Tectonics: 1.8 - Making Waves

Question 1

Subduction

Answer 1

Denser oceanic crust descends under the less dense continental crust

Question 2

Tsunami initiation

Answer 2

Subduction causes continental crust to thrust upwards (megathrust), triggered by an earthquake

Megathrust displaces the column of water above it, increasing amplitude of waves above -> tsunami waves

Question 3

Tsunami development

Answer 3

Tsunami waves radiate outwards from epicentre. When it reaches shallower coastal regions the waves slow down due to friction with seabed

As the waves from after meet the waves that have already slowed down, the wavelength shortens and the amplitude increases massively until the wave breaks on land

Question 4

Variables of tsunamis: distance from epicentre

Answer 4

Waves lose energy over long distances

Question 5

Variables of tsunamis: size of megathrust

Answer 5

Determines how much water is displaced

Question 6

Variables of tsunamis: coastal topography

Answer 6

More gentle slop -> more buildup of friction -> wave increases in amplitude earlier -> stronger tsunami

Taller the coastline, the hard it is for tsunami waves to break on land

Question 7

Variables of tsunamis: offshore bathymetry (depth of seabed)

Answer 7

Shallower seabed -> more friction -> waves slow down more