Tsunamis

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  • Created by: Megan
  • Created on: 30-04-14 14:25

Tsunami Formation

1)Displacement of a large area of sea floor

2) Ocean is displaces, waves radiate from the source in all directions

3) As Water shallows, waves slow down and increase in height to produce onshore waves upto 30m

4) Wave energy is crowded into a smaller volume of water

5) Waves which were 1m in deep water may reach 30m by the time they reach the shore

THe 4th or 5th wave is often largest - in a wave 40% of energy is scattered back to sea and 60% is expended at/near the ciast. Sea floor irregularities reflect some wave energy so that less energy reaches the coast. The sea-floor topography in the coastal zone is important in the nature of the tsunamis at the run-up stage. 

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Characteristics

...most commonly associated with destructive boundaries. 90% are located arouund the Pacific Ring of Fire but the North and Mediterranean sea have both experienced tsunamis

Characterisitcs:

  • The length and shape of hte coastal shelf determines the degree to which a wave is slowed by friction
  • Wave period can be 10-60 minutes
  • Water at the coast is often drawn out to sea before the waves hit
  • Series of waves with 4th/5th being the largest
  • Upto 600mph speeds n deep dea
  • WAve heights upto 30m
  • waves can travel 1-2miles in land adn wavelength can reach 300 miles (500km)
  • As the wave speed decreases due to friction in shallow waters, the height of waves grow.
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Boxing Day Tsunami

...after a 9.1magnitude earthquake in the Sunda Trench just off the coast of Indonesia, a huge tsunmai was triggered..

Primary Impacts:

  • Death Toll:- 230,000+
  • 23 couuntries hit
  • 45,000 injuries
  • 1.7million people displaced as homes were destroyed
  • Roads, communications and thousands of buildings were severly damaged if not completely destroyed
  • 1500 villages were entirely destroyed in Sumatra
  • 60% of Sri Lanka's fishing fleet was destroyed
  • Sea water and sewage contaminated drinking water
  • Severe damage to habitatsL- mangroves, coral reeks, forests and coastal wetlands
  • Agricultural areas were destroyed
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Secondary Impacts

  • unburied boidies increased the likelihood of disease such as Cholera and helped it to spread througgh populations
  • As many hospitals were destroyed, there was little immediate help for those severely injured by the tsunami or earthquake
  • There has been severe trauma to those who survived and many will need long term treatment to help them recover, id addition to physical injuries
  • The roads destroyed prevetned air reaching remote areas and it took days for rescue teams to get to some areas
  • Sri Lanka's economy suffered greatly as fishing was a primary source of foreigh trade
  • Contaminated water meant people wither died of dehydration or got waerbourne diseases by drinking it
  • Tourism fell inthe area, damaing the local economy as people avoided the are for fear of a repeat event for months after
  • Many of the ecosystems destroyed were used partly for commercialproduction so this further damges the local economies
  • $5billion in costs
  • THe altered seabed in the Malacca Strait, made it even more dangerous for shipping to continue
  • Destroyed agriculture meant that thousands of subsistence farmers were left unable to feed themselves - it also meant that food was in limited supply and very expensive after the tsunami itself for those survivors
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