Volcanoes [EARTH SCIENCE]

• crust

  This is the thinnest layer of Earth where the different landforms may be found.
• asthenosphere

  It literally means “weak layer” where the molten rocks are located.
• boundary

  A plate ___ is the point where two tectonic plates interact.
• Pacific Ring of Fire

  This contains many of the world's active volcanoes.
• subduction

  It is a process in which a plate goes beneath another plate because of the density difference in a convergent boundary.
• mafic

  This type of magma has less silica content, making it less viscous and more fluid.
• felsic

  This magma is more viscous which can trap gases and build up pressure resulting in violent eruptions.
• tectonic plate

  It is a slab of landmass that holds either a continent or an ocean floor.
• volcanic ash

  This is any solid material that came out of a volcano during an eruption.
• fault

  A ___ is a natural crack on Earth’s crust.
• Volcanoes are land or underwater features that form when magma reaches Earth’s surface. They are formed when tectonic plates interact with one another. Most of the world’s active volcanoes are found along convergent boundaries where two or more plates collide. When the plates are being pushed together, the denser plate subducts beneath the less dense plate and sometimes, the magma finds its way to escape and reach the surface to form volcanoes.
• Pacific Ring of Fire is a horseshoe-shaped zone that outlines the Pacific Ocean where volcanic and seismic activities are most active.
• The Alpine-Himalayan Belt is a volcanic and seismic zone formed by the interaction of the African Plate and the Indo-Australian plate.
• There are three types of volcanoes according to their activity (frequency of eruption): active, dormant, extinct
• Active volcano

  • may erupt anytime and has recent seismic activities.
  • Erupts regularly
  • Potentially active volcanoes are young-looking with no historical records of eruptions
• Dormant volcano

  • Inactive but still capable of erupting again in the future
  • hasn’t erupted for a while and has no recent seismic activities
• Extinct volcano

  • a volcano that hasn’t erupted for a long period of time
  • Have no records of eruptions
  • No significant seismic activity in historical time
• A volcano becomes active when there is an active plate movement beneath the plate where it lies. The pressure build-up forces the magma to rise to the surface. Heat and pressure cause the rocks to melt and become magma. Since magma is less dense than the surrounding rocks, the buoyant force causes it to rise to the surface.
• volcanoes can also be classified according to their structures: stratovolcano, cinder cone volcano, shield volcano
• Stratovolcano

  • A large cone-shaped mountain
  • Built from alternating layers of rock particles and lava
  • Formed through violent eruptions
  • has the steepest slope
• Cinder Cone volcano

  • made up of tephra which is accumulated after a violent eruption around its crater
  • They have a narrow base and steep sides.
  • Built from pyroclastic materials ejected from a vent
  • Formed through explosive eruptions
• Shield volcano

  • Broad and slightly dome-shaped
  • Produced by the accumulation of fluid basaltic lava
  • Formed through quiet eruptions
  • gently sloping landform
• vent

  The secondary hole where molten rocks come out of a volcano
• lava

  Molten rocks that reach Earth’s surface
• convergent

  Type of boundary where two plates meet or collide
• lahar

  Dangerous mixture of hot rocks, gases, ashes, and water
• composite

  Type of volcano that has the most violent type of eruption
• volcano

  Opening on Earth’s crust where molten rocks can get out either violently or quietly
• active

  Volcano that has the most recent volcanic and seismic activities
• crater

  Opening at the topmost part of a volcano
• extinct

  Volcano that has no volcanic activity for a long period of time
• shield

  Has gentle slopes and erupts quietly
• In the Philippines, there are many volcanoes due to their location in the Pacific Ring of Fire. This made the volcanoes in the Philippines hazardous and a threat to the Filipinos especially those living near volcanoes. The volcanoes are formed due to the collision of the Eurasian Plate and the Philippine plate. Here are some of the Philippines’ most active volcanoes:

  • Mayon
  • Mt. Kanlaon
  • Taal
• height/size

  Stratovolcano: high

  Cinder cone: high

  Shield: low
• type of lava

  Stratovolcano: granitic

  Cinder cone: basaltic

  Shield: basaltic
• type of eruption

  Stratovolcano: loud/violent

  Cinder cone: loud/violent

  Shield: quiet
• steepness of slope

  Stratovolcano: steepest

  Cinder cone: steep

  Shield: gentle
• PHIVOLCS is the agency that monitors volcanic and seismic activities in the Philippines
• Volcanic hazards

  • volcanic ash
  • lahar and landslides
  • gases
  • pyroclastic flows
  • lava flows
• Volcanic ash comes with molten material when a volcano erupts. It is abrasive and becomes heavy and slippery when mixed with water.