Tsunamis Flashcards
What is a tsunami?
A single or series of waves generated by a sudden displacement of oceanic water
How are tsunamis characterised?
Large wavelengths of up to 100km and up to hours between waves travelling at speeds of approx. 800km/hour across thousands of kilometres
What may cause a sudden displacement of oceanic water?
Earthquakes, volcanoes along destructive plate margins, underwater landslides, explosions and cosmic bodies
What happens when a tsunami wave approaches the shore?
It behaves like a normal sea wave when friction against a shallow seabed slows the wave and causes it to rise, variations in offshore profiles and coastline configurations effects its height against the shore
Describe the Indian Ocean (Boxing day) tsunami of 2004
- Triggered by 9.0 earthquake
- 294,000 deaths
- 5 million homeless
- 2 million job losses
- Worst affected: Sumatra, Sri Lanka, Thailand, Maldives, India and Maldives
What happened in Sri Lanka as a result of the 2004 tsunami?
- Vessels swept on streets
- Express train was washed off tracks killed 600 people
- Bodies decomposed in rivers
- Malaria and cholera epidemics
Why was the 2004 tsunami so devastating?
- 9.0 earthquake
- Tsunamis not common
- Coastlines low-lying and densely populated especially with tourists
- LEDCs with inadequate warning systems as the only one in Thailand failed
How did the world respond to the 2004 tsunami?
- UK donated £32m by NYE
- Over £700m donated globally in a week
- Emergency supplies flown in globally
How can the tsunami hazard be reduced?
ADVISORY: PTWC (Pacific Tsunami Warning Centre) issue hourly bulletins if an earthquake occurred in Pacific basin
WATCH: Local officials should prepare for evacuation for an at least two hour travel time
WARNING: Advise evacuation
Why do tsunamis not resemble normal waves?
- Longer wavelengths
- Only grow in height near the shoreline
- Caused by a seabed displacement
- Waves can be minutes to hours apart
When are tsunamis the most dangerous?
As they approach the coastline
What is the term for the time between waves?
The wave period
What physical factors affect the impact of a tsunami?
- Duration
- Amplitude, column displacement and fetch
- Coast depth and gradient of the shoreline
- Coastal ecosystem
- Time of day
What are the human factors that affect the impact of a tsunami?
- Warning system quality
- Coastal development and proximity
- Coastal defences
Describe the distribution of global tsunami events
90% in the pacific basin
25% along subduction zones around Japan-Taiwan
Some in S.America and Aleutian Islands geographic region
Name three economic impacts of the Boxing day tsunami
- More than 60% of the fishing fleet and industrial infrastructure destroyed
- Thai tourism lost $25m a month
- $10bn total cost
Name four social impacts of the Boxing day tsunami
- Up to 70% of villagers killed in some regions
- 1500 villages destroyed in Sumatra
- 120k jobs lost in Thai tourism
- Total 289,601 dead
Name four environmental impacts of the Boxing day tsunami
- Infrastructure destroyed e.g. Nicobar islands isolated as jetties washed away
- Ecosystem damage and flooding
- Vegetation and topsoil removed 800m inland
- Freshwater and agriculture contaminated by sea water and made infertile
Give four key facts of the Japan tsunami 2011
- Magnitude 9 Tohoku earthquake
- Global affects e.g. Antarctic ice sheet
- Tsunami half an hour after the earthquake
- 1 minute warning before earthquake
What was the total cost of the Japan tsunami 2011
$235 billion
Give four social impacts of the Japan tsunami 2011
- 150k evacuees
- 50k still in temporary housing
- 15,894 dead
- 2.5k missing
Give two environmental impacts of the Japan tsunami 2011
- 120k buildings destroyed
- Nuclear power plant failed, the chemicals leaked were detected along the N. American coast
