Topic 2 : Tectonics Cluster

1. What is the plate tectonic theory?

1. Plate tectonic theory

a) Earth’s internal structure consists of core, mantle and crust, including continental and oceanic crusts

b) explains how forces within Earth drives global plate movements

2. Convection currents

a) within the hot softened mantle below the crust

b) being the driving force of overlying plates

3. Slab-pull force

a) gravity-controlled subduction of denser oceanic plate

b) drags the rest of the plate along

2. How does seafloor spreading support the plate tectonic theory?

1. Seafloor spreading

a) magma rises through mid-ocean ridges

b) forms new oceanic crusts

2. Evidence from age of rocks

a) younger rocks are found nearer to the crest of mid-ocean ridges

b) rocks get progressively older further away from mid-ocean ridges

3. Evidence from limited sediment accumulation

a) destruction of older oceanic crusts at trenches

b) oceanic crusts younger than continental crusts

3. How does magnetic striping support the plate tectonic theory?

1. Magnetic striping

a) normal and reversed polarity

b) stripes of rock on the seafloor with alternating magnetic properties

2. Evidence from rock composition

a) basalt is a volcanic rock that forms the oceanic crust

b) contains minerals that can be influenced by Earth’s magnetic field

3. Evidence from rock patterns

a) alternating polarity forms a striped pattern

b) not random or isolated occurrences

4. What will happen to different tectonic plates when they move at the different plate boundaries?

1. Divergent plate boundaries

a) plates move away from each other

b) results in mid-oceanic ridges, volcanoes including submarine volcanoes and volcanic islands, rift systems and earthquakes

2. Convergent plate boundaries

a) plates move towards each other

b) results in fold mountains, volcanoes including submarine volcanoes, oceanic trenches and earthquakes

3. Transform plate boundaries

a) plates slide past each other

b) results in faults and earthquakes

1. How do tectonic processes affect the magnitude of earthquakes?

1. Tectonic processes of earthquakes

a) stress builds up and exceeds strength of the fault

b) sudden release of seismic waves, radiating energy from the focus

2. Magnitude of earthquakes

a) affected by amount of energy released through ground movement

b) recorded using seismometers

3. Measuring earthquakes

a) Richter Scale measures local magnitude of earthquakes

b) Moment Magnitude Scale measures larger earthquakes more reliably

2. How do tectonic processes affect the magnitude of volcanic eruptions?

1. Tectonic processes of volcanic eruptions

a) magma consisting of dissolved gases is less dense

b) forces its way upward and breaks through weak areas in the Earth’s crust

2. Magnitude of volcanic eruptions

a) determined by amount of dissolved gases and magma viscosity

b) stratovolcanoes erupt violently and shield volcanoes emit magma gently

3. Measuring volcanic eruptions

a) Volcanic Explosivity Index measures relative explosivity of historic eruptions

b) considers the volume of ejected materials, height of eruption cloud and duration of the eruption

3. How might distribution of earthquakes and volcanoes influence the spread of tectonic hazards?

1. Distribution of earthquakes

a) along all plate boundaries

b) largest concentration at the Pacific Ring of Fire

2. Distribution of volcanoes

a) located near convergent and divergent plate boundaries

b) hot spot volcanoes are found away from plate boundaries

3. Distribution of tectonic hazards

a) most located near plate boundaries, and near earthquakes and volcanoes

b) tsunamis and volcanic ash may spread beyond geographic region

4. How might tectonic hazards affect the natural and human systems?

1. Earthquake hazards and their impacts

a) hazards include ground shaking, soil liquefaction, landslides and tsunamis

b) impacts include destroying ecosystems, properties and infrastructure; disrupting services; and causing injury and loss of life

2. Volcanic eruption hazards and their impacts

a) hazards include tephra, volcanic gases, lava flows, pyroclastic flows, lahars and volcanic landslides

b) impacts include destroying ecosystems, properties and infrastructure; disrupting services; and threaten public health and cause injury and loss of life

3. Benefits of volcanic eruptions and living near volcanoes

a) volcanic eruption provides fertile soil for farming after volcanic materials are broken down and weathered, and makes available valuable minerals and building materials

b) living near volcanoes allow harnessing of geothermal energy and tourism activities

1. How does disaster risk management help achieve sustainable development?

1. Disaster risk management

a) prevent, reduce and manage disaster risks thus strengthening resilience

b) apply plans and actions which are developed into various strategies by communities

2. Disaster risk and loss

a) brings serious economic, social and environment consequences

b) is costly for individuals and countries, and may hinder their development

3. Reducing disaster risks

a) important for disaster-prone developing countries

b) a cost-effective investment in preventing future losses, thus contributing to sustainable development

2. Why do disaster risks caused by earthquakes and volcanic eruptions vary across places?

1. Tectonic disaster risk

a) is the interaction between tectonic hazards, and vulnerability and exposure to earthquakes and volcanic eruptions

b) results in potential loss of human lives and damage to properties

2. Factors influencing disaster risks caused by earthquakes

a) nature of hazards including duration and time of shaking

b) vulnerable conditions including quality of building design and construction, and soil and rock properties; and exposure including population density and distance from epicentre

3. Factors influencing disaster risks caused by volcanic eruptions

a) nature of hazards including chemical composition of magma

b) vulnerable conditions including availability of surface and ground water in the development of lahars, prevailing wind conditions affecting direction and distribution of tephra; and exposure including presence of human settlements

3. How effective are the strategies in building communities’ resilience to earthquakes and volcanic eruptions?

1. Strengthening resilience

a) important for communities living in hazard-prone zones

b) to resist, adapt and recover from impacts of disasters in a timely and efficient manner

2. Strategies in building community resilience

a) reducing exposure including land use planning; reducing vulnerability including hazard-resistant building designs, and monitoring and warning systems

b) increasing preparedness for response and recovery

3. Challenges in building community resilience

a) extent of community’s resources

b) capability of community to organise itself for disasters

4. How effective are the disaster management strategies after an earthquake or a volcanic eruption?

1. Disaster management

a) organisation, planning and application of strategies

b) for responding to and recovering from disasters

2. Disaster management strategies

a) disaster response includes search and rescue efforts, timely evacuation, and provision of basic social and psychosocial services to affected communities

b) disaster recovery includes restoring and improving facilities and living conditions of affected communities

3. Challenges in disaster management

a) lack of domestic resources, including technology and finances

b) engaging relevant stakeholders to collaborate and integrate disaster management strategies into their practices