option D LO1 more or less Flashcards
CC divergent landforms 2
-rift valleys + block mountains
- rift volcano
OO divergent landforms 3
- submarine basaltic volcano
- mid oceanic ridge
- island arc
OC convergent landforms 4
- andesitic volcano
- oceanic trench
- volcanic arc
- fold mountains
CC convergent landforms 2
fold mountains
rift valley
CC convergent example
himalayan mountains
- indian and eurasian plate
OO convergent landforms 3
- submarine basaltic volcano
- oceanic trench
- island arc
transform landforms
faults
rift valleyst
transform boundary examples 2
north anatolian fault
- eurasian and anatolian plate
san andreas fault
- pacific and NA plates
action of OO divergent pb 5
- When 2 O plates move away from eo – gap in lithosphere
- Molten magma from astheno fills gap
- Magma contacts cold seawater = solidifies to form new crust
- A ridge forms along length of boundary
- landform – mid oceanic ridge eg Mid Atlantic Ridge (NA diverging from eurasian plate)
CC divergent pb action 2
- continental crust ripped apart (bc tensional forces caused by convection currents, tensional stress bc plumes)
- formation of rift vlleys and block mountians
OC convergent boundary 6
- denser O plate subduscts beneath C plate (forced into astenosphere)
- subducting plate heated and melted = magma
- magma less dense = rises, escapes thru cracks
- forms volcanoes – grows into volcanic arc
- point of subduction = deep trench
(6. tensional forces may have relief of stress thru seismic activity)
2 how is seismic activity geerated
- massive friction and stress (between…)
- tremours generated by magma rising thru plate
OO convergent pb actions 4
- 2 O plates converge
- subducted plate younger, less dense BUT denser than mantle so sinks and melts
- magma rises and builds to form volcanoes – grow above sea line = volcanic island arc
- point o subduction = trench
CC covergence pb actions 2
- CC plates collide = massive crustal deformation (NO SUBDUCTION)
- forms fold mountains
what happens at transform boundaries
- paltes move past e/o along transform fault
- shallow focus earthquakes occur
volcanic hotspots are formed by _______ ______ rising _______ the plate
mantle plumes
within
5 steps volcano formation
- magma rises thru cracks in crust
- pressure builds
- eruption – pressure released at pb
- lava erupted cools into new crust
- successive euptions = built up
5 parts of volcano
- magma chamber
- pipe/conduit
- vent
- crater
- caldera / bigger crater
3 types of volcanoes and their characteristics
cinder vs shield vs composite
small vs VERY wide vs medium
short vs TALL vs medium
composite most eruptive
which volcano type is most eruptive
composite
eg mt fuji
3 types of lava
basaltic vs andesitic vs rhyolitic
fast vs medium vs slow
low viscosity vs medium vs high
lower silica = ___ viscous
lower temp = ____ viscous
less
more
lava definition
molten magma erupted onto earth surface
pyroclastic materials def
loose unconsolidated volcanic materials ejected from a volcano
3 compontents of pyroclastic materials
- volcanic ash – very fine particles, ash flows up to 200km/h
- lapilli: fine particles
- volcanic bombs
characteristics of shield volcano
- low, gently sloping sides
- low viscosity lava (basaltic)
- gentle eruptions
- usually divergent boundaries/tensional
characteristics of composite/strato volcanoes
- highand steep profile
- alternating eruptions of pyroclasts and lava
- pyroclastic flow
- usually convergent pb
- secondary cones?
ash cinder volcanoes characteristics
- solid mat and lava blobs ejected
- material blown violently, pieces settle around vent = builds cone
nature and type of eruption is determined by amt of ______
silica
2 types of lava flow
pahoehoe
- smooth, ropey appearance
A’a
- denser, more viscous, thick
4 types of pyroclastic eruptions
- strombolian eg stromboli volcano italy
- vulcanian eg vulcano volcano italy
- pelean eg mt pelee
- vesuvian
define pyroclastic flow
dense, fast moving flow of solidified lava pieces, volcanic as, hot gases
pri hazard
what are secondary hazards of volcanoes
flooding, lahars
- melting / mixing with snow and ice
what are volcanic landslides
- large masse of wet/dry rock and soil fall/flow rapidly due to gravity
- can transform into a lahar (high water and fine mat)
what is a lahar
hot/cold mixture of water and rock that flows down volcano slopes
lahar formation 3
- eruptions melt snow and ice
- pyroclastic flows mix with snow and ice
- high vol of rainfall during/after = rainwater transports fine/loose volcanic sediment
what index is used for measurement of volcanic eruptions
volcanic explosive index (vei)
- based on amt of mats, cloud height, damage
define earthquakes
sudden vibrations in earths crust in response to geologic forces
features of earthquakes 3
- focus (shallow <70km, deep >300)
- epicentre (point on ground above focus)
- seismic waves (P and S waves)
what seismic wave is responsible for most earthquake damage
secondary waves bc it goes up and down
3 severity factors for earthquakes
- magnitude
- dist from focus/epicenter
- local geologial conditions (rock soft/hard, water content)
richter scale vs mercalli scale
measures magnitude vs measures intensity and damage (based on perception)
4 human triggers for earthquakes
- construction of large dams (incr load = destabilises land)
- mining (material removed = instablility = sudden collapse = eq)
- hydraulic fracturing (fracking – injecting liquid at high pressure)
- testing nuclear weapons
4 earthquake secondary hazards
- tsunamis
- landslides
- liquefaction
- transverse faults
how do earthquakes cause tsunamis
2 underwater tectonic plates – 1 subducts = sudden vertical displacement of water
= huge waves
- incr friction with seabed slows waves = incr amplitude
define mass movement
DOWNSLOPE movement of masses of rock
under the pull of GRAVITY
shear strength vs shear stress
internal resistance of body to movement
vs
causes movement parallel to slope
factors affecting shear strength 5
- internal cohesion (betw particles)
- vegetation (binding action of plant roots)
- frictional resistance
- pore water pressure (rain, irrigation, dam leakage)
- geographical – rock structure
factors affecting shear stress 5
- steeper slope = incr
- slope gradient = gravity
- loaded (Adding weight)
- undercutting (roads, wave action)
- external shocks eg eq
3 factors affecting mass mvoement
- gravity
- slope angle
- pore water pressure (incr = ability to move)
2 steps slope failure
- decr in shear strength / internal resistance
- incr shear stress = pull down
role of water in mass movements
- replaces air in pores of rock = icnr weight
- saturated materials = liquefaction bc vibrations
- water reduce friction (sliding surface)
- can change angle of repose (steepest angle where pile remains stable)
