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part 1a > The Earth > Flashcards

The Earth Flashcards

1
Q

How much of the Earth’s volume is the mantle

A

84%

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2
Q

what is the core mostly made of

A

iron

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3
Q

what silicate minerals is peridotite composed of

A
  • olivine
  • 2 kinds of pyroxene
  • garnet
  • plagiocase feldspar
  • small quantities of metal oxides
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4
Q

what elements compose over 99% of peridotite

A
  • oxygen
  • silicon
  • magnesium
  • iron
  • aluminium
  • calcium
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5
Q

how do we know the mantle is solid

A

it transmits certain kinds of EQ waves which cannot pass through liquid

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6
Q

what is mantle creep

A
  • combination of heat and gravity cause mantle to flow by a slow process
  • crystals slip past each other,
  • atoms and ions diffuse from one place to another
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7
Q

lavas pouring out of a volcano can reach temps of?

A

well over 1100 degrees C

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8
Q

what are the sources of primordial heat

A
  • internal heat dating back to the formation an infancy of the Earth
  • kinetic energy of meteorite hails
  • chemical reactions
  • decay of some very ephmeral but fiercly radioactive elements
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9
Q

aside from primordial heat, what are the other sources of continuing heat in the Earth’s interior?

A
  • crystallisation of the core
  • radioactive decay of lingering isotpes of uranium, potassium and thorium
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10
Q

why is the Earth cooling

A
  • it loses heat through convection into space
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11
Q

electromagnetic radiation indicated a background temperature of space of…

A

-270 degrees

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12
Q

% of mantle mass that is silica

A

45%

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13
Q

% of basaltic magma that is silica

A

45-52%

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14
Q

% of intermediate magma that is silica

A

52-63%

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15
Q

% of silicic magma that is silica

A

63%+

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16
Q

typical temperature of the mantle

A

1300 degreees +

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17
Q

typical temp of basaltic magma

A

1100 degrees

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18
Q

typical temp of intermediate magma

A

1000 degrees

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19
Q

typical temp of silicic magma

A

800 degrees

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20
Q

two types of melting in mantle

A

decompression melting
flux induced melting

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21
Q

what % of the peridotite usually partial melting

A

1-20%

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22
Q

how the mantle’s composition changed over geological time

A

mineral constituents with lowest melting points have been extracted and cooled into the crust and continents

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23
Q

a typical decompression event will yield a liquid with what composition…and called what

A

mixture of pyroxene, plagioclase feldspar and a little olivine
* basaltic melt

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24
Q

once basalt melt has been produced, what does the pressure do

A

pressure squeezes melt from the crystals remaining in the mantle
the melt then percolates upwards forming pools of magma which continue to rise due to lower densities

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25
Q

what % of heat and magma extracted from the Earth’s mantle is from mantle plume

A

5-10%

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26
Q

what can happen when a mantle plume impinges on continents

A

initiate rifting like in East Africa

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27
Q

what is the Eart;s main means of cooling its infernal depths

A

creation of new oceanic crust at ridges and its consumption at subduction zones

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28
Q

what do black smokers do

A
  • black smokers are chimneys which belch hot fluids charged with minerals rich in sulphur
  • these nutrients feed bacteria which then nourish an entire ecosystem of creatues thriving in the stygian waters
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29
Q

stygian meaning

A

very dark

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30
Q

how is serpentinite ormed

A
  • seawater percolates and circulates deep into brand new oceanic crust
  • seawater reacts with the hot volcanic rock, extracting sulphur (black smokers) and hydrating olivine
  • crystals accommodate a quantity of water molecules, forming the slippery green rock
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31
Q

how is the oceanic crust and seabed hydrated as it trundles along

A
  • percolation and circulation of seawater into crust hydrating olivine and forming serpentinite
  • seabed accumulates water rich clays and other waterlogged sediments
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32
Q

how does the incarcarated water percolate to the mantle at the subduction zone

A
  • sinking oceanic plate carries the water into Earths interior
  • once it reaches a depth of 100km, clay minerals, along with olivine and pyroxene crystals that had trapped seawater at the ridge, are under too much pressure to contain the water
  • water is expelled and percolates into overlying mantle
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33
Q

once water at subduction percolates into mantle…now what?

A
  • water dramatically decreases melting point of mantle causing partial melt
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34
Q

in what form is the solid component of magma

A

crystals of one or more minerals (ie olivine, feldspar, pyroxene, quartz)
* Generally suspended in a silicate melt

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35
Q

outline the composition of the silicate melt

A
  • dominated by loose arrangements of silicon and oxygen atoms
  • brew of other elements like Al, Na, K, Ca, Mg and Fe
  • plus volatiles like water, CO2, sulphur and lesser amounts of halogens and trace metals
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36
Q

what would the silicate melt look like at the atomic level

A
  • silicon and oxygen atoms bind together to form tetrahedra (Si in middle and O on 4 corners)
  • tetrahedra shares electrons establishing bonds making the magma more viscous
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37
Q

gas form of magma

A
  • bubbles of volatiles
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38
Q

how do volatile bubbles form in magma

A
  • when mantle melts, volatiles are prefentially extracted out into new liquid
  • under very high pressures they are normally dissolved into the melt
  • as nascent magma ascends into crust it feels less weight - less pressure - bubbles can form - known as exsolution
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39
Q

what are bubbles in magma composed of

A

volatiles
* deep in crust dominated by CO2
* but as magma rises other volatiles exsolve - water, sulphur diozide and hydrogen flouride

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40
Q

what happens with magma at the level of neutral bouyancy

A
  • the magma has ascended to between 3-30km deep where it has the same density as the host rock
  • gravity no longer acts to propel it further upwards
  • with sustained melting of the mantle, magmas drip feed into this zone, accumulating into magma chambers.
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41
Q

what is pumice

A
  • Type of extrusive rock produced when lava with very high water and gas content is discharged from a volcano
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42
Q

extrusive rock

A

rock formed when magma rises, erupts as lava, then cools and crystallises on the earths surface

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43
Q

the more magma that collects in the magma chamber….

A

the greater the potential for a larger eruption

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44
Q

what is a dike and how is it formed

A
  • cracks filled with magma that cut through the crust
  • cracks initially form due to the pressure of magma in the magma pool
  • if they reach the surface fissure eruption occurs
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45
Q

example of a fissure eruption

A

first phase of Ejyafjallojokull 2010

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46
Q

outline fractional crystallisation of magma and the resulting eruption

A
  • subterranean distillation - opposite to partial melting
  • magma will cool in chamber - minerals with higher melting points (like olivine) will crystallise first - this may precipitate to bottom or plaster onto walls.
  • olivine is low in silica, so when it crystallises it increases the silica and volatile content in the remaining magma
  • the higher volatile content will lead to bubble formation, bubbles will expand and pressurise the chamber leading to eruption
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47
Q

what do long lived magma chambers erupt (and give an example)

A

example - Yellowstone
* erupts rhyolites

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48
Q

silica content % of ryholites

A

over 73%

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49
Q

which type of magmas typically have the highest amounts of volatiles - and why

A

subduction zone magmas- they have derive plenty of water, sulphur and chlorine from the subducted crust
* they also reside in thicker crust for longer, so melt the rocks surrounding the magma chamber acquiring more volatiles

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50
Q

what do bubbles do to rising magma

A
  • lower its density and increase the volumes
  • accelerates the magma towards the surface
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51
Q

what does water do to rising magma - and what types of magma is this especially important to

A
  • when water is disolved in melt, it inhibits the bonding between silica tetrahedra
  • as water moves from the melt into bubbles, the tetrahedra increasingly string together into chains
  • this increases magma viscosity so it moves more sluggishly
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51
Q
A
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52
Q

water has caused resistence to magma flow while volatiles are bubbling…. what does this mean?

A

if pressure is suddenly released, for example when chamber walls fail and dikes zip to surface - then highly explosive eruption

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53
Q

what happens when magma meets water?

A
  • sudden production of steam and accompanying expansion can yield extremely violent eruptions
  • hydrovolcanic
  • can happen when seawater gains access to vent of island volcano - like Eyjafjallokull 2010 with glacial melt water
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54
Q

what is the eruption like with low volatile magma

A
  • gas bubbles can escape freely leaving a slow flow of mostly melt and crystals
  • it erupts peacefully in the crater or down the flanks of the volcano
  • known as effusive eruptions
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55
Q

products of explosive and effusive eruptions

A
  • explosive - tephra (pumice, ash, bombs - aka pyroclasts
  • effusive - just lava
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56
Q

2 fundamental eruption parameters

A

magnitude and intensity

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57
Q

how are volcanic eruption magnitudes measured

A

mass or volume of erupted products (better mass as densities vary)

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58
Q

what does VEI stand for

A
  • volcanic explosivity index
    *
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59
Q

Pinatubo 1991 Magnitude scale

A

Me 6.1

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60
Q

how many VEI categories are there

A

7

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61
Q

what is the intensity of an eruption

A

the rate at which magma is erupted (typically measured in mass)

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61
Q

how does eruption intensity link to height of ash columns and gases

A
  • it strongly influenecs the plume altitude
  • the most intense eruptions develop ash columns over 30km above sea level
  • both intensity and column height are related to the heat flux of eruption
  • if intensity is greater, there is a faster rate of heat being pumped into the atmosphere - this means the volcanic cloud will ascend further
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62
Q

how does intensity infuence effusive eruptions

A

it strongly influences the speec and distance over which a lava flow will advance

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63
Q

What is a strombolian eruption

A
  • type of eruption with relatively mild blasts
  • typically VEI of 1-2
  • consists of ejections of incandescent cinders, lapilli and volcanic bombs - to altitudes of 10s-100sm
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64
Q

what is a plinian eruption

A
  • produces tall, sustained, ash and columns - into the stratosphere
  • typically involve intermediate or silicic magmas
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65
Q

what drives the height of plinian eruption clouds

A
  • mostly heat
  • kinetic energy of the eruption amounts to much less than 10% of the thermal energy
  • the nascent plume travels at 350kmph - rapidly ingests surrounding air and heats it up
  • reduced density of hot air compensates for the dense as particles and pumice suspended in the plume
  • once sufficient air is sucked in and heated, the plume becomes less dense than the ambient air and convects up to a neutral density level.
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66
Q

what factors
1. promote air entrainment for column
2. inhibit air entrainment and collapse column

A
  1. high eruption velocities of gas charged magmas through narrow vents
  2. high mass eruption rates, low exit velocities, low gas contents and wide vents
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67
Q

what is a pyroclastic current and how does it form

A

currents of searing mixtures of ash, rock and gases that flow under gravity of speeds up to 200km/h

  • often formed from the collapse of explosive eruption columns
  • can form on volcanoes with active lava domes - initiated by gravitational collapse of portions of the dome or by detonations of pressurised gas close to surface
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68
Q

outline the features of ejected pyroclasts frmom basaltic volcanoes

A
  • They are often larger due to less fragmentation of magma in the eruption conduit
  • less efficient in transferring heat energy as magma is a poor conductor - so wont scale the same heights as plinian eruption columns (less than 10km tall)
  • in fire mountains - clots of lava will stay molten unlike plinian as dont release thermal energy to atmosphere
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69
Q

what are the sizes of ash, lapilli and bombs

A
  • ash <2mm
  • lapilli - up to 6.4cm
  • bombs >6.4cm
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70
Q

what are the negative impacts of ash fallout

A
  • heavy ash fall can destroy buildings - Pinatubo - ash and rain mixed to form a concrete like mixture
  • crushes crops and contaminates pasture - contains flourine - which is digested by animals when eating soil killing them
  • toxic - causes lung disease
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71
Q

what is an ignimbrite

A

pyroclastic deposits from eruptions of Me 6 and upwards

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72
Q

outline the positive impact of ash fertilisation

A
  • volcanic soils have a good reputation for fertility
  • occasional dustings provides nutrients like sulphur and selenium to soils
  • in oceans it provides macronutrients and trace metals which are vital for phytoplankton growth
  • potential substantial removal of CO2 from the atmosphere
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73
Q

why are pyroclastic currents so lethal

A
  • cause heat induced shock, asphyxiation, thermal injury of lungs and burns
  • incredibly fast moving so difficult to avoid
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73
Q

how are co-ignimbrite plumes (phoenix clouds) formed

A
  • the upper parts of pyroclastic currents entrain air like plinian eruption columns due to their heat energy and turbulence
  • they develop bouyant thermal plumes that punch up into the sky - co ignimbrite plumes
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74
Q

which lavas are more viscous

A

intermediate and silicic compositions

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75
Q

example of lava flo causing loss of life (which is normally rare)

A

Nyiragongo 1977 2002

100s of lives lost

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76
Q

possible causes of gravitational failure of volcano flank

A
  • destabilising effects of magma intrusions into the cone
  • ground shaking detonations of explosive eruptions
  • local or large EQs
  • heavy rainfall
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77
Q

outline characteristics of debris avalance

A
  • rarest event of gravitational failure
  • collapse of an entire sector of a volcano * enormous gravity driven rock avalanches that run out for 10s km
  • can trigger an eruption like Mt St Helens 1980
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78
Q

Outline mudflows/lahars

A
  • moving debris is water saturated and runs down drainage channels
  • consists a significant fraction of clay sized particles
  • Can pick up further water and debris, while dropping coarser denser material
  • gradually transform into syrupy clay and water rich flows
  • can also occur when lava/hot tephra is erupted onto ice or snow , when explosive eruptions take place beneath volcanic lakes, when there is intense rainfall on loose deposits
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79
Q

example of lahar tradegy

A

1985- nevado del ruiz in Colombia
* 23k people died
* drowning, burial, destroyed buildings
* mudflow travels 60km to the town

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80
Q

hazards from debris flow and mudflows

A
  • burial
  • property damage
  • downing
  • overloading river systems leading to floods
  • can take centuries for landscape to readjust
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81
Q

how can volcanoes cause tsunamis

A
  • landslides and avalances - displaced material drops into sea
  • pyroclastic currents hitting the water
  • collapse of the crust above a magma chamber during caldera formation on an undersea volcano
  • hydrovolcanic explosions - caused by seawater entering eruption vent
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81
Q

what is a caldera

A
  • large depression formed when a volcano erupts and collapses
  • when large volumes of magma are erupted over a short period, structural support for rock above magma chamber is gone - leading it to collapse
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82
Q

what is the most important volcanic gas in climate change

A

sulphur

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83
Q

at what altitude does the statosphere begin

A

11-17km

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84
Q

how high did the pinatubo cloud peak in 1991

A

35km above sealevel

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85
Q

what happens to the amount of silicate ash in the stratosphere after an eruption

A

immediately there will be significant quantities of silicate ash lofted into the stratosphere, but this will sediment in a matter of days-weeks

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86
Q

what happens to gaseous SO2 erupted

A
  • it oxidises and forms sulphuric acid aerosols in the stratosphere
  • once most has been converted, little more aerosol is formed and the total stratospheric aerosol load decreases as particles subside into the troposphere
  • they are then rapidly deposited to the surface by rainfall and other process
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87
Q

height of the tropopause

A

10km in the poles and 18km in the tropics

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87
Q

settling rate for small sulphur aerosols

A

4 months for every 10km

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88
Q

what do aerosols do to solar radiation

A

scatter incoming UV and visible radiation, directing some back into space and some sideways and forwards. Some is also aborbed

89
Q

what is needed for the aerosol to have warming outbalance cooling. and what was pinatubo

A

aerosols radius should exceed 2 thousands of a mm. pinatubo was 0.5 thousands.

90
Q

what is the tropopause

A

boundary between stratosphere and troposphere

91
Q

why is tropopause higher at equator

A

the equator is warmer, so currents of air expand the thickness of the troposphere at poles

92
Q

outline the stratosphere

A
  • extends from 6-20km up to around 50km
  • temperature increases with height. heat is produced in formation of ozone
  • warmer air is therefore above cooler air, meaning **no convection **as no upwards vertical movement of gases
  • bottom of layer is readily seen with tops of cumulonimbus clouds
  • transition to troposphere is the tropopause
93
Q

outline the troposphere

A
  • almost all weather occurs in this region
  • 6-20km high
  • density of gas decrease with height, thus also temperature
94
Q

what does LIP stand for

A

large igneous province

95
Q

which eruption serves as the foundation on understanding climatic impacts of eruptions

A

pinatubo 1991

96
Q

How long can aerosols persist in the stratosphere

A

couple of years

97
Q

how long can be the impact on climate of gases and particles in the stratosphere and troposphere

A
  • stratosphere 1-3 years
  • troposphere 1-3 weeks before being pulled back by precipitation
98
Q

how much SO2 released into Stratosphere by Pinatubo

A

18 megatonnes

99
Q

how much was the albedo of Earth increased by in 1991 Pinatubo

A

5%

99
Q

how much was direct sunlight cut by Pinatubo 1991

A

25-30%

100
Q

how much did temperatures cool by after pinatubo 1991

A

0.5 degree C

101
Q

when did the net flux of energy return to normal levels after pinatubo

A

2 years later in 1993

102
Q

how do volcanic eruptions link to ozone depletion

A

aerosols produced by major erptions accelerate ozone destruction. Particles provide a surface where chemical reacitons can take place, enhancing chlorine driven ozone depletion.

103
Q

what are LIPs

A

large igneous provinces are areas of high volume magmatic acitvity which can span as large as millions of km^2 occuring with a maximum life span of 50myr.

104
Q

atleast four of the 5 mass extinctions….

A

overlap in the time of LIP events

105
Q

how long did the sulphur injection from the Siberian traps last

A

100-200years

106
Q

how do LIPs cause warming

A

emissions of GHGs like CO2

107
Q

why was photosynthesis encouraged in some regions after Pinatubo 1991- despite cooling

explain the positive feedback

A
  • reduction in direct sunlight reaching the surface - many plants dislike very intense light
  • increase of scattered light in the sky - which penerates more vegetation canopy than direct sunshine thus more leaves
  • means we saw a positive feedback with more carbon sink, furhter pushing cooling
108
Q

why was coral killed after pinatubo 1991

A

cool air temps in Red sea enhanced mixing in water column, bringing nutrients to surface, stimulating algal blooms
* waters turend green with chlorophill, shading corals and hampering water. stagnated water built up hydorgen sulphide, killing much of the coral.

109
Q

how can volcanic eruptions deplete ozone

A
  • sulphuric acid particles provide surfaces where ozone destroying reactions can occur
  • chlorine is trasnformed from stable compounds like hydrogen chloride to reactive forms like hypochlorous acid which destroy ozone
110
Q

why might humans still be a factor of volcanic eruption ozone depletion

A
  • most of the stratospheric chlorine in Pinatubo that reacted was sources from CFCs
  • chlorine erupted from a volcano is in the form of hydrogen chloride, which dissolves into water and moist air
110
Q

what is the relationship between sulphur solubility and silica content of magma

A

inverse. basaltic magmas contain 0.1% by mass of disolved sulphur while silicic magmas contain as little as 0.002%

111
Q

what type of magma are nearly all explosive eruptions

A

silicic

112
Q

what is an oxidising agent

A

chemical species that will accept electrons from another species - for example iron

113
Q

what is the relationship between sulphur dissolving and oxidiation

A

magmas can take in more sulphur when highly oxidising or highly reducing

114
Q

factors making magmas sulphur rich

A
  • silica content
  • oxidising/reducing
  • temperature and pressure
115
Q

what is the saturation effect of sulphuric acid in stratosphere

A
  • general trend that bigger eruptions and more sulphur rich magmas will cause stronger perturbations to climate
  • however, more sulphur in stratosphere means larger particles will form - thee are less effective in scattering sunlight and drop out of atmosphere faster
  • the atmosphere is saturated with injections a few times larger than Pinatubos
116
Q

whats the relationship between injection height of sulphur and climate impact

A
  • if column is confined to the troposphere then the atmospheric processing of the S is spred up due to rapid rain deposition
  • more explosive eruptions will loft S gases to the stratopshere where they can generate climatically effective aerosol
117
Q

which is the least best understood type of volcanism

A

hotspot

118
Q

temperature of magmas at
* hotspots
* subduction zones

A
  • 1200 degrees
  • less than 1000 degrees
119
Q

axes on the phase diagram

A

x = temperature
y = pressure and depth

120
Q

what is the rate of movement of convecting peridotite

A

10-20cm a year

121
Q

where is peridotite thought to come from in the hotspot plumes

A

much deeper than ocean ridges, near the boundary with the outer core

122
Q
  • mid ocean ridges
  • subduction zones
  • hotspots

explain what happens to the geotherm and solidus at each to form magma

A
  • mid ocean ridge - lower pressures as peridotite rises mean the geotherm shifts to cross solidus
  • subduction zones - solidus crosses geotherm as flux of water changes composition and lowers melting point
  • hotspot - higher mantle temperatues means geotherm shifts to cross solidus
123
Q

3 major components of magma and what does this mean for viscosity

A
  • crystals
  • glass
  • gas

the balance between these 3 determines the viscosity and behaviour of magma.

123
Q

more silica means magma is more

A

viscous!

124
Q

what are the most explosive magmas

A

rhyolitic magma

125
Q

what is the most explosive type oferuption

A

plinian

126
Q

what does an eruption need to generally be to cross the tropopause in the tropics than mid to polar latitudes

A

explosive erption needs greater intensity at tropics, as tropopause is higher.

127
Q

what are the two factors that counteract climatic impact of high latitude eruptions

A
  • the biggest impact of aerosols is scattering sunlight back into space - but there is less solar energy to intercept at high latitudes
  • atmospheric circulation means winds at altitude blow from polewards from tropics - therefore eruptions at high latitudes will go against the temperature gradient and not flow to the southern hemisphere
128
Q

why does an eruption cloud rise higher in a humid atmosphere

A
  • the latent heat released when water vapour entrained in plume condenses out and freezes on altitide - additional source of thermal energy to drive plume ascent
129
Q

how does timing of the year affect ITCZ - and what does this mean for eruptions

A
  • shifts north of Equator during N hemisphere summer and south during winter.
    *
130
Q

landforms found on oceanic oceanic boundary

A

deepsea trench and volcanic island arc

131
Q

example of mountain belt found on convergent plate boundary

A

the andes

132
Q

how deep does the marianas trench reach…and what type of boundary is it

A
  • over 11km deep, oceanic-oceanic convergence
133
Q

example of island arcs

A

Aleutian islands off Alaska.

134
Q

what are the x and y axis on the phase diagram

A

x = temperature
y = pressure

135
Q

define geotherm

A

the geothermal represents how the Earths internal temperature changes with depth (pressure)

136
Q

define solidus

A

the solidus is the line showing the temperature and pressure at which a substance begins to partially melt

137
Q

where does the geotherm kink

A

lithosphere-asthenosphere boundary

138
Q

what is the rate of temp increase in the lithosphere

A

25-30 degrees / km

139
Q

how old are the oldest volcanic rocks

A

2.9 bilion years

140
Q

what is the least understood type of volcanism

A

hotspot!

141
Q

temp of magma at hotspots and subduction zones

A

1200, below 1000

142
Q

what moves solidus/geotherm during subduction

A

solidus

143
Q

what determines the viscosity of magma

A

the balance of 3 components:
solid crystals, liquid and gas

144
Q

what does more silica do to magma viscosity

A

silica tetrahedra polymerise together and make long chains

145
Q

why does higher viscosity magma make explosive eruptions

A

it is more polymerised and dense, bubbles cannot move around the melt. the gases expand and expand fragmenting the magma and explodign

146
Q

3 types of effusive eruptions

A

stormbolian, fissure and Hawaiian

147
Q

3 types of explosive magmatic eruptions

A

pinion, vulcanian, pelean

148
Q

what type of eruption happens at mid ocean ridges

A

phreatomagmatic.

149
Q

how is magnitude of an eruption measured

A

total mass/volume of deposit/lava

150
Q

how is eruption intensity measured

A

eruption rate in mass/volume per unit time

kg/s

151
Q

3 ways to quantify eruptions

A

intensity, magnitude, duration

152
Q

what magnitude was pinatubo

A

6

153
Q

what is volcanic degassing responsible for in the first place

A

making the atmosphere breathable in the first place

154
Q

how does monitoring gas help predict eruptions

A

magma rising will release gases, so the greater presence of gases indicates magma

155
Q

define lava lake

A

large volume of molten lava, usually basaltic, contained in a volcanic vent, crater or broad depression.

156
Q

what are lava domes and how are they foremd

A

circular mound shaped protrusion resulting from the slow extrusion of viscous lava from a volcano

157
Q

how does a Strombolian eruption occur

A

when there is a bit of gas in the magma. occurs sporadically in open vent volcanoes where the vent is filled with magma.
large bubbles of gas coalesce together and then rise and explode

158
Q

how tall are lava fountains

A

up to 2km tall

159
Q

what do lava fountains produce

A

scoria

160
Q

what happens and what is formed when hydrovolcanism happens on land

A

explosive eruption creating tuff cones

161
Q

where does subglacial volcanism occru

A

iceland

162
Q

what is a tuya

A

flat topped steep sided volcano formed when lava erupts through a thick glacier/ice sheet

163
Q

what type of eruption was Vesuvius 79

A

plinian

164
Q

how long are pinion eruptions

A

hours to days

165
Q

how tall are eruption clouds of plinian eruptions

A

known to be as tall s 40km

166
Q

where is the tropopause located at poles and tropics

A

20km at tropics
10km at poles

167
Q

largest eruption of 20th cent

A

pinatubo 1991

168
Q

how wide was the cloud of pinatubo

A

100km

169
Q

impacts of ash fallout

A

respiratory damages
roof collapse

170
Q

what are pyroclastic flow

A

fast flowing currents of rock, ash and hot gas produced during eruptions

171
Q

how fast can pyroclastic flows be

A

200km/hr +

172
Q

explain the formation of pyroclastic flows

A

explosive eruptions eject pyroclastic material, which ascends due to its higher temperature and bouyancy

due to gravity the cloud becomes denser and collapses. this triggers it to cascade down the sides of the volcano, with the Material above pushing the lower material downhill

173
Q

how are mudflows caused and what are they also called

A

lahars

the large accumulation of ash that is unconsolidated, followed by rain.

174
Q

where is pinatubo located

A

Luzon, Philippines
100km from manilla

175
Q

when did pinatubo start and climax

A

June 12th

June 15th

1991

176
Q

what landform was created by pinatubo

A

caldera , 2km wide!

177
Q

how high was the tropopause above pinatubo

A

17km

178
Q

how much SO2 was released by pinatubo

A

20 million tonnes

179
Q

what happens to the SO2 in the atmosphere

A

it reacts with water and is oxidised forming stratospheric solid sulphate aerosol

180
Q

what is the correlation between sulphur aerosols and visible light

A

the size of aerosols is similar to the wavelength of light
0.4-0.7 microns

181
Q

why was it significant the Pinatubo eruption happened near the equator

A

the aerosol clouds could spread in both hemispheres

182
Q

what are the primary gases given by eruptions

A

CO2 and H2O

183
Q

how long before the ash fallout from explosive eruption

A

2-3 weeks

184
Q

how long can fine ash last in the stratosphere and how small it is

A

1 micron, very fine

for up to a year

185
Q

after the eruption what happens to materials that only reach the troposphere

A

will be washed out, including gases

186
Q

as a consequence of global cooling after pinatubo what happened at the tropics

A

drought

this affects the monsoon system

187
Q

aside from Pinatubo what other eruption recently caused cooling

A

el chichon

188
Q

what conditions are needed for an eruption to cool the climate

A

large emission of SO2

preferably explosive to get the SO2 into the stratosphere

tropical latitude to spread in both hemispheres

should happen in summer for greater impact

189
Q

why does eruption size not necessarily correlate with climate effect

A

big eruptions may have magma high in gas, so there is not much sulphur
while smaller ones may have more sulphur

190
Q

how many years for temp to recover after pinatubo

A

5

191
Q

how many years for temp to recover after toba

A

10

192
Q

how much did temperatures drop by toba eruptions

A

12 degrees

193
Q

how do we know of past eruptions

A

ice cores!

we look at fine ash (which settles after a year )
as well as sulphur (Which settles 2/3 years )

spikes in acidity = eruption

194
Q

how may halogens affect climate from eruptions

A

chlorine, bromine, iodine from magma

they react with ozone and cause catalytic destruction

195
Q

where have we studied halogens in ozone

A

el chichon 1982

196
Q

what does LIP stand for

A

large igneous province

197
Q

what type of eruptions form LIPs

A

effusive

198
Q

where do LIPs form

A

over hotspots

199
Q

how long do LIPs take to form

A

centuries to millenia

200
Q

what are the LIP magmas rich in

A

CO2, sulphur and chlorine

201
Q

how did Siberian traps effect end permian

A

triggered significant warming due to the continuous injection of SO2 and greenhouse gases into the troposphere over millennia

202
Q

what can most mass extinctions be linked to

A

LIPs

203
Q

how did samalas eruption effect Europe

A

led to a colder few years from 1257 leading to famine and bad harvest
1.5million died

204
Q

how did pinatubo affect the ocean

A

acidification

205
Q

define LIP

A

exceptional volcanic events in Earths history characterised by large total volume of mainly magic magma erupted in a brief period of time (less than 1 million yrs)

206
Q

compare the volume of magma
pinatubo and siberian traps

A

5 km3

over 15 million km3

207
Q

what are the characteristics of LIPs

A
  • iron and magnesium primitive rich lavas
  • millions of km3
  • from potentially a focus source/fissure
  • presumed to be caused by Giant mantle plumes
208
Q

how is tephra dated

A

argon argon dating

209
Q

how are LIPs formed

A
  • formed due to anomalies within interior
  • deep plumes from the mantle rise towards the surface
  • at the top, the mantle melts thorugh decompression melting
210
Q

how may Siberian traps have caused end permian extinction

A

ozone depletion by halogens - led to over 1000 as much UV radiation

greenhouse gases

all led to rapid warming

211
Q

aside from ozone depletion, list the other ways LIPs may have caused large scale species extinctions

A

oceanic anoxia
ocean acidification
sea level changes
toxic metal input
essential nutrient decrease

212
Q

how is the cenozoic cooling thought to be caused

A

Mountain uplift all across the earth

213
Q

what is key to establish links of cause and effect on whether LIPs impacted climate

A

geochronological precision

214
Q

what Does VEI stand for

A

volcanic explositivity index

215
Q

how much ash and pumice was expelled by pinatubo 1991

A

10 trillion kg

216
Q

what is the average length of a volcanic eruption

A

1 month

217
Q

how do ice cores indicate former volcanic eruptions

A

spikes in electrical conductivity and acidity are caused by sulphur fallout
from major eruptions

218
Q

DVI and VSI

what are they

A

dust veil index
developed by Hubert lamb, it looks at how dust vails affected radiation reaching the earths surface

volcanic sulphur index
measures eruptions based on tonnage of sulphur ejected

219
Q

how do local people view Mauna Kea

A

home to the goddess Pele, she lives in side and can create or destroy land, can have sudden rage

Hawaii is her land and they should respect her. they offer berries to her

220
Q

which types of magma are higher in gas -basaltic or silicic

A

silicic

221
Q

why is pinatubo so important for understanding climate impacts

A

it was because it could be monitored by satellites

222
Q
A

part 1a (9 decks)

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