tectonics ao1 Flashcards
define tectonic hazard
event caused by the movement of tectonic hazard that has the potential to threaten human life, property, the environment, and the economy
what is the difference between rhyolite and basaltic magma and how do they affect eruptions
rhyolite lava has a high gas content, high viscosity and low temperature
whereas basaltic magma has a low gas content, low viscosity and high temperature
rhyolite lava causes more explosive eruptions
what is the difference between continental and oceanic crust
continental is older, less dense, thicker
oceanic crust is younger, denser, thinner
name the three plate boundaries and what happens at them
convergent - plates move towards each other
conservative - plates move past each other
divergent - plates move way from each other
what happens at convergent plate boundaries in terms of volcanic activity, earthquakes and landforms
high magnitude earthquakes
continental/continental - no volcanoes, fold mountains
continental/oceanic - explosive eruptions, ocean trench
oceanic/oceanic - explosive submarine eruptions, island chain
what happens at conservative plate boundary in terms of volcanic activity, earthquakes and landforms
shallow high magnitude earthquakes, no volcanoes
what happens at divergent plate boundary in terms of volcanic activity, earthquakes and landforms
effusive volcanoes, low magnitude earthquakes, rift valley
what is a volcanic hotspot
mantle plume (stationary upwelling of abnormally hot rock) creates pressure melting parts of mantle and crust, leading to volcano
as plates move over mantle plume, volcanic island chain forms
what is structure of earth and each layers properties
inner core - solid
outer core - liquid, creates magnetic field
mantle - solid
asthenosphere - partially melted, allows tectonic plates to move
lithosphere
what is mantle convection
magma heats up in centre of earth, rises to surface, moves, cools, sinks
what is slab pull
when crust is denser than asthenosphere it subducts
weight of downwards movement of subduction pulls the rest of the plate
what is ridge push
magma pushes upwards at divergent plat boundary causing gravity to pull plates down and apart
explain seafloor spreading and paleomagnetism
when lava moves away from mid ocean ridge and cools, the minerals in it align with direction of magnetic field
when magnetic field flips, cooling minerals align in opposite direction
stripes of oppositely aligned rock can be seen moving apart on the seafloor
explain Alfred Wegener’s evidence of continental drift and Pangaea
continents fit together like puzzle pieces
freshwater animal fossils found on opposite sides of ocean
plant fossils in antarctica
similar rock layers on different continents
glacial deposits in now deserts
name 5 secondary hazards of earthquakes
disease
crustal fracturing
landslide
liquefaction
tsunami
explain how a tsunami is formed
submarine earthquake or volcano causes vertical water column displacement, causing wave to travel in all directions which slows down and gains height in shallower water
name 7 secondary hazards of volcanoes
lava flow
pyroclastic flow
ash fall
gas eruption
wildfire
lahar
jokulhlaup
define disaster
realisation of a hazard when it has a significant impact on a vulnerable population
define vulnerability
high risk combined with inability of people and communities to cope
what is pressure and release model
demonstrates how disasters are shaped by processes seemingly unrelated
root cause - dynamic pressures - unsafe conditions - disaster - natural hazards
what is the degg model
shows that disaster occurs when there is interaction between hazard and vulnerable population
what is modified mercalli scale
measures intensity from roman numerals 1-12
what is the MMS
logarithmic scale of magnitude of an earthquake on scale of 1-10
what is VEI
measures magnitude of volcanoes on logarithmic scale from 0-8
based on volume of material ejected, eruption cloud height, duration
