Earth Flashcards
Plate boundaries
12 major plates
Continental 35 km thick, oceanic 6.5 km
interglacial/glacial cycles can change pressure on crust -
- more pressure, less magma activity, interglacial
- decompressed crust stimulates lava flow, glacial
Internal heat budget
heat from accretion, compression, core formation, radionuclides.
geothermal gradient
change in earths temp with rspect to depth
solidus
temperature below which rock is completley solid
Hydration melting
oceanic crust, minerals hydrate, denser, subduct
slab has water, is expelled when reaches a depth due to pressure, lowers melting point
higher explosivity at SZ water becomes gas, inc pressure
(Oppenheimer, 2011)
Adiabatic melting
no change in heat, change in pressure, decreases melting point
partial melting can occur
partial melting
pyroxene and plagioclase melt most in decompression melting (45% silica by mass, basaltic)
strombolian activity
mild end of explosive eruptions, open vent volacnoes, sends blobs of lava on projectiles
tuya
prolonged subglacial eruption
plinian eruptions
sustained explosive eruptions. When plume reaches maximum height, ash sinks and spreads forming umbrella cloud
Pinatubo 1991
100 km from capital
No monitoring, not considered active
April, signs of change, rapid geological survey, monitoring set up
June eruption starts
Plinian cloud collapse - pyroclastic flow
Typhoon Yunya simultaneously
Caldera formation
Pyroclastic flows changes topography
Mudflows and lahars for decade after
climatic impacts
gases in strat dispersed by winds
in trop gas remains
trop is lower at equator
halogen compounds emitted (H2O, CO2, SO2)
aerosols
SO2 oxidises to form stratospheric sulphate aerosol
0.5 microns, same wavelength as suns radiation, scatters it
clouds absorb IR radiation, heat, ground temp cools, therefore imbalance
pinatubo in tropics, aerosols spread globally, 0.7K drop until 1997
Robock 2000
Tambora 1815
The summer following an eruption shows the largest temperature drop
Modelling shows 12 degree drop in northern hemisphere, 8-9 years to recover
The cooling is dependent on: latitude, height of sulphur, amount of sulphur, season
Stratospheric geoengineering
Use aerosols to scatter radiation
Acidification of oceans
Regional climate change
Colonisation of the atmosphere
Who will it benefit?
eruption precursors
Mass distribution
Density
Chemistry
Thermal regime
EM properties
seismology
magma ascends, rock breaks, sends seismic signals
geodesy
surveying surface, expansion of resovoir changes ground tild
Interferometric Synthetic Apeture Radar (INSAR)
satellites absorb waves, is phase changes between measurements ground has changes
Iceland
Reykjanes peninsula, erupted rocks show their origination and its conditions
Several seismometers triangulate to find source
Photogrammetry, lava flow volume and effusion rate, flow modelling
Hazard zonation map
Phanerozoic Eon -
Last 500 million years, 6 mass extinctions. Occur every time there is a large change in climate
Large Igneous provinces
Siberian traps, largest continental province, 7 million km^2, 250 million years ago, each ‘step’ corresponds to a lava pulse.
Deccan Traps, ⅓ on land, 65 million years ago, 4000m in elevation
Mainly mafic lava, intraplate activity (plumes), short duration (<5 million years) or are short pulses over few tens of Myr
formation of LIP
Large mantle plumes for Large Low Shear Velocity Provinces (LLSVPs)
Mantle has different composition, result of earth’s formation
Rapid ascent through mantle compared to regular (20Ma opposed to 80Ma)
Can uplift crust by up to 1km
Tectonic plate continues to move, disperses head of plume, leaves tail to create hotspot volcanoes
Climatic impacts of LIP
Gases, explosive magma is depleted in CO2, mafic magma is richer
SO2 causes cooling for 1-2 years
Halogen ozone depletion
Biosphere poisoning
Models show only SO2, cooling up to 15 degrees
Only CO2, temp increase up to 20 degrees
Had an initial warming of 8 degrees, hot house state, feedback loops meant a total increase of 34 degrees
Permian mass extinction, 96% of species died.
Kilauea Hawaii
2-3 eruptions per year
pele godess of hawaiis volcanoes
power to create and destroy land
Oldonyo Lengai, Tanzania
‘mountiain of the god’ in Massai
offer sacrifices for cattle and children
volcanic eruptions cleanse land, killing insects and parasites (does happen at an ash fallout)
Ruapheu, new zealand
sacred to brandch of maori tribe
systems of knowlege through dances, storytelling, writing and drawing
recollection of past erutopns over centuries allowed response to be generated
hazard map - ‘sacred locations’ correlate with highest risk
water level in river
what happens if SO2 only reaches troposphere
fall as acid rain (robock, 20115)
what happenes if it is SO2 rich and reaches stratosphere
1-3 year ong aeroso coud of suphate aerosols
block incoming solar adiation
radiative forcing
Pinatbo cloud
extratropical aerosol cloud
radiative forcing up to 80% stronger than tropical eruptions due to their confinement to one hemisphere
18Mt of SO2
0.5 degree global cooing following year
warmed tropics more than high latitudes, large pole-equator temp gradient
jet stream - strenglthens polar vortex (NH winter warming)
SO2 and ozone
enhanced depletion of ozone, more UV
anthropogentic influences must pre-exist (CFCs)
