headlands
2. Barrier beach becomes separated from the mainland to create a barrier island
35
Barrier island
Where barrier beaches become separated from the mainland
36
Example of barrier islands
West Frisian Islands, Netherlands
37
3 steps of how an offshore bar is formed
1. Sand is deposited as waves don't have enough energy to carry the sediment to shore
2. Absorb wave energy so reduce impact of wave energy
3. Act as sediment sinks
38
8 steps of how a sand dune is formed
1. Wind blows sand landwards from beach
2. Large tidal range allows the sand to dry, therefore light enough to be transported by the wind to the back of the beach
3. Dunes develop due to vegetation succession
4. Pioneer species (couch grass) create embryo dune and help to stabilise the sediment
5. Dunes grow and become out of reach of high tide and become yellow dunes
6. More sand accumulates and organic matter (humus) is added, called grey dunes
7. Dune slacks occur between the dunes the water table is at the surface
8. Mature dunes are the climatic climate when trees are able to colonise the area to create woodland
39
Embryo dune (6)
- less than 1 metre
- 80% exposed sand
- humus content <1%
- pH 8-8.5
- couch grass, sea rocket
- 'fore dunes'
40
Yellow dune (5)
- 5 metres
- 20% exposed sand
- humus content 2.5%
- pH 7.5
- marram grass
41
Grey dune (5)
- 8-10 metres
- <10% exposed sand
- humus content 10%
- pH 6.5
- low shrubs (brambles)
42
Dune slack (4)
- humus content 25%
- high moisture levels
- pH 5.5
- aquatic plants
43
Woodland (4)
- 100% vegetation cover
- humus content 40+%
- pH 4.5
- gorse, oak trees, pines
44
Succession
Cumulative change in the types of plant species that occupy an area of land through time
45
2 types of estuarine landforms
Mudflats
Saltmarshes
46
steps of how a mudflat/saltmarsh is formed
1. Formed at low energy coastlines
2. Flowing water carrying lots of suspended sediment meets saline sea water which causes flocculation to happen as clay particles join together (aggregate)
3. Larger, heavier particles sink to the bed of an estuary or behind a spit
4. They become exposed at low tides and can become saltmarshes where vegetation grows
47
Sea level
Mean level between high tide and low tide
48
Eustatic sea level change
Change in the relative level of sand and sea due to rises and falls in the global sea level
49
Isostatic sea level change
Rise and fall of land in relation to the sea level
50
3 causes of isostatic change
Tectonic activity
Glaciation
Post-glacial readjustment
51
Tectonic activity impacting sea level change (I)
Land can move up and down with tectonic activity
Making the sea level rise/fall
52
Glaciation and post-glacial readjustment impacting sea level change (I)
During ice ages, glaciers and ice sheets form over land in cold areas
Puts pressure on the mantle and causes the land surface to be pressed
After the ice age when the ice melted, caused the aesthenosphere to rebound back up (isostatic recovery)
Causing relative sea level rise
53
3 causes of eustatic sea level change
Thermal expansion of water
Changes in ice sheet extent
Tectonic activity
54
Thermal expansion of water (E)
As water heats up, it expands
Mass of the ocean stays the same but warmer oceans have a larger volume to occupy more space
Causing sea level rise
55
Changes in ice sheet extent (E)
Ice forms on land during glacial periods, removes water from other stores including oceans
Causing sea level fall
When ice melts on land, sea levels then rise
56
Tectonic activity (E)
New land can be formed when tectonic plates move apart
Takes up space in the ocean
Water is displaced and sea levels rise
57
3 emergent coastline landforms
Raised beaches
Relict cliffs
Raised marine platforms
58
3 submergent coastline landforms
Rias
Fjords
Dalmatian coasts
59
Previous sea level changes
Always been rising
60
9 impacts of sea level change
1. Major UK cities at risk of inundation
2. UK agricultural land may be lost through flooding and coastal erosion
3. Major road and rail links are at risk
4. Power stations, gas and oil terminals often built along the coast are at risk of flooding
5. Groundwater (aquifers) may become contaminated with sea water
6. River flooding may increase
7. Loss of coastal habitats#
8. Submergence of low-lying islands (Maldives)
9. Migration of people away from coastal areas
61
Offshore bar
Submerged (partly exposed) ridges of sand or coarse sediment created by waves and currents offshore from the coast
62
Raised beaches
Where sea level drops relative to the land
What was the beach becomes stranded at the high-water mark
Once above high-tide level, vegetation grows
63
Relict cliffs
Caves left above the high-tide level
64
Raised marine platform
Relatively flat surface which lies above the current sea level
65
Rias
Flooded river mouths/valleys
Example: Mouth of the River Exe, Poole Harbour
66
Fjords
Flooded glacial valleys
Very steep sides
67
Dalmatian coasts
Where river systems flow parallel to the coast
Parallel to the coastline
Long islands which would have previously been hills along valley sides
