EQ3-Coasts Flashcards
1
Q
What three factors causes sea level to change on a daily basis ?
A
Tides, atmospheric pressures and winds
2
Q
How do high and low tides affect sea level ?
A
They cause the sea level to rise and fall every hour
3
Q
How does atmospheric pressures affect sea level ?
A
High pressure slightly lowers sea level, while low pressure raises it
4
Q
How do winds affect sea level ?
A
Winds push water toward the coast, altering wave height daily
5
Q
What is isostatic change ?
A
Local sea level change
6
Q
What are the 3 causes of isostatic sea level change ?
A
Land subsidence, post-glacial rebound, and accretion
7
Q
What is post glacial adjustment ?
A
When land rises after ice melts, causing sea levels to fall or rise locally
8
Q
What is eustatic change ?
A
Global sea level change
9
Q
How does accretion affect sea level ?
A
Sink regions in the sediment cell are experiencing net deposition, land is built up, leading to a fall in sea level
10
Q
What are the 3 causes of eustatic sea level change ?
A
Tectonic movement, ice ages, and steric effects
11
Q
How do ice ages affect sea level ?
A
Sea levels fall during ice ages as water is frozen, and rises in interglacial periods
12
Q
How do tectonic movements affect sea level ?
A
They can reshape open basins, altering global sea levels
13
Q
How do steric movements affect sea level ?
A
Thermal expansion causes sea level to rise as warmer water expands and takes up more space in an ocean
14
Q
What are two examples of emergent landforms ?
A
Fossil cliffs and raised beaches
15
Q
What are fossil cliffs ?
A
When coastline emergence from the sea, the fossilised remains of marine creatures can be seen in cliffs
16
Q
Give an example of a fossil cliff
A
Maria island, Tasmania
17
Q
What are raised beaches ?
A
Former wave cut platforms that are now above sea level due to uplift
18
Q
What are three examples of submergent landforms ?
A
Rias, Fjords, Dalmatian coastlines
19
Q
What are rias ?
A
River valleys that have been drowned through sea level rise or sinking land. They are not very deep and are v-shaped. They are carved by rivers.
20
Q
What are fjords ?
A
Drowned glacial river valleys formed as glacier melted and sea levels increased, which caused water to enter the valleys. They are u-shaped, carved by glaciers and they are very deep
21
Q
What are dalmatian coastlines ?
A
Anticlines and synclines are a result of plate folding due to tectonic activity. They were drowned after sea levels rose
22
Q
How does climate change cause eustatic sea level rise ?
A
Global warming leads to the melting of glaciers and polar ice sheets melting leading to the increased amount of water in the ocean
23
Q
What percentage sea level rise does the IPCC attribute to ice sheet melting ?
A
50% (greenland ice sheet 15%, Antartica ice sheet 10%)
24
Q
What percentage sea level rise does the IPCC attribute to thermal expansion ?
A
40%
25
How does tectonic activity contribute to sea level change ?
It can heat ocean water, change ocean basin volume and cause uplift or subsidence to the land
26
From 1990 until 2010 that IPCC claims that ice sheet melting caused 50% of sea level rise, thermal expansion caused 40% of the seal level rise but what was the other 10% ?
Thermal expansion
27
How can underwater volcanic activity cause thermal expansion ?
The emission of geothermal heat causes thermal expansion of ocean water
28
How does rising magma at constructive plate boundaries impact sea level ?
Rising magma domes the crust along mid-ocean ridges, reducing ocean basin volume and raising sea levels
29
How does folding at destructive plate margins causes sea level to fall ?
falling of plates increases of ocean basis volume
30
How do earthquakes contribute sea level change ?
Earthquakes can cause the seafloor to rise by uplifting the crust, reducing ocean basin volume, which raises sea level
31
How much did the 9.3 magnitude earthquake from the 2004 boxing day tsunami raise sea levels by, after lifting sections of the indian ocean bed ?
0.1mm
32
How can tectonic activity cause isostatic change ?
Faulting can raise or lower sections of the earth's crust, which can change sea levels by up to 2m
33
How much did Turakirae Head near wellington uplift in the 1855 earthquake ?
6m
34
What are the 3 geological physical factors that influence rapid coastal recession ?
Long wave fetch, cliffs with structural weaknesses and lithology
35
What are the 2 marine physical factors that influence rapid coastal recession ?
Strong longshore drift and destructive waves
36
What are the 2 human physical factors that influence rapid coastal recession ?
Dredging and coastal management
37
How does dredging contribute to rapid coastal recession ?
Dredging removes sand and gravel from the beaches, disrupting sediment cells
38
What is an example of dredging ?
Hallsands
39
Who decided to dredge hallsands ?
Sir John Jackson
40
How much sand and gravel was dredged at hallsands ?
1600 tonnes per day
41
By 1917 erosion at hallsands caused what ?
Only one house to be habitable
42
What is a case study on how coastal management can cause rapid coastal recession ?
The holderness Coast
43
The holderness coast experiences some of the highest rates of coastal in europe, with up to ..... of coastline eroding every year
2 metres
44
What material is the holderness coast made up of ?
Boulder clay / glacial till
45
What areas along the holderness coast have coastal defences ?
Hornsea, Mappletown, withernsea
46
The groynes at withernsea trap how many tonnes of sediment per year ?
12000 tonnes
47
How have the coastal defences at hornsea, mappletown and withernsea caused increased coastal recession ?
The defences have starved areas downdrift of sediment, leaving areas like spurn head to be more susceptible to erosion
48
The environmental agency notes that spurn head could lose up to .. ....... of land in the next 50 years if no further action is taken against the coastal defences causing the starvation of sediment
30 metres
49
What are deltas ?
Deltas are wetlands that form when a river empties its sediment into another body of water, with lower velocity such as an ocean
50
How does river flow slow down at the mouth to begin forming a delta ?
As the river approaches the mouth, it becomes wider, causing the water to spread out. This increases friction and reduces kinetic energy, slowing the flow of the water.
51
What happens when the river flow slows down in a formation of a delta ?
As the river slows, it deposits sediment through gravity settling. The river splits into distributaries, with heavier, coarser material settling first, and finer material like silt carried further downstream, this builds up new land forming a delta.
52
What is the finest material deposited by rivers in the formation of a delta called ?
Alluvium or silt
53
What are the properties of alluvium and silt ?
Very nurient rich with better water retention than sand and clay
54
Where are alluvium and silt deposited when a delta is formed ?
Beyond the rivers mouth
55
What is a delta case study ?
A nile delta
56
How many people live on the nile delta ?
39 million people
57
How much of egypts agricultural production is on the nile delta ?
2/3
58
What is offered around the nile delta , making it a hotspot for tourists ?
Leisure cruises and tours
59
What was built in the 1960's that altered the dynamic equilibrium that previously existed at the nile delta ?
The Aswan dam
60
Previously the nile delta was eroded by the mediterranean sea but wasn't largely impacted why is this ?
The delta had dynamic equilibrium as the material that was eroded was replaced by sediment deposition from the river
61
Why was the Aswan dam built ?
To stop flooding and provide hydroelectricity
62
How did river discharge per year change after the Aswan dam was built ? Why ?
River discharge fell from 35 million m³ per year to 10 million m³ per year.
63
Why did the river discharge per year at the nile delta fall after the aswan damn was built
Water was withdrawn from the reservoir behind the damn, Lake Nassar, for industry, cities and farming
64
How much did sediment volumes per year decrease after the construction of the aswan dam ?
Sediment volumes fell from 130 million tonnes to 15 million tonnes per year
65
Why did sediment volume fall at the nile delta following the construction of the aswan dam ?
Sediment is trapped by the reservoir and dam
66
What are the 4 temporal variations in coastline recession ?
-Wave direction and fetch
-tides
-seasons
-weather systems
67
How does wind direction and fetch affect coastline recession ?
Winds with a large fetch can build destructive waves and cause rapid coastal recession, especially when the wind direction aligns with the largest fetch
68
The north norfolk coastline has a rare dominant wind from the north, with a 16km fetch across the norwegian and norths, which can produce recession rates up to ?
8m per annum
69
Why are rates of coastal recession more rapid during high tide ?
Deeper water in the foreshore zone allows waves to reach higher energy when they reach the backshore, increasing erosion.
70
What causes particularly high spring tides ?
Spring tides occur twice each lunar month when the gravitational pull of the moon and sun align
70
How often do high tides occur ?
Twice a day often 12 hours apart
71
Why is coastal recession faster in the winter than summer ?
Storms are more frequent in winter due to a greater contrast in temperature and pressure between tropical and polar air masses
72
How does winter affect the coastal recession at the holderness beach ?
Erosion rates of 2-6m are common
73
What two things can combine to make for the most effective coastal recession ?
Spring tides and winter storms
74
What are two main types of weather systems that affect coastal recession ?
High pressure anticyclones and low pressure depressions
75
How do anticyclones affect coastal recession ?
Anticyclones cause gentle winds and small waves, leading to low rates of coastal recession
76
How do depressions affect coastal recession ?
Depressions create strong winds and large waves leading to rapid coastal recession
77
What is coastal flooding ?
Coasal flooding occurs when the sea floods onto land due to weather systems or rising sea levels
78
How can mid latitude depressions cause coastal flooding ?
Depressions are low pressure systems formed by warm tropical and cold polar air meeting, leading to storm surges
79
In Dhaka, Bangladesh how many people live on a delta that is prone to flooding ?
14 million
79
How do hurricanes contribute to coastal flooding ?
Hurricanes are low pressure systems that form near the equator, generating large storm surges and heavy rainfall
80
Why are deltas particularly vulnerable to coastal flooding ?
Sea level rise can easily disrupt the dynamic equilibrium between erosion and deposition, increasing flood risks
81
By how much does the IPCC predict sea levels could rise by 2100 ?
55cm
82
What is a storm surge ?
A change in sea level due to low air pressures, caused by deppresions or hurricanes
83
What are the 5 factors that could change the impact of a storm surge ?
-Coastal topography
-strong winds
-high/spring tides
-land subsidence
-vegetation removal
84
How does coastal topography affect storm surges ?
Narrow coastlines, like in the north sea, funnel water into a smaller area, increasing coastal flooding risk
85
How do strong winds worsen storm sturges ?
They push waves onshore, increasing wave height essentially raising sea levels
86
How can high or spring tides make storm surges worse ?
They add extra height to the sea level, making flooding more severe
87
How does land subsidence contribute to storm surges ?
Tectonic activity or post glacial rebound lowers land height, making sea levels rise in relation to sand
88
How does vegetation removal increase storm surge risk ?
Removing natural buffers like mangroves increases flood risk as roots help to build soil, slow water flows, encourage deposition and reduce erosion
89
What is an example of a storm surge ?
The 2013 north sea storm surge
90
What was the 2013 uk storm called that caused the storm surge ?
Storm xavier
91
What factors contributed to the 2013 north sea storm surge ?
A combination of low pressure and high spring tides
92
How many deaths occured in the uk due to the 2013 north sea storm surge ?
2
93
How many homes were flooded in the uk due to the 2013 north sea storm surge ?
1400 homes were flooded
94
How did the thames barrier help during the 2013 north sea storm surge ?
The thames barrier being raised was estimated to protect 800,000 homes according to the environment agency
95
What was estimated the total amount of economic loss of the 2013 storm surge ?
100 million
96
What happened in 2007, Bangladesh ?
A tropical cyclone
97
What was the economic status of bangladesh at the time of the 2007 tropical cyclone ?
An LIC
98
What category was the tropical cyclone in bangladesh, 2007 ?
Category 4
99
How much road infrastructure was destroyed in the 2007 bangladesh cyclone ?
8000km of roads
100
How many people died in the 2007 bangladesh cyclone ?
over 3000
101
How many homes were lost in the 2007 bangladesh tropical cyclone ?
1.5 million
102
What was the total costs of damages in the 2007 bangladesh tropical cyclone ?
1.7 billion
103
What percentage of the population in bangladesh lived below sea level during the 2007 bangladesh tropical cyclone ?
46%
104
How did the bangladeshi government cause the flooding from the cyclone to be worse ?
They allowed for mass deforestation of mangrove forests
104
What topographic feature of bangladesh made it more vulnerable to the 2007 tropical cyclone ?
Low lying land, in the funnel shaped bay of bengal
105
How many islands make up the maldives ?
Around 1200 islands
106
What is the population of the maldives ?
340,000 people
107
What would a 50cm sea level rise by 2100 cause in the maldives ?
The maldives would lose 77% of its land area
