Tectonic Hazards Flashcards

Question

How is ground shaking a primary hazard of earthquakes?

Answer 1

Causes buildings roads and infrastructure to collapse - killing or injuring those nearby Example = Haiti 2010, many poorly built buildings, especially slum housing, and around 230,000 died

Answer 2

The ground shaking places stress on slopes so they fall, resulting in land/rock/mudslides or avalanches. Many of these effects account for a large proportion of the damage and injuries caused by an earthquake including a quarter of deaths in China 2008 earthquake were caused by landslides

Answer 3

Violent shaking causes surface rocks to lose their strength and liquefy; the subsoil can no longer support the foundations of buildings or other structures, so buildings/roads may tilt/sink Example = Loma Prieta California 1989, the freeway collapsed because it was built on soft mud, killing > 40; this can hinder rescue efforts and disrupt underground power/gas lines

Answer 4

It affects the strength of an earthquake: - shallow focus = high speed, causes greater damage at the surface - Deep focus = happen in Benioff zones, have a larger magnitude, and release more energy

Answer 5

the Benioff zone is an area of the Earth's crust where earthquakes occur at a destructive plate boundary.

Answer 6

Micro = strengthening individual buildings and structures against hazardous stress

Answer 7

Macro = large-scale protective measures designed to protect whole communities

Answer 8

Mitigation is about the modification of the loss burden – insurance is a simple way of achieving this

Answer 9

95% occur close or at a plate boundary At the 'Ring of fire'

Answer 10

Convergent or Conservative

Answer 11

Do not happen at plate boundaries - often linked to hot spots or old fault lines

Answer 12

Convergent and Divergent 'Ring of Fire' Hot spots in the middle of plates like Hawaii in the central pacific

Answer 13

Convergent boundaries Over 70% occur around the Pacific Ocean 15% Mediterranean Sea, 9% Caribbean Sea and Atlantic Ocean, 6% Indian Ocean

Answer 14

Oceanic-Continental Oceanic-oceanic Continental-continental (also known as a collision boundary)

Answer 15

Continental = thicker (45-50km), less dense layer (mostly granite) Oceanic = thinner (6-10km), denser layer, (mostly granite)

Answer 16

Seven major and several minor tectonic plates

Answer 17

It is the boundary between the crust and the mantle is also known as Moho

Answer 18

Between the crust and core - is the widest layer

Answer 19

Lithosphere = the rigid layer above the asthenosphere which together with the crust makes the lithosphere Asthenosphere = semi-molten, plastic type layer, which moves under high pressure

Answer 20

The intense pressure, at depth

Answer 21

Inner - solid centre, mostly composed of iron Outer - semi-molten, mostly liquid iron and nickel

Answer 22

1912 = Wegeners theory of continental drift 1940 = Sonar and Radar used to reveal the shape of the ocean floors (Harry Hess) 1960s = Crust samples gathered and radiometric dating carried out 1963 = Theory of sea floor spreading proposed by Wilson 1965 = Wilson and Hess propose the theory of plate tectonics combining sea floor spreading with continental drift Scientists agree that the plates move, but there is still debate over the mechanisms that cause the movement

Answer 23

The heat from radioactive decay in the core moves upwards into the mantle It creates convection currents, which push up into the spreading mid-ocean ridges, forcing them further apart called the ridge push

Answer 24

The heavier subducts = forms deep ocean trenches and island arcs Submarine volcanic eruptions, lead to crust building up and rising above sea level

Answer 25

A series of volcanic islands, formed in an arc shape E.g the Caribbean

Answer 26

The Mid-Atlantic Ridge

Answer 27

both may fold and deform e.g. the Himalayas are formed by the collision of the Eurasian and Indian plates

Answer 28

two plates of similar density

Answer 29

they are crushed, crumpled and forced upwards, usually folding in the process

Answer 30

This creates collision fold mountains

Answer 31

the Himalayas, which are still being formed upwards, at a rate of 1cm/annum

Answer 32

As there is no subduction, there is no volcanic activity

Answer 33

Earthquakes are the main hazard at this type of plate boundary

Answer 34

At divergent boundaries: - Earthquakes tend to be mild and shallow - Eruptions tend to be small and effusive - The eruptions are usually of basalt lava: Low gas content Low viscosity Higher temperature At convergent boundaries: - Friction and pressure build up in the Benioff zone (the area within the subduction zone where most friction and pressure build up occurs) causes strong earthquakes - Volcanic eruptions tend to be explosive as the magma is forcing its way to the surface - These eruptions are often rhyolite lava: High gas content High viscosity Lower temperature At transform boundaries: - Plates can stick causing a significant build up of pressure and powerful earthquakes

Answer 35

Pyroclastic flow - a mix of dense, hot, rock, ash and gases Lava flow - most move slowly enough that they are not a risk to human life but can reach over 1000oC Ash falls - can travel many km, causing injuries, damage, deaths and disruption to transport Gas eruptions - gases trapped in the magma are released during an eruption, they may form gas clouds which are hazardous to health

Answer 36

Lahars - a mixture of rocks, mud and water which flow down the volcano. They are fast-flowing and destroy everything in their path Jökulhlaups - floods caused by a sudden release of water and rocks when glacial ice is melted by the eruption

Answer 37

When an earthquake occurs beneath the sea bed this can lead to a tsunami As the sea bed jolts water is displaced and forced upwards creating a wave As the wave approaches the land they slow and the wavelength becomes compressed This leads to an increase in wave height: they frequently reach 5-10 meters, but can reach 30 meters As the wave reaches the shore a vacuum is created and the water recedes rapidly out to sea leaving the sea bed exposed

Answer 38

Close to plate boundaries and are most common in the area surrounding the Pacific Ocean - 'Ring of Fire'

Answer 39

Landslides which may be due to earthquakes and volcanic eruptions displacing the water Underwater volcanic eruptions Rarely they can be caused by a meteor strike

Answer 40

an event which has the potential to cause harm to the environment, people or the economy

Answer 41

A natural hazard is an event caused by environmental processes and would occur without the presence of humans The term hazard is used because of the potential impact when the natural event interacts with humans

Answer 42

A disaster occurs when harm actually occurs to the environment, people or the economy

Answer 43

Vulnerability is how susceptible an area or population is to damage from a particular hazard event This can be affected by a number of factors including: Level of development Population density Size of hazard Preparation and planning

Answer 44

The greater the vulnerability and the lower the capacity to cope, the greater the risk to the population, environment and economy The greater the hazard magnitude and the lower the capacity to cope, the greater the risk of disaster Risk = Hazard x Vulnerability/Capacity to cope The hazard risk equation allows a judgement to be made regarding an area's resilience The equation can help explain why hazards such as the Nepal (2015) earthquake and the New Zealand (2016) earthquake can be similar in magnitude but have such different impacts Almost 9,000 people died in Nepal whereas only 2 people died in New Zealand

Answer 45

Population density Level of urbanisation Infrastructure quality Wealth Healthcare system Emergency services Education Level of corruption Building construction

Answer 46

takes into account the socio-economic context of a hazard

Answer 47

The pressure model demonstrates how there are a range of factors which increase vulnerability and why some areas lack resilience Within the pressure mode, there are: - Root causes = related to resources, decision making and governance, these lead to dynamic pressures - Dynamic pressures = relate to education, urbanisation and population change which create unsafe conditions - Unsafe conditions = poor quality housing and infrastructure, poverty These are then combined with the hazard itself to increase the risk

Answer 48

The release model demonstrates vulnerability can be reduced and resilience increased by addressing: Safety Reducing the pressures Addressing the root causes Hazard mitigation

Answer 49

Using the magnitude

Answer 50

It measures the energy released at the source (focus)

Answer 51

The magnitude can be measured on different scales but the one which is reported on the news when a earthquake occurs is the Moment Magnitude Scale (MMS)

Answer 52

It is measured using seismographs

Answer 53

The MMS goes from 1 which are not felt by humans to 10 The MMS is a logarithmic scale which means that a 6 on the scale is a ten times increase in amplitude from a 5 The energy release is 32 times greater

Answer 54

The intensity of an earthquake is its impact on people, as well as the built and natural environments The Modified Mercalli Intensity Scale is used to measure the intensity The scale goes from I to XII

Answer 55

Every eruption is unique some are gentle, others are hugely explosive The Volcanic Explosivity Index (VEI) is used to measure the size of an eruption This can not be measured on a scientific instrument so is calculated based on a series of measurements and observations These include: Height of material ejected into the atmosphere Volume of material Duration of the eruption This is a logarithmic scale from 0-8

Answer 56

Hazard profiles can be used to compare tectonic hazard events Hazard profiles usually include information about: Magnitude Speed of onset Areal extent Duration Frequency Spatial predictability Max Spends All Day Farting Sausages

Answer 57

Hazard profiles can be used to compare: - Different hazards - Same hazards with different processes - a volcano on a destructive boundary compared to one on a constructive boundary - Same hazards with different human vulnerabilities - an earthquake in a developed country compared to one in a developing country They can also be used to plan for future events They are useful when looking at one hazard such as an earthquake

Answer 58

Hazard profiles do have disadvantages: Other factors may have a greater influence on the impact They focus on physical factors when human factors may be the most important Multi-hazard events are not easily represented on a hazard profile They are subjective

Answer 59

The greater the levels of inequality experienced the more vulnerable the population

Answer 60

Education Housing Healthcare Income

Answer 61

The level of development

Answer 62

Lower education levels which means that people have a lower awareness of the risk and less perception of the hazard Poor quality housing, unregulated building and the use of poor construction materials A lack of access to healthcare Poor access to clean water and a healthy diet during 'normal times'

Answer 63

High population density Young population Poor infrastructure Rapid urbanisation

Answer 64

good governance = well run and the local or national government is effective These areas are more able to cope with hazard events and will have a faster recovery weak/poor governance = increased vulnerability and impacts the area's ability to cope with a hazard event Poor governance impacts on the ability of governments to: - PLAN for hazard events using techniques such as hazard mapping and land use zoning - EDUCATE the population about the risks and how best to protect themselves - PREDICT events as they do not have the technology and equipment available - PREPARE by ensuring that stocks of water, food, medical equipment and shelter are available

Answer 65

The way in which a country or region is run is known as governance, this also impacts vulnerability and resilience

Answer 66

National governance refers to how the whole country is run

Answer 67

Local governance is how local areas are run

Answer 68

A lack of openness which means that governments are not held to account Corruption can have a number of impacts: - Money is not spent on preparation - Construction companies can get around building regulations or land use zoning by bribing officials EXAMPLE = In Turkey corruption related to construction led to increased deaths in the Izmit earthquake (1999) and the more recent Kahramanmaras (2023) earthquake

Answer 69

Population density - a higher population density: - Makes it harder to evacuate - Buildings are more tightly packed which increases the impact if some collapse Accessibility/isolation - the more inaccessible or isolated an area is: - The more difficult it is to reach and supply aid - in Nepal 2015 some of the hardest hit regions were remote rural areas and they were not reached for days - The less likely people are to have methods of communication - The poorer the infrastructure will be - The fewer facilities there are such as medical assistance Urbanisation - the increasing numbers of people living in cities means: - There is a higher concentration of people and buildings - In developing and emerging countries large numbers of poorly constructed houses on steep slopes are particularly vulnerable

Answer 70

Increased population - the world population has grown from 3 billion to over 8 billion since 1960 This means more people are likely to be impacted by any hazard event Increased population density in urban and coastal areas increases the vulnerable population Increased monitoring and reporting means more hazard events are recorded Most of the increase has been the result of floods and extreme weather

Answer 71

Improved building construction, design and materials Increased monitoring Greater preparation and planning - hazard mapping, land use zoning, evacuation planning Education - earthquake drills Improved warning systems Increased development

Answer 72

Magnitude Level of development Location

Answer 73

The impact of a mega-disaster such as the Indian Ocean earthquake and tsunami may skew the overall trend because it leads to so many deaths Volcanic eruptions are less frequent than earthquakes and deaths from eruptions are now rare due to improved monitoring, exclusion zones and evacuation plans

Answer 74

The economic cost of disasters has increased since 1960 As countries develop the cost of repairing infrastructure and rebuilding increases Increased wealth means people have more possessions and property to be damaged and destroyed Infrastructure is more sophisticated and expensive to replace, for example, electric grids As more people are affected the cost increases

Answer 75

The economic impact of disasters is affected by whether the country is developing (LIC) or developed (HIC) The economic cost in US$ tends to be higher in developed countries The impact on the GDP tends to be much greater in developing and emerging countries

Answer 76

The focus when a disaster strikes and in the weeks that follow is on search, rescue and recovery In remote rural areas it may be difficult to collect data

Answer 77

Tectonic mega-disasters are high impact, high magnitude hazard events which affect several countries either directly or indirectly

Answer 78

Prediction is knowing when (temporal scale) and where (spatial scale) a hazard will occur

Answer 79

Forecasting gives a percentage chance of a hazard occurring over a set period of time

Answer 80

An understanding of tectonic activity can help scientists identify areas most at risk Over 90% of earthquakes occur on or near plate boundaries

Answer 81

Seismic gap theory - to highlight areas at high risk as they have not experienced an earthquake for some time Radon emissions Animal behaviour No method has yet proved to be reliable

Answer 82

There are signs warning of an eruption before most volcanic eruptions Volcanologists (scientists who studied volcanoes) monitor changes using GPS, tilt meters, satellites, seismometers and gas detection Signs of an eruption include: - Magma rising which can be detected by heat sensors and satellites - Changes in surface level as rising magma causes bulges - Increased emissions of sulphur dioxide and other gases - Increased seismic activity caused by magma movement detected by seismometers Improved prediction of volcanic eruptions has led to a decrease in the death toll

Answer 83

When the earthquake happens this will be detected by the global network of seismometers, these will locate the epicentre of the earthquake Ocean monitoring technology can then be used to detect tsunami Warnings can then be issued to coastal areas which may be affected

Answer 84

Systems are regularly updated and reviewed particularly after a hazard event In the Asian 2004 tsunami errors in the system increased the number of deaths In Indonesia the sensor system had been struck by lightning so did not work In India the warning went to the wrong official The sensors in the region were limited In the 2011 Japanese tsunami the height of the tsunami was underestimated so the warnings were not accurate

Answer 85

The hazard management cycle is how the events of one hazard event inform planning and preparation for the next hazard event The time taken for each stage will vary due to: - Level of development - Magnitude of the hazard - Quality of governance - Aid available These factors will have most impact on the response and recovery stages

Answer 86

It can be used by organisations and individuals The cycle enables them to both prepare for and respond to hazardous events It identifies potential hazards Reduces the risks and saves lives Improves the level of preparation

Answer 87

It may not be possible for smaller or less wealthy communities/countries to implement the hazard management cycle Some hazards are less predictable, which means hazard management cannot account for every eventuality Implementation of strategies may face opposition from local communities Communication of the strategies may not reach all communities

Answer 88

'The disaster response curve' = This shows the impact of a hazard event on people's quality of life over time The curve demonstrates where different management strategies are implemented before, during and after the event

Answer 89

Depending on the level of: - Preparation and planning - Development - Aid both national and International Developing countries tend to be impacted more and recover more slowly

Answer 90

It can be applied to a range of hazards The model can be used to assess risk and provide a framework for preparedness The level of economic activity and social stability are shown, which makes it easy to compare differences based on the level of development Useful to analyse the responses to a hazard event and the sequence of events

Answer 91

It only shows the impact of a single event Quantitative data, such as the number of deaths and building destruction, is not shown Preventative measures are not shown The resources required may mean that smaller/less developed communities can not afford to implement it

Answer 92

Event Vulnerability, increasing resilience Loss These strategies involve mitigation or adaptation

Answer 93

This happens before the event occurs Modifying earthquakes is challenging because they occur without warning Construction of earthquake-resistant buildings can help to reduce the impacts on people

Answer 94

Hazard risk mapping using Geographic Information Systems (GIS) to identify areas at highest risk followed by land use zoning to prevent development in these areas Draining crater lakes reduces the chance of lahars Barriers and channels can also be constructed to divert lava flows

Answer 95

Using land use zoning to prevent construction at the coast Building offshore barriers Building sea walls - Japan has increased the height of sea walls in some areas to over 12 meters Replanting mangrove forests

Answer 96

This happens before the event occurs Vulnerability can be reduced and the resilience of populations increased in a number of ways: - Land use zoning - ensuring that people are not living in high-risk areas - Hazard resistant buildings Improved services and infrastructure - Hazard risk mapping using Geographic Information Systems (GIS) to identify areas at highest risk - Planning of evacuation routes - Education of the population to ensure that they know the actions to take when a hazard event occurs - earthquake drills - Improved storage of food, water and medical supplies so sufficient are available - Monitoring and warning systems to allow people time to evacuate

Answer 97

This happens after the event occurs Loss can be reduced by efficient and effective aid and recovery, which can be achieved in a range of ways: - Evacuation - moving people away from the area that has experienced destruction/damage This is particularly important after earthquakes when there are likely to be aftershocks which cause further damage - Search and rescue teams, who are well-equipped and trained - Emergency aid - food, water, medical aid to ensure survival - Short-term aid - shelter, reconnecting of water and electricity supplies - Development aid - long-term aid to help with reconstruction and recovery - Insurance - to help people rebuild - Local communities - supporting each other, providing shelter and helping with the search and rescue effort

Answer 98

Aid may be provided by: - Non-governmental Organisations (NGOs) such as the Red Cross, Medicin San Frontiers and Disasters Emergency Committee - Intergovernmental Organisations (IGOs) such as the UN and World Bank National and local government

Answer 99

Over 70% of tsunamis occur around the Pacific Ocean 15% Mediterranean Sea, 9% Caribbean Sea and Atlantic Ocean, and 6% Indian Ocean They are caused by tectonic activity Most occur due to activity at convergent boundaries When an earthquake occurs beneath the sea bed this can lead to a tsunami As the sea bed jolts water is displaced and forced upwards creating a wave As the wave approaches the land they slow and the wavelength becomes compressed This leads to an increase in wave height: they frequently reach 5-10 meters, but can reach 30 meters As the wave reaches the shore a vacuum is created and the water recedes rapidly out to sea leaving the sea bed exposed Other causes of tsunami include: - Landslides which may be due to earthquakes and volcanic eruptions displacing the water - Underwater volcanic eruptions - Rarely they can be caused by a meteor strike Tsunami usually occur close to plate boundaries and are most common in the area surrounding the Pacific Ocean - 'Ring of Fire'

Answer 100

Types of Volcanoes Shield Volcano Wide, gently sloping shape Frequent, non-explosive eruptions Runny basaltic lava (low silica) Found at constructive boundaries and hotspots Example: Mauna Loa, Hawaii Composite Volcano (also called Stratovolcano) Tall, steep-sided with layers of lava and ash Explosive, dangerous eruptions Andesitic or rhyolitic lava (thicker, more viscous) Found at destructive (convergent) plate boundaries Examples: Mount Fuji (Japan), Mount St. Helens (USA) Cinder Cone Volcano Small, steep-sided, made of ash and rock fragments (tephra) Short-lived, usually found near larger volcanoes Basaltic or andesitic lava Example: Parícutin, Mexico Lava Dome (Acid Dome) Small, dome-shaped volcano Very viscous rhyolitic lava Can have violent, sudden eruptions Often forms inside larger craters Example: Mount Pelee, Caribbean Caldera Huge crater formed by the collapse of a volcano after an explosive eruption Can form lakes or be reactivated Found at subduction zones Example: Yellowstone (USA), Krakatoa (Indonesia)

Tectonic Hazards Flashcards

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