tectonic hazards

• The Plate boundaries

  • Destructive(convergent)
  • Constructive(divergent)
  • Conservative(transfrom)
  • Collision(destructive)
• Convection currents disproven

  • Heat generated from convection is not enough to pull plates
  • The slab pull theory is supported
• Slab pull theory

  • slab pull is the force generated when a dense, sinking ocean plate at subduction zone pulls the rest of the tectonic plate along with it
• Slab pull explanation

  • Cause: As oceanic plates move away from mid-ocean ridges, they cool down and become denser. When these plates eventually reach a subduction zone, the dense slab begins to sink into the hotter, less dense mantle due to gravity.
  • Effect: The weight of the sinking slab pulls the rest of the tectonic plate toward the subduction zone, facilitating the movement of the entire plate.
  • Importance: Slab pull is considered one of the most significant forces driving the motion of tectonic plates, along with ridge push (from mid-ocean ridges) and mantle convection.
• define subduction

  • when one tectonic plate moves beneath another
  • usually whena oceanic plate slides under a continental plate.
  • this happens along the junction of two plates known as a subduction zone
• Ridge push

  • it is the force that drives tectonic plate movement, caused by the weight of elevated mid ocean ridges.
  • Gravity pushes the plates away from the ridge, contributing to the plate ,motion
• Destructive(convergent) plate margins

  1. oceanic plate moves towards a continental plate
  2. The heavier denser oceanic plate is subducted beneath the lighter continental plate.
  3. as it is forced downwards, pressure at the margins increases, and forms a mid ocean ridge. this can result in violent earthquakes
• Constructive(divergent) plate margins

  • The Earth's crust is forced apart
  • Magma rises and solidifies to create a new oceanic crust and forms a mid ocean ridge
  • This ridge is made from igneous rock; such ridges usually form below sea level on the seabed.
• Collison plate margins

  • occurs when two plates(continental crust) move together
  • Continental crust cannot sink or be destroyed, as a result the land between them is pushed upwards to form high 'fold' mountains like the Himalayas
  • Earthquakes are common but no volcanoes
• Conservative(transform) plate margins

  • Two plates sliding past each other slowly
  • This creates friction and pressure builds up; the release of this pressure creates a severe earthquake.
• Why do consrvative plate margins have no volcanic eruptions

  • the crust is neither being created nor destroyed
• An example of a conservative plate margin

  • Haiti, Christchurch
• An example of a constructive plate margin

  • Iceland
• An example of a destructive plate margin

  • Chile
• Intraplate tectonics(middle of plates)

  • Associated with ancient faults such as the Rhine rift valley
  • this is the result of solid crust cracking as it travels over millions of years
  • the east african rift valley is a new fault which may create a new plate
  • associated with magnitude earthquakes
• Examples of volcanic hotspots

  • Hawaii
  • Nyirangongo(african plate)
  • Yellowstone (on north american plate)
• Yellowstone Caldera chain

  • current caldera has a series of eruptions that span millions of years
  • The north american plate is moving west over a stationary hotspot. As the plate moves the hotspot produces an enormous eruption every few million years
  • This has produced a chain of Rhylotic calderas(circles,in million of years)
• Where are earthquakes and volcanoes found

  • clusters along plate boundaries
  • 70% are found in pacific ring of fire in the pacific ocean
  • most powerful-destructive or conservative boundaries
• ocean fracture zone

  • occurs along mid ocean ridges such as around Africa to the middle east
• continental fracture zone

  • occurs where continental plates meet such as Alps and Himalayas
• Seafloor spreading

  • New crust is formed at mid ocean ridges, the crust pushing the plates apart
• What process plays a pivotal role in sea floor spreading

  • ridge push
• Paeleomagnetism

  • Studies in the 1950s shows that magnetic fields of the rock that had been created had changed over time
  • This shows the magnetic orientation of the new crust created
  • Magnetic fields of the earth change every 400,000 yrs. leaving their imprint in rocks. can be measured
• Subduction

  • It is when one tectonic plate slides beneath another and sinks into the Earth's mantle.
  • This usually happens when a denser oceanic plate collides with a less dense continental plate, or another oceanic plate, forcing the denser one to descend.
• Facts on oceanic plates

  • denser
  • Made from Basalt
  • youngest rocks on earth
  • can be created and destroyed
• Facts on continental plates

  • thick
  • less dense
  • ancient
  • 4 billion yrs old and are not being formed today
  • Made of granite (less dense and 30-60km thick)
• .Basaltic means

  • Basic magma
• Andesetic means

  Intermediate magma
• Rhyolotic means

  Acidic magma
• Supervolcanoes

  • they have long time gaps between each eruption period but they have significant impacts upon the planet
• Examples of supervolcanoes

  Yellowstone

  Taupo in New Zealand
• Basaltic volcanoes

  • very hot
  • iron rich
  • silica poor
  • very hot runny lava
  • Effusive
  • sheild style volcanoes
• Andesitic volcanoes

  • hot
  • iron poor
  • silica rich
  • explosive
  • can take decades and centuries between eruptions
• Rhylotic volcanoes

  • cooler lava
  • iron poor
  • High silica content
  • high gas content
  • erupt rarely or devastating
• what determines the volcanic eruption style

  • crystal, gas content and temperature of magma
• Crystals and gases in magma

  • it is more viscous as it cools
  • so magma with high crystal content is more likely to explode than flow
  • therefore gases build up as they cannot easily escape from the viscous magma
• Temparature and gases in magma

  • hotter magmas release gases as they are more fluid
  • high temperature magmas usually erupt effusively as they cool much slower
  • low temperature magmas cannot flow easily and are more likely to erupt explosively
• Primary Hazards

  • lava flows-hawaii
  • pyroclastic flows-Montserrat
  • Tephra/Ash fall-Eyjafjallajokull
  • Gas eruptions-Mnt st. Helens
• secondary hazards

  • Lahars-e.g pinatubo
  • Jokulhlaup-Eyjafjallajokul
  • landslides
  • Tsunamis
• Orogeny

  • the geological process that leads to the formation of mountain ranges, via tectonic forces such as plate collisions, subduction, and continental collision. It involves large-scale deformation of the Earth's crust and can result in various geological phenomena such as folding, faulting, and metamorphism.