Volcanic hazards

• Composite and shield volcanoes are found along plate margins and have distinctive characteristics and can have both positive and negative effects on people and the landscape.
• Composite volcanoes, also known as stratovolcanoes, are found on destructive plate margins, where the oceanic crust sinks beneath the continental crust, and are characterized by acidic lava, steep sides, alternate layers of ash and lava, and violent eruptions with longer periods between eruptions.
• An example of a composite volcano is Mount Pinatubo in the Philippines.
• Shield volcanoes are found on constructive plate margins, where two tectonic plates are moving away from one another, and are characterized by basic lava, gentle sides, no layers, and less violent eruptions with shorter periods between eruptions.
• Mauna Loa is a shield volcano, but was formed over a hot spot, rather than at a constructive plate margin, like other volcanoes.
• Monitoring volcanoes is popularly done through seismic monitoring, which involves measuring the changes in the Earth's surface caused by volcanic activity.
• The benefits of living by a volcano include the potential for economic growth due to tourism and the availability of geothermal energy.
• There are two main types of volcano - composite and shield.
• Composite volcanoes, also known as stratovolcanoes, are found on destructive plate margins, where the oceanic crust sinks beneath the continental crust, and are characterized by acidic lava, steep sides, alternate layers of ash and lava, and violent eruptions with longer periods between eruptions.
• An example of a composite volcano is Mount Pinatubo in the Philippines.
• Shield volcanoes are found on constructive plate margins, where two tectonic plates are moving away from one another, and are characterized by basic lava, gentle sides, no layers, and less violent eruptions with shorter periods between eruptions.
• Mauna Loa is a shield volcano, but was formed over a hot spot, rather than at a constructive plate margin, like other volcanoes.
• Monitoring volcanoes is popularly done through seismic monitoring, which involves measuring the changes in the Earth's surface caused by volcanic activity.
• The benefits of living by a volcano include the potential for economic growth due to tourism and the availability of geothermal energy.
• There are two main types of volcano - composite and shield.
• Composite volcanoes, also known as stratovolcanoes, are found on destructive plate margins, where the oceanic crust sinks beneath the continental crust, and are characterized by acidic lava, steep sides, alternate layers of ash and lava, and violent eruptions with longer periods between eruptions.
• An example of a composite volcano is Mount Pinatubo in the Philippines.
• Shield volcanoes are found on constructive plate margins, where two tectonic plates are moving away from one another, and are characterized by basaltic lava, gentle sides, no layers, and less violent eruptions with shorter periods between eruptions.
• Mauna Loa is a shield volcano, but was formed over a hot spot, rather than at a constructive plate margin, like other volcanoes.
• Monitoring volcanoes is popularly done through seismic monitoring, which involves measuring the changes in the Earth's surface caused by volcanic activity.
• The benefits of living by a volcano include the potential for economic growth due to tourism and the availability of geothermal energy.
• A supervolcano is a volcanic centre that has had a very large eruption in the past.
• Volcanic eruptions are classified using the Volcanic Explosivity Index, or VEI.
• Like with earthquake magnitude the VEI is a logarithmic scale.
• An increase of one in VEI number is equivalent to a tenfold increase in volume of erupted material.
• A supervolcano is a large volcano that has had an eruption of magnitude 8, which is the largest value on the VEI.
• Supervolcanoes occur when magma in the mantle rises into the crust but the magma can’t break through.
• Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure.
• Supervolcanoes can occur at hotspots or at subduction zones.
• Super-eruptions are dominated by explosive activity, where the erupting magma is torn apart by gases dissolved in it.
• A super-eruption includes a tall plume of ash rising into the air and fragments moving down the slope of the volcano as a hot liquid known as a pyroclastic flow.
• A pyroclastic flow is very dangerous and destructive but only travels a few kilometres.
• Plumes of ash can spread over vast areas.
• A super eruption in the Taupō Volcanic Zone could cover most of the North Island in over a metre of ash, depending on the wind direction during the eruption.
• Supervolcanic eruptions can cover huge areas with lava and volcanic ash.
• The spread of ash in the atmosphere can cause long-lasting climate change as the ash stops energy from the sun reaching the Earth’s surface.
• Super-eruptions could cause a lowering of temperatures and trigger an ice-age.
• In the last 2.6 million years there have been 10 super-eruptions worldwide.
• Four of these have been in the Taupō Volcanic Zone.
• The other super-eruptions during this time include: Yellowstone – Idaho, United States, Long Valley – Eastern California, United States, Toba – Sumatra, Indonesia, Cerro Galán - Argentina.