Geography - Natural Hazards

Geography - Natural Hazards

1. El Nino and La Nina

   • El Nino
     • CASE STUDY:- EL NINO 1991/92
       • Effected 100 million people
       • Led to Cholera epidemic in 1991 in Peru
       • Brought worst drought in the 20th century for Africa
       • Heavy rains and severe flooding in Peru and Chile, severe drought in Africa
     • Weak trade winds lead to eastward flow
     • Cold Peru current is suppressed thus fish don't migrate to the Peruvian coast - Leads to economic decline in fishing and tourism is affected by the reduction on sea birds as they have no food to eat
     • High pressure in Africa - Anti-cyclonic condition persist
     • Low pressure in South America brings heavy persistent rains
     • Usually 12-18 months long
     • Warm water that lacks nutrients moves off the east coast creating the rainfall
   • La Nina
     • Low pressure in Africa bringing storm clouds with strong intensity
     • Warm water pushed towards the Australian coast
     • High pressure over South America bringing low temperatures and drought
     • 1996 sardine and anchovy catches were much higher due to cold nutrient rich waters off the east coast of South America
     • Very strong west trade winds with a high altitude flow being experienced in the upper atmosphere

2. Volcanoes

   • Conservative Boundary
     • These create high fold mountains
     • Two similar plates are converging with the plates being forced together thus creating a huge strain of the earths crust
     • Gentle eruptions with runny lava
   • Constructive Boundary
     • Volcanoes mainly at the sea
     • Two plates diverging
     • Gentle eruptions with runny lava - Shield Volcano
   • Destructive Plate Boundary
     • Heavy plate sinks beneath the lighter plate. They plate is usually the oceanic plates sinking under the lighter continental plates
     • This creates violent eruptions
     • Strato Volcanoes
     • CASE STUDY:- MOUNT PINATUBO1991
       • Refer to casse study mind map

3. Drought

   • EFFECTS OF PROLONGED DROUGHT:-
     • Leads to rising food prices
     • More wildfires
     • Rapid migration to urban areas
     • Water shortages
     • Human and livestock death through lack of water
   • Definition: An extended period of below average precipitation that causes water shortages
   • 4 MAIN CAUSES OF DROUGHT:-
     • 1. High pressure know as anti-cyclones block low pressure from moving in bringing weather fronts with them
     • 2. Warm oceans cause moist air to rise forming clouds over the ocean. If winds are too weak to blow clouds onto land then no rainfall occurs over land
     • 3. Weather front may not bring rain in example with southern Europe once the front has gone over the UK
     • 4. If oceans are colder then less moist air will rise, thus less clouds from which would subsequently bring rain
   • SOLUTIONS:-
     • Reduce water usage e.g. crop irrigation and water wastage
     • Compulsory water meters
     • Construction of reservoirs
     • Tax large corporations for heavy water usage
   • CASE STUDY:- EASTERN/SOUTHERN AFRICA 2002
     • The main affect was 90% loss in the harvest in ETHIOPIA AND ERITREA
     • Over 30 million people affected (East)
     • Severe droughts occured in Africa; both north and south of the equator
     • Over 20 million people affected (South)
     • Over 20% of people in Southern Africa are HIV positive so escalated the problem as they people became vulnerable to droughts and the lack of nutrition that comes along with it
     • Oxfam has many projects such to help in the dorught such as:-
       • Helping people in Malawi to improve simple irrigation systems
       • Helping people to plant an emergency winter crop
   • DROUGHT MITIGATION:-
     • Soil and water preservation. By protecting soil it is better at absorbing percipitation
     • Water desalinisation and water recycling reduces dependency on rain water
     • Water conservation; In Las Vegas exerophytic plants are used outside as they use less water

4. Flooding

   • CASE STUDY:- PAKISTAN 2010 AND 2011
     • 2.74 MILLION PEOPLE AFFECTED IN THE SINDH REGION
     • 483,000 Homes destroyed in the PUNJAB region
     • In 2010, Pakistan suffered its worst floods for 80 years
   • Human factors:-
     • Deforestation means steep slopes have low infiltration rates thus water flows straight into rivers
     • Nearly 70% of pakistans population work in agriculture and live close to rovers to irrigate their crops; this means they're vulnerable when the rivers flood their banks
   • Why do monsoon rains vary:-
     • Changing ITCZ
     • Impact of a warming atmosphere
     • Temperatures in central Pakistan
     • Role of Enso