Tectonic Hazards

• What are convection currents?

  movements of heats
• Why is the Earth's core so hot?

  -its under enourmus pressure, cant melt

  -rdioctive decay of naturally occuring chemical elements such as uranium releases energy to form heat which slowly rises to the Earths surface
• how can convection currents move tectonic plates?

  Convection currents exert a weak 'pull' on plate above. They cause tectonic plates to move apart or close together or slide past each other
• What is a hot spot?

  A hot spot is a section of the Earth's crust where plumes of magma rise weakening the crust these are usually away from the plate boundaries.
• Ways to describe volcanoes

  - active and erupt frequently

  - dormant (temporarily inactive but not fully apart)

  -extinct (never likely to erupt again)
• Where are sheild volcanoes found?

  Constructive boundaries
• How are sheild volcanoes formed?

  Eruptions of thin runny lava (basaltic) which flows out of the ground freely and isn't explosive
• How are the eruptions in shield volcanoes?

  Gentle
• example of shield volcano

  Mauna Loa, Hawaii
• Describe a sheild volcano

  They're low with gentle sloping sides
• What are composite volcanoes made up of?

  alternating layers of lava and ash
• Where are composite volcanoes found?

  Destructive plate boundaries
• Describe composite volcanoes lava

  It has andesitic lava, which is less fluid and more viscous and has more gas bubbles in it and is more likely to explode out of the ground
• What is the flow of eruptions from a composite volcano?

  Pyroclastic flow rather than a lava flow.
• What is a pyroclastic flow?

  a mixture of hot steam, ash, rock and dust
• What does a pyroclastic flow do?

  It can roll down the sides of a volcano at very high speeds and with temperatures over 400•c
• What is an example of a composite volcano?

  Mount Pinatubo in the Philippines
• What are the two parts the upper mantle divide into?

  Lithosphere (oceanic and continental crust)

  Asthenosphere
• Describe a Lithosphere

  Surface to 35km deep

  Split into tectonic plates

  Solid rock, temperature from air temp to 900•c
• Describe an Asthenosphere

  75-250km deep

  Top layer of the mantle

  Partially molten, the plates float on top of this 900-1600•c
• Describe oceanic crust

  Thin (6-8km thick)

  Denser basalt
• Describe continental crust

  Thick (30-50km thick)

  Less dense granite
• Describe upper mantle

  Mostly solid 35-700km deep
• Describe the lower mantle

  700-2900km deep

  Solid rock 1600-4000•c
• Describe the outer core

  2900-5270km deep

  Liquid, 4000-5000•c
• Describe the inner core

  5270-6370 km deep
• What happens in convergent/destructive (-><-) plate margins?

  Oceanic crust is heavier/ denser and sinks beneath continental. Forms deep sea trenches where it sinks and island arcs with volcanoes
• What earthquakes/volcanic activity happens in convergent/destructive plate(-><-) margins?

  Violent volcanoes and earthquakes and tsunamis
• Examples of convergent/destructive(-><-)plate margins

  Pinatubo 1991- Eurasian and Philippine plates

  Indian Ocean tsunami 2004- Indo-Australian and Eurasian plates
• How are tsunamis created at destructive plate boundaries?

  Pressure builds as the plates get stuck

  Plate thrusts upwards and displaces water creating a wave
• How are fold mountains formed at collision zones?

  Collision zones are where two continental plates meet and form fold mountains eg. The Himalaya- Indian and Eurasian plates
• What happens in divergent/constructive (<- ->) plate margins?

  Two plates move apart. Magma seeps up from the mantle to form new oceanic crust- mid sea ridges with volcanoes
• What is the earthquake/volcanic activity of a divergent/constructive (<- ->) plate margin?

  Gentle volcano and earthquake
• Examples of divergent/constructive (<- ->) plate margins?

  Iceland volcano 2010

  Mid Atlantic Ridge between Eurasian and North American plates
• What happens in conservative plate margins?

  Two plates move past each other- land is neither formed nor destroyed
• What earthquake/volcanic activity is in conservative plate margins?

  Violent earthquakes (but no volcanoes)
• Examples of conservative plate margins

  San Andreas Fault, California- Pacific and North American Plates
• What is a lahar?

  A destructive volcanic landslide or mudflow, consisting of a mixture of volcanic debris, mud, rock and water
• What is lava?

  Molten rock released from the Earths cove in a volcano or a fissure most lava is slow moving and is not a big hazard to life, but can damage property