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Natural Disasters. Earthquakes Floods Storms Cyclones. © Karen Devine 2010. Earthquakes. Earthquakes occur due to movements in the continental plates of the earth’s crust. This is known as tectonic movement.

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natural disasters

Natural Disasters

Earthquakes

Floods

Storms

Cyclones

© Karen Devine 2010

earthquakes
Earthquakes
  • Earthquakes occur due to movements in the continental plates of the earth’s crust. This is known as tectonic movement.
  • Earthquakes have a focal point known as an epicentre where the greatest shocks occur.

© Karen Devine 2010

earthquakes3
Earthquakes
  • Earthquakes can result in:
  • significant property damage
  • damage to infrastructure
  • damage to services
  • landslides and mudslides
  • tsunamis
  • land subsidence
  • injury or death.

© Karen Devine 2010

earthquakes4
Earthquakes
  • An earthquake’s strength or intensity is measured by the Modified Mercali Scale.
  • Earthquake rates are generally very low in Australia because it is situated in the middle of the continental plate.

© Karen Devine 2010

earthquakes5
Earthquakes
  • Nations which are located on the fault lines are more likely to experience earthquakes as the continental plates move against each other.

© Karen Devine 2010

floods
Floods
  • Whilst Australia is prone to droughts, it can also be subject to flooding.
  • There are 3 types of floods:
  • Flash floods: result from periods of extreme rainfall and occur very quickly.
  • Slow onset floods: also result from heavy rains, yet the water takes significantly longer to reach properties.
  • Rapid onset floods: result from waters flowing quickly out of steep inland rivers.

© Karen Devine 2010

floods7
Floods
  • Floods occur naturally when rivers overflow their banks.
  • The waters run over their floodplains and eventually cover roads, properties and towns.
  • A floodplain is a flat area adjacent to a river.

© Karen Devine 2010

floods8
Floods
  • Floodplains consist of alluvial deposits which are fine materials eroded by the river.
  • Floodplains are highly fertile areas.

© Karen Devine 2010

floods9
Floods
  • The rains which contribute to flooding result from:
  • low pressure systems which move across Australia
  • cold fronts or the front of a cold air mass which causes very heavy rainfall
  • storms which may be cyclones or thunderstorms.

© Karen Devine 2010

floods10
Floods
  • Communities can contribute or cause flooding by:
  • removing vegetation near river zones
  • farming on floodplains
  • failing to develop levees
  • building towns in low-lying areas or below sea level
  • constructing low-lying roads
  • failing to build appropriate drainage.

© Karen Devine 2010

thunderstorms
Thunderstorms
  • A thunderstorm is an atmospheric disturbance which may result in:
  • thunder
  • lightning
  • torrential rain
  • hail
  • cyclones
  • tornadoes or water spouts.

© Karen Devine 2010

thunderstorms12
Thunderstorms
  • Cumulonimbus clouds are responsible for thunderstorms.
  • Thunderstorms develop when the following conditions occur:
  • high humidity
  • very hot ground surfaces
  • cold fronts pushing under warmer, humid air masses.

© Karen Devine 2010

thunderstorms13
Thunderstorms
  • Thunderstorms can have the following features:
  • Lightning: which can cause loss of life or start bushfires.
  • Hail: caused by the freezing of rain droplets
  • Flash floods: very heavy rain is associated with thunderstorms
  • Gusty winds: often caused by rainfall generating downdraughts
  • Tornadoes: not a common occurrence in Australia. Result from rotating or funnel shaped descending air flows.

© Karen Devine 2010

thunderstorms14
Thunderstorms
  • Thunderstorms can have significant impacts such as:
  • death
  • property damage agricultural losses or damage
  • large insurance claims.

© Karen Devine 2010

tropical cyclones
Tropical Cyclones
  • Tropical cyclones are types of storms.
  • A cyclone has the following features:
  • a low pressure system
  • warm waters over 27° C
  • tropical location
  • exists over oceans or occurs near coastal areas
  • occurs between January and March.

© Karen Devine 2010

tropical cyclones16
Tropical Cyclones
  • A cyclone exists when warm air rises and rotates around a central core followed by very gusty winds and heavy rains.

© Karen Devine 2010

tropical cyclones17
Tropical Cyclones
  • Tropical cyclones can result in:
  • heavy rains > 2000 mm/day
  • wind speeds > 300 km/hr
  • storm surges when sea levels rise due to wind pressure on the ocean’s surface
  • property loss due to fierce winds, flooding or storm surges
  • erosion of beach sands by large waves
  • damage to coral reefs.

© Karen Devine 2010

tropical cyclones18
Tropical Cyclones
  • Australia experiences approximately 10 cyclones per year.
  • Most move inland or away from the tropical zones where they lose their intensity.

© Karen Devine 2010

tropical cyclones19
Tropical Cyclones
  • Cyclone Tracy is Australia’s most well known cyclone.
  • It struck Darwin on Christmas Day 1974.

© Karen Devine 2010

pause point
Pause Point
  • Play Cyclone Tracy Newsreel.

© Karen Devine 2010

question time
Question Time?
  • How are cyclones named?

© Karen Devine 2010