volcanic formation

• Volcano


  An opening in the earth's crust for lava, ash, and gases.
• Magma


  Beneath a volcano, molten rock containing gases.
• Low Silica Content


  Results in low viscosity, allowing gas to escape easily.
• High Silica Content


  Leads to high viscosity, trapping gases.
• Effusive Eruptions


  Occurs with less viscous magma, allowing gas to escape.
• Explosive Eruptions


  Happen with viscous magma trapping gases, causing pressure buildup.
• Subduction Zone


  Where tectonic plates collide, with one sliding beneath the other.
• Pacific Ring of Fire


  Location where most volcanoes form due to tectonic plate boundaries.
• Hotspot Volcano


  Forms when water lowers rock melting point, creating a volcano.
• Volcano


  An opening in the earth's crust for lava, ash, and gases.
• Magma


  Beneath a volcano, molten rock containing gases.
• Low Silica Content


  Results in low viscosity, allowing gas to escape easily.
• High Silica Content


  Leads to high viscosity, trapping gases.
• Effusive Eruptions


  Occurs with less viscous magma, allowing gas to escape.
• Explosive Eruptions


  Happen with viscous magma trapping gases, causing pressure buildup.
• Subduction Zone


  Where tectonic plates collide, with one sliding beneath the other.
• Pacific Ring of Fire


  Location where most volcanoes form due to tectonic plate boundaries.
• Hotspot Volcano


  Forms when water lowers rock melting point, creating a volcano.
• cinder cone may occur as secondary volcano or single volcano. they are also called as parasitic cones
• stratovolcano is also known as composite volcano. they build up over time by alternating layers of lava flow, volcanic ash and other volcanic materials. they can be highly explosive due to magma's high viscosity.
• shield volcano is characterized by its broad, gently sloping profile which resembles a warrior's shield
• lava dome is a rounded mound of lava. it forms near the vent of a volcano. it is made up of thick, sticky lava that does not flow far before it cools and hardens. it can grow slowly over time as more lava pushes out from the volcano's vent
• caldera is a bowl-shaped depression formed when a volcano collapses into the void left when its magma chamber is emptied

  
• volcanic plugs occur when magma solidifies in the fissure of a volcano. the hard dense rock may form a "neck" that remains when softer surrounding rock have been eroded

  
• tuff cones are shallow flat-floored craters that scientists think formed as a result of a violent expansion of magmatic gas or steam

  
• active volcanoes

  • if a volcano is currently erupting or is expected to erupt in the near future
  • 500 volcanoes are classified as active
  • 50-70 volcanoes erupt each year
• dormant volcanoes


  one that is not currently erupting but are expected to erupt in the future
• extinct volcanoes


  volcanoes that are considered dead
• erupting volcanoes


  can either be explosive or quiet (effusive)
• lava flows

  • fluid flows are hotter and move the fastest. they form streams and rivers
  • viscous flows are cooler and travel shorter distances. they form lava domes and volcanic plugs
  • most lava flows can be easily avoided by a person on foot because they don't flow much faster than walking speed
  • lava flows cannot be avoided or diverted
• pyroclastic density currents

  • mixtures of pulverized rock, ashes and hot gases from a volcanic and can travel up to hundreds of miles per hour
  • pyroclastic surges are diluted pyroclastic currents
  • pyroclastic flows are concentrated pyroclastic currents
  • pyroclastic density currents are gravity-driven (flow down slopes)
• pyroclastic falls occur when tephra is ejected from a volcanic vent during an eruption and falls to the ground some distance away from the vent
• lahars are specific kind of mudflows made up of volcanic debris. they are not as fast or hot as other volcanic hazards but they are extremely destructive
• gases

  • water vapor (h2o)
  • carbon dioxide (co2)
  • sulfur dioxide (so2)
  • hydrogen sulfide (h2s)
  • fluorine gas (f2)
  • hydrogen fluoride (hf)
• 3 types of volcanic earthquakes

  1. volcanic-tectonic - represents a brittle failure of rock. this process occurs along tectonic faults. this earthquake occurs due to normal processes such as movement of magma, fluids and existing rocks
  2. Long period or Low-frequency - these are caused by cracks resonating as magma
  3. tremors - a continuous high amplitude signal that can be caused by multiple processes. a continuous flow of volcanic-tectonic earthquakes
• fault lines are fractures along tectonic plates
• Shield volcano's lava is basaltic in composition
• kilauea is an active volcano that has been erupting since 1983
• mauna kea is a dormant volcano which erupted 3500 years ago