volcanoes

• primary hazards of volcanoes

  ash falls (tephra) is a solid material of varying size is ejected into the atmosphere

  buildings often collapse under the weight of ash falls

  air becomes thick with ash and is difficult to breathe and cause respiratory problems
• primary hazards of volcanoes

  volcanic gases can be poisonous

  e.g. carbon dioxide, carbon monoxide

  • lake nyos in Cameroon caused a lot of gases
• primary hazards of volcanoes

  pyroclastic flows are very got and have a high velocity and is a mix of gases and tephra

  pyroclastic flows can destroy everything in its path

  e.g. mount Vesuvius Pompeii and mount st helens
• primary hazards of volcanoes

  lava flows are not usually a major threat when they are molten and slowly moving
• secondary hazards of volcanoes

  lahars are fast mudflows that happens when rain mobilises deposits of volcanic ash
• secondary hazards of volcanoes

  flooding (jokulhlaups) happens when glaciers or ice caps melt
• what is a consequence of ash falls

  building collapse
• tsunamis are a big hazard for many places in the world, they are a secondary hazard of some earthquakes
• most tsunamis are generated by submarine earthquakes at subduction zones

  the seabed is displaces vertically and displaces a large volume of water in the ocean
• characteristics of tsunamis

  long wavelength at sea

  tsunamis have a very high velocity and move very quickly and slow down as they reach shallow water

  drawback- localised drop in sea level