natural hazards and plate margins Flashcards
(34 cards)
what are natural hazards
a natural process which could cause death, injury, disruption to humans, or destroy property and possessions.
what can human activities influence on natural hazards
frequency and severity
difference between geological and metrological hazards
o Geological – caused by land and tectonic processes e.g. volcanoes, earthquakes, landslides, and avalanches.
o Meteorological – caused by weather and climate e.g. tropical storms, heatwaves, droughts.
examples of climatic and tectonic hazards (3)
volcanic eruptions, tsunamis, avalanches
droughts, tropical storms, tornadoes
difference with short and long term effects in developed and developing countries
death rate lower, but higher economic cost in developed vice versa
developing countries may be slower to repair damaged infrastructure, decreasing tourism and valuable income
what increases risks of hazards
pop growth, urbanisation and changes to natural environment
what makes up the earths structure
inner core, outer core, mantle, crust
how do Nature of Natural Hazards affect hazard risk
type frequency and magnitude
Type – the risk from some hazards is greater than others e.g. earthquakes are very sudden and unpredictable.
Frequency – natural hazards that occur more often carry a higher risk.
Magnitude – more severe natural hazards cause greater damage e.g. 9.0 magnitude earthquakes are more severe than 6.0
how is vulnerability a factor affecting hazard risk
The greater the population density is in an area, the greater the probability they will be affected.
how are HICs more likely to be less affected by hazard risk
HICs can cope better with natural hazards because they can afford better protection and more advanced technology.
Plate Tectonics Theory
Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core. These currents move the plates.
Constructive Plate Margins:
2 plates move apart, and magma rises through the crust and cools, forming new crust.
Sometimes magma erupts as lava, forming shield volcanoes.
Pressure builds up in faults and energy is released as an earthquake.
what can 2 oceanic and 2 continental plates create at constructive plates
2 oceanic plates form mid-ocean ridges and volcanic islands.
2 continental plates create rift valleys.
destructive plates
2 plates move towards each other and the denser oceanic plate is subducted under the continental plate, forming an ocean trench.
As the crust enters the mantle, it melts in the subduction zone.
Hot magma rises up through the overlying mantle and lithosphere, and erupts as lava forming composite volcanoes (Both volcanic and earthquake activity).
how can earthquakes be formed at destructive plates
When 2 continental plates converge, the crusts ‘crumple up’ to form chains of fold mountains.
In the collision zone, pressure builds up and when it is released, the rocks fracture causing an earthquake (No volcanic activity).
Conservative Plate Margins
2 plates move alongside each other (can be same/opposite direction) at different speeds.
As the plates move, friction and pressure build up and the plates become stuck.
When pressure is released, the energy causes violent earthquakes (No volcanic activity).
Reasons People Live in Areas at Risk of Tectonic Hazards
Geothermal energy: Using steam from underground allows free hot water and heating
Tourism: Volcanoes and hot springs attract tourists; creates employment and has a multiplier effect.
Minerals: Magma/lava may contain copper, gold, and diamonds - extracted
Fertile Soil: Ash lots of minerals and forms nutrient rich soil; used to produce rich harvests.
Social Ties: People have nowhere to go, or their family/friends live there; good preparation and engineering (e.g. reinforced buildings) make them feel safe.
how do HICs and LICs differ with Reducing Risk of Tectonic Hazards
HICs have finances to invest in expensive, effective technology and systems.
LICs are densely populated and have poor management (no access to communication).
Monitoring and Prediction in volcanoes and earthquakes
o Volcanoes: Measuring volcanic gas concentrations, using thermal heat sensors to detect changes in temperature of volcano’s surface.
o Earthquakes: Using seismometers to detect small earthquakes and tremors. Impossible to predict.
protection from volcanoes and earthquakes
o Volcanoes: Using earth embankments or explosives to divert lava flows away from property.
o Earthquakes: Earthquake-resistant buildings e.g. rubber shock absorbers in foundations, steel frames that move during Earth’s movements.
Planning in volcanoes and earthquakes
o Volcanoes: Hazard maps show dangerous volcanoes and areas likely to be affected, restricting certain land uses. People are educated such as wearing masks and identifying evacuation centres.
o Earthquakes: Drills/practices for hospitals, emergency services, and people to increase chance of survival. Setting emergency evacuation plans and identifying evacuation centres.
what happens at low and high pressure
Low Pressure – warm, moist air rises, then it cools and condenses forming clouds and then rain rainfall.
High Pressure – cold air descends, weather is dry and clear.
what areas do surface winds move from
from areas of high to low pressure. Insolation is concentrated near the Equator
From the equator – Hadley, Ferrel, then Polar Cell.
Evidence for more Extreme Weather in the UK (2)
Temperature: The UK has had a temperature increase of 1°C since 1980 which has linked to hotter summers and greater chance of drought.
Rainfall: There is evidence of more persistent and excessive winter rain since 1980 which has increased the frequency and magnitude of river flooding.
