10. Tsunamis

Question 1

What happens to wave height?

Answer 1

Low wave height (< 1m) but on reaching the shore they can reach to over 25m.

Question 2

What is the wavelength like?

Answer 2

Long wavelength -> in open water can be anything from 100-1000 km

Question 3

What are wave speeds like?

Answer 3

Reach speeds between 640-960 km/hr

Question 4

What does a tsunami usually consist of?

Answer 4

A series of waves, with first not always being the biggest

Question 5

How long between each wave?

Answer 5

Between 10-60 mins

Question 6

What happens upon approaching the coast?

Answer 6

On approaching the coast, especially if funnelled into an inlet, they will slow down and pile up a massive wall of water.

Question 7

What are the factors affecting the severity of a tsunami’s impacts?

Answer 7

• education
• population density
• economic development -> LICs have less money to build defences/ stronger buildings
• height of waves and distance travelled
• length of event at source
• coastal geography, both offshore and on coastal area
• coastal land use and population density
• extent to which warnings could be given
• magnitude

Question 8

What happens in the first stage?

Answer 8

Generation of a tsunami in deep ocean -> tsunamis are difficult to detect by ships due to small wave height and long wave length

Question 9

What happens in stage 2?

Answer 9

Tsunami run-up
Nature of the waves will depend upon:
- Cause of the wave e.g. eruption or earthquake
- Distance travelled from the source, as energy is lost as they travel
- Water depth over route affects energy loss through friction
- Offshore topography and coastline orientation

Question 10

What happens in stage 3?

Answer 10

Landfall -> death and destruction will depend upon land uses, population density and any warning given, as well as the physical geography or relief of coastal areas