Volcanoes

"At the same time the Lord rained down sulphurous fire upon Sodom and Gomorrah." (Genesis, Chapter 19, verse 24)

Iceland has hundreds of volcanoes, varying in age, maturity and activity. Many are extinct, but there are 27 central volcanoes of various sizes and activity considered active at the moment. Some of those haven't erupted for a few centuries, but some are possibly erupting under glaciers when this is written. This amount of volcanoes makes Iceland not only the largest volcanic island in the world, but also a country with more skiable volcanoes than all of Europe (apart from Iceland, obviously) put together.
Iceland therefore creates an interesting challenge, not just for skiers, but also mountain climbers, off-roaders, historians and geologists.

A short compilation of information on the most famous and active volcanoes in Iceland follows.

Katla's history
Katla lies under the glacier Myrdalsjokull and is one of the most active and most dangerous volcanoes in Iceland and was named after a housekeeper that was said to have magical powers.
As the story goes, she is meant to have fled and vanished into the glacier. Not long after, there was a volcanic eruption from the place she vanished, resulting in the melting of part of the glacier.
The water from this activity headed for the monastery that she used to serve in and was therefore believed to be her revenge. From that day forth, the crater was known by her name - Katla.
Some nearby areas bear her name as well.

Katla's activity
Katla is believed to be the center of an 80km long, U-shaped volcanic area. This area includes, amongst other places, the Westman Islands.
When Katla erupts, its smoke forms a 20km high ash plume in the air, which can easily be seen from Reykjavik. That is, however, by no means the most dangerous thing about Katla's eruptions. It is the melting glacier that goes with the eruption, which poses the greatest threat and the most destructive power.
The amazingly powerful water flow, known as "jökulhlaup" , has been known to carry with it icebergs as high as 18m and as long as 200m!

Despite this extreme force of the Katla eruptions, they usually do not last very long (having said that, there are instances where they have lasted as much as 5 months) and due to the seismic activity that precedes them, we usually have close to a 6 hour warning. In the time that Iceland has been occupied (close to 1300 years now) it has erupted as many as 20 times.
The time between eruptions has usually ranged from 60-80 years, although once there were only 13 years between eruptions.
Although there was great fear in 1999 that an eruption might be starting (it didn't), the last eruption was in 1918. With a maximum of around 80 years between eruptions, well...you do the math.

There is one more interesting thing about Katla's eruptions and that is that they only ever occur between May and November, but in that period they have been known to stop and start a few times, as if she were going into hiding or trying to lure you back, before continuing the eruption.
This has no doubt helped keep the story of the lost housekeeper alive.

Lastly, although Katla hasn't erupted since 1918, there is a possibility that there was a small eruption in 1955, but no plume was observed. It is also possible that during the last few months a very thick slab of magma has been rising into the ice in the flanks of the calderas of Katla.

Grimsvotn
Grimsvotn is the most active central volcano of Iceland. The Grimsvotn volcanic system has erupted 9 times in the last century and at least 71 eruptions have occurred in historical times. Grimsvotn lies under Vatnajokull and is located near a Triple Point - a point where three crustal plates meet (actually there is a small microplate in southern Iceland, which is "stuck" between the American and Eurasian plates). The fact that it is one of Iceland's many ice-capped volcanoes* makes it almost impossible to have an exact number of eruptions, as many occur beneath the ice without ever being noticed.

Grimsvotn last erupted in 1998, but in 1996 a new volcanic ridge, Gjalp, was formed under the glacier. This eruption melted huge amounts of ice and the melt water travelled tens of kilometres under the icecap, before emerging onto the sand "Skeidararsandur", swallowing every thing in its way to the ocean.

A description of that can be found at http://www.lpi.usra.edu/meetings/polar2000/pdf/4021.pdf and at http://wdcgc.spri.cam.ac.uk/jokulhlaup/

And some photographs, which better illustrate that event, by Magnus Tumi Guðmundsson and Finnur Pálsson, can be found at http://www.hi.is/~mmh/gos/photos3.html

"Eruptions from partly ice-covered and ice-capped volcanic systems constitute nearly 60% of all known historical (i.e. in the past 11 centuries) eruptions in Iceland" from Gudrún Larsen's "Volcano-Ice Interaction on Earth and Mars" paper. See end of text for details.

Hekla
Hekla has a height of 1491m an age of 5.000-10.000 years and used to be known by people all over Europe as the gateway to hell, as there used so many eruptions there, many hundreds of years ago. There were even theories that Hekla actually was hell and that the flames of hell were so awesome that sometimes they would even reach all the way up through the mountain. Hekla is the second most active volcano and its eruptions have become more and more frequent over the last 50 years at the cost of ever-smaller eruptions.

As I mentioned, Hekla is the second most active volcano in Iceland, only surpassed by Grimsvotn. Hekla, however, holds the first place if you compare the amount of lava and other debris from her eruptions.
Hekla doesn't give nearly as much warning as Katla, and when there has been any warning at all, it has only been around an hour before the eruption.

For an exceptional picture featured in National Geographic, of Hekla's 1991 eruption taken by an Icelandic photographer, Sigurður Hrafn Stefnisson, have a look at:
http://www.nationalgeographic.com/ngm/100best/wallpaper09.html

Krafla
Located in the North of Iceland, not far from the exquisite (to say the very least) sites of Myvatn and Namafjall geothermal area (more on that in the geology section - geology.html). Both an amazing sight to see.
Krafla lies in a very active area, which has frequent, long periods of eruptions/activity all over it. The last of these active periods ended in 1989 - although even to date, seismic activity persists to some extent - after 14 years and 10 eruptions!

Krafla's history of activity is believed to cover around 200.000 years, although substantial information only exists on the eruptions of the last 3000 years or so.

Lastly, in the vicinity of Krafla, there is a large geothermal power station, utilising the energy of the volcano. An interesting thing that happened there during the eruptions (that ended) in 1989 was that one of the few "man-made volcanoes" erupted.
In order to acquire hot water and steam, holes are drilled into the ground, boreholes. As the workers were working on one of those boreholes, an earthquake took place and opened a fracture between the borehole and a source of magma. As a result, the borehole erupted! (You can just imagine the utter amazement of the workers.)
This, however, was not a big eruption. All in all it will not have reached more than 4 or 5 cubic meters.

Askja
Located in the North, North-East of Iceland in the middle of Odadahraun is Askja.
Odadahraun is Iceland's biggest lava field, consisting of lava from numerous eruptions, mainly in the last 10.000 years.
The field is just under 4.000 km2 in size and contains many mountains and craters, including a group of active mountains known as Dyngjufjoll, and the Caldera in the middle, known as Askja.

Askja - Craters
Askja is around 50 km2 in size, with water covering a part of it known as Oskjuvatn, or Lake Askja. This lake is believed to be the deepest in the country, at around 224m in depth. Not a lot is known about Askja's history, apart from the last 100-200 years.
Askja has got a lot of craters in it, the most famous one (and probably one of Iceland's most impressive) being Viti, which literally means hell (if you've read about Hekla as well, you will see how obsessed people were in linking fire, glowing lava and volcanos to hell in previous centuries).

Askja - Viti and the rest
Viti is around 130 years old, 100m in width and 60m deep and is currently filled with water. Previously that water used to be boiling hot (literally) but now it is no more than a nice warm hot tub which you cannot pass without bathing in. (Just ignore the immense stench of sulfur...)
There are also quite a few mudpools close to Askja, and these can be quite handy in monitoring possible future volcanic activity.

Askja is one of the most popular areas for tourists and scientists alike and never ceases to amaze people with it's origin, surroundings and activity.

As for Askja's eruptions, it's main known eruptions are the ones that took place around 1875 - which resulted in thousands of Icelandic people moving over to Canada for a new start, after having had everything taken away from them - and the few smaller ones that have occurred in the last 100 years. The last eruption in Askja took place in 1961, but the last active period of Askja was between 1920 and 1930 with 7 eruptions in only 8 years.

Vestmannaeyjar (the Westman Islands)
Two eruptions in the Westman Islands area are the most noteworthy. These are the Surtseyjargos in 1963 and the Heimaeyjargos in 1973.

Surtsey
The Surtseyjargos is the name of underwater volcanic activity, that took place on the seabed not far from Heimaey and lasted 4 years (1963-1967).
(For pictures of that activity, see the "geology" category.)
This activity created the island Surtsey (the island of "Surtur", which was one of the names for the devil - but also means black) and 2 smaller islands, which have since then gone underwater.

Research
Surtsey is a National Reserve, used for scientific research and is invaluable in monitoring what happens to an island from it's birth. Many smaller islands have made an attempt at existance by forming in the ocean like that, but none have been able to withstand the forces of nature in their constant battle (ie. wind and water).

A good example are the 2 previously mentioned and an island that was known as Nyey, or "New Island", which was created in an underwater eruption in 1783 and was dedicated to the King of Denmark - as he was our ruler at the time. A year later, that island was gone.

Heimaey
Heimaeyjargos, refers to the island Heimaey (or "Home-Island") which is the main island of the Westman Islands, the one that is inhabited and the one that contains the volcano Eldfell (or fire-mountain) where the main eruption took place.
Actually, the eruptions started in a 700m string of craters, as many as 30-40, but then got reduced and eventually all the activity had moved to Eldfell, accumulating the power of all the others in one place.

As a side note, there was also an eruption on the seabed in the ocean between "the main-land" and the Westman Islands, at the same time the Heimaeyjargos took place.

Destruction and creation
After 6 months of activity on Heimaey, 250 million m3 of lava, ashes and debris had appeared, burying more than a quarter of the homes on the island, damaging another quarter, and expanding the island by 20%.
Part of that expansion made the harbour much bigger and stronger and made a protective wall for the island, from the forces of nature. Some say forces of nature did this to protect the island from it's own forces, others say that it was god's way of protecting the inhabitants, especially as no one lost their life and only material belongings were lost.
The reasons for the eruptions are not for us to say, but I can tell you a bit more about the inhabitants' and other Icelander's behaviour at the time.

The effort
A lot was done both during and after the eruptions, including clearing ashes and lava off the houses every day, to prevent them being buried. Moving people's personal belongings away from the island. Providing accommodation and work for the inhabitants while they had no place (or work) to go to.
As has become quite famous now (including inspiring a Hollywood film), there were also attempts at stopping the lava flow when it had already calmed down but was heading for even more of the town. Extraordinary amounts of sea water were pumped and dumped on the edge of the lava flow and eventually resulted in the edge cooling down enough to stop the lava from flowing any further into the town. The eruptions stopped around the same time as well.
The actual role of the water in stopping the flow is highly debatable. But at the very least, the people's efforts and bravery have to be commended.

(It should be noted that the idea of using water for repelling lava is a very old one,
originating from battles with Mt. Etna. Those attempts were, however, somewhat different.)

Life
Their lives never halted to a standstill. The whole time, people were actively doing their best to save what they could and the rest went on with their lives. They kept on fishing around the islands, they got jobs on "the main-land" and as soon as they could they were back on the island to get on with their lives.
Another good thing to come out of these eruptions, is much more geothermal heat on Heimaey. This heat is now used to heat up the homes on the island and other effects of the eruptions can still be seen very clearly with some houses still half covered by lava and the ground being very hot.

(So hot in fact, that it is used to bake bread amongst other things...)

This just goes to show that 5000 years of inactivity, are no guarantee for the future.
And for those interested in such things, this was 25 years later the scene for releasing the "Free Willy" whale "Keiko" back into the ocean.

For interesting graphical representations of Surtsey, see http://denali.gsfc.nasa.gov/research/garvin/surtsey.html
and for more information on Surtsey see
http://www.volcanoworld.org/vwdocs/volc_images/europe_west_asia/surtsey.html
http://www.geophys.washington.edu/People/Students/throstho/articles/surtsey.pdf

Skaftareldar

The last eruptions in Vatnajokull took place 1996 and 1998, but the most damaging and perhaps famous eruption started in the summer of 1783.
Skaftareldar (the fires of the river Skafta) are one of the worst things to ever happen in the history of Iceland.

Powerful volcanic eruptions, destructive glacial water forcefully flooding everywhere, ashes and debris falling from the sky all over the country, acid rain, earthquakes non-stop, lava rocks being thrown into the air, travelling more than 100km, all-consuming fiery lava flows drowning villages, thunder and lightning adding to the effect, with the lightning sometimes providing the only visibility.

Fire mass
Everything was either black with darkness, or on fire.
It's no wonder that people feared the end of the world and started to repent their sins.
After this had gone on for 7 weeks, the local priest (Rev. Jon Steingrimsson) gathered all the remaining people together in his church and started praying to god.
Praying that he would stop this destruction and reconsider his judgement over the people of Iceland.
"Everyone repents their actions, is full of remorse and will change their actions according to your will", was his message as he begged the lord for forgiveness and the people joined in.

During this sermon, the main surrounding lava flow started to slow down and stopped in some places. This was believed to be the result of the people's prayers and the reverend's mass was from there on known as Eldmessa (the Fire Mass).

Aftermath
The activity remained in other places however, and didn't come to a halt until 7 months later, in February 1784. But the horrific weather and 600km2 of lava, still remained. The effects on the world were also quite noticeable as it not only affected the weather, but ashes fell in various places all over mainland Europe and even as far as China the air became foggier as a result and dry fog was reported in N-America.
Not surprising, as the smoke clouds during the eruptions are believed to have reached as high as 1.4km in the air!

The ash, acid rain and toxins left behind all contributed to the nightmare that followed.

The next couple of years crops were ruined, livestock died and so did people, both due to the toxins and the famine that came with it. A quarter of the population perished in just 2 years.
Even though the main reason for all of this was, as previously stated, the damage left by the eruptions, a lot of this horrible aftermath could have been avoided with better organisation. There was no money set aside as a disaster fund, so there wasn't really enough money to do anything properly in order to swiftly change matters for the better.

Don't get knocked down
But eventually, with some help from abroad, the Icelandic people got back on their feet and went on with their lives and once more history books recorded how mankind sticks together when things go bad.

[Please bare in mind that the world is far from perfect today and that natural - and man made - disasters are shaping our world ever day!]

An interesting quote from:

IJR Ebenezer Henderson. Iceland; or the Journal of a Residence in That Island, during the Years 1814 and 1815. Containing Observations on the Natural Phenomena, History, Literature, and Antiquities of the Island; and the Religion, Character, Manners, and Customs of Its Inhabitants. 2nd edition. Edinburgh: Printed for Waugh and Innes, Edinburgh; and T. Hamilton, J. Hatchard, and L. B. Seeley, London, 1819.

on the subject of the eruptions in Laki in 1783 (Skaftareldar) can be found at http://www.library.wisc.edu/etext/Jonas/Biography/Biography.2.html (the 8th paragraph).

For more on volcanoes, also see the "Glaciers" section, as most of them are actually on top of active volcanoes!

The rest:
As a source for some of the material in this category, I got some assistance from

Gudrún Larsen, of the University of Iceland's Science Institute.
Including her writings in the paper titled "Volcano-Ice Interaction on Earth and Mars", printed in 2002 by the Geological Society of London's Special Publications (202, 81-90).

Bergur Sigfússon.

Myndun og Mótun Lands, an Icelandic book on Geology by Dr. Þorleifur Einarsson, published 1991 by Mal og Menning (see his text in English by the name of "Geology of Iceland"),

http://www.islandia.is/hamfarir/jardfraedilegt/eldgos/islenskeldfjoll.html
which I thoroughly recommend for anyone that reads Icelandic...

For further information, check out
http://www.norvol.hi.is/
http://www.geo.ed.ac.uk/tephra/systems.html
and
http://www.geokem.com/volcanic-atlantic.html

Or for further information on volcanoes in general, Volcano World (http://www.volcanoworld.org/vw.html) is usually quite good.

The remaining information is all thanks to the Icelandic Educational system.