Tectonics Flashcards
1
Q
What is a Seismic Hazard?
A
- A hazard that affects rocks within 700km of the Earth’s surface
2
Q
What is a Volcanic Hazard?
A
- A hazard that involves eruption events
3
Q
What is an Oceanic Fracture Zone?
A
- A belt of activity through the oceans in Africa, Red Sea, Dead Sea and California
4
Q
What is a Continental Fracture Zone?
A
- A belt of activity following the mountain ranges in Spain and the Alps. It runs across to the Middle East, the Himalayas and East Indies.
- it cuts off in the Philippines
5
Q
What are Ancient Fault Lines?
A
- Old tectonic fault lines that are constantly under stress but hardly tremor
- E.g -> Stretton Fault Line in South Shropshire UK
6
Q
What is the Hotspot Theory?
A
- High heat and lower pressure at base of Lithosphere allow rocks to melt
- Magma rises though cracks + erupts to form active volcanos
- As plate continues to move over plume, land passes over hotspot + another volcano forms
- Creates volcanic island chains like Hawaii
7
Q
What is a Volcanic Hotspot?
A
- An area in the mantle from which heat rises as a thermal plume from deep on the Earth
8
Q
What are the three important theories linked to convection currents?
A
- Continental drift
- Sea floor spreading
- Palaeomagnetism
9
Q
What evidence is there for the Continental Drift Theory?
A
- Continental Fit -> Visible that countries slot together
- Geological evidence, rocks of the same age and type found where countries would have fit together
- Similar fossil formations found in separated areas
- Climatological evidence, places that are no longer tropical, have evidence of once being tropical
10
Q
What evidence is there for the Sea Floor Spreading Theory?
A
- Harry Hammond -> Dive in the ocean and found mid-ocean ridges, above sea level
- Sea floor at the ridges was younger than to the side
- Rock near the ridges formed by the spreading of the rock
11
Q
What evidence is there for the Palaeomagnetism Theory?
A
- Vine and Matthews -> Very young rock at places on or near ocean ridges
- Magnetic domains within iron-rich minerals in lava are aligned with the magnetic field of the Earth -> Means they can record polarity of the earth
- Shows the polarity changes every 400,000 years -> Poles switch
12
Q
Wha are Benoiff Zones?
A
- Path of a subducting plate
- Angle of subduction tells us where earthquakes may occur
- Different speeds + movement of rock at this point produce numerous earthquakes
- Medium + deep focused earthquakes
- Important in determining earthquake magnitude
- Determines position and depth of hypo centre
13
Q
What are Locked Faults?
A
- Significant tectonic hazards
- Usually found at leading edge of subduction zone
- Stuck due to frictional resistance being greater that the sheer stress
- can store strain for extended periods -> Eventually released in large magnitude earthquakes
14
Q
What is the Slab Pull Theory?
A
- Plates are ‘pulling’ themselves along
- Thinner plate subjects and pulls on plate behind it
- Magma in the mantle helps to pull the slabs due to convection currents
15
Q
What is a Divergent (Constructive) plate margin?
A
- Two plates moving apart, forms new crust
- Forms mid-ocean ridges in the ocean and on continents forms riff valleys
16
Q
What is a Convergent (Destructive) Subduction plate boundary?
A
- Oceanic plate is denser than continental plate
- Oceanic plate slides beneath continental plate into mantle
- Crates deep ocean trenches and forms fold mountains
17
Q
What is a Convergent (Destructive) Collision plate boundary?
A
- Two continental plates meet
- Plates are less dense than asthenosphere which means no subduction occurs
- Particles crumple and form fold mountains -> Like Himalayas
18
Q
What is a Conservative/ Transform plate boundary?
A
- Two plates slide past each other forming a conservative margin
- Breaks the crust
- Called a fault
19
Q
What are the 4 types of Seismic Waves?
A
- Primary
- Secondary
- Rayleigh
- Love
20
Q
What are Primary Waves?
A
- Seismic waves that occur immediately during an earthquake
- They are a bodywave
- Travel through liquids and solids
- Push and pull the earth in the same direction as the waves
- Fastest waves
21
Q
What are Secondary Waves?
A
- Seismic waves that occur immediately after an earthquake has happened
- Are a bodywave
- Only travel through solid -> Not the core
- Move body + surface from side to side
22
Q
What are Rayleigh Waves?
A
- Surface wave
- Travel through solids + liquids
- Move surface in a rolling motion
23
Q
What are Love Waves?
A
- Surface wave
- Travel through solid but not liquid
- Move through surface
- Move 10 Degrees side to side
24
Q
What are causes and impacts of earthquakes?
- Is it a primary or secondary hazard?
- Case Study?
A
- Primary Hazard
- 95% occur along plate boundaries -> When they rub together and build up pressure
- Pressure is released at focus/ hypo centre -> Most damage occurs at epicentre on surface
- 10,000 people die every year as a result
- Case study = Haiti 2010
25
What are causes and impacts of Landslides + Avalanches?
- Are they Primary or Secondary?
- Case Study?
- Secondary Hazard
- Ground shaking destabilises cliffs + Steep slopes -> Causes landslides, rockslides, mudslides and avalanches
- More likely as a result of heavy rain + unconsolidated or fractured rocks
- Many effects account for damage caused by earthquake
- Case Study = Christchurch 2010, Nepal
26
What are causes and impacts of Tsunamis?
- Are they Primary or Secondary?
- Secondary Hazard
- Generated by an earthquake under the ocean -> When large amounts of water is displaced by moving of tectonic plates
- Can move with speed
- Wall of water that can sweep miles inland destroying everything in their path
27
What are causes and impacts of Fire?
- Are they Primary or Secondary?
- Secondary
- Caused by fractured gas mains following and earthquake in built up areas
- Water mains may also be fractured making fire hard to extinguish
- Spread quicker in LIC's where properties are built with wood
28
What are causes and impacts of communications + infrastructure destroyed?
- Are they Primary or Secondary?
- Secondary Hazards
- Road + Rail links often damaged to destroyed
- Telephone masts + wifi down = hard to call for help + find loved ones
- Hampers rescue effort as well as causing injury + loss of life
29
What are causes and impacts of Liquefaction?
- Are they Primary or Secondary?
- Case Study?
- Secondary Hazard
- Violent shaking of ground can cause surface rock to lose strength + become more liquid than solid
- Marshy or saturated land can lose its strength and act like liquid
- Soils underneath building foundations causes them to fail and sink
- Case Study = Christchurch 2010
30
What are causes and impacts of Aftershocks?
- Are they Primary or Secondary?
- Case Study?
- Secondary Hazard
- Smaller but significant earthquakes after main earthquake
Can continue in following weeks + months of an earthquake
- Rescue workers at risk of collapsing buildings
- Larger the earthquake, the more aftershocks there are
- Case Study = Christchurch 2010
31
What are causes and impacts of Quake Lakes?
- Are they primary or Secondary?
- Secondary Hazard
- Earthquakes trigger landslides which can block rivers + cause flooding
- Water collects, creating 'quake lakes' + flooding huge areas
- Aftershocks can collapse dams sending a torrent downstream
32
What are causes and impacts of Disease?
- Are they Primary or Secondary?
- Secondary Hazard
- Lack of water + sanitary = diseases such as cholera + dysentery to spread quickly
- Dead bodies buried in rubble + unregulated mass graves spread disease and cause pollution
33
What is basaltic lava?
- Lava that is low in silica and therefore tends to be very fluid
34
What is andesitic lava?
- Silica-rich (Acid) magma which is often viscous.
- Often solidifies before reaching the surface, causing pressure which leads to explosive activity
35
What is the Volcanic Explosively Index?
- Relative measure of explosiveness of volcanic eruptions
- Volume of products, eruption cloud height + qualitative observations to determine explosivity value
- Scale = open ended with targets volcanoes in history being given Magnitude 8
- Logarithmic scale
36
What are the 4 volcanic hazards?
- Volcanic gasses
- Tephra
- Pyroclastic flows
- Lava flows
37
What are Volcanic gasses?
- Gasses associated with explosive eruptions and lava flows
- Mix normally includes water vapour, Sulphur dioxide, Hydrogen and Carbon monoxide
- Dangerous as carbon monoxide is colourless and odourless -> Carbon Monoxide usually the biggest cause of death
38
What is Tephra?
- Material such as rock fragments that are ejected into the atmosphere as a result of a volcanic eruption
- Can vary in size from 'bombs' to 'fine dust'
- Ash and large materials can cause building roofs to collapse as well as start fires on the ground
39
What are Pyroclastic Flows?
- Responsible for most volcanic related deaths
- Result of frothing of molten magma in the vent of the volcano
- hot gasses and pyroclastic materials, which contain glass shards, pumice, crystals and ash, are ejected from the side of the volcano
- Clouds can be up to 1000 degrees Celsius
- Can travel extremely quickly
40
What are Lava Flows?
- Lava that erupts out of a volcano
- Viscosity determined by amount of silicon dioxide it contains
- Can take up to a day to cool and is very slow moving
41
what 5 ways are there to classify volcanoes?
- If they are active
- By their characteristics (The Landform)
- VEI - Volcanic Eruption Index
- Type of eruption
- Type of magma
42
How can you classify volcanoes by their activity?
- Active volcano still erupts
- Dormant volcano is not erupting but is supposed to erupt again
- Extinct volcano has not erupted for at least 10,000 years
43
How can you classify volcanoes by their characteristics?
- By what the volcano physically looks like:
- Shield Volcano = Wide and Gentle slopes (Divergent plate boundary)
Composite Volcano = Steep sloping sides, with layered composition and typically a lot more violent
44
How can you classify volcanoes by the VEI?
- Using several volcanic characteristic to judge the size or an eruption:
- Eruption cloud height
- Volume of products erupted
- More subjective qualitative observations
45
How can you classify volcanoes by the type of eruption?
- Based upon their explosivity, and their names are generally derived from volcanoes which chow characteristics of those eruptions
- E.g Hawaiian Eruptions = Lava is more basic and basaltic, with low gas pressures and low silica content
46
How can you classify volcanoes by the type of magma?
- Characteristics of molten rock give different eruption types
- There are 3 main types of lava
- Lava can be basic or acidic:
- Basaltic
- Andesitic
- Rhyolitic
47
What are primary effects of volcanoes?
- Tephra
- Pyroclastic flows
- Lava
- Volcanic gasses
48
What are secondary effects of volcanoes?
- Lahars = Volcanic mudflows
- Flooding
- Tsunamis
- Volcanic landslides
- Climatic change
- Jokulhlaup = Glacial outburst floods
49
What is the PAR model?
- Pressure and Release model
- Root Causes -> Dynamic Pressures -> Unsafe conditions -> Disaster <- natural Hazards
- Shows progression of vulnerability and demonstrates how it is a snowball effect
50
What is the PAR model?
- Pressure and Release model
- Root Causes -> Dynamic Pressures -> Unsafe conditions -> Disaster <- natural Hazards
- Shows progression of vulnerability and demonstrates how it is a snowball effect
51
What is the equation for disaster risk?
Hazard X Vulnerability
Disaster Risk = -------------------------------
Capacity to Cope
- Disaster risk = Hazard + Vulnerability
52
What do root causes involve in the PAR model?
Limited access to:
- Power
- Structure
- Resources
Ideologies:
- Political Systems
- Economic Systems
53
What do Dynamic Pressures involve in the PAR model?
Lack of:
- Appropriate skills
- Training
- Local Investment
- Press Freedom
- Ethical Standards in Public Life
Macro-forces:
- Rapid population Change
- Rapid Urbanisation
- Deforestation
- Arms Expenditure
- Debt Repayment Schedules
54
What do unsafe Conditions involve in the PAR model?
- Fragile Physical Environment
- Fragile local economy
- Vulnerable society
- Public Actions
55
what factors effect risk?
- Education
- Frequency
- Geographical location
- Level of Development
- Magnitude
- Natural factors
- Population density and distribution
- Time
56
What are the 4 scales used to measure tectonic hazards?
- Richter scale
- Mercalli Scale
- Moment Magnitude Scale (MMS)
- Volcanic Explosivity Index (VEI)
57
What is the Risk-Poverty Nexus?
- Illustrates that differences in risk inequality is linked to many different elements
Has factors that are all interlinking:
- Extensive and intensive risks
- Disaster Loss
- Poverty Outcomes
- Everyday risks
- Multidimensional poverty
58
What factors can lead to inequalities within a country?
- Wealth
- Political -> Access -> ability to vote/ represent
- Social -> housing in vulnerable areas
-> access to regular income -> living in hazard exposed areas
- Asset -> housing + security of tenure -> Agricultural productivity + goods saving
- Entitlements -> Access to public services + welfare systems -> Inequality in rule of law
59
What is Forecast of a hazard?
- The statistical likelihood of a event occurring
60
What is Prediction of a hazard?
- Knowing when, where and the magnitude of an event
61
How are Earthquakes forecasted and predicted?
- Forecast based on statistical likelihood -> based on seismic monitoring networks and historic records
- Long term forecasts are more reliable than short term
- Forecasting still important as encourages governments to enforce better building regulations or improved evacuation procedures
- Not possible to make accurate predictions of Earthquakes
62
How are Volcanoes forecasted and predicted?
- Remote sensoring
- Earthquake + Lahar sensors
- Satellite
- Thermal imaging
- Cameras
- Tilt meter
- Ground vibration
- Deformation
- Gas -> airborne + ground
- GPS
- Surveying
63
What is Mitigation?
Examples in Haiti and Christchurch
- Identifying potential natural hazards and taking steps to reduce their impact.
- The main aim is to reduce the loss of life and property
Haiti:
- Minimal -> No earthquake proof buildings
Christchurch:
- A lot of Aseismic buildings
64
What is Preparedness?
Examples in Haiti and Christchurch
- Minimising loss of life and property and facilitating the response and recovery phases
- Many activities are developed and implemented by emergency planners in both governments and aid organisations
Haiti:
- Lack of preparation -> Emergency services didn't know what to do
Christchurch:
- in an earthquake hotspot so would have done lots of drills
65
What is Response?
Examples in Haiti and Christchurch
- Coping with disaster
- the main aims are to save lives, protect property, make the effected areas safe and reduce economic losses
Haiti:
- Spent money on disease rather than restoration
Christchurch:
- Enforced law
- Pop-up hospitals created
- Over 300 police flown in to help
66
What is Recovery?
Examples in Haiti and Christchurch
Short-term:
- This focuses on people's immediate needs, so it overlaps with the response phase
- Although called short-term these activities may last for weeks
Long-term:
- This involves some of the same actions but may continue for months or even years
- it includes taking steps to reduce future vulnerability, which overlaps with the mitigation and the cycle continues
Haiti:
- $13 Billion of aid donated
- Overseas companies managing restoration
Christchurch:
- Constructed of homes
- Earthquake proof (Aseismic) housing
- Water + Sewage restored
67
What is the Parks Model?
and what are the 5 stages?
- Shows how an area responds after a hazard
- Can vary dues to size of hazard, predictability of hazard, vulnerability of area
- Stage 1 = Modifying the cause and event
- Stage 2 = Hazardous event
- Stage 3 = Search, rescue and Care
- Stage 4 = relief and rehabilitation period -> May include outside help (National or International)
- Stage 5 = Nature of recovery related to:
-> the need to reduce vulnerability
-> the need to restore normality as soon as possible
