global hazards two Flashcards
what is a drought
a long period when rainfall is below average
what are the causes of a drought
changes in atmospheric circulation such as El Niño.
high pressure weather systems
what is at the centre of the earth
a core
- the inner is a ball of solid iron and outer is liquid
what is around the core
the mantle
what is around the mantle and how big is it
the crust which is about 10-70km thick
what are tectonic plates made from
continental crust- thicker and less dense
oceanic crust -thinner and more dense
how do tectonic plates move
due to convection currents in the mantle
what is a destructive plate boundary
where two plates move towards eachother
what happens when an oceanic plate meets a continental plate
a destructive plate boundary occurs and the denser plate (oceanic) is forced downing mantle and destroyed
what di destructive boundaries create
volcanoes and ocean trenches
what is a collision plate boundary
both planets are made from continental plates and move towards each other which causes both plates to be forced upwards creating mountains.
what is a constructive plate boundary
two plates moving away from eachother and causes magma to rise to fill the gap and cools creating a new crust.
what is a conservative plate boundary
when two plates are moving sideways past eachother or in the same direction and crust isn’t created or destroyed
where are volcanoes found
destructive and constructive plate boundaries
how is volcano created at a destructive plate boundary
oceanic plate moves down into the mantle where its destroyed
a pool of magma forms and rises through the cracks in the crust called vents
magma erupts onto the surface forming a volcano
