Volcanoe shapes, lava and eruptions

• Pyroclastic flow - fast moving cloud of hot gas and rock fragments
• Lahar - mudflow caused by volcanic ash mixing with water
• Name the types of volcanic eruptions that occur at Constructive plate boundaries <-- --> :

  1. Icelandic eruptions
  2. Hawaiian eruptions
  3. Strombolian eruptions
• Name the types of volcanic eruptions that occur at destructive plate boundaries --> <-- :

  1. Vulcanian eruptions
  2. Vesuvian eruptions
  3. Pelean eruptions
  4. Plinian eruptions
• What is Tephra?

  any solid material thrown into the air by volcanic activity. It includes ash, larger rock fragments, and even tiny glass shards.
• Lapilli - small particles of rock that are ejected from a volcano during an eruption. They are typically 2 to 64 millimetres in diameter.
• Name the 2 types of explosive lavas:

  1. Rhyolitic lava
  2. Andesitic lava
• Which type of lava has the highest gas content?

  Andesitic lava (4-6%)
• Explosive lavas such as andesitic and rhyolitic lava are found at what type of plate boundary?

  Destructive (convergent --> <--)
• What are effusive eruptions?


  eruptions which are dominated by lava and have lower gas content
• What are explosive eruptions?


  eruptions that involve magma that is more viscous and has a higher gas content
• What are fissures?

  A fissure is a long, narrow opening or crack, often formed in rock or earth due to geological activity.
• Name the 7 different types of volcanic eruptions:

  1. Strombolian
  2. Hawaiian
  3. Vulcanian
  4. Icelandic
  5. Vesuvian
  6. Pelean
  7. Plinian
• Name the 3 different types of lavas in order of destructiveness:

  1. Rhyolitic
  2. Andesitic
  3. Basaltic
• Which type of lava is effusive?

  Basaltic lava
• Give the characteristics of Basaltic Lava:

  • Effusive
  • -1 to 2 % gas content (lowest)
  • 50 % Silica content
  • Low viscosity
  • Higher temperature (1000 - 12,000 degrees Celsius)
  • found at constructive margins
  • smaller but more frequent eruptions
• What is viscosity?

  Resistance to flow

  Low viscosity is runny and fast like water

  High viscosity is thick and slow like honey
• State the characteristics of Andesitic Lava (medium explosiveness) :

  • Explosive
  • 3 - 4% gas content
  • 60% silica content
  • High viscosity
  • Intermediate temperatures (900 - 1000 degrees Celsius)
  • Found at destructive margins
• Give the characteristics of Rhyolitic lava (the most explosive) :

  • The most explosive
  • Less frequent but violent eruptions
  • Highest viscosity (Fast flowing but travels shorter distances)
  • lower in temperature (750 - 900 degrees Celsius)
  • 4 - 6% gas content (highest amount)
  • Silica content 70% (highest amount)
  • Found at destructive margins
• The shape of a volcano is dependent on the type of lava that comes out of it
• What type of lava comes out of Icelandic eruptions?

  Basaltic
• What type of lava comes out of Hawaiian eruptions?

  Pahoehoe - a type of Basaltic lava
• What type of lava comes out of Strombolian eruptions?

  Thick basaltic lava
• What type of lava is ejected out of Vulcanian eruptions?

  Andesitic
• What type of lava is found at Vesuvian eruptions?

  Andesitic
• What type of lava is produced at Pelean eruptions?

  Thick andesitic lava
• What type of lava is found at Plinian eruptions?

  Rhyolitic
• Give the characteristics of Icelandic eruptions:

  
  

  • Eruption height - no higher than 1km into the atmosphere
  • Mostly lava (no gas) - forming lava plateaus
  • Regular/ continuous eruptions
  • Basaltic (runny) lava flows gently from a fissure
• What type of Volcanic eruption is this?

  A) Icelandic

  
• Give the characteristics of Hawaiian eruptions:?

  • Basaltic lava flows gently from a central vent
  • Calm eruptions with lots of fluid lava, not much gas
  • lava can be referred to as Pahoehoe which means smooth and ropey
  • up to 1km ejected high
  • Form Shield volcanoes
  • Found at constructive plate boundaries
  • Frequency = Regular
  • Effusive
• What type of volcanic eruption is the photo showing?

  A) Hawaiian

  
• Give the characteristics of Strombolian eruptions:

  • Slightly thicker basaltic lava flows
  • Small but very frequent
  • Explosive eruptions often with lots of tephra and steam
  • Short lava flows but due to high amounts of gas in the magma below ground lava arcs can be seen often
  • Volcanic bombs often ejected along with lapilli
  • Form at constructive plate boundaries
• What type of volcanic eruption is the picture showing?

  A) Strombolian

  
• What are the characteristics of Vulcanian eruptions?

  • more violent but less frequent
  • tend to be mostly andesitic lava
  • lava is thicker
  • gases can not escape leading to a build-up of high pressure - making eruptions explosive
  • often eject lava 5 - 10 km into the atmosphere
  • Things ejected = Volcanic bombs, pyroclastic flow, fined grained ash
  • Form at destructive plate boundaries
• Name the type of volcanic eruption shown in the photo:

  A) Vulcanian

  
• Give the characteristics of Vesuvian eruptions:?

  • Violent explosions after long periods of inactivity
  • Andesitic lava flows
  • very violent gas explosions blast ash high into the sky - causing ash clouds
  • build up in gases leads to a frothy lava
  • Eruptions can be up to 15km high
• Which 2 types of volcanic eruptions look like the one in the photo?

  A) Plinian

  B) Vesuvian

  
• What are the characteristics of Pelean eruptions?

  • Violent explosive eruptions followed by pyroclastic flows
  • Lava is much thicker and is andesitic
  • Large amounts of gas / lava / dust / ash are blown out of the volcano
  • Bulges can be seen on the sides of the volcano before eruptions as the material collapses in on itself - causing huge landslides (pyroclastic flows)
  • Very dangerous eruption
• What type of volcanic eruption is the photo depicting?

  A) Pelean

  
• What are the characteristics of Plinian eruptions?

  • Rhyolitic lava flow
  • Explosive
  • Composite volcanoes
  • Violent eruptions of gases, ash and pumice
  • Reach far into the sky - up to 17km
  • Mixed with bad weather conditions these can cause lahars (molten material + water)
  • Heavy pumice fall and pyroclastic flows (collapse of material)
  • Begins with dissolved gases stored in the magma chamber - accumulating and rising - eventually exploding
  • Eruptions can last from days to hours