Valcano Hazard

• Vulcanism


  Refers to a variety of processes associated with the surface discharge of magma or hot water steams, such as volcanoes, geysers, fumaroles, and hot springs. All these are fueled by the underground's powerful heat source.
• Geysers


  A surface vent that periodically ejects a column of hot water and steam.
• Fumaroles


  A geothermic vent that emits volcanic gases such as CO2, NO2, CO, HS. They are fed by conduits that pass through the water table before reaching the ground's surface.
• Hot Springs


  Also called a thermal spring. A source of geothermally heated water rising to the surface. It emerges when precipitation or groundwater is heated by magma beneath.
• Volcano


  Volcanoes are fascinating geological features that are formed when molten rock, ash, and gas escape from the Earth's surface. They can be found all around the world and come in many different shapes and sizes.
• Parts of a Volcano

  • Crater
  • Magma Chamber
  • Conduit
  • Fumarole
• Caldera


  Some volcanoes have large craters called calderas that can exceed about 1km in dm. They are formed when the summit of the volcano collapses during violent eruptions.
• Shield Volcanoes


  • It has a wide base with gently sloping sides. The cone is made up purely of lava that has poured out and solidified during a mild or quiet eruption.
• The largest volcano in the solar system is the Olympus Mons found in Mars. This volcano was though to be extinct. Shield volcanoes in Mars are higher and more massive than those on Earth.
• Stratovolcanoes/Composite


  • These are tall, steep-sided volcanoes with a classic, cone-shaped appearance. They are formed by alternating layers of lava, ash, and other volcanic debris. Have explosive or non-explosive eruptions and are known for their powerful explosions and pyroclastic flows.
• Cinder Cones


  • These are small, steep-sided volcanoes made up of loose, pyroclastic material such as ash, cinders, and volcanic bombs. They are usually formed by explosive eruptions that eject the material from a single vent, piling it up around the vent.
• Types of Volcanoes According to Activity

  • Active Volcanoes
  • Dormant Volcanoes
  • Extinct Volcanoes
• Active Volcanoes


  A volcano is considered active if it is currently erupting or showing regular signs of activity like earthquake activities and significant gas emissions. Has a record of eruption within 50 years.
• At present, of 859 active volcanoes in the world, more that 75% of them are located in the CIRCLE OF FIRE (Pacific Ring of Fire). This circle is the belt of volcanoes that rings the Pacific Ocean.
• Dormant Volcanoes


  Those that have currently erupted and then enter a long period of inactivity. Seismologists have found out that the longer period pf dormancy between volcanic eruptions, the greater the chance of having a very explosive eruption in the future.
• Extinct Volcanoes


  Those that have not shown signs of activity for a long period of time. It has no record of volcanic eruption in the past thousand years. Whether the volcano is truly extinct is often difficult to determine.