volcanology masterclass

8/8/2019 Volcanology Masterclass

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Volcanology Masterclass

because lifes too short to stayaway from molten rock


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Rebecca Hearne

Third year Geology

at Canterbury Uni,originally fromLeicester Uni in

England.

(NZ is way better)


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I need your help!

Next Friday, the 21st May, I needyou to come to Canterbury

University to take part in myDisaster Simulation Project.

You will be in charge of aneruption scenario!


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Volcanoes are complicated

so please ask plenty of questions.


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Now lets see some action.

Come outside to the playgroundto see a real (well, not quite)

volcano erupting.

start thinking about volcanoesyou already know about. Do theyall behave the same?


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What is magma?

Rock in the Earths mantle thatis superheated through

radioactive decay.

Convection currents transport

it around the mantle and driveplate tectonics.


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Not liquid like water

More like plasticine. We say its ductile.

Certain conditions can allow the magma tomelt into a more liquid state and rise upthrough the crust and reach the

surface.

When this happens, we can get aneruption of lava.


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Lava contains

Mainly different molten mineral crystals the ingredients which determine the

lava type

dissolved water andgas

some whole mineralsdepending on the lavas overalltemperature


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Viscosityresistance to flow

A thick lava with high resistance toflow is very viscous

A runny lava with low resistance to

flow is non-viscous.

Water VS golden syrup VS ice cream


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Viscosity isaffected by the

amount of dissolvedvolatiles (amongst

other things)


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Reduce pressure = more gas

bubbles.

If the magma is runny, the bubbles can comeout easily. Imagine blowing bubbles through a

straw into water.

If the magma is thick, like golden syrup oreven ice cream, how easily will the bubbles

come out?

What happens to the bubbles?


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Gas = explosive!

If lava contains few gases, it is safe tostand next to. The gas comes out easilyand escapes away.

If the lava is gas-rich, it is explosive. Runny lava will splatter everywhere and

can produce fountains and debris piles. BUT thick lava with lots of gas is the

most dangerous dont stand too close!


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Any questions so far?Viscosity refers to the thickness of

the magma.

If magma contains a lot of gas, it ismore explosive than one that doesnt

have much gas.

Viscosity determines how easily gascan escape from magma.


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More about volcanic hazards Ash fall

- Affects human respiratory system;

- Can cover plants and crops;

- Abrasion can affect cars, houses andequipment;

- Can contaminate water supplies;

- Reduces visibility;

- Can cause roof collapse, especially if it getswet;

- All of these lead to other problems


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Pyroclastic flows collapsed

eruption column.http://www.youtube.com/watch?v=vPRoTQYXwuY

Maurice and Katia Krafft

HOT (hundreds of degrees C),

FAST (up to 200km/h),

AND EXTREMELY DANGEROUS!

Evacuation is a good idea


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Lahars and mud flows http://www.youtube.com/watch?v=WEAfXO7q8Xs&feature=related

When rainwater or melt water mixes withvolcanic ash and debris it forms a fast-

flowing lahar.

These sweep away anything in their path andsolidify like concrete.

Can occur weeks or months after an eruption, asthe ash becomes remobilised.


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Lava flows http://www.youtube.com/watch?v=KsYmXFUwU_A

Lava flows are generally the least hazardous,surprisingly.

They can be explosive, but may flow quiteslowly.

However, can set roads, trees and houses onfire!

Can fragment and produce pyroclastic flows ifthe topography is steep.


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Why might it be difficult for me

to fly back to the UK in a fewweeks time?

Eyjafjallajkull!

+ +


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Started to erupt on 10th March 2010.

By April, an ash plume had risen 9km intothe jet stream combined with a

Westerly wind, bad news for air traffic in

Europe!


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Monitoring ground deformation

In Feb 2010 a GPS about 15km south ofEyjafjallajokull showed displacement of3cm, with a 1cm displacement happeningin just 4 days!

Why is ground deformation a goodindicator of increased activity?


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Ground tilt

Measured by GPS systems which canmonitor their own positions, and whenthey change.

Tiltmeters are used, the same asregular spirit levels.

Electronic Distance Measuring, withlasers.


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Monitoring seismic activity

At Eyjafjallajkull, seismic activityincreased between 2006-2009.

In 2006, earthquakes below the volcanowere 8 12km deep

By 2009, they were 7 10km deep, andin their hundreds!


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Harmonic tremors

A continuous agitation of the groundas magma rises, rather than a suddensharp shock like a normal earthquake.

Distinctive on seismographs.

Seismologists feel confident that aharmonic tremor can be used to predict

an eruption.


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We can also measure gas.

As magma rises to the surface, gasesare released. The closer to the surface,the lower the pressure, therefore more

gas can come out.

We measure CO2 and SO2 although

these arent the only gases in magma.

A huge increase in gas means?


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Ash at Eyjafjallajokull

Because the eruption was under aglacier, the hot lava that came outcooled very quickly and shattered into

ash fragments which were very sharpand glassy.

These were carried into the atmosphere

and spread out over thousands ofkilometres. My mum, in England, had ash on her car!


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Electrical storms wow!

Ash clouds can generate powerful

electrical fields producing intense andfrequent lightning storms, which can

interfere with radio communications and

cause power cuts, as happened inIceland!


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We monitor volcanoes before,

during and after an eruption using

Seismic surveys monitoring earthquake

activity;

Gas levels monitoring increase in

concentration of SO2

and CO2

;

Ground deformation.


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Alert Level system

Used by geologists to communicate howsevere an eruption is, depending on what hasalready happened.

Levels 0 (no activity) to 5 (full eruption) thisis the New Zealand system.

This is useful so other geologists know

exactly whats going on, and is also useful forthe general public as its simple to follow, andsays exactly whats happening.


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A simple alert level system:

0 No eruption, regular background activity. 1 A change from background activity. More ash,

gas or earthquakes than usual.

2, 3, 4 Minor eruptions. Ash, pyroclastic flows,small amounts of lava.

5 Full blown eruption.

Its up to the hazard team (that will be you) todecide when the volcanos alert level needs toincrease (or decrease).

volcanology masterclass

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