Volcano

• Volcano – a vent on the Earth’s surface that opens downward to a

  pool of molten rock, debris, and gases
• Subduction – takes place when two plates converge
• Subduction Zone – plates where two plates converge and the

  volcano is formed
• Active – currently erupting or is showing signs of volcanic

  eruption. It should have erupted within the last 600 years
• Potentially Active (Dormant) – one that has erupted and then

  entered a long period of inactivity
• Inactive (Extinct) – one that has not shown any sign of activity for

  a long period. Has no record of volcanic eruption in the past

  thousand years
• Lava Flow – mass of magma flows down the slope of the volcano
• Pyroclastic Flow – hot dry masses of fragmented volcanic

  materials that move along the slope and the ground surface at a

  speed greater than 60 km/hr.
• Pyroclastic Surges – are turbulent low-concentration density

  currents of gases, rock debris and in some cases, water, that move

  above the ground and surface at high velocities
• Tephra Falls – showers of fine to coarse-grained volcanic materials

  and other airborne products of a volcanic eruption. The ash can

  reach distant places since it is carried by the wind.
• Ballistic Projectiles – rocks that are released into the air by an

  erupting volcano.
• Volcanic Gas – one of the basic components of magma or lava.

  Active and inactive volcanoes may release gases into the

  atmosphere.
• Lahar – flowing mixture of volcanic debris and water