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Discover Iceland’s captivating underground world of volcanic caves and lava tubes, where nature’s artistry is on full display. This guide will unveil the geological wonders hidden beneath the surface, offering insights into their formation, must-visit sites, and essential tips for safe exploration.
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Julia Hammond
Content Writer
Published:
9 Jan 2025
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Guides, Travel tips
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Iceland’s long volcanic history means there’s a wealth of caves and lava tubes waiting to be explored. We’ll take a look at the processes that created such landforms and uncover the unique geological formations within them. With practical advice on safety, gear and seasonal change, this article is a must-read for anyone intending to add such a visit to their Iceland holiday itinerary.

How are Volcanic Caves and Lava Tubes Formed?

The spaces we identify as volcanic caves and lava tubes form as a volcanic eruption progresses and wanes. As we watch lava fountains burst from a volcano’s craters and rivers of lava flow along its flanks, activity is also taking place out of sight. Molten magma flows beneath the surface through channels called dykes as the magma chamber steadily empties.

On the surface, the lava spreads out, filling valleys and overflowing smaller hills and peaks. As the top of these flows come into contact with the open air, they start to cool and solidify. But beneath the blackened crust that we see at ground level, lava flows continue. As the magma flow subsides, these tunnels empty. Sometimes the tops of them remain intact to form the roofs of a lava tube.

Underground, magma works its way through fissures in the rock known as dykes. As it does so, it too can partially solidify, creating a conduit through which the magma flows. When the eruption draws to a close, these conduits can eventually drain to become empty tubes. If, as is often the case, an eruption starts up again, you might also see layering which is evidence of multiple lava flows within the tubes.

During the process, volcanic gases can collect which keeps the pressure up against the tube’s roof, preventing a collapse. A process called oxidation can lead to intense heat within the tunnel or cavernous space. Where this happens, the temperature increases allowing some of the rock to melt again. When this occurs, you’ll find stalactites in the places where it has dripped from the ceiling.

Long after they’ve cooled, you can see from the patterns in the floor that you’re standing where an ancient river of lava once passed. Given that thousands of years have passed, the caves and tubes stabilise. However, in the past there may have been strong earthquakes and these might account for any rock falls you might encounter within the lava tube.

Where to Find a Lava Tube That You Can Visit

Iceland has a lot of lava tubes. The figure is thought to be in excess of 500 though no one knows exactly how many there are. Some of these landforms are situated within a short drive of Reykjavik, so they’re easy to slot into your travel plans.

Let’s start by taking a look at three unmissable destinations.

Raufarhólshellir

This lava tube is one of the longest in Iceland, measuring 1360 metres from end to end. Thanks to its proximity to Reykjavik, one of its most visited. Raufarhólshellir provides us with tangible evidence of an eruption that took place around 5200 years ago when Leitahraun burst into life.

Lava tube caves in Iceland are relatively common but this 30 metres wide and 10 metres high cave is unusual in that it’s closer to the surface than is often the case. In places, the roof has collapsed and it feels open to the elements. Water ingress has led to the formation of stalactites and stalagmites, while in winter, heaps of snow collect on the floor.

Visiting Raufarhólshellir requires no caving experience, though access is with a guide. Tours run all year round and children as young as three are invited to participate. It’s a fascinating excursion for anyone with even a passing interest in geology or keen to learn about Iceland’s incredible landscapes.

Víðgelmir

Víðgelmir is Iceland’s largest lava tube, situated on the Hallmundarhraun lava field. Formed during an eruption about 900AD, it is more than a kilometre and a half long. Unlike some, this cave is easy to access: it boasts a sturdy walkway and is well-lit, showing off the dazzling array of colours within the cave to great effect.

Víðgelmir lava cave is a popular stop Silver Circle tours, which circles packages up the highlights of West Iceland and includes visits to Langjökull, Deildartunguhver (Europe’s most powerful hot spring) and beautiful Hraunfossar – also known as Lava Falls because like Víðgelmir it’s also located on the Hallmundarhraun lava field.

Þríhnúkagígur

Of all Iceland’s volcanic caves, this is easily the most impressive. Þríhnúkagígur’s name translates to “three peaks crater”. Unusually, when the eruption finished 2000 years ago, the empty magma chamber didn’t collapse. Because of this, tourists can descend into the depths of this long-dormant volcano to inspect its magnificent cave. It’s the only place on the planet where it’s possible to descend into a magma chamber.

Visitors first need to hike for around 45 minutes across a striking lava field. Mostly, the walk is on a flattish trail, though the final 50 metres are a little steep. On arrival at the entrance to the lava chamber, you’ll be given a harness and a helmet to put on. Then, you’ll step into an open-sided lift for a seven minute descent, 213 metres down into the bowels of the earth.

At the bottom, you’ll have about 30 minutes inside the volcano, which is enough time to walk around and take a closer look at the minerals that show up as red, yellow and green colouration on the walls of this vast space. It’s so big, in fact, that you could even fit Hallgrímskirkja inside and have room to spare. Tours run from early May until the end of October.

Inside the Volcano

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Practical Advice for Travellers Visiting Iceland’s Volcanic Caves and Lava Tubes

Booking a guided tour to visit a lava tunnel in Iceland means you can take advantage of expert local knowledge and be confident that under their watchful eye your safety is as much a priority as your enjoyment. Reputable operators will ensure that you have all the correct gear and that full instruction is given before anyone enters the cave or lava tube. Let’s take a closer look at what that’s like in practice.

Safety

No activity is without its risks, but some environments are a little more hazardous than others. Visiting a volcanic cave or lava tube is not a walk in the park and certain safety considerations must be taken into account before and during your visit. This isn’t the kind of place you should explore alone, particularly if you’re inexperienced.

It’s highly unlikely you’ll have any mobile phone reception as you’ll be below ground, so don’t expect to rely on it to call for help – remain with your guide and tour group at all times. In Iceland caves and tubes may also have icy floors, particularly near the entrance, but your tour operator will issue crampons if that’s the case.

Remain aware of your surroundings and don’t blindly follow your guide or others in your party without making sure it’s safe for you to proceed too. It’s vital that you don’t grip or bump into the fragile rock formations on cave and tube walls and ceilings as these break off easily. Icelandic law protects these delicate environments and any damage, accidental or otherwise, is taken extremely seriously.

We strongly advise against visiting any cave without a skilled local guide and proper safety equipment. Many of these caves are situated on private land with access limited to authorized guided tours.

What to wear

If you’ve been considering a visit to an Iceland cave or lava tube, you’ve probably been wondering what you need to do to prepare for the activity. Firstly, you’ll need to take account of the temperature within the cave, which is typically about 0-4°C all year round. That means you’ll need to dress warmly – don’t forget your gloves.

Just as you would for a hike above ground, begin with thermal base layers and add other clothing on top, preferably bearing in mind you want something that will wick away sweat. A waterproof coat and hat are also a good idea as water often drips down through caves. Sturdy hiking boots with a thick tread and ankle support are essential too. Make sure they’re properly worn in and wear suitable socks so you’re untroubled by blisters.

Required gear

You don’t have to be a world-class speleologist to be able to visit a lava tube cave or lava tunnel in Iceland. When choosing which tour to book, take a look at the small print as this should indicate the level of fitness required. But many are large enough to have been fitted out with staircases and walkways, so it’s unlikely you’re going to be issued with ropes and harnesses. Most tours are family-friendly and suitable for anyone with reasonable mobility.

On guided tours, we’ll make sure you are also kitted out with a helmet. Sometimes, rocks can become dislodged; these loose rocks aren’t something you want to be underneath if they fall. Keep the helmet on at all times for your own protection. Another item that’s important is a flashlight – usually a head torch is handy as it means you can keep both hands free.

If you’re keen to explore the fascinating world of Iceland’s volcanic caves and lava tubes, why not take a look at one of our volcano tours?

Find Your Volcano and Lava Cave Tour

3 hours

The Lava Tunnel

Delve deep underground on this adventurous lava tunnel tour, just 30 minutes from Reykjavík. Raufarhólshellir is an ideal tour for geology buffs and adventure-seekers. You will see the inner workings of a volcanic eruption while walking in the path of lava that flowed thousands of years ago. This is an easy, guided tour with no caving experience required

From €104/person
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Golden Circle & Lava Tunnel - Combo Deal

Nature, culture, and history prevail in this combination tour, which takes you to the sites of the Golden Circle and inside the Lava Tunnel Raufarhólshellir cave. Experience a new world of Iceland's natural wonders -- Gullfoss waterfall, the Geysir geothermal region, Þingvellir National Park and the raw beauty of a lava tunnel. This is an easy, guided tour with no caving experience required.

From €169/person
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Snorkel in Silfra & Lava Tunnel

Experience Iceland's natural wonders: snorkel in Silfra's crystal-clear waters between tectonic plates, enjoy lunch at Reykjadalur Lodge, and explore the stunning Lava Tunnel's volcanic formations.

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Volcanic Wonders with Grindavik Visit

Once a bustling fishing village, Grindavík now serves as a stark reminder of nature’s relentless power. After a recent volcanic eruption forced the evacuation of its residents, much of the town remains uninhabitable, its landscape forever marked by the destructive forces of the earth.

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The Volcanic Trails

Unveil Iceland's wild beauty on a 5-day trek through Vatnajökull National Park. Traverse moss, waterfalls, canyons, and deserts. An untamed Icelandic odyssey.

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Eyjafjallajökull Summit Hike

Hike to the summit of Eyjafjallajökull Volcano—a thrilling day hike for experienced hikers seeking a manageable challenge. Traverse rugged terrain and enjoy breathtaking views of the Highlands, Mýrdalsjökull, and Vestmannaeyjar Islands.

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Questions and Answers about Volcano and Lava Cave Tours in Iceland

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Golden Circle & Lava Tunnel - Combo Deal

Nature, culture, and history prevail in this combination tour, which takes you to the sites of the Golden Circle and inside the Lava Tunnel Raufarhólshellir cave. Experience a new world of Iceland's natural wonders -- Gullfoss waterfall, the Geysir geothermal region, Þingvellir National Park and the raw beauty of a lava tunnel. This is an easy, guided tour with no caving experience required.

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Volcanic Wonders with Grindavik Visit & the Blue Lagoon

Embark on a carbon-neutral journey through Iceland’s stunning volcanic landscapes. Enjoy a refreshing hike across a lava field, formed by recent eruptions, and then unwind with a soothing soak in the healing geothermal waters. This perfect combination of adventure and relaxation offers an unforgettable way to experience the raw power and serene beauty of Iceland’s natural wonders.

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The Lava Tunnel

Delve deep underground on this adventurous lava tunnel tour, just 30 minutes from Reykjavík. Raufarhólshellir is an ideal tour for geology buffs and adventure-seekers. You will see the inner workings of a volcanic eruption while walking in the path of lava that flowed thousands of years ago. This is an easy, guided tour with no caving experience required

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Lava Cave & Geothermal Adventure

Discover the magic of Borgafjörður, celebrated by Lonely Planet as a top region to visit. From Europe's mightiest hot spring, Deildartunguhver, to the captivating cascade of Hraunfossar and the mystique of Vidgelmir lava cave, embark on an adventure through Iceland's geothermal wonders and rich history.

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Experience Iceland's natural wonders: snorkel in Silfra's crystal-clear waters between tectonic plates, enjoy lunch at Reykjadalur Lodge, and explore the stunning Lava Tunnel's volcanic formations.

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Volcanic Wonders with Grindavík Visit & the Sky Lagoon

Discover Iceland’s geothermal heart in the UNESCO-recognized Reykjanes Geopark, where continents meet and drift apart. Explore a vibrant geothermal area, hike to freshly-formed lava fields, and visit the resilient fishing village of Grindavík. This carbon-neutral journey ends with pure relaxation at Reykjavík’s Sky Lagoon, where you can soak in warm waters and unwind with a luxurious spa ritual.

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