The restless earth Flashcards
(41 cards)
Structure of the earth?
inner core
outer core
Mantle (convection currents)
Crust
Features of Continental crust
Older
Less dense
Doesn’t sink
Never destroyed or renewed
Feature of Oceanic Crust?
Newer
Denser
Sinks (below continental crust)
Destroyed and renewed
What happens at a destructive boundary?
Plates move together
Subduction - oceanic subducts beneath continental
Collision - 2 continentals collide and buckle
What happens at a constructive boundary?
The plates move apart
What happens at a conservative boundary?
The plates move past each other
similar directions
different angles and speed
What makes the plates move?
the convection currents in the mantle
What forms at destructive subduction boundaries?
(Oceanic crust melts to form magma)
Fold mountains
Ocean trenches
What forms at destructive collision boundaries?
Fold mountains (e.g alps) composite volcanos
What forms at Constuctive plate margins?
Shield Volcanos
ocean ridges
What forms at conservative boundaries?
Upland ridges
EARTHQUAKES
Composite volcanoes
at DESTRUCTIVE plates boundaries steep sides made of lava, ash, lava, ash eruptions are infrequent and violent often have PYROCLASTIC flows (hot steam, ash, rock, dust)
Shield Volcanoes
at CONSTRUCTIVE plate boundaries gentle, sloping sides low, rounded peak made of lava eruptions frequent and non-violent RUNNY lava (little ash)
Using fold mountains case study
the ALPS
destructive collision boundary (African + Eurasian)
Border France, Italy, Switzerland etc.
Land uses in Alpine valley
1) Farming
SOUTH facing (warmer)
Transhumance - seasonable movement of animals
In summer: animals high up grazing, crops growing in valley bottom
In winter: Animals eating crops in barns
Changes:
cable cars mean milk is transported instead of being changed to butter and cheese
farmers buy feedstuffs so animals can be on valley bottom all year
Land uses in Alpine valley
2) Forestry
Coniferous trees on NORTH facing slopes
main building material and fuel in alps
Sawmills on valley bottom near to riversq
Land uses in Alpine valley
3) Hydro- electric power (HEP)
Steep slopes high precipitation summer melting of glaciers = FAST FLOWING RIVERS narrow valleys are easy to dam lakes to store water
Energy used by:
Industries (e.g sawmills)
exported to other regions
Land uses in Alpine valley
4) Tourism
major industry ALL YEAR Winter: Snow resorts (e.g Chamonix) flatter land on high-level benches for restaurants and hotels steep slope for ski runs and views Summer: Summer resorts (e.g Garda) large glacial lakes on valley floor beautiful mountain scenery
= better resources for locals also (e.g roads)
Land uses in Alpine valley
5) Mining
(not that big in The Alps)
salt, iron-ore, silver, copper
large quarries
nearby industries to send minerals to
In decline due to cheaper foreign sources
Case study of a volcanic eruption
NAME
DATE
PLATES
Mt St Helens, Washington State, USA
18th May, 1980
Destructive : Juan de fuca + North American
Primary effects of St Helen eruption
about 60 dead (also from poisonous gases)
Lahars (ash and water mudflows)
forests destroyed
extensive area destroyed (27km north of eruption)
Secondary effects of St Helen eruption
ash blocked rivers = flooding and destroyed fishing patches
flood = destroyed communications (roads, bridges) and crops and livestock
made land more fertile
Short term responses of St Helen eruption
rescuing survivors
mobilising helicopters
clearing roads
giving shelter to stranded
Long term responses of St Helen eruption
buildings + bridges rebuilt
forests replanted
encouraging tourism again (now is major industry - 3 million per year)
more careful monitoring
