tsnamis and boxing day case study Flashcards
what are tsunamis?
giant sea waves generated by shallow focus earthquakes that are underwater
what are the characteristics of tsunamis?
long wave length and short wave height
how quickly do they travel?
over 700 km an hour
when does wave height increase>
when approaching shallow water, idea from coastal waves
what is the first warning that a tsunami is coming?
the wave trough, results in a reduction of sea level, water is drawn backwards
what height scan tsunamis reach?
over 25 metres
is the largest waves always first?
no
what do the effects of a tsunami depend on?
- height of waves
- distance travelled
- length of event
- extent to which warnings could be given
- coastal geography
- lang use and population density
how far inland do tsunamis have an effect?
500-600m
what is Krakatoa an example of?
how an volcanic eruption can create a tsunami
when did Krakatoa explode?
1883
how many people drowned in Krakatoa?
35,000
what percentage of tsunamis are generated in the pacific basin?
90%
what is the main case study for tsunamis?
the boxing day one
what year did the boxing day tsunami take place?
2004
what ocean did the boxing day tsunami occur in?
the Indian ocean, off Sumatra
what was the boxing day T generated by?
a 9.0 earthquake
how far below was the earthquake that caused the boxing day T sea floor?
25km
how many poeple were killed?
300,000 estimated
how many countries were affected in 2004?
13
why was the 2004 T so devastating?
- epicentre close to coastal areas that were built up
- lack of warning
- many countries are LEDC
how many left homeless in 2004?
1.7 million
why was there a threat of disease 2004?
mixing of fresh and sewage water, stagnant water
how many villages destroyed in northern Sumatra?
1,500
what percentage of sri lankas fishing fleet destroyed 2004?
60%
what were environmental effects 2004?
- farm land affected by salinisation
- crops destroyed
- 8 million of oil escaped
how many litres of oil escaped 2004?
8 million
what did the insurance companies estimate the event would cost 2004?
5 billion dollars
what was a positive outcome to the tsunami?
a early warning system was adopted by the indian ocean
