Rigorous Rabbit Holes

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Iceland Fought a Volcano With Seawater, and Won (Heimaey 1973)

In 1973, lava was swallowing an Icelandic fishing town and heading for its harbor. So they sprayed it with the ocean, for five months.

Published · Watch on YouTube · 22 sources

The rabbit hole

The extra context that didn't fit in the Short. Little numbers link to the sources below.

The man with the idea

The Short says “a physicist.” His name was Þorbjörn Sigurgeirsson, and he proposed cooling the lava’s front with seawater along with others, including Sveinn Eiríksson 4. Firemen tried it first with ordinary hoses on February 7, 1973 4.

How big the fight got

  • Pumps: 43 of them, with more than 30 km (19 miles) of pipe 11.
  • Water: about 6.2 million tonnes of seawater from February to July 10 11.
  • Salt: the seawater left about 220,000 tonnes of salt on the lava 11. That’s what’s left when you boil off the ocean.
  • People: about 75 men at the April peak, working 13 days on, 2 off 7.
  • Roads: bulldozed up lava edges 25 to 30 meters (80 to 100 feet) high. One road got shoved 10 meters overnight by the moving lava 8.

About “ten times”: the US pumps took the flow from about 100 liters a second (the hoses) to about 1,000 6. The dredger Sandey was already adding around 400 liters a second before that, so compared with hoses plus dredger, it was closer to double 6. Still a huge jump.

Why plastic pipes didn’t melt on lava

The question everyone asks. USGS’s answer: the plastic pipes “did not melt from the heat as long as water flowed through them” 8. The cold water inside carried the heat away faster than the lava could put it in. It’s the same reason you can hold a paper cup of water over a candle without it burning: the water soaks up the heat. That’s why the water had to start flowing the moment a pipe went down.

Did they really “stop” the lava?

Mostly, and with an honest caveat. USGS says the cooling kept the lava from closing the harbor and turned about 70% of the flow’s volume into solid rock 21. The front they fought froze into a wall about 100 meters short of the harbor mouth 12.

But a lot of the flow also went elsewhere: east, into the sea, building new land 17. Benjamin Andrews of the Smithsonian describes it as partly diverted as well as stopped, and today’s lava defenses tend to favor earth barriers 21. So the lesson isn’t “seawater beats any volcano.” It’s that in this place, at this front, it worked.

The lava paid the heating bill

After people came home, the lava under the new land was still hot. So the town tapped it:

  1. Pipes sprayed water onto the ground above the cooling lava.
  2. The water trickled down, hit hot rock and turned to steam.
  3. Steam wells collected it, and heat exchangers warmed the town’s heating water 18.

The first house was connected in early 1974. By early 1982 nearly every home on the island was on it 18. After about a decade the lava had cooled, and the same network switched over to oil and electric boilers 19.

Then one more twist: since May 2019, a seawater heat pump supplies about 93% of the town’s heat 20. The same sea that stopped the lava now heats their homes.

What the new land is now

The island grew by about a fifth 17. The ash, about 800,000 tons of it cleared from the town by volunteers, helped lengthen the island’s runway 16. And the lava tongue that nearly closed the harbor is now its breakwater 13.

Sources

Every claim in the Short and in this write-up, numbered, with where it comes from. Spot a mistake? Email hello@rigorousrabbitholes.com and we'll fix it in public.

Source being added marks a claim we're still attaching a source to.

  1. The eruption began just before 2 a.m. on January 23, 1973, from a fissure about 2 km long at the edge of town on Heimaey.USGS: "Man Against Volcano: The Eruption on Heimaey" (Williams & Moore); USGS Open-File Report 97-724 (link to come)Oregon State University's Volcano World gives the same date and fissure.
  2. The fishing fleet happened to be in port, and within six hours boats had carried almost all of the 5,300 people to the mainland.USGS: "Man Against Volcano" (link to come)USGS: "The fishing fleet in port expedited the evacuation." Some articles add that bad weather kept the fleet home; USGS doesn't say that, so we don't.
  3. The harbor was the town's lifeline; the fishing economy depended on it. Source being addedOur research log; a specific source for this line still needs to be attached.
  4. A physicist proposed spraying the lava with seawater to freeze its front into rock.USGS (lava-cooling methods page); Popular Science (link to come)Professor Þorbjörn Sigurgeirsson proposed it, with others including Sveinn Eiríksson. Firemen started with hoses on February 7, 1973.
  5. A dredging ship joined in, pumping straight from the ocean.USGS: "Man Against Volcano" (link to come)The dredger was the Sandey. By March 23 it had pumped about 0.4 million tonnes, and other equipment about 0.1 million.
  6. Pumps leased from the United States pushed the flow to about 1,000 liters a second, ten times what the hoses could do.Popular Science; USGS (water-pumping page and "Man Against Volcano") (link to come)Hoses ran about 100 liters a second; by early April the harbor pumps delivered about 1,000 (USGS: 1.3 cubic yards per second). "Leased" is USGS's word. The first US pumps arrived March 26, all connected by April 4. Honest framing: that's ten times the hoses. Counting the dredger's ~400 liters a second too, it's about double.
  7. It became a five-month battle; crews worked 13 days straight, 8 a.m. to 10 p.m., then got two days off.USGS (manpower page) (link to come)About 75 men at the April peak. Pumping ended July 10, 1973.
  8. They bulldozed roads up onto the lava and dragged plastic pipes across it; the pipes survived only because water was flowing through them right away.USGS (manpower page); USGS "Man Against Volcano", p. 15 (link to come)Access roads were pushed up lava edges 25 to 30 meters high; one was shoved 10 meters overnight. USGS p. 15: the plastic pipes "did not melt from the heat as long as water flowed through them."
  9. The steam got so thick they drove bulldozers through it by walkie-talkie.USGS (manpower page) (link to come)
  10. Remarkably, there were no serious accidents.USGS (manpower page) (link to come)Word for word: "No serious accidents happened during the cooling." People did get burns to their hands and feet, so we don't say nobody was hurt.
  11. The lava kept pushing, and they pumped about six million tons of seawater in all.USGS (water-pumping page) (link to come)About 6.2 million tonnes, through 43 pumps and more than 30 km (19 miles) of pipe. It left about 220,000 tonnes of salt on the lava.
  12. The lava stopped about 100 meters short of sealing the harbor.USGS Open-File Report 97-724 (link to come)
  13. That frozen wall is still there, shielding the harbor from storms better than before.USGS: "Man Against Volcano"; Popular Science (link to come)USGS: the tongue that nearly closed the harbor "is now acting as a breakwater."
  14. About 400 buildings were lost, roughly a third of the town.USGS: "Man Against Volcano"; Mental Floss; Fish Focus (link to come)USGS counts about 300 buildings engulfed or burned by early May 1973, plus 60 to 70 homes buried by ash. One source says 800+; it's the outlier, so we don't use it.
  15. One man died breathing carbon dioxide that pooled inside a building.USGS: "Man Against Volcano" (link to come)USGS: "One fatality resulted from breathing gas within a building"; the gas "contained 98 percent carbon dioxide." One popular article says no lives were lost; that's wrong.
  16. The volcano's ash was used to lengthen the island's runway.Three independent sources in our research log, including the Smithsonian (link to come)Volunteers cleared about 800,000 tons of ash from the town (Smithsonian).
  17. The lava grew the island by about a fifth.USGS: "Man Against Volcano" (link to come)USGS: about 20%, "nearly a square mile". Another source says about 10%; we go with USGS.
  18. The lava heated nearly every home on the island for about a decade.USGS: "Man Against Volcano"; Verkís (Icelandic engineering firm) (link to come)The first house was connected in early 1974 and nearly every home by early 1982. It was projected to last about 10 years. One source says until 1988; we go with USGS and Verkís.
  19. When the lava cooled, they switched the same pipes over to boilers.Verkís (link to come)Oil and electric boilers on the same district-heating network.
  20. Since May 2019, a seawater heat pump has supplied about 93% of the town's heat.Verkís (link to come)
  21. The lava was partly diverted as well as stopped, and modern lava defenses tend to favor earth barriers.Benjamin Andrews (Smithsonian), quoted in Popular Science (link to come)USGS says cooling kept the lava from closing the harbor and turned about 70% of the flow's volume to solid rock.
  22. The animated maps are adapted from a USGS map.USGS: "Man Against Volcano: The Eruption on Heimaey" (Williams & Moore), map on p. 6 (link to come)A US government work, in the public domain. Simplified from the original.