tsunamis

• what are tsunamis?

  a series of large waves caused by the displacement of large volumes of water --> secondary hazards that usually occur at subduction zones
• what are tsunamis caused by?

  submarine earthquakes cause the seafloor to uplift - displacing the water column above. waves radiate out in all directions from the epicentre
• what makes big tsunami waves?

  the greater the movement of the seafloor, the greater the volume of water displaced, and the bigger the wave
• explain the speed and height of tsunami waves out at sea?

  they are small and very fast as there's no friction to cause them to slow down
• what happens to tsunami waves as they approach the coast?

  the waves lose energy and slow down due to friction with the rising seabed. this causes the waves to grow in height
• how do you get more powerful tsunami waves?

  if the epicentre is close to the coastline or is travelling through very deep water it has less time to lose its energy
• describe the global distribution of tsunamis?

  around 90% of tsunamis have occured within the Pacific Basin, associated with activity at the plate margins

  most are generated at subduction zones, particularly off the Japan-Taiwan island arc, South America and Aleutian islands --> 25% of tsunamis have been recorded in this region
• impacts of tsunamis?

  travel inland - sweeping away buildings, trees, bridges ans people

  wash away soil - undermining the foundations of infrastructure, uprooting and destroying farmland
• how do tsunamis cause deaths?

  most tsunami-related deaths are from drowning, but many people are also killed or injured by collapsing buildings or being hit by large debris such as floating vehicles or trees. the flooding inland can also contaminate food and water supplies with salt and raw sewage which can lead to diseases such as cholera