Unit B6 Managing Hazards

Types of Plate Boundaries

There are different types of plate boundaries:

Constructive Plate Boundary

• Oceanic Crust - Oceanic Crust
• Plates move AWAY from each other
• Crust is FORMED

Destructive Plate Boundary

• Continential Crust - Oceanic Crust
• 2 Plates move towards each other
• Oceanic Crust goes under Continental Crust
• Crust is DESTROYED

Conservative Plate Boundary

• 2 Plates Move side to side at different speeds or in opposite directions
• No crust is created or destroyed
• Earthquakes are common at these plate boundaries

• Power measured using RICHTER SCALE
• Focus - Where plate collision occurs
• Epicenter - Point on land directly ABOVE Focus

Earthquake-proof structures - buildings

• Rolling wights on roof to counteract shock waves
• Automatic shutters to prevent pedestrians below being showered with glass
• Identification number visible for helicopters assessing damage after earthquake
• 'Birdcage' interlocking steel frame
• Reinforced lift shafts with tensioned cables
• Panels of marble and glass flexibly anchored to steel superstructure
• Open areas where people can assemble if evacuated
• Reinforced latticework foundations deep in bedrock
• Rubber shock-absorbers between foundations and superstructure

Earthquake-proof structures - bridges

• Steel cables attached to bridge girders and to columns to restrain movement
• New concrete walls added between existing columns to make structrure more rigid
• Concrete columns encased in steel jacket to keep concrete from crumbling when shaken by earthquake

Cyclone One Bravo

Names to remember:

• Areas most heavily affected: Chittagong, Cox's Bazaar and Teknaf
• Made landfall near Chittagong on 19 May 1997
• 111 people died, 7,000 injured

Impacts on People:

• 111 people die, 7,000 injured
• 500,000 left homeless
• 608 educational institutions damaged
• Ponds & wells contaminated by salt water - 1 million people with no access to fresh water.
• Large number of fishing boats and nets were destroyed in towns along coast
• Electricity supply disrupted - only partially restored after 1 week
• Outbreaks of diarrhoea

Impacts on environment

• Crops destroyed in low-lying islands of Bay of Bengal
• 30,000 hectares of crops damaged, 2,000 cattle were lost
• Much of the year's rice harvest in storage was destroyed
• Widespread destruction of infrastructure
• Communication lines cut - difficult to receive damage & casualty reports

Influence of state development on impact

• Earth embankments constructed along the coast
• Cyclone shelters constructed above floodwater levels - approx. 1 million ppl used these
• Education programmes for inhabitants about storm warnings
• Poor families went to desperate lengths to save possessions - fear of them being stolen
• Low tide, good visibility, ppl were better able to access emergency shelters
• The Bangladesh Red Crescent had a cyclone preparedness programme
• 15,000 volunteers in the area contributed to successful evacuation.
  

Why people still live in these areas

• Fertile area of Bangladesh
• Good for growing of crops
• 000s of ppl with no work/money if they moved away
• Many people depend on fishing
• Ppl cannot afford to move
• They don't think it'll happen again

Hurricane Floyd

Background

• Made landfall on US mainland at Cape Fear, NC on 16 September 1999
• Moved up the coast, weakening and dissipated near New England

Impact of storm on people

• 79 deaths and 000s of injuries attributed to Floyd
• 47 deaths in NC after 500mm of rain and flooded 30,000km squared
• 4 million ppl evacuated in NC, SC, GA, FL
• 1 million ppl - no electricity or water supplies
• 4,000 ppl in PA left homeless
• 42,973 homes damaged, 11,779 destroyed or heavily damaged
• 14 states from FL to ME affected, NC most seriously hit
• 25,000 Flood insurance claimants received tital of $460 million - benefits
• 144,854 in 9 states registered for state & federal assistance
• 10% crop was lost

Impacts on environment

• Storm surge caused a number of boats to be beached or sunk
• Large areas of dunes and beaches were destroyed
• Oak Island lost 20m of beach
• Agricultural losses estimated at $1 billion

What was done to lessen impact

• Good prediction and warning center by National Hurricane Center in Miami, FL
• 2.5 people successfully evacuated
• Evacuation effective - fatalities low
• FEMA provides advice to families and businesses on how to protect themselves during hurricanes
• US has building codes to construct hurricane-proof building
• This includes storm shutters and shatter-resistant windows
• Limited development allowed in areas of high risk from hurricanes - coastal zones

Why do people still live in those areas

• People have a full life with jobs & families
• Well-insured
• No worries about damage to property
• Good warning systems
• Help from FEMA providing disaster kits and plans