Volcans
Torfajökull Volcano: Iceland’s Most Colorful and Unique Rhyolite Volcano
Discover Torfajökull, Iceland’s vibrant rhyolite volcano, known for colorful landscapes and unique volcanic geology
In a country defined by stunning black basalt, erupting fountains of fire, and flowing lava fields, Torfajökull stands apart. This central volcano, tucked into the remote south-central Highlands, is Iceland’s largest and most spectacular rhyolitic system. It’s a place where magma evolves, colors explode across the landscape, and eruptions behave very differently from the familiar fissure events of recent years.
It’s also a volcano often described as “overdue.”
That word tends to raise eyebrows… and blood pressures. A volcano known to produce large, explosive eruptions being overdue is anxiety-inducing. But in geology, “overdue” rarely means what people think it does.
Quick Facts about Torfajökull
Main Eruption Dates: Last known eruption 1477; largest modern eruption in ±877
Location: South-central Iceland (Fjallabak Nature Reserve, near Landmannalaugar)
Volcanic System type: Central volcano with caldera (~12 × 18 km); known local fissures
Explosion type: short-lived Plinian eruption with tephra column ±20 km vertical
Eruption & Lava Type: Silicic (rhyolitic), often explosive, with mixed chemistry lava fissures
Fissure Length: Typically short fissures (1–2.5 km clusters over area of 40 km)
System Area: total area of exposed extrusive material is 450 km2; geothermal area is 150 km2
Longest Lava Flow: Limited; rhyolite tends to form short, thick flows, and more basaltic fissures have maximum flow length 2 km
Gas Emissions: not a lot of historical evidence about this; possible there was local fluorine and sulfur-based emissions
Significance: Iceland’s largest rhyolite system and largest geothermal system; key to understanding continental crust formation in an oceanic setting, and one of the rare places where extensive rhyolite erupts on oceanic crust. Also produced a layer of ash named The Settlement Layer.
A hiker stands amongst the rhyolite mountains of the Torfajökull volcanic system and looks over the famous Grænihryggur green hill. The vibrant green color is caused by geothermal alteration, where minerals such as chlorite, epidote, and celadonite have formed within the rock.
What makes Torfajökull a special volcano?
While Torfajökull may not have rare lava, compared to many lavas erupting around the world, what makes it special is how rare this type of lava is on oceanic and new crust systems.
In Iceland, the overwhelming majority of eruptions produce basalt, a lava that is runny, dark, and derived directly from the mantle along active rift zones. Torfajökull breaks that pattern, however. It sits on the fringes of Iceland’s active rift zones, where tectonic stretching, magma supply, and crustal processes interact in a more complex way. Instead of simply delivering fresh basalt straight to the surface, this volcanic system allows magma to stall, evolve, and chemically differentiate over time.
The result is a large central volcano dominated by rhyolite, a silica-rich, viscous magma more commonly associated with continental settings than with a mid-ocean ridge environment. This alone makes Torfajökull unusual. But its geography adds another layer of uniqueness: a broad caldera system, shaped by past eruptions and collapse events that span hundreds of thousands of years (maybe more!), surrounded by geothermal fields and rhyolitic mountains that record repeated cycles of heating, alteration, and eruption.
This combination of factors creates something rarely seen in Iceland. Rather than vast lava plains stretching for kilometers, like the fields of lava you see as you drive from Keflavík airport towards Reykjavík, Torfajökull produces shorter, thicker lava flows, domes, and explosive deposits. Over time, this has produced a striking terrain of multicolored mountains, obsidian flows, tephra layers, and steaming earth, most famously expressed in areas like Landmannalaugar.
What truly sets Torfajökull apart, then, is the story that lava tells and the laboratory the mountains become for unique crust formation. It represents a place where Iceland’s typically simple volcanic processes become more complex: where basalt evolves into rhyolite, where oceanic crust begins to behave more like continental crust, and where the landscape reflects that transformation in vivid, unmistakable ways.
This area is time and time again listed as a top hiking destination globally. But isn't this volcano overdue to erupt? Should you be concerned?
View of Landmannalaugar, one of the world’s premier hiking regions, on the north end of the Torfajökull volcanic system. Evidence of century’s old rhyolitic eruptions and geothermal alteration color the landscape.
Is the Torfajökull volcano “overdue” to erupt?
Many volcanoes in the south and east of Iceland have been labeled as “overdue.” Fortunately, this is usually a made-up statistic used to drum up engagement in a social media post or publicity for a documentary. So why is Torfajökull, which has not erupted in 550 years, NOT overdue? Let’s look at scientific reasons why volcanoes cannot be overdue:
Volcanoes are not on timers. Yes, some volcanic systems do appear to be quite regular (we are looking at you, Reykjanes volcanic systems), but they are still not clocks, with set schedules. Volcanoes do not work that way. There are very few things in geology that are that predictable. Even Reykjanes appears to have 100s of years of “wiggle room” between predicted cycle starts.
Eruption intervals aren’t on a fixed countdown. Most volcanoes are tens of thousands or millions of years old, and most modern historical records on eruptions only account for a small portion of a volcano’s life. It is hard to make a predictive trend with so few data points.
Our data isn’t perfect. Most data about volcanoes in Iceland has been blurred from understanding because of either (a) extensive glaciation eroding past evidence of eruptions, or (b) hydrothermal alteration skewing older rocks over time. And without modern historical records to tie eruptions to specific dates, the predictive error bars on most older eruptions is hundreds to thousands of years of timing range.
Use modern monitoring to inform understanding. Most volcanoes in Iceland have active, extensive monitoring on-going with modern digital tools. But that was not always the case. This means that any predictivity with regards to the volcano was formed with non-direct evidence or less-qualitative tools. But this also means, scientists and natural hazards experts are closely monitoring Iceland’s volcanoes at all times, and sound the alarm as needed to keep the public informed in real-time.
Torfajökull Volcanic System Q&A
Q: Is Torfajökull dangerous right now?
A: No signs suggest an imminent eruption. It is monitored, but currently quiet.
Q: Could it erupt this century?
A: Yes. But that’s very different from saying it will erupt soon.
Q: Would an eruption look like Reykjanes?
A: Not likely. Expect more explosive behavior, shorter flows, and possibly ash.
Q: Why is the Svartsengi system considered overdue and not a system like Torfajökull?
A: The current eruptions happening north of Grindavík in the Svartsengi system have many indicators of being active, like ground inflation, frequent seismicity, magma in-fill, and previous related eruptions in the past two years; nothing like this is currently happening at Torfajökull, even though it has not erupted since 1477.
Q: Is “overdue” a useful term?
Not really. It’s catchy, but scientifically misleading.
Q: Why is the area so colorful?
A: Rhyolite + geothermal alteration = minerals stained in reds, yellows, greens, and blues. While the volcanic system may not be active right now, the geothermal system is active, and altering the rocks in the area as we speak.
The Final Thoughts on Torfajökull Volcano
Torfajökull is Iceland’s reminder that volcanoes don’t follow scripts.
Its rhyolitic magma tells a slower, more complex story than the fast-moving basalt eruptions dominating today’s headlines. And its so-called “overdue” status highlights a fundamental truth of geology: time alone does not trigger eruptions, geological processes do.
At the Lava Show, most visitors see molten basalt lava, the same type erupting at Svartsengi and across the Reykjanes Peninsula.
Torfajökull tells the other half of the story. Its rhyolite rocks answer the questions:
Why some eruptions explode instead of flow;
Why this lava barely moves at all;
What happens when magma evolves over time?
Lucky for us, the Lava Show features no volcanic explosions, only explosions of insight and information!
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This article is written by geologist Jessica Poteet. Listen to the interview with her on the Lava Academy Podcast.
