Iceland Has Entered a New Volcanic Era

On the evening of 19 March 2021, a fissure 180 metres long opened in an uninhabited valley on the Reykjanes peninsula, about half an hour's drive from Reykjavík. Nothing had erupted on that peninsula for 781 years.

Over the following six months roughly 356,000 people walked out to look at it. On an island of fewer than 400,000 residents, that is a remarkable number, and it made Geldingadalir the most-visited eruption in modern history. It was also, in retrospect, the easy one.

What happened next is the part worth understanding before you plan a trip, because it is not a story about one eruption. It is a story about a region waking up, and the geologists studying it have been unusually clear about the timescale.

Icelandic has a specific term for a volcanic episode that goes on for years across a rift system: eldar, meaning fires. It has been applied to the Mývatn Fires of 1724 to 1729 and to the Krafla Fires of 1975 to 1984. Both names describe long sequences of separate eruptions from the same restless piece of crust, not single events.

The current episodes have been named the same way in the peer-reviewed literature: the Fagradalsfjall Fires and the Sundhnúkur Fires. One published title even renders the second as running from 2023 with the end date left as a question mark.

I find that naming choice more informative than any forecast. Scientists do not reach for a word meaning a decade-long sequence unless they expect a decade-long sequence.

This is where the historical record is genuinely useful, because Iceland has kept one for a thousand years.

The Krafla comparison is the most instructive, because it is the same mechanism in the modern instrumental era. Nine years. About twenty rifting events. And most of those events produced no eruption at all, just the ground pulling apart underground, which is a detail that matters if you are planning a trip around seeing something.

The mechanism is worth a paragraph because it explains the rhythm.

Magma accumulates in a shallow reservoir a few kilometres beneath the Svartsengi area, fed from a much deeper source under Fagradalsfjall at nine to twelve kilometres. As the shallow reservoir fills, the ground above it visibly inflates, which satellite radar and GPS both measure. When the pressure passes a threshold, the crust fails and magma runs sideways into a vertical crack, a dyke, which may or may not reach the surface.

When it does reach the surface, it can move astonishingly fast. Modelling of the November 2023 dyke that ran beneath Grindavík put magma flow rates in the thousands of cubic metres per second, and the crack propagated some fifteen kilometres in a matter of hours. That is why warning times in this sequence have been measured in tens of minutes rather than days.

The whole peninsula has pulled apart by roughly four metres across the episodes measured so far. That is what a plate boundary looks like when you catch it in the act.

Check the official source, not a travel page. The Icelandic Meteorological Office runs the monitoring and publishes the hazard assessment for the peninsula, including a map with an explicit valid-until date. Travel sites, including the semi-official ones, have been observed carrying eruption status text that was many months out of date.

Understand what closed means. When Icelandic authorities close an area they mean it, and the reasons are usually gas and ground instability rather than lava, both of which kill people who are otherwise standing somewhere that looks fine.

Do the things that do not depend on it. The 2021 to 2023 lava fields are there, they are extraordinary, and walking on rock that did not exist when you were last thinking about a holiday is its own experience. The lava shows in Reykjavík and Vík run on a timetable. The lava tubes and the Reykjanes geothermal landscape are unaffected by any of this.

And if something does open in a place they let you walk to, drop the itinerary and go. Those windows have historically lasted weeks.