Tectonics Flashcards
1
Q
Earthquake
A
A sudden violent shaking of the ground caused by the sudden release of energy in the earths lithosphere that creates seismic waves
2
Q
Volcano
A
An opening in the earths crust where magma - a mixture of red hot liquid rock, mineral crystals, rock fragments and dissolved gases from inside the planet erupts onto the surface
3
Q
Collision plate margin
A
A type of plate where two continental plates collide, resulting in the land being pushed upwards forming fold mountains
They cause earthquakes, but not volcanoes due to the lack of subduction
4
Q
Divergent plate boundary
A
Two tectonic plates move apart
5
Q
Convergent plate boundary
A
Two plates are moving towards each other
6
Q
Conservative plate boundary
A
Two plates slide horizontally past each other
7
Q
Subduction
A
The process that occurs when two tectonic plates meet at convergent boundaries, and one of the plates moves under the other due to gravity and differences in density
8
Q
Continental crust
A
The thicker, less dense, and older layer of the earths lithosphere
9
Q
Intra plate earthquakes
A
An earthquake that occurs within a tectonic plate rather than at a plate boundary, often linked to ancient fault lines or hotspots
10
Q
Intra plate volcanoes
A
Volcanic eruptions that occur within a tectonic plate, far from a plate boundary often associated with hotspots and mantle plumes.
11
Q
Mantle plume
A
A large column of hot semi molten rock rising from the earth mantle causing volcanic activity and the formation of hotspots and volcanic island chains
12
Q
Hot Spot
A
Volcanoes found away from the plate boundary, due to a magma plume closer to the surface.
13
Q
Jokulhaup
A
A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption.
14
Q
Lahar
A
A flow of mud and debris.
15
Q
Lithosphere
A
The upper crust of the Earth, with an average thickness of 100km.
16
Q
Love Waves
A
A surface earthquake wave with horizontal displacement.
17
Q
What is the earths internal structure?
A
Inner core, outer core, mantle, crust
18
Q
Convection
A
The movement of particles through a substance transporting their heat energy from hotter areas to cooler areas
19
Q
Oceanic Crust
A
Crust, usually thinner than continental crust, that forms the sea floor, on average 7km thick.
20
Q
Paleomagnetism
A
The alternating polarisation of new land created; as magma cools, the magnetic elements align with the Earth’s magnetic field.
21
Q
Ridge push
A
The force that causes oceanic plates to move away from mid ocean ridges due to the higher elevation and gravitational pull of the Newley formed warmer crust
22
Q
Constructive plate margin
A
Two tectonic plates move apart allowing magma from the earths mantle to rise and form new crust.
23
Q
Primary Waves
A
An earthquake wave causing compressions within the body of rock.
24
Q
Pyroclastic Flow
A
A mixture of gases and rock fragments, at high temperatures travelling at rapid speeds.
25
Sea floor spreading
The geological process where new oceanic crust is formed at mid ocean ridges as tectonic plates pull apart allowing molten magma to rise and solidify creating new oceanic crust floor and contributing to plate movement.
26
Destructive plate margin
Two tectonic plates collide and one plate is forced beneath the other (subduction) leading to earthquakes and volcanic activity
27
Secondary Waves
An earthquake wave causing vertical displacement within the body of rock.
28
Seismic Waves
The energy released during an earthquake, in the form of Primary, Secondary, Love, and Rayleigh Waves.
29
Slab Pull
The force contributing to the movement of tectonic plates, due to the weight of the plate.
30
Tsunami
Initial vertical water displacement (often from a submarine earthquake) creates waves with large destructive power.
31
Transform plate margin
Two tectonic plates slide past one another horizontally brother creating nor destroying crust
32
Focal depth
The depth in which and earthquake starts
33
Benioff zone
A region of the subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate.
34
How many earthquakes occur close too or at a plate boundary
95%
35
Which plate boundaries do earthquakes occur at?
Convergent or conservative
36
When do intrastate earthquakes occur
When major ancient fault lines are reactivated by tectonic stress
37
What percentage of earthquakes occur around the ring of fire?
75%
38
At which plate boundaries do volcanoes occur
Convergent and divergent
39
When do intraplate volcanoes occur?
Isolated plumes of convected heat called mantle plumes rise towards the surface of the earth and break through the crust particularly if it is weaker or has faults.
This generates volcanoes that erupt constantly.
40
What do tectonic plate boundaries represent?
The locations of ascending and descending arms of convection currents in the mantle
41
Crustal fracturing
The earths crust cracks
42
Liquefaction
A hazard in areas where the ground consists of loose sediment
Ground shaking compacts the sediment forcing water out undermining foundations and causing buildings to sink
43
Landslides
A mass movement of material such as rock earth or debris, down a slope
44
Lava flows
A flow of magma that runs down the surface of a volcano
45
Ash falls
A solid material of varying grain size ejected into the atmosphere
46
Gas eruptions
The release of volcanic gases either during and eruption or through vents when the volcano is dormant
47
At what speed do tectonic plates move?
2-5cm per year
48
49
What type of volcanoes do constructive plate margins create?
Small effusive eruptions
This id due to low gas eruptions and low viscosity lava
50
What type of volcanoes do destructive plate margins create?
The descending plate melts creating magma with a high gas content which erupts with an exploding force
51
What type of earthquakes do constructive plate margins create?
Shallow and low magnitude (>0.5)
52
What type of earthquakes do destructive plate margins create?
They follow the line of the Benioff zone yielding large earthquakes up to a 9.0 magnitude
53
What type of earthquakes do conservative plate margins create?
Shallow focal depths meaning high magnitude, very destructive
54
In which order do seismic waves occur.
P waves
S waves
L waves
55
Which type of seismic wave causes the most damage?
L waves
56
What are secondary hazards of earthquakes?
Landslides and liquefaction
57
What are primary hazards of earthquakes?
Ground shaking and crustal fracturing
58
What are the primary hazards of volcanoes?
Lava flow
Pyroclastic flow
Ash fall
Gas eruptions
59
What are the secondary hazards of earthquakes?
Lahars
Jokulhlaups
60
How does a tsunami occur?
When oceanic crust is jolted during an earthquake all water is displaced
Due to gravity the water is pulled back down and the energy generated by this travels through the water like a wave
As the water gets closer to the coast the sea level decreases creating friction between the sea bed and waves
The waves slow down creating a wall of water aka the tsunami
61
Where do tsunamis mostly occur?
In subduction zones
62
What do the impacts of tsunamis depend on?
Various human and physical factors such as:
Population density
Coastal defenses
Duration
Shape of land
Warning and evacuation
Level of economic and human development
63
Natural hazard
A natural event that threatens people or has the potential to cause damage, destruction and death
64
Disaster
A serious disruption of a community or society, involving significant human,material, economic, and environmental losses, exceeding the communities ability to cope using its own resources
65
Vunerablilty
The risk of exposure to hazards combined with the inability to cope with them
66
Community
A group of people who share a sense of place, social connections and often a common identity whether based on location, shared interests or other characteristics
67
Hazard risk equation
Risk = hazard x vulnerability / capacity to cope
It helps understand the likelihood of a hazard causing harm, considering the nature, vulnerability and capacity to cope
68
Pressure and release model
A framework that explains how disasters occur by analysing the interplay of root causes, dynamic pressures, and unsafe conditions with a natural hazard leading to social vulnerability
69
Mercalli scale
Measures the intensity of an ear quakes effects on people, buildings, and landscape
70
Moment magnitude scale
A measure of an earthquakes energy released, considered the most accurate measure
71
Volcanic explosively index
A measure of the magnitude of a volcanic eruption
72
Magnitude
The side or strength if a hazard event measured as the amount of energy released
73
Speed of onset
how quickly a natural hazard event, like an earthquake or flood, reaches its peak and impacts an area, ranging from instantaneous to gradual
74
Areal extent
the size or geographical area affected by a particular phenomenon or hazard
75
Duration
the length of time a phenomenon or process lasts, while extent describes the area or scope over which something occurs or is visible
76
Frequency
how often a specific hazard (like an earthquake or volcanic eruption) occurs
77
Spatial predictability
the extent to which the location of a hazard or phenomenon can be known in advance
78
Hazard profiles
a tool that summarizes the physical characteristics of a specific hazard, including its magnitude, speed of onset, areal extent, duration, frequency, and spatial predictability
79
Population density
the number of people living in a specific area, usually expressed as the number of people per square kilometer or square mile
80
Degree of urbanisation
the proportion of a country's population living in urban areas (towns and cities) compared to rural areas
81
Resilience
the ability of a system, community, or society to absorb, adapt to, and recover from a hazard or shock, maintaining its essential functions and structures
82
Mega disaster
a high-magnitude, high-impact, infrequent disaster that affects multiple countries, either directly or indirectly, leading to regional or even global consequences
83
Multiple hazard zone
a location where two or more natural hazards, both geophysical and hydrometeorological, can occur, potentially interacting to cause complex disasters
84
Hydrometeorolocial
a natural hazard caused by a combination of water-related (hydrological) and weather-related (meteorological) processes
85
Prediction
knowing when, and where, a natural hazard will strike so that meaningful action can be taken
86
Forecasting
predicting future events or conditions, often related to natural hazards or weather patterns, based on scientific knowledge and data analysis, with a focus on providing a percentage chance of an event occurring
87
Hazard management cycle
a systematic process that outlines the stages of managing hazards, aiming to reduce the impact of disasters through proactive planning, effective response, and learning from past events, encompassing preparedness, response, recovery, and mitigation
88
Parks model
A model describing the decline and recovery of country overtime following a natural disaster
89
Mitigation
strategies and actions aimed at reducing the severity or impact of a hazard, such as earthquakes or volcanic eruptions, by addressing the underlying causes and minimizing potential damage
90
Land use zoning
the allocation of different land uses (like residential, commercial, industrial) to specific areas, especially in urban contexts, to mitigate risks from natural hazards like earthquakes or other tectonic events
91
Adaptation
the adjustments made by ecosystems, societies, or individuals to cope with actual or expected climate change impacts, aiming to minimize harm and potentially benefit from new opportunities
92
What are the threshold levels for an event to be classed as a disaster?
10 or more deaths
100 or more people effected
US $1 million in economic losses
93
Why is the relationships between risks, hazards and people complex?
Unpredictability of hazards
Lack of alternatives e.g. people staying pour due to work etc
Dynamic hazards e.g. threats changing overtime
Cost benefit
Russian roulette reaction e.g. acceptance of the risks whatever you do
94
What three types are the impacts of hazards?
Social e.g. deaths, injuries
Economic e.g. the loss of property, businesses, infrastructure
Environmental e.g. damage or destruction of physical systems
95
Why is comparing the impacts of hazards between countries difficult?
Both the physical nature of the event and the socio-economic profiles of affected places are different
Differences include:
Economic costs
Deaths
Type of hazard
96
How does low level of development increase risk?
Population growth
Urbanisation and urban sprawl
Environmental degradation
Loss of community memory about hazards
Very young, or very old population
Ageing, inadequate infrastructure
Greater reliance on power, water and communication systems
97
Why is vunerablility higher in low human development countries?
many people lack basic needs of sufficient water and food even in 'normal' times
much housing is informally constructed with no regard for hazard resilience
access to healthcare is poor, and disease and illness are common
education levels are lower, so hazard perception and risk awareness is
98
What is the link between governance and vulnerability?
**Meeting basic needs** - When food supply, water supply and health needs are met the population is physically more able to cope with disaster
**Planning** - Land-use planning can reduce risk by preventing habitation on high risk slopes, areas prone to liquefaction or areas within a volcanic hazard zone
**Environmental Managament** - Secondary hazards, such as landslides, can be made worse by deforestation. The right monitoring equipment can warn of some hazards, such as lahars.
**Preparedness** - Education and community preparation programmes raise awareness and teach people how to prepare, evacuate and act
**Corruption**- Siphoning off money ear-marked for hazard management or 'kick-backs' and bribed to allow illegal or unsafe buildings increase vulnerability.
kick-back = illicit payment made in exchange for facilitating a transaction
**Open-ness** - Governments that are open, with a free press and media, can be held to account, increasing the likelihood that preparation and planning take place.
99
What geographical factors influence the nature of tectonic hazards?
**Population density** : highly populated areas may be hard to evacuate and are likely to be hit harder by an earthquake
**Degree of urbanisation**: when cities are struck by major earthquakes, death tolls can be high because of the concentration of at-risk people.
**Isolation and accessibility**: often rural areas are hit less hard than urban areas by the initial impact of the disaster, but isolation and limited access can slow the rescue relief effort.
100
What are the 3 trends for all disasters?
1. Deaths have fallen over time because of better response management, preparation and, in some cases, prediction. Numbers of deaths have fallen, especially since 2000, which may be due to vastly improved mobile communications to warn people about disasters.
2. The number of reported disasters increased then stabilised as improvements in data coverage and the accuracy of databases increased. Decades ago, many disasters in isolated areas simply went unreported. More recently, the number of reported disasters have fallen, suggesting fewer hazard events are becoming disasters.
3. The number of people affected by disasters continues to rise as populations grow and more people live in risky locations.
101
Have economic losses from tectonic hazards risen or fallen?
Economic losses from tectonic disasters continues to rise. More people, who are more affluent, have more property to lose. This is increasingly true in emerging countries as well as developed ones.
102
What are the characteristics of multiple hazard zones?
- are tectonically active and so earthquakes (and often eruptions) are common
- are geologically young with unstable mountain zones prone to landslides
- are often on major storm tracks either in the mid-latitudes or on tropical cyclone tracks
- may suffer from global climate perturbations such as El Niño and La Niña
103
Prediction and forecasting of earthquakes
- Cannot be predicted (despite decades of scientific research)
- Only areas at high risk can be identified (risk forecasting), plus areas that are likely to suffer severe ground shaking and liquefaction; this can be used for land-use zoning purposes
- 'Seismic gaps', i.e. areas that have not experienced an earthquake for some time and are 'overdue' can point to areas of high risk
104
Prediction and forecasting of volcanoes
- Can be predicted
- Sophisticated monitoring equipment on volcanoes can measure changes as magma chambers fill and eruption nears
- Tiltmeters and strain meters record volcanoes 'bulging' as magma rises and seismometers record minor earthquakes indicating magma movement
- Gas spectrometers analyse gas emissions which can point to increased eruption likelihood.
- The minimal death toll from volcanic eruptions (despite 60-80 eruptions per year) can be mainly attributed to vastly improved prediction of these events.
105
Prediction and forecasting of tsunamis
- Can be partly predicted
- An earthquake-induced tsunami cannot be predicted
- However, seismometers can tell an earthquake has occurred and locate it, then ocean monitoring equipment can detect tsunami in the open sea
- This information can be relayed to coastal areas, which can be evacuated.
106
What are the 4 stages of the hazard management cycle?
1. **Response** - Immediate help in the form of rescue to save lives and aid to keep people alive, emergency shelter, food and water.
2. **Recovery** - Rebuilding infrastructure and services, rehabilitating injured (physically and mentally) people and their lives
3. **Mitigation** - Acting to reduce the scale of the next disaster: land-use zoning, hazard-resistant buildings and infrastructure.
4. **Preparedness** - Community education and resilience building including how to act before, during and after a disaster, prediction, warning and evacuation technology and systems
5. (Repeat)
107
What does the recovery stage of the hazard management cycle depend on?
- the magnitude of the disaster - bigger means longer
- development level - lower means longer, as poorer people are more severely affected
- governance, because well governed places will divert resources more effectively to recovery efforts.
- external help, i.e. aid and financing to help the recovery effort
108
What are advantages of hi-tech scientific monitoring in predicting volcanic eruptions?
- In most cases, predicting an eruption is possible
- Warnings and evacuation save lives
109
What are disadvantages of hi-tech scientific monitoring in predicting volcanic eruptions?
- Costly, so not all developing world volcanoes are monitored
- May suffer from 'cry wolf syndrome' if predictions are not accurate. This is where predictions (and evacuation) are wrong, so people are less lively to believe the next one.
- Does not prevent property damage
110
What are advantages of community preparedness and education?
- Low cost, often implemented by NGOs
- Can save lives through small actions
111
What are disadvantages of community preparedness and education?
- Does not prevent property damage
- Harder to implement in isolated rural areas
112
What are advantages of adaptation?
- save both lives and property
113
What are disadvantages of adaptation?
- High population densities prevent it
- Disrupts people's traditional homes and traditions
114
What are advantages of short term emergency aid?
- Reduces death toll by saving lives and keeping people alive until longer-term help arrives
115
What are disadvantages of short term emergency aid?
- High cost
- Difficult to distribute in isolated areas
- Emergency services are limited and poorly equipped in developing countries
116
What are disadvantages of long term aid?
- Very high costs
- Needs are quickly forgotten by the media after the initial disaster
117
What are advantages of long term aid?
- Reconstruction can 'build in' resilience through land-use planning and better construction methods
118
What are advantages of insurance?
Allows people to recover economically by paying for reconstruction
119
What are diadvantages of insurance?
- Does not save lives
- Few people in the developed world have insurance.
120
What are strategies of modifying loss?
- short term emergency aid
- long term aid
- insurance
121
What are strategies of modifying vulnerability?
- high tech scientific monitoring
- community preparedness and education
- adaptation
