volcanic hazards

• Where is the most active volcanoes?

  75% are around the ring of fire srrounding the pacific ocean
• What is the vulcanicity at a constructive margin?

  They are more effusive and small
• What is the lava like at constructive margins?

  Basaltic lava, Low gas content, Low viscosity, Higher temperatures
• What is the vulcanicity at destructive plate margins?

  More explosive as magma is forces its way up.
• What is the lava like at destructive margins?

  They have andesitic or rhyolitic lava. They have high gas content, High viscosity and lower temperatures
• Where else can volcanoes form?

  They can be found at hotspots in the middle of the plates such as as Hawaii
• How can we measure magnitude of volcanoes?

  Volcanic Explosivity index (VEI) on a scale from 0-8. It is calculated based on height of material ejected into the atmosphere, Volume of material and Duration of the eruption.
• What are some primary hazards?

  Tephra, Ash fallout, Pyroclastc flow, Lava flow, volcanic gases
• Tephra


  bits of rock or solidified lava dropped from the air. Rages from ash to volcanic bombs
• Ash fallout


  Large quantities of ash carried by the wind and deposited on the ground. Can travel many kms which can cause respiratory problems, injuries, deaths and disruption to transport. Example Eyjafjallajokull eruption in Iceland disrupted the air travel in europe for weeks
• nuee ardente


  Known as pryoclastic flow. It's a mix of gas and tephra that flows at speeds of up to 700km an hour. Example : Fuego volcano erupted in Guatemala in 2018 which destroyed serval towns
• Lava flow


  Lava flows travels at different speeds and the gradient of the volcano sides, temperature and viscosity. Most lava flows are slow so it can be outran and not a high risk but it can still cause major damage to the infrastructure. Fastest it can reach up to 60mph. Example : eruption of Mount Nyriagongo in DRC, lava flow travellld over 10km and killed 30+ people.
• Volcanic gas


  Eruptions releasing large quantities of gases such as sulphur dioxide and carbon dioxide. Hazardous to the human health and cause respiratory problems. Example: Kilauea in Hawaii releases large amounts of sulphur dioxide and it lead to air quality alerts and heath warnings for resistant
• What are some of the secondary hazards?

  Lahars, Jokulhlaups and acid rain
• Lahars


  They are mudflows that occur when tephra mixes with water from rainfall or melted snow and ice. They are fast flowing and can destroy everything. Example : Mount Pinatubo erupted in philippines in 1991 causing extensive damage and disruption
• Jokulhlaups


  They are floods caused by sudden release of water and ricks when glacial ice is melted by the eruption. Example: 2010 Iceland eruption triggered jokulhlaups which destroyed serval bridges and roads.
• Acid rain


  Formed when sulphur dioxide is emitted and reacts with water vapor's to form sulphuric acid. These can damage crops, forest and aquatic ecosystem
• What are the types of volcanoes?

  Shield and stratrovolcanoes
• Where are shield volcanoes found?

  At constructive plate margins and are typically high frequency but low magnitude eruptions
• Where are stratovolcanoes found?

  Founded at destructive plate margins and are low frequency but high magnitude eruptions.
• What are the characteristics of a sheild volcano?


  Gentle sloping slides due to runny lava. Made from cooled lava
• What are the characteristic of a stratovolcano?

  Steep sides due to thick sticky lava. Made from layers of ash and lava
• How can scientist predict an eruption?

  Using past eruptions, gas emissions, thermal radiation, Tilt metres satellites, seismometers
• What are some signs of an eruption?

  Magma rising detected by heat monitors, Ground deformation as magma rises and causes bungles, Increase emissions of sulphur dioxide and other gases, Increased seismic activity caused by magma movement detected by seismometers.
• What are some of the social primary impacts?

  Deaths and injuries, Displacement of people, Damages to properties and infrastructure causing disruption to peoples lives.
• What are some social secondary impacts?

  Mental health such as stress and anxiety, homelessness, disruption to services such as healthcare, loss of cultural heritage sites
• What are some economic primary impacts?

  Destruction of properties and infrastructure leading to significant costs for repair and reconstruction. Disruption of trade and economic activity. Loss of income and employment. Costs of immediate response such as food aid and temporary shelters
• What are some ecomomic secondary impact?


  Slower economic growth and development. Increased coming inequality as impacts are more vulnerable to people with a lower income. Increased costs of insurance and hazards management strategies
• What are some environmental primary impacts?

  Poor air and water quality. Loss of biodiversity. Destruction of habitats and ecosystems
• What are some environmental secondary impact?

  Acid rain damaging ecosystems. Release of greenhouse gasses leading to global temperatures rising. Ash clouds leading to a fall in global temperatures due to solar energy being reflected back into space.
• What are some political primary impacts?

  Pressure on government to coordinate with emergency responses. Social unrest and political instability.
• What are some political secondary impacts?

  Conflicts over government response and food shortages. Changes in government policy and regulations to reduce future risk
• What are some short term responses?

  Evacuation, search and rescue and emergency aid
• What are some long term responses?

  Hazard mapping and lad use zoning, building codes and education and training
• Examples of preventions


  Permanent structures and overnight camping are prohibited around St Helen's
• Examples of preparedness


  The Phillipines has a text message alert system for warning about immediate eruptions
• Example of mitagation


  Iceland built a 4m high earth wall to divert lava away from vital infrastructure such as toads and power cables
• Example of adaptation


  Montserrat government promoted tourism as an alternative instead of providing jobs for local people as an alternative.