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Flashcards in Tsunamis Deck (22)
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1
Q

What is a tsunami?

A

A single or series of waves generated by a sudden displacement of oceanic water

2
Q

How are tsunamis characterised?

A

Large wavelengths of up to 100km and up to hours between waves travelling at speeds of approx. 800km/hour across thousands of kilometres

3
Q

What may cause a sudden displacement of oceanic water?

A

Earthquakes, volcanoes along destructive plate margins, underwater landslides, explosions and cosmic bodies

4
Q

What happens when a tsunami wave approaches the shore?

A

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

5
Q

Describe the Indian Ocean (Boxing day) tsunami of 2004

A
  • 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
6
Q

What happened in Sri Lanka as a result of the 2004 tsunami?

A
  • Vessels swept on streets
  • Express train was washed off tracks killed 600 people
  • Bodies decomposed in rivers
  • Malaria and cholera epidemics
7
Q

Why was the 2004 tsunami so devastating?

A
  • 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
8
Q

How did the world respond to the 2004 tsunami?

A
  • UK donated £32m by NYE
  • Over £700m donated globally in a week
  • Emergency supplies flown in globally
9
Q

How can the tsunami hazard be reduced?

A

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

10
Q

Why do tsunamis not resemble normal waves?

A
  • Longer wavelengths
  • Only grow in height near the shoreline
  • Caused by a seabed displacement
  • Waves can be minutes to hours apart
11
Q

When are tsunamis the most dangerous?

A

As they approach the coastline

12
Q

What is the term for the time between waves?

A

The wave period

13
Q

What physical factors affect the impact of a tsunami?

A
  • Duration
  • Amplitude, column displacement and fetch
  • Coast depth and gradient of the shoreline
  • Coastal ecosystem
  • Time of day
14
Q

What are the human factors that affect the impact of a tsunami?

A
  • Warning system quality
  • Coastal development and proximity
  • Coastal defences
15
Q

Describe the distribution of global tsunami events

A

90% in the pacific basin
25% along subduction zones around Japan-Taiwan
Some in S.America and Aleutian Islands geographic region

16
Q

Name three economic impacts of the Boxing day tsunami

A
  • More than 60% of the fishing fleet and industrial infrastructure destroyed
  • Thai tourism lost $25m a month
  • $10bn total cost
17
Q

Name four social impacts of the Boxing day tsunami

A
  • Up to 70% of villagers killed in some regions
  • 1500 villages destroyed in Sumatra
  • 120k jobs lost in Thai tourism
  • Total 289,601 dead
18
Q

Name four environmental impacts of the Boxing day tsunami

A
  • 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
19
Q

Give four key facts of the Japan tsunami 2011

A
  • Magnitude 9 Tohoku earthquake
  • Global affects e.g. Antarctic ice sheet
  • Tsunami half an hour after the earthquake
  • 1 minute warning before earthquake
20
Q

What was the total cost of the Japan tsunami 2011

A

$235 billion

21
Q

Give four social impacts of the Japan tsunami 2011

A
  • 150k evacuees
  • 50k still in temporary housing
  • 15,894 dead
  • 2.5k missing
22
Q

Give two environmental impacts of the Japan tsunami 2011

A
  • 120k buildings destroyed

- Nuclear power plant failed, the chemicals leaked were detected along the N. American coast