Tsunamis

Question 1

Describe a Tsunami and what causes them.

Answer 1

• 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

Question 2

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?

Answer 2

• 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.

Question 3

How is a tsunami caused by an earthquake? Give an example.

Answer 3

• 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

Question 4

How do volcanoes cause tsunamis? Give an example.
(hint: 2 ways)

Approx. what % of tsunamis are caused by volcanoes?

Answer 4

-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

Question 5

CASE STUDIE: Boxing Day 2004

1. Cause
2. Main impacts
3. Effects
4. Response

Answer 5

1. indio-australian plate subducting under eurasian plate causing 9.0 quake
2. • 1/4 million people died
   • 2 million made homeless
   • 13 countries affected, worst being Indonesia
3. •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
4. • $7billion provided in aid
   • foreign troops involved involved in emergency relief effort
   •early warning system set up

Question 6

CASE STUDY: JAPAN 2011

1. causes
2. effects

Answer 6

1. caused by a 9.2 tsunami off the north coastline of japan
2. •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

Question 7

How does morphology effect tsunami power?

Answer 7

-shallow coastline and exposed beaches= suffer greater impacts S shallow gradient amplifies wave

Question 8

How do landslides cause tsunamis?

Answer 8

• generated on impact as rapidly moving landslide mass enters the water
• or as a water displaces behind and ahead of rapidly moving underwater landslides