Strokkur: Why It Stopped Erupting - and the 1963 Drilling That Brought It Back

Strokkur stopped erupting in the autumn of 1896, when earthquakes in South Iceland shifted the plumbing beneath the Haukadalur hot spring field. For sixty-seven years it did almost nothing. In July 1963 the Geysir Committee had a borehole drilled into it, 39.4 metres deep. The drill cut into a single water vein at the bottom of the hole and it erupted immediately. It has erupted ever since.

Strokkur goes off every few minutes — roughly nine times an hour, with something like seven minutes between eruptions on average. The crowd stands in a loose ring behind the rope, phones up, and waits. The water swells into a blue dome a second before it goes, which is the moment everyone is trying to catch and mostly misses.

It is the most reliable geyser in Iceland, and reliability is why it is on every itinerary in the country. What almost nobody standing there knows is that the reliability is recent, and that it was arranged.

This trips up most visitors, and a fair amount of published writing too.

Geysir — the original, the one that gave every geyser in every language its name — is dormant. It has been more or less quiet for decades. What you see there now is a large, still, steaming pool.

Strokkur is a separate hot spring a short walk away. Smaller, and the one actually erupting. Nearly every photograph captioned “Geysir erupting” is Strokkur.

The two are connected underground, and their histories run against each other: through the recorded past, when one has been active the other has tended to be quiet.

The idea of intervening at Strokkur is not modern.

In 1708 Strokkur was deliberately blocked with turf and stones. The reason was agricultural: it was damaging the hayfield at Laug, the farm alongside the hot spring field. A hay meadow was worth more than a spouting hole in the ground.

Worth holding onto that, because the question people ask about 1963 — whether it is acceptable to interfere with a natural feature like this — was answered by the people who lived here 255 years earlier, in the other direction.

In 1789 a strong earthquake struck the region and Strokkur began erupting powerfully.

Four years later, in 1793, the naturalist Sveinn Pálsson recorded the geyser and its name. Strokkur means “churn” — the wooden butter churn, with its plunger driven up and down. Anyone who had made butter recognised the motion immediately.

The nineteenth-century record is a list of heights, and it reads like a decline with interruptions.

1804: around 45 metres, with Geysir reaching 65. 1809: 45 metres again, sustained for something like an hour and a half. 1810: 24 metres. 1815: over 60. By 1830 it was clearly weakening. In 1863 it managed 15 metres — but that eruption was induced, with gravel. By 1871 there was virtually no natural activity at all. In 1880 it was back to 25 or 28 metres.

That word induced is the part usually left out. For much of the nineteenth century Strokkur erupted mainly when people made it. Turf and gravel were thrown into the conduit to choke it and force a reaction, and visitors who had travelled a long way expected a show. The later soaping of Geysir was the same instinct with better chemistry.

So by the time anyone arrives at 1963, the site already has a two-hundred-year history of people reaching into it — first to stop it, then to start it.

In the autumn of 1896 a sequence of earthquakes struck South Iceland, and the hot spring field rearranged itself.

Strokkur stopped almost completely. Geysir took over, erupting powerfully for the next two decades — which is precisely the period when Geysir’s international fame was established.

You will see 1907, 1920 and vague phrases like “around the turn of the century” given as the date Strokkur went quiet. Those are wrong. The event is the 1896 earthquake sequence, and the local record is clear about it.

Sixty-seven years.

Over that time the water level in the conduit fell steadily. In 1931 the water stood about a metre below the surface, with a surface temperature of 80.5 degrees. In 1937 the conduit was measured at 11 metres. By the early 1960s the water was 1.6 metres down and the geyser itself was about 5.6 metres deep, with rubble and debris filling it down to around 12 metres, where solid rock began.

The clearest description of what it had become comes from Kristbergur Jónsson, who lived at Laug. He described a hole around 12 metres deep, narrowing as it went, with no standing water — only a small pool at the very bottom. Part of that account he had from his mother.

That is what was there in the summer of 1963. Not a geyser. A hole with rubble in it.

I met his son. Jón Kristbergsson lived in a turf house that is still standing near Strokkur, and my father took me there when I was eight or nine years old. My father was a tall man and had to bend to get through the doorway. We sat inside and drank black coffee. I was too young to ask him about Strokkur, which I have regretted since.

What I remember is him telling my father how strange he found it that the tourists coming to watch Strokkur had no idea the whole thing was partly man-made. He had been alive when it was not erupting. I do not remember his exact words — I was a boy, and it was a long time ago — but that was the sense of it, and it stayed with me.

In July 1963 the Geysir Committee had Strokkur drilled, with the stated aim of bringing it back.

The borehole went down 39.4 metres. A great deal of debris came up as the work went on. And at the very bottom the drill cut into a single water vein — one vein, right at the end of the hole — and Strokkur erupted immediately.

The record is thinner than it should be for something this consequential. It does not say whose rig it was. No photograph of the work has surfaced. If you know otherwise, I would like to hear from you.

I was born five years after they drilled it. I have never seen Strokkur do anything but erupt.

Strokkur has erupted continuously since that July, and it is the borehole that made it dependable rather than occasional.

Measurements since: a flow of about 2.5 litres per second in 1967, and roughly 2 litres per second measured for Iceland’s Nature Conservation Council on 17 September 1994, with water temperature at depth somewhere around 120 to 125 degrees.

The old habits took a while to die. Geysir was still being coaxed into performing after 1963, and the method was soap — poured in to lower the surface tension and set off an eruption on demand, usually for an audience.

My sport teacher at grammar school was one of the men who soaped Geysir. He went up at night, because it was not really permitted.

The site is now protected. Since 17 June 2020 it has been a protected natural monument, and interventions of the 1963 kind are no longer on the table.

Partly. Honestly, yes, partly.

The heat is natural. The water is natural. The conduit is natural, and it erupted on its own for long stretches of the eighteenth and nineteenth centuries. But the Strokkur you watch today — the one that goes off nine times an hour, reliably enough to build a tour schedule around — exists in that form because a rig drilled 39.4 metres into it in July 1963. Without that, it would be a small pool. Roughly what Geysir is now.

That is not a scandal, and it is not a secret. It is the continuation of something that had been going on at this site since at least 1708: people blocking it, choking it, throwing turf into it, soaping it, drilling it. The 1963 borehole is the most successful thing anyone has done to it, not the first.

What strikes me most about 1963 is that they simply did it. The public record does not show much in the way of study beforehand — whether the drill might damage the conduit, what it would do to the other hot springs around it, how the veins under the field connect. A committee decided, a rig came, and it worked.

Nobody would do that now. Geysir sits quiet a short walk away, and the reason nobody drills it is that the ground underneath is not well enough understood to know what a borehole would do to the rest of the field. That caution has been argued out in public, in the newspapers, over years. Strokkur got no such debate.

I am not sure the caution is wrong. But it is worth saying plainly that the same caution, applied in 1963, would have left Haukadalur with two silent pools and nothing to watch.

Ingólfur Guðnason, “Strokkur og hverasvæðið í Haukadal”, Litli-Bergþór, magazine of Ungmennafélag Biskupstungna.

Helgi Torfason, article on Strokkur in Eyjar í eldhafi (1995), festschrift for Jón Jónsson.

Helgi Torfason, “Geysir vakinn upp”, Náttúrufræðingurinn 53 (1–2), 1984, pp. 5–6.

Ísleifur Jónsson, “Hvers vegna sefur Geysir?”, Morgunblaðið, 22 July 1997, pp. 26–27.

Umhverfisstofnun, Stjórnunar- og verndaráætlun — Geysir 2022–2031.