1 - Hazardous Environments Flashcards
(22 cards)
Examples of Geological Hazards
Earthquakes
Volcanoes
Landslides
Examples of Climactic Hazards
Storms
Floods
Drought
Constructive/Divergent Plate Margin
Plates moving apart. eg- African and North American Plate
Destructive/Convergent Plate Margins
Heavier plate subducts below the other plate. Volcanoes can be formed; can also cause earthquakes. Eg. Pacific subducts Eurasian.
Collision Plate Margins
Two plates meet head-on and are of equal density and strength.
The sediments between the plates are squeezed upwards to form fold mountains Eg. Himalayas, Eurasian and Indo-Australian plates.
Conservative Plate Margins
Two plates sliding past each other. Only causes earthquakes. Eg. In California, Pacific and NA plate.
Global Distribution of Volcanoes
Along destructive margins. Eg. Ring of Fire and African Rift Valley.
Global Distribution of Earthquakes
Along destructive and conservative plate boundaries around the Pacific Ocean. Eg. Ring of Fire.
Characteristics of Earthquakes
Sudden, brief period of intense ground shaking. Vertical and horizontal movement.
Measuring Earthquakes
Richter Scale, Seismographs. Scale is Logarithmic.
Mercalli Scale, based on damage and human experience. Eg. 2 = Not felt but recorded, 5 = Felt by everyone, 8 = Large scale damage to buildings, 12 = Landslides, total destruction.
Define - Focus
Underground point where the shock waves originate from.
Define - Epicentre
Point directly above the focus, most damage inflicted here.
Effects of earthquakes
Burst gas mains cause fires. Eg Kobe, Jan 1995
Liquefaction of rocks means they lose their load-bearing ability. Eg Kobe, Jan 1995
Tsunamis are particularly deadly. Eg. Boxing Day Tsunami, December 2004
Effects of Volcanoes
Lava Flow - Destroy infrastructure and farmland but rarely kill.
Pyroclastic Flow -A pyroclastic flow is fast-moving hot gas and volcanic matter (aka tephra), which reaches speeds moving away from a volcano of up to 700 km/h.
Ash - Prevents flights when carried by wind. Blankets large areas, asphyxiates animals/people. Can crush roofs due to immense weight.
Gas Emissions - Sulphur, C02 and Cyanide are released; due to high density they keep close to the ground.
Define - Liquefaction
Rocks are broken into small, pebble like, sizes when the shock waves pass through them. Happens most commonly at the epicentre. Causes foundations to collapse.
Causes of TRCs
Need warm water of 27°. Water heats air above creating area of low pressure. Hot rising air quickly cools down to form dense cumulo-nimbus clouds.
Causes of Volcanoes
Magma rises through cracks in crust, once pressure is great enough.
Characteristics of TRCs
Large areas of low pressure, 100 km diameter. Bring torrential rain and very strong winds 250 km/h (esp. in Tropical Regions).
Global Distribution of TRCs
Form in between the tropics over warm water. Occur between 5-20 times every year; in Summer/Autumn.
Causes of Earthquakes
Rocks along faults break under the immense pressure which releases a huge amount of energy.
Effects of TRCs
Wind - Destroys trees, crops, infrastructure, and buildings.
Storm Surges - Between 1-5 metres.
Rainfall - Widespread flooding can cause landslides and floods.
Reasons for living in high-risk areas
- Lack of education means locals are unaware of the risk, especially if the hazard is low frequency. Eg. Dormant Volcanoes.
- Job insecurity can cause residents to remain despite knowledge of risk.
- Cannot afford to move.
- Tourism.
- Volcanoes offer benefits:
(a) Minerals brought to surface
(b) Fertile soils due to volcanic ash
(c) Geothermal Energy in springs
