PLATE TECTONICS Flashcards
who came up with the continental drift theory
Alfred wegener
what’s the name of the one land mass?
panagea
what is the name of the 2 land masses once it split?
laurasia and gondawanaland
what evidence is there to prove plate tectonics?
fit of continents
fossils
climate and ice
palaeomagentism and sea floor spreading
what is palaeomagentism?
magnetic field of igneous rock containing minerals(eg. iron) which aligned at time of cooling.
EG. symmetrical pattern either side of mid atlantic ridge
structure of the earth
inner core
outer core mantle
upper mantle (aethenosphere and lithosphere)
crust
what is moho discontinuity?
change in composition between thin outer skin of crustal rock and upper mantle.
what are the 4 plate boundaries?
constructive(divergent)
destructive(convergent)
conservative(transform)
collision
what is a constructive/divergent plate boundary?
2 plates move apart
gentle volcanic activity and minor earthquakes
new islands form as crust emerges
what is a destructive/convergent plate boundary?
subduction zone
2 plates move towards each other
-trenches,earthquakes,violent volcanos
oceanic under continental
what is a conservative/transform plate boundary?
2 plates sliding past each other
earthquakes
crust not lost or made
what is a collision plate boundary?
continental plate colliding
fold mountains
violent earthquakes
crust not lost or made
characteristics of a oceanic plate
8km thick
3.2g/cm^3
iron and magnesium
characteristics of a continental plate
30-70km thick
2.7g/cm^3
silicone and aluminium
how to plates move?
convection currents
what is orogenesis?
process of mountain building
what is orogeny?
period of time mountains take to form
what is the basic process of orogenesis?
compression
folding
uplift
what are fold mountains?
folding of rock in strata in the upper part of the crust
sedimentary rock
what is a volcanic island arcs form?
volcanoes in a arc shape
generally due to subduction of oceanic plate
how do oceanic trenches form?
long narrow depressions in sea floor
deepest part of ocean
moves from few mm to over 10cm
occurs at a subduction zone
case study : how do the Himalayas form?
60 million years ago - indian and Asian plate collide
push against each other
crust squeezed upwards
40 million years ago- heavy sediment sinks under Asian plate. closing up the Tethys sea
20 million years ago- Tethys sea gone. sediment pushed up to from Himalayas. Tibet begins to rise
today - indian plate continues to rise due to squeezing
predictions for 10 million years from now
Nepal no longer exists. mountains continue to form advancing edge of india.
what is a volcano?
a volcano is a vent in the earth’s crust geographical landform where magma erupts through the surface.
what are the 3types of lava?
basaltic, andesitic and rhyolitic
what are the properties of andesitic lava?
high silica content less frequent 800c viscous violent ash,steam,lava,tephra
what are properties of basaltic lava?
frequent gentle low viscosity 1200c lava and steam low silica content
what are the 6 types of volcanos
fissure shield ash/cinder caldera strato/composite acid/dome
what is a fissure volcano?
basaltic lava
effusive eruptions
spreads wide and far
what is a shield volcano?
builds up from previous eruptions
basaltic lava
slightly domed
what is a ash or cinder volcano?
mainly ash and tephra
30m to 400m high
pyroclastic material
what is a caldera?
circular depression
huge eruption
collapse of magma chamber
what is a strato or composite volcano?
basaltic and andesitic lava
layers in rock
tall/concial mountain
what is an acid/dome?
steep sided
convex cone
andesistic lava
2 examples of igneous rock
granite and basalt
properties of basalt
extrusive
small crystals- short time to cool
dense
constructive plate boundary
properties of granite
large crystals long time to cool less dense destructive plate boundaries long time to cool in aesthenosphere
what is a lava plateau?
intrusive and extrusive
flat/wide surface
lava spreads quickly
what are the 2 types of plutons?
batholith and laccoliths
what is a batholith?
under earths surface molten rock injected into crust
1 to 100 cubic km
what is a laccolith ?
close to earths surface
causing rock to bend
intrusive
what is a dyke?
discordant
cuts across layers of bedding
crystalised or fine grains
what is a sill?
concordant
sheetlike
injection into current bedding rock
1 to 100 metres thick
what is an extinct volcano ?
extrusive
no lava supply
no longer near an active hotspot
case study : mount etna location plate boundary type of volcano impacts
location: east coast sicily Italy. 100km south of messina and 30km north of Catania
plate boundary: subduction of African under Eurasian. destructive plate boundary
type of volcano: stratovolcano on top of shield volcano
3323m high, explosive eruptions. acid lava
2002-2003 impacts social:
1000 leave their homes
100 homes damages
schools shut
2002-2003 impacts environmental:
crops damaged
pine forest damaged
2002-2003 impacts economic:
tourist resorts affected
damage to business
crops =livelihood
