Silfra Lake
Silfra is a tectonic fissure in Þingvellir National Park where the North American and Eurasian plates are slowly pulling apart, widening the crack by around 2 centimetres per year. The fissure is filled with glacial water that has filtered through the porous lava of the Langjökull glacier catchment area for decades before emerging here, exceptionally pure and with underwater visibility regularly reaching 100 metres. It is the only place on Earth where you can snorkel or dive directly between two continental plates, and the experience of drifting through the clear water of Silfra Cathedral, the widest section of the fissure, is described by most visitors as one of the most otherworldly things they have ever done. Tours depart year-round and operate in water temperatures around 2 to 4 degrees Celsius.
The Only Place on Earth to Snorkel Between Two Tectonic Plates, in Water Clear Enough to See 100 Metres
Silfra formed where the Mid-Atlantic Ridge runs through Iceland, marking the boundary between the North American and Eurasian tectonic plates. As the two plates pull apart, the lava field cracks and shifts, opening fissures that fill with water. Silfra is one of these fissures, located at the northern edge of Lake Þingvallavatn in Þingvellir National Park. The water that fills it is glacial meltwater from Langjökull, Iceland's second largest glacier, which seeps into the lava field and filters slowly through the porous rock over a period of 30 to 100 years before reaching Silfra. This filtration removes virtually all particulate matter, producing water of extraordinary clarity. PADI named Silfra one of the world's top 17 dive sites in 2024. The fissure was formed in its current recognisable shape by earthquakes in 1789 accompanying the ongoing plate separation.
The snorkeling route through Silfra passes four distinct sections. Silfra Crack is the narrow entry, with walls close on both sides. Silfra Hall opens into a wider passage with vivid blue-green light filtering through the water. Silfra Cathedral is the most dramatic section, a wide, deep chamber where the water's colour shifts through shades of turquoise and the visibility makes the far walls appear almost impossibly distant. Silfra Lagoon is the shallow exit section, carpeted with the bright green algae known as troll hair. The water temperature hovers between 2 and 4 degrees Celsius year-round, and all snorkeling is done in a drysuit provided by the tour operator. The tour takes around 30 to 40 minutes in the water. In places within Silfra it is possible to touch the rock face of both the North American and Eurasian plates simultaneously.
Silfra is inside Þingvellir National Park, a UNESCO World Heritage Site, around 50 kilometres from Reykjavík on the Golden Circle route. Access is guided only: independent snorkeling requires a permit and qualifying dive certification, and for most visitors booking with an authorised operator is the practical and required approach. Tours depart daily year-round, morning and afternoon. The minimum age is typically 12 and participants must be able to swim; no prior snorkeling experience is required for the snorkel tours. Scuba diving tours are available for certified divers. Silfra combines naturally with Þingvellir's other attractions and the rest of the Golden Circle on the same day.
