tectonic hazards section A(p1) Flashcards
What is a ‘natural hazard’?
A natural event that threatens people or has the potential to cause damage, destruction and death.
(for example earthquake, volcanic eruption, tropical storm, flood)
What are the two main types of natural hazards?
Geological hazards - caused by land or tectonic processes(earthquake, volcanic eruption)
Meteorological hazards - caused by weather or climate (tropical storm, flood)
hazard risk?
the probability of people being affected by a hazard in a particular area.
Factors affecting hazard risk
Human
- level of development
- urbanisation
-Education
- population density
Physical
- geology of land
- topography (the arrangement of the natural and artificial physical features of an area)
- Magnitude of the event
Frequency of the event
what trend relates hazard risk to a countries lattitude?
countries closer to the equator are exposed to greater risk of hazards.
define primary effects
An impact or effect of a hazard that occurs as a direct consequence of that hazard.
examples of primary effects (Chile)
Chile
- 12,000 injured
- over 800,000 affected
220,000 homes, 4500 schools, 56 hospitals and 53 ports were destroyed.
- disrupted power, water supplies and communications across Chile
examples of primary effects (Nepal)
Nepal
- 19,000 injured
- over 8 million affected
- 3 million made homeless
- disrupted power, water supplies and communications across Nepal
- 7,000 schools destroyed
- hospitals and airports became congested
- 50% shops destroyed
define secondary effects
These are hazards caused as a result of the primary effects but often happen at a later date.
examples of secondary effects (Chile)
- Tsunami waves devastated towns (warnings prevented loss of life)
- a fire at the local chemical plant lead to local area being evacuated
- Landslides destroyed up to 1500KM of roads
examples of secondary effects (Nepal)
- Avalanches and slides of of Mount Everest hampered the relief effort
- 19 people lost their lives on Mount Everest from avalanches.
- 250 people missing in Lang Tang region due to avalanches
- Kali Gandaki river blocked from landslides causing flood risk and people to be evacuated.
- economic decline in tourism and employment
- farms effected caused food shortages effecting food security and income loss.
examples of immediate responses (Chile)
- field hospitals set up
- within 24 hours the north-south highway was temporarily repaired to allow aid to be transported over the Country.
- Within 10 days most homes had restored power and water.
- a national appeal raised 60 million dollars to fund 30,000 small shelters.
examples of long term responses (Chile)
the government launched a housing reconstruction plan one month after the earthquake to help nearly 200,000 families.
- chiles strong economy reduced need for foreign aid.
- took over 4 years to recover.
examples of immediate responses (Nepal)
- india and china provided 1 billion in national aid
- 100 search and rescue responderswith 3 chinooks from the UK
- GIS mapping to coordinate a response
- 500,000 tents provided for Tent city in the capital kathmandu
- field hospitals set up
examples of long term responses (Nepal)
- UK provided £73 million and 30 tonnes of humanitarian aid
- Landslides cleared and roads repaired
- Stricter building regulations put in place
- Over 7000 schools rebuilt
- Everest base camp repaired and new routes were established ( good for tourism and income)
reasons for living near hazards
- DON’T SAY BECAUSE ITS CHEAPER
- views
- Geothermal energy
- Fertility of land
- Mineral extraction
- Tourism
- Religious beliefs
- preferred climate
- Hazards can’t always be predicted
name the 4 management strategies for managing tectonic hazards
Monitoring
Prediction
Planning
Protection
Examples of 4 management strategies for Earthquakes
- Monitoring
seismometers -> creates early warning systems.
ground deformation
tiltmeters - prediction
cannot be predicted when can be predicted where (plate boundaries) - Protection
reinforced concrete buildings can be built, steel frames used to reinforce infrastructure. automatic shut off switches to prevent gas and electricity leaks that may result in fires
swaying buildings and rolling weights
lattice cross bracing
shock absorbing foundations
-Planning
education, planned evacuation routes, Emergency supplies, hazard maps
Examples of 4 management strategies for Volcanoes
-Monitoring
signs of a volcano e.g small earthquakes, escaping gas, changes in shape of the volcano. sea level fluctuating
- prediction
predicting from the results of monitoring
- protection
buildings strengthened to withstand the weight of ash, Lahars put in place( barriers to divert lava flow) - planning
education, planned evacuation routes, Emergency supplies, hazard maps.
name the 7 largest tectonic plates
North American
Eurasian
Nazca
Pacific
Antarctic
South American
African
Indo-Australian
three reasons for crust movement?
convevtion currents
ridge push
slab pull
define convection currents in the mantle?
1) Magma near the core heats up and rises
2) the magma reaches the crust and moves either left right. this movement forces the plates apart
3) the magma cools down and begins to sink towards the core before it heats up again
4) this cycle repeats
define ridge push
- happens at a constructive plate boundary
- the process of hot magma pushing up through the earths crust to form a mid Atlantic ridge. the ridges on either side are then pulled down by gravity.
define slab pull
- destructive plate boundaries
- when an oceanic pate subducts beneath the continental plate, the heaviest part of the plate pulls the rest of the plate downwards due to gravity.
compare the two different types of crust
CONTINENTAL CRUST - older, lighter and is permanent (cannot be destroyed).
They range between 25-70km thick
OCEANIC CRUST - younger, heavier, and constantly being destroyed and replaced.
5-10 km thick.
what is a destructive plate boundary
where an oceanic plate meets a continental plate
the denser oceanic plate subducts beneath.
Benioff zone created causing earthquakes
composite (triangle) volcanoes form and oceanic trenches
examples: Japan (Mariana trench)
Chile, Nazca plate
constructive plate boundary
rising magma forms new crust between two oceanic plates.
forced apart due to ridge push and convection currents .
creates the mid Atlantic ridge.
Conservative plate boundary
any two plates moving alongside each other either at different speeds or different directions.
this only causes very violent earthquakes due to the strike slip fault theory. no volcanoes.
collision plate boundary
two continental plates that collide but they cannot subduct so they fold inwards forming fold mountains.
example of this would be Everest/ Himalayas
they don’t produce volcanoes but very violent earthquakes.
what is Wegener’s tectonic theory?
Crustal evolution
during the pangaea era 250 million years ago the UK was on the Equator.
Wegeners evidence
- Study of fossils
similar fossils have been found on different continents such as Lystresaurous fossils, a mammal which cannot swim, can be found in Antarctica, India and Africa. - pattern of rocks
same rocks found in east of Canada and the west of Scotland. - shape of continents
South America and Africa fit together.
scales used for measuring earthquakes
Richter scale
measured from 1-10
a logorithmic scale measuring energy and movement
each level on the scale is 30x more energy and 10x more movement
measured using a seismographic
Merculli scale (less efficient)
measures how much damage has been sustained by observations
measured 1 - 12 using roman numerals
