Images from: Boston.com

Ireland in the shadow of a volcano:

Understanding the 2010 eruption at

Eyjafjallajökull, Iceland.

Chris Bean, School of Geological Sciences, UCD.

World Quakes and Volcanoes1960 - 2010

../../../../Public/Desktop/Smithsonian Exhibit Version.lnk

What is driving the plates?

-The mantle undergoes convection

- But why is the mantle hot?

There are two primary sources of heat:

-Heat remaining from the formation of the Earth

-Heat as a by-product of radio active decay

By the way:

In 1897, Lord Kelvin assumed that the Earth was originally molten and calculated a date based on cooling through conduction and radiation.His age for the Earth was calculated to be about 24-40 million years…

It’s actually about 4.5 billion year old (he didn’t know about radioactivity)

Numerical Simulation of Mantle convection:

From: http://www.ipgp.jussieu.fr/~labrosse/movies.html

MantleConvectionSimulation.mpeg

- Plate boundariesEarth’s crust...* Continental (silica rich – ‘sticky granites’)* Oceanic (silica poor – ‘flowing basalts’)

Remote GPS station near Katla volcano

Observations from Space:

Some GPS station locations in SW Iceland

From: Thora Arnadottir

Continuous GPS recordings in SW Iceland

Volcanoes – not all the same ...

Most volcanoes occur near plate boundaries ... But maps like this one are misleading as perhaps up to 80% of activity occurs below the oceans –mainly at mid-ocean ridges (divergent boundary).Three groups of volcanoes ...

Mt St Helens, May 1980.

Trees blown over like match sticks by the blast. Note how they follow the topographic contours.

Photos from USGS archive

If Iceland lay below the sea... What would it look like?

- lava- ocean chemistry

pillow_lava.movSCsmoker2.lg.mpg

But Iceland is special ...

Its on the ridge, but lies above the sea surface ... But why was eruption so explosive, producing lots of ash?

Volcanic Ash – what and how?

-Consists of small bits of pulverised rock and glass (< 2mm in diameter).

- Main causes of ash production:

• Gas release under decompression – this is important where gas is trapped in sticky magma

• Thermal contraction on contact with water

• Steam ejection ripping particles off surrounding rock fragments – steam driven explosions fragment rock.

Microscope image of ash from Mt St Helens –yellow scale bar is 0.5 mm wide

Eyjafjallajökull.

Formation of Surtsey - 1963

Volcanic Activity_ The Formation of Surtsey(2).mp4

After Páll Einarsson.

Schematic

Eyjafjallajökull – vital stats.

- Stratovolcano, 1650 m high

- Crater 3-4 km in diameter

- Part of a chain of volcanoes on Iceland

- Nearest neighbour, Katla (about 15 km away)

- Last eruption end of 1821-1823 (lasted for just over one year).

Eyjafjallajökull – 2010 eruption

-Dec 2009, thousands of small deep earthquakes detected (7-10km below volcano)

- Feb 2010, inflation of the earth’s crust and additional seismic activity detected

- First eruption, March 20th, occurred on the flank, not under the glacier ... was an effusive fissure eruption

- Second eruption, April 14th, occurred beneath the glacier and was explosive.

- June 3rd – no ash emissions, just steam.

After Páll Einarsson.

Schematic

Sub Glacial Floods are a major hazard in Iceland.

Gjalp, Iceland, 1996 (Image: Iceland Met Office)

What now? ...

Volcano Monitoring: Seismic system on Mt Etna

Images: INGV

Monitoring:

- Earthquakes ...

From: USGS

Monitoring:

- Deformation ...

Satellite interferograms (after Andy Hooper).

Monitoring – what else:

- Gas and liquid chemistry

- Flood monitoring (water levels)

- Gravity

Climate change & volcanoes?

- Large eruptions usually cause a short term cooling of Earth (depends on sizes of particles emitted).

- Global warning is melting the glaciers that cover many of the world’s high altitude / high latitude volcanoes. This decompresses the volcanoes (500 m of ice exerts pressure of about 45 time atmospheric).

- But more eruptions led to more cooling (usually) – so there is a feedback – and predicting the outcome is very challenging.

What next from Iceland ... ?

Katla? – Eyjafjallajökull’s big neighbour

Schematic of volcano monitoring. Real-time information flows back to ‘interpretation centres’ at observatories. Civil protection authorities are kept informed by observatory scientists – civil protection makes the decision to evacuate or not, based on scientific advice.

Monitor:

-Gas output- Fluid chemistry- Deformation (GPS)- Tilt- Gravity changes- Seismic signals