Global Hazards pt2-volcanoes and earthquakes Flashcards
what are the layers of the earth?
crust, lithosphere, mantle, outer core, inner core
how thick is the crust?
1-90km
what is the difference between shield and composite volcanoes?
shield volcanoes have less explosive eruptions and are flatter
what are the 4 plate boundaries and what happens at all of them?
constructive- moving away
destructive- one goes under the other
collision- collide together to form mountains
conservative- sliding past each other
what is subduction?
when a denser plate moves under the other causing it to melt and become molten
how do convection currents work?
magma gets heated up from the inner core and starts to rise. then when it reaches the lithosphere, it spreads to the sides and cools. since it cools it then sinks and goes back.
what is lahar?
a volcanic mudflow which usually runs down a valley side on the volcano.
what are some warning signs for volcanoes?
small earthquakes, temperatures rising, and volcanoes start to release gases
what is a seismometer?
an instrument that responds to ground noises and shaking.
what’s the difference between oceanic and continental plates?
oceanic are denser and thinner and continental are thicker but less dense
how do we measure earthquakes?
a Richter scale, it’s a scientific measurement based on the energy released. measured by seismometers using measurement from 1 – 10
what’s the difference between each point in a seismometer
each point up the scale is 10 times greater than the one before.
what is an epicentre?
is the point directly above the focus on the earth’s surface. This is where most of the damage happens.
what causes earthquakes?
when two plates become locked causing friction to build up. then pressure will eventually be released.
what is the focus?
the place inside Earth’s crust where an earthquake originates.
what is aftershock?
a sudden movement of the earth’s surface that often follows an earthquake and is less violent.
what is a hotspot?
where mantle plume comes through thin crust and causes an active volcano
what is a seismic wave?
Fast wave of energy generated from the focus.
what is a seismic gap?
How long since the last earthquake (the longer the bigger earthquake)
what are some primary impacts of earthquakes?
ground shaking, liquification and infrastructure destroyed.
what are some secondary impacts of earthquakes?
tsunamis, landslides, injuries
what plate boundry do shallow focuses occur at and give an example?
collision.
Nepal.
what is ridge push?
new crust rises
what is slab pull?
old crust sinking
