Yr 12 UCAS Tectonic Hazards Flashcards
where are most earthquakes and volcanoes found
along plate boundaries, 70% of earthquakes found in the Ring of Fire in the Pacific ocean
what is a divergent plate boundary
when two plates move away from each other, 2 continental magma rises to fill the gap creating a rift valley, two oceanic plates it forms a submarine volcano
what is a convergent plate boundary
when two plates move towards each other, when two oceanic the denser plate subducts, when oceanic and continental the oceanic subducts. causes earthquakes due to friction, two continental plates it forms fold mountains
what is a Conservative plate boundary
when two plates slide past each other, sinistral ( left) or dextral (right), causes shallow earthquakes
what is a hotspot
a volcano created in the middle of the plate, caused by a mantle plume which melts the oceanic crust and forms a submarine volcano which grows into an island arc as convection currents cause the plates to move which forms new volcanos e.g Haiwaiian Ridge
what are the three theories of plate tectonics
layers of earth, continental drift, seafloor spreading
what are the four layers of the earth
crust, mantle, outer core, inner core
what is the Benioff zone
an area of seismicity corresponding with a slab being thrust down into the subduction zone
what are p waves
vibrations caused by compressions
what are s waves
vibrate at right angles to direction of travel and can’t pass through liquids
what are love waves
surface waves which can cause large amounts of damage
what is liquefaction
cause buildings to settle, tilt and collapse, lateral spreading causes damage to roads and bridges. Secondary effect
what are landslides
occur when slopes weaken and fail, in Kashmir earthquake 1/3 of all deaths due to landslides. Secondary effect
what is pyroclastic flow
mixture of dense hot rock, lava, Ash and gases that are ejected, 700 degrees and 100km/h, Primary Hazard
what is tephra
pieces of rock and Ash that blast into the air during eruptions, Primary hazard
what are lava flows
streams of lava that are 1170 degrees and take years to cool completely but are slow, primary hazard
what are volcanic gases
water vapour, CO2, sulphur dioxide and can be potentially hazardous, primary hazard
what are lahars
masses of rock mud and water that travel quickly down the flanks of a volcano, 10m/s, when eruption melts ice and snow, secondary effect
what is jokulhaup
heat of volcano melts snow and ice and causes flooding, secondary effect
what is a hazard
a perceived natural event that has the potential to threaten both life and property
what is a disaster
a serious disruption of the functioning of a community, which exceeds the ability of the affected community to cope using its own resources
what is the risk equation.
hazard x exposure x (vulnerability/ manageability)
what is continental drift
there was a super continent called Pangea that became separated, evidence was that Africa and South America looked like a jigsaw, Scotland and Canada have matching rock sequences, Fossils in India and Australia matched
what is seafloor spreading
by studying the age of rocks on either side of the Mid-Atlantic Ridge Harry Hess realised that the Earth’s polarity swaps every 400,000 years (Palaeomagnetism)