Tectonics Lesson 8: Tsunamis

Question 1

Define tsunami

Answer 1

Series of larger than normal waves

Question 2

What can cause a tsunami?

Answer 2

Underwater earthquakes, small number by landslides, or by asteroid strikes
Energy released during the earthquake causes the sea floor to uplift displacing the water column

Question 3

Define the water column

Answer 3

Area of seawater from the surface to the sea floor

Question 4

How are tsunamis formed?

Answer 4

1) Generation of tsunami in deep ocean - small wave height and long wave length.
2) Water column is displaced by the displacement of a large area of the sea floor.
3) As water shallows, waves slow and increase in height to produce high waves.
4) Wave energy is concentrated into a smaller volume of water
5) Friction from the seabed causes the wave to form into an elliptical shape and curl due to the peak being faster than the trough

Question 5

How high can some waves reach?

Answer 5

Up to 30m high

Question 6

How fast can a tsunami move?

Answer 6

500mph

Question 7

What happens to the tsunami when it reaches the shore? Main characteristic

Answer 7

Wave crest reaches the shore and a vacuum effect is seen, as the water is sucked out to sea, exposing a large amount of the sea floor

Question 8

Can tsunamis be predicted?

Answer 8

No because most are caused by underwater earthquakes which cannot be predicted

Question 9

What can be done instead of prediction to prevent loss of life?

Answer 9

Early warning systems before a tsunami reaches the coast and threatens lives

Question 10

What is the early warning system in place and where?

Answer 10

DART - Deep-ocean Assessment and Reporting of Tsunami

Indian Ocean

Question 11

How does the DART system work?

Answer 11

Uses seismic sensors to detect submarine earthquakes or a change in pressure
A signal is transmitted to a surface buoy, which sends a signal to a satellite, then to ground stations

Question 12

Pros of computer modelling

Answer 12

Can save lives

Information can be reviewed regularly due to multiple sensors and sea surface buoys

Question 13

Cons of computer modelling systems

Answer 13

Faulty equipment will lead to inaccurate data

Shallow earthquakes can cause equipment to be damaged

Question 14

Short term social impacts of the Indian Ocean tsunami

Answer 14

300,000 died
9000 tourists died
Some villages saw up to 70% die

Question 15

Medium term social impacts of IOT

Answer 15

Andaman and Nicobar Islands all but cut off, as jetties washed away

Question 16

Long term social impacts of IOT

Answer 16

Coastal settlements devastated
Sumatra up to 1500 villages destroyed
Infrastructure destroyed
1.7 million displaced

Question 17

Short term economic impacts of IOT

Answer 17

60% the fishing fleet and industrial infrastructure destroyed
120,000 workers lost their jobs

Question 18

Medium term economic impacts of IOT

Answer 18

Thailand’s tourism lost US$25 million a month

Question 19

Long term economic impacts of IOT

Answer 19

Ports ruined
Reconstruction costs US$15 billion
Communication links damaged e.g. roads

Question 20

Medium term environmental impacts of IOT

Answer 20

Freshwater supplies and agricultural soil was contaminated by salt water
8 million litres of oil escaped from plants in Indonesia

Question 21

Long term environmental impacts of IOT

Answer 21

Ecosystems severely damaged e.g. mangroves, coral reef, forests and wetlands
Most vegetation and topsoil was removed up to 800m inland