plate tectonics 2

• Three types of families of volcanoes:

  • Dome volcano: formed from viscous (acidic) lava, steep-sided cone, e.g. Soufriere Volcano, Montserrat
  • Ash and cinder volcano: formed from acidic lava, violent eruptions, volcanic cone mainly made out of ash and cinder (small cooled fragments of volcanic lava), e.g. Paricutin, Mexico
  • Composite volcano (Strato-Volcano): has alternating layers/bands of ash and cooled lava, violent eruptions, e.g. Soufriere Volcano, St. Vincent
  • Shield volcano: gentle slope, formed from basic, less viscous lava, e.g. Mauna Loa, Hawaii
• The Ring of Fire is located around the edges of the Pacific Ocean
• The tectonic plate that moves in a zig-zag pattern is the San Andreas Fault plate
• Convergent Plate boundaries are also called subduction zones
• Volcanoes exist in the geosphere

  • Parts of the geosphere that contribute to the development of a volcano are the lithosphere and asthenosphere
• Volcanoes can be:

  • Active: where eruptions occur frequently
  • Extinct: where the volcano has not had an eruption in at least 10,000 years and will never erupt again
  • Dormant: where eruptions are infrequent and have not occurred for some time
• Intrusive volcanic features:

  • Secondary Vent
  • Batholith: forms when a giant underground reservoir of magma cools and hardens
  • Laccolith: the result of a relatively large amount of magma moving between bedding planes, causing the overlying layers of rock to arch upwards
  • Sill: formed when magma moves horizontally and lies along bedding planes when it cools and solidifies
  • Dyke/Dike: formed when magma moving diagonally up towards the surface cools and solidifies within the crust
• Types of lava:

  • Acidic lava: rich in silica, viscous (thickness), explosive, violent eruption, produces steep-sided volcanic cones, takes a longer time to cool
  • Basic lava: low in silica, non-viscous, less violent eruption, produces lower, less steep-side cones (gentle gradient), cools quickly (solidifies on contact with air)
• Extrusive volcanic features:

  • Dome volcano: formed from viscous (acidic) lava, steep-sided cone, e.g. Soufriere Volcano, Montserrat
  • Ash and cinder volcano: formed from acidic lava, violent eruptions, volcanic cone mainly made out of ash and cinder, e.g. Paricutin, Mexico
  • Composite volcano (Strato-Volcano): has alternating layers/bands of ash and cooled lava, violent eruptions, e.g. Soufriere Volcano, St. Vincent
  • Shield volcano: gentle slope, formed from basic, less viscous lava, e.g. Mauna Loa, Hawaii
• Earthquakes are the sudden movement of the Earth's crust which causes gentle to violent tremors on the Earth's surface
• Seismic activity (earthquakes) occur when plates slide past each other, causing huge pressure to build up. When this pressure is released suddenly, an earthquake occurs
• Anatomy of an earthquake:

  • Crust
  • Focus: the source or origin of an earthquake
  • Fault line
  • Epicentre
  • Seismic waves (tremors)
• Features of an earthquake:

  • Focus/hypocenter: the point where the first and strongest seismic waves are felt
• Seismic waves are vibrations/shock waves given off from an earthquake. There are two types of seismic waves:

  • Primary (P) waves: the first waves felt which travel through solids, liquids, and gases. The particles in motion move in a back and forth (lateral) motion
  • Secondary (S) waves: the second waves felt which travel through solids only. The particles in motion move vertically (up and down)
• The strength of an earthquake is described as the magnitude. It is measured on a moment magnitude scale. The Richter scale is also used to measure magnitude