Describe a Tsunami and what causes them.
- a series of water waves caused by the displacement of a large body/volume of water, generally an ocean
- earthquakes, volcanoes, landslides and other disturbances all have the potential to create a tsunami, meaning not all tsunamis are tectonically generated
what do tsunamis generally consist of?
what % occur in the pacific ocean and why is it so high? (hint: subduction zones)
where are the limited to?
- consist of a series of waves called periods ranging from minutes to hours, arriving in a so called ‘wave train’
- 80% occur in pacific oceans (where the most destructive earthquakes occur due to the predominance of subduction zones)
- coastal areas but their destructive power has the potential to do damage to entire coastal areas.
How is a tsunami caused by an earthquake? Give an example.
- generated when the sea floor abruptly deforms and vertically displaces overlying water
- tectonic EQ occurs beneath the sea and water above is displaced from its equilibrium position
- usually the result of a thrust fault (destructive margins) moving abruptly, resulting in water displacement large enough to be a tsunami
EG: Indian Ocean 2004 caused by 9.0 EQ- earthquake caused by sinking of indian ocean plate under eurasian plate
How do volcanoes cause tsunamis? Give an example.
(hint: 2 ways)
Approx. what % of tsunamis are caused by volcanoes?
-result from violent submarine explosions
-also by caldera collapses, tectonic movement from volcanic activity, flank failure into a water source or pyroclastic flow discharge into the sea
EG: most serious volcanic induced tsunami in modern times occurred in Indonesia in 1979 when illiwerung erupted
-approx 5% of tsunamis are volcanically generated
CASE STUDIE: Boxing Day 2004
- Cause
- Main impacts
- Effects
- Response
- indio-australian plate subducting under eurasian plate causing 9.0 quake
- • 1/4 million people died
• 2 million made homeless
• 13 countries affected, worst being Indonesia - •level of damage to economy depends- local economies= devastated. Overall impact to national economies= minor
• 2 main sources of income= fishing and tourism- huge impact on coastal communities
• spreads of diseases due to contaminated water and tropical climate
•loss of tourist revenue - • $7billion provided in aid
• foreign troops involved involved in emergency relief effort
•early warning system set up
CASE STUDY: JAPAN 2011
- causes
- effects
- caused by a 9.2 tsunami off the north coastline of japan
- •1/2million displaced
•10,000 people missing
•16,000 deaths
•economic damage in terms of agriculture
•had protection in place (tsunami walls) but coastline shifted
How does morphology effect tsunami power?
-shallow coastline and exposed beaches= suffer greater impacts S shallow gradient amplifies wave
How do landslides cause tsunamis?
- generated on impact as rapidly moving landslide mass enters the water
- or as a water displaces behind and ahead of rapidly moving underwater landslides
