HEIMAEY, ICELAND 1973By: Liz Anderson, Mark Hargis, Megan Pugh, and Emily Williams

Introduction

The 1973 Heimaey eruption started on 23 January with the opening of a 1600 m long fissure on the east side of the island, about 400 m east of the outskirts of the town. During the first hours lava issued from the entire fissure in 50-150 m high glowing fountains. A day later the eruption continued from two craters, and on 6 February only one crater remained, where activity continued until 26 June, when the eruption came to an end. By that time 417 houses had been destroyed by lava and tephra and the remainder of the town was covered with millions of tons of tephra. The total volume of the eruption products was 250 million cubic metres (230 million m3 as lava and 20 million m3 as tephra). The chemical composition of the products is alkali basalt, murgearite to hawaiite.

Background Information

-Heimaey is an island that sits off the south coast of Iceland.

-Iceland sits on the Mid-Atlantic Ridge, and it is here that the North American Plate and the Eurasian Plate are moving apart, making Iceland one of the most volcanic areas.

-Since the island sits on a plate boundary, the tremors were considered somewhat of a normality for the location.

Eruption Details

The volcanic eruption began on January 21st, 1973, some ten years after a previous eruption underwater that created a large island close to Heimaey.

The eruption was caused by numerous small tremors that began around Heimaey.

The tremors were small, and many went unnoticed by residents. Miles away, seismic stations recorded around 100 tremors from

January 22nd coming from the Heimaey area. The largest of these tremors measured a 2.7 on the Richter Scale.

Early in the morning on January 23rd, a large fissure opened up on the East side of the island.

The fissure grew very rapidly and soon reached a length of 2 kilometers.

Lava continually shot into the air throughout the whole fissure, with some of the lava reaching 150 meters high.

Eruption Details Continued

The fissure eruption lasted for nearly 5 months, and as it continued it created a volcanic cone where most of the eruption continued.

Over 1/3 of the island was destroyed by the lava flows and falling debris and ash.

The lava flows from the volcanic eruption nearly buried the town and came close to shutting down the town’s harbor.

In order to stop the spread of the molten rock, seawater was pumped onto the flow to cool it. In total, some 8 million gallons of water were pumped onto the molten rock.

The amount of energy produced from the eruption was around 130 times greater than the energy produced from the explosion of the atomic bomb.

The eruption spread enough molten rock across the island to the shore that there was two and a half square kilometers of land added to the island.

The total size of Heimaey increased by nearly 20%.

History of Volcanic Activity

Iceland is one of the world’s most active volcanic areas Most volcanic activity in Iceland comes from fissures, not from volcanic

mountains Iceland is a volcanic Island which straddles the Mid-Atlantic Ridge On one side of the country rests the North American tectonic plate which

moves westward; on the east side rests the Eurasian plate which moves in an eastern direction.

A continuous rift valley follows the Reykjanes Ridge which enters the southwest end of the island and ends in the middle. The Kolbinsey rift enters on the north coast and ends in the island as well; to the east is a third rift zone

Due to the divergent boundary Iceland straddles, the country is being pulled apart at a rate of 2 cm per year

As the plates pull apart molten rock or magma continually erupts from fissures and volcanoes to fill the gaps

Throughout Iceland there have been 27 eruptions with VEI’s of 4 to 5 since the country was settled, on average 2 or 3 per century

Iceland’s Tectonic Plate Boundaries

www2.warwick.ac.uk

Science Behind It

At 11 square Kilometers, Haimaey is the largest of the Vestmann Islands

With a population of 5,300, Heimaey is the only Vestmann Island to be inhabited and is of great importance due to its excellent harbor and fishing grounds.

The Heimaey eruption was preceded by low magnitude earthquakes caused by opening fissures at a low depth.

Fissures ripped open a rift which spanned a full kilometer and a half traversing the eastern part of the island from shore to shore.

Science Continued

These fissures produced fiery mountains of fragment material and voluminous lava flows. Ash almost buried the town of Vestmannaeyjar, where residents were both evacuating and preparing to fight the onslaught.

Severe shaking severed undersea pipelines and cables from the mainland which supplied the town with fresh water, electricity, and phone service.

Magma flowed upwards of 10 kilometers in less than 24 hours. With a high viscosity, and massive blocky aa lava flow, the material destroyed part of the town and threatened to overrun the harbor.

Eldfell

The stratovolcano created and later dubbed, Eldfell was estimated to have a maximum VEI of 4.

Eldfell, June 2007 Elevation 200 m (656 ft) http://en.wikipedia.org/wiki/Eldfell

Effects

Lava poured over 40 to 50 cubic meters per second eastward and northward, ash covered the town 50 meters deep in some places.

There was 250 million cubic meters of material produced by the eruptions, adding 2 square kilometers to Heimaey.

The eruption continued for 5 months.

The Intervention

Heimaey eruption is significant in that it was the first time man attempted to intervene in such a large scale manner to decrease the damages posed by a volcanic eruption.

The townsfolk began an attempt to slow the lava progression by spraying fire engine hoses on the highly viscous material in an attempt to cool it. Although it slowed the progress a little, the people knew it would take more water than a fire hose to be effective.

A dredging boat; the Sandy, was brought in to spray water on the lava to slow its progress and prevent the destruction of the harbor.

Attempts at Cooling Lava

The Icelanders obtained 32 large water pumps and began pumping sea water onto the lava at a rate of 1000 liters per second (265 gallons).

Changes to Heimaey

Sometime after the preventative efforts began a large chunk of Eldfell later dubbed “the Flakkarinn” (the wanderer); broke off the summit and flowed down the side.

Due to the efforts of the Icelanders to slow the progression of the volcanic material, a dam had formed at the base of the cone just before the harbor. When Flakkarinn struck it, the manmade barrier held and the harbor was spared.

The Heimaey eruptions were significant in the establishment of procedures such as lava cooling, that may potentially save other towns in the future.

This preventative operation cost $1,447,742, and the city received over 2.1 million dollars in federal aid and required additional taxes from Icelanders to repair the damages.

Sketch showing the changes to Heimaey caused by the eruption of Eldfell

http://en.wikipedia.org/wiki/Eldfell

Human Toll

The people of the village of Heimaey were given enough notice to evacuate all the 5,500 people to the mainland with out the loss of any lives.

Air planes and fishing boats were used to safely evacuate the villagers.

200 firemen and rescue workers remained, but there was not much they could do.

Half a million tons of ash fell on Heimaey destroying 350 houses and damaging more than 400 homes.

Interesting Facts

3 square miles of land was covered with lava that was up to 200 feet deep.

After returning to the village, the people used Halgafell as an energy source.

The heat from the slowly cooling lava provided hot water and generated electricity and provided up to 40 megawatts of power.

Video of Eruption

If you have time, please view this video to see images and learn more about the eruption.

http://www.youtube.com/watch?v=ghl33n26d44

Eyewitness Account

“The harbor was of priceless value to the town that depended on fishing and fish processing. Therefore great emphasize was put on saving the harbor from blockage or filling by lava. This was mostly done by pumping enormous amount of sea water onto the edge of the lava to diverting the lava flow. For water cooling to be effective, water had to penetrate down into the lava through cracks and joints that form during the initial cooling period. About 6 million m3 of sea water, containing about 220,000 tons of salt, was pumped onto the lava. Beside lava there were many other dangers there. Because of tephra falling over the town, we had to wear steal helmets and sometimes run for shelter. Sometimes glowing tephra broke it’s way through roofs and windows and thus setting the houses on fire. This risk was reduced by covering the windows, facing

the volcano, with corrugated iron sheeting and steel plating. Many houses collapsed under great weight of tephra, which increased daily. To try to prevent this, tephra was swept of the roofs. The roofs were also strengthened by placing props and rafters under them. The ash had a sandblasting effect on painted surfaces of vehicles. Motors not protected by air cleaners and filters, particularly gear boxes, required frequent maintenance.”- Kristján H. Kristjánsson

Resources

http://en.wikipedia.org/wiki/Eldfellhttp://pubs.usgs.gov/gip/heimaey/http://vulcan.wr.usgs.gov/Volcanoes/Iceland/

Publications/ManAgainstVolcano/heimaey_1973_eruption.html

http://www.eyjar.is/eyjar/eruption.htmlhttp://

library.thinkquest.org/C003603/english/volcanoes/casestudies.shtml