Tectonics Flashcards
What is the temp, density, composition, physical state and what seismic waves do the crust have?
Temp- 400 degrees
Density- Low
Composition- Granite + Basalt
Physical state- Solid
Seismic waves- Surface and
body waves pass
through
What is the temp, density, composition, physical state and what seismic waves does the mantle have?
Temp- 870 degrees
Density- Medium
Composition- Peridotite
Physical state- Liquid/solid
Seismic waves- Body waves pass
through at
variable rates
What is the temp, density, composition, physical state and what seismic waves does the outer core have?
Temp- 4400- 6100 degrees
Density- Dense
Composition- 12% sulphur
88% iron
Physical state- Liquid
Seismic waves- P waves
What is the temp, density, composition, physical state and what seismic waves does the inner core have?
Temp- 7000 degrees
Density- Very dense
Composition- 20% nickel
80% iron
Physical state- Solid
Seismic waves- P waves
What happens at a divergent plate boundary?
- Plates move apart
- Shield volcanoes form
- Mt Nyiragongo is an example
What happens at a destructive plate boundary?
- Oceanic crust subducts beneath the continental plate
- Creates earthquakes and volcanoes
What happens at collision plate boundaries?
- Two continental plates collide
- Neither can sink and so the land buckles upwards forming mountains
- E.g. the Himalayas
- Earthquakes can occur here
What happens at conservative plate boundaries?
- Plates slide past one another
- Pressure builds up
- Energy is released causing an earthquake
What discovery was made in 1915
Alfred Wegener publishes his theory on continental drift, which states that Earth’s landmasses are constantly moving
What discovery was made in 1918
Sonar technology developed during WW1 which revealed details about the ocean floor, scientists now know that the crust exists under the world’s oceans, it becomes an assumption that the ocean floor moves as well as continents
What discovery was made in 1919
Arthur Holmes develops a theory that explains how the large landmasses move from convection currents through the mantle the same way that heated air circulates a room
What discovery was made in 1946
Scientists make use of the military sonar tech to map ocean floor
What discovery was made in 1954
First world map of volcanic eruptions and earthquake zones is published by a French seismologist J.P. Rothe
What discovery was made in 1960
Harry Hess and Robert Dietz propose the theory of sea floor spreading where magma oozes up from the Earth’s interior along the mid-oceanic ridges
What discovery was made in 1963
A pattern of magnetic striped rock on the ocean floor that provides evidence to support Hess and Dietz’s theory of sea floor spreading
What discovery was made in 1965
J Tuzo Wilson proposed that the entire crust of Earth is made of separate sections called plates
What discovery was made in 1983
GPS becomes available for public use and is able to track movement of plates
What are some primary hazards of earthquakes?
- Crustal fracturing
- Ground shaking
What is a secondary hazard of earthquakes?
Landslides
What determines the impact of a tsunami?
- Duration of event
- Wave amplitude
- Physical geography of the coast
- Degree of coastal development
- Timing of the event
Order low-high damage caused from different types of magma, reasons and example
- Basaltic low viscosity (Hawaii)
- Andesitic moderate viscosity (Andes)
- Rhyolitic high viscosity (Yellowstone)
What are pyroclasts?
Hot broken fragments of rock ejected at high velocities
What are landslides?
Huge flows of rocks, mud and tephra
What are poisonous gases?
CO2, HCL, SO2
What are lahars?
Volcanic mudflows generally composed of relatively fine sand and silt material
Case study lahar
- Town of Armero, Colombia
- Buried by a lahar from the Nevado del Ruiz volcano in 1985
- 60km/h
What are Jokulhlaups?
Catastrophic glacial outburst flood, where water accumulates in a subglacial lake beneath a glacier and the flood is initiated following the failure of an ice dam
What is a disaster?
Interaction of tectonic hazard with vulnerable population
What does Degg’s model show
It shows that a natural disaster only occurs when a vulnerable population is exposed to hazard
What are the three categories which affect the hazard vulnerability of a country (Relating to Degg’s model)
- Physical environment
- Lack of resources available
- Local scale
What is hazard vulnerability?
The capacity of a person or group to anticipate, cope with, resist and recover from the impact of a natural hazard
Formula for risk
Frequency or magnitude of hazard X level of vulnerability / Capacity of population to cope
What does Park’s disaster response model show?
The effects of a disaster on the quality of life of a population over time, it can either improve the country, return to what is was, or never goes back to what it was
What does the pressure and release model show?
The root cause, dynamic pressures, unsafe conditions and the hazards of an event
Most vulnerable groups of people
Poor- Cant afford to leave, informal housing
Elderly- Physical unable, isolated
Women- Primary care givers to elderly and children, less able to access resources
What is the richter scale?
A logarithmic scale used to measure the strength of earthquakes, uses a seismometer
What is the moment magnitude scale?
Uses the energy released by all shockwaves as well as area of rupture and movement
What is the mercalli scale?
Measures intensity of the earthquake and the amount of damage caused by the earthquake
What is the volcanic explosivity index?
Logarithmic scale comparing the energy released and the type of eruption
What 9 factors determine the severity of a hazard?
- Duration
- Magnitude
- Predictability
- Regularity
- Frequency
- Speed of onset
- Spatial concentration
- Areal extent
- Number of hazards (type)
What is speed of onset?
How long until a hazard reaches people
What is spatial concentration?
Whether it happens in a known area as people will be more prepared if it is
What is areal extent?
The size of the area impacted
Define inequality
Usually refers to an unfair situation or distribution of assets and resources
4 components of vulnerability
- Social
- Economic
- Environmental
- Political
What are some political factors regarding vulnerability?
- Communications
- Corruption
- Conflicts
- Effectiveness of emergency services
- Investment into infrastructure
- Geopolitical relationships
What is governance?
Process of overseeing and controlling the direction of an organisation or country
Which 3 factors can influence governance?
- Economic
- Political
- Administrative
What is an example of a disaster management agency in the USA?
FEMA- helps people and communities prepare for, respond to, and recover from disasters
What is an example of an under funded and under resourced agency in the Philippines?
PHIVOLCS
What should governance be considered against?
- Increase in global economic activity
- Increased activity of institutions such as the EU operating across national borders
- The rise of neo-liberal ideology values
- The spread of info tech
What are the nature of tectonic hazards impacts influenced by?
- Population density
- Degree of urbanisation
- Isolation and accessibility
What is Reason’s swiss cheese model?
Highlights the fact that a particular disaster can be linked to a single hazard event, but then there is a cascade of other events that provide context for the hazard
A hazard therefore becomes a disaster when several holes line up, creating the conditions for loss of life, property and livelihood
What is a mega disaster?
Either:
- Over 2000 deaths
- Over 200,000 made homeless
- GDP of a country is reduced by at least 5%
- Dependence on aid from abroad for a year or more after the event
Where are multiple hazard zones likely to be found?
Where plate boundaries intersect
How can we predict volcanoes?
- Change in the shape of the volcano
- Laser beams
- Changes in temperature
- Modelling
How can we predict earthquakes?
Cannot accurately predict as tectonic plates are so complicated
However, animals can predict as they sometimes abandon their habitat before it occurs
What is the mitigation stage of the hazard management cycle?
- Identifying hazards and taking steps to reduce the impact of them
- Aim to reduce loss of life
What is the preparedness stage of the hazard management cycle?
- Minimising loss of life and property
- Facilitating response and recovery
- Education
What is the response stage of the hazard management cycle?
- Coping with the event
- Search and rescue
- Evacuation
What is the recovery stage of the hazard management cycle?
- Short term (providing services and temporary shelter
- Long term (rebuilding, reopening)
What is hazard mitigation?
Strategies meant to avoid, delay or prevent hazard events
What is hazard adaptation?
Strategies designed to reduce the impacts of hazard events
Ways to earthquake proof a building?
- Movement frames
- Braces
- Shear wall
- Dampers
- Liquid filled damper
- Seismic base isolator
How can we modify the event for tsunamis?
- Physical barriers e.g. seawalls
- Using sand dunes as it provides protection against coastal flooding
- Minimising new development in tsunami hazard zones
How can we modify the event for volcanoes?
- Spraying sea water on approaching lava
- Monitor volcanic activity with seismometers
- Lava diversion
- Minimising new development in volcano hazard zones
What is land use zoning?
Divides land into different areas for specific uses, such as residential, commercial, industrial, or agricultural in order to protect people from a hazard
What is meant by modifying the event?
Increasing the resilience of a community to increase their capacity to cope
What is the K-NET?
Network of strong motion seismographs installed at approximately 1000 locations in Japan
What are the warning signs for volcanoes?
Numerous small earthquakes and a swelling of the ground surface
What are the 4 stages of the hazard management cycle?
Recovery, prevention and mitigation, response and preparation
What is the role of aid donors?
To provide financial assistance, goods, or technical expertise to another country
What is internal governmental aid?
Typically used in emerging and developed countries where the disaster mitigation is achieved by spreading the financial load throughout the tax payers of the country
What is the role of NGO’s in disaster management?
When the local government is struggling to respond, or doesn’t have the resources to do so as they can provide funds, co-ordinate search and rescue and help develop reconstruction plans
What is the role of insurance in disaster management?
Natural disasters are expensive and the economic costs can be staggering
Provides businesses and individuals the money they need to repair and rebuild
What is the role of communities in disaster management?
Local people respond first and are crucial in search and rescue efforts
Can take days or weeks for aid to arrive
How can governance decrease a country’s vulnerability?
- Land use planning and zoning during construction
- Environmental management to prevent factors such as deforestation
- Providing education
