The world is splitting apart here – and you can slip through the crack

It’s too dangerous to visit but tourists can still swim through nearby waters where the world is being torn apart 

It’s impossibly blue, remains 4°C or below all year and is the only place in the world you can snorkel between two tectonic plates. This is Iceland’s Silfra fissure. 

There’s only one place on the planet where you can jump into the water and swim between two tectonic plates: Silfra fissure in Iceland. 

Silfra is part of a system of tectonic fissures: deep cracks created as the North American and Eurasian tectonic plates (enormous chunks of rock that make up the outer layer of the Earth) pull away from one another. These plates are edging further apart all the time: separating at a rate of just under one inch per year. 

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It’s around an hour’s drive from Reykjavík, inside the protected Þingvellir National Park and directly on the Mid-Atlantic Ridge. 

This natural marvel was widened in 1789 by a series of earthquakes that tore the land apart. According to Silfra Fissure’s website, “those earthquakes opened new fissures in the Þingvellir area. One of the cracks connected to an underground spring system and filled with glacial meltwater.”

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But Silfra must be much older than this, says the Thingvellir National Park website: “It is not known entirely when it was formed,” they write, “but according to records of the speed of the continental drift, a 10-metre-wide fissure would take at least 1500 years to form, given a drift of 5 millimetres per year.”

The waters are cold and clear. Water temperatures linger between 2°C and 4°C year-round, even on warm summer days (when air temperatures can reach 18°C at their hottest but more typically linger between 10°C and 15°C) or in sub-zero winters.

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This is because of how long it takes the fresh meltwater to travel the 30-odd miles from the Langjökull glacier to Silfra. “It travels underground for decades and filters through volcanic rock before reaching the fissure,” writes Guide to Iceland on its website. During the years-long journey, it’s shielded from surface heat that would warm it up, keeping it at a cool, steady temperature. 

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This long filtration through the rock also gives the water astonishing clarity: “The result is water so pure that visibility often reaches 330 feet (100 metres),” they add. 

Those brave enough to face an icy dip can snorkel or scuba dive between the tectonic plates, wearing drysuits to keep warm (and, importantly, warming up with hot chocolate afterwards). 

Measuring around 600 x 200 metres in total, Silfra is made up of several interconnected sections. Some parts are restricted for safety reasons. These include a tunnel known as the toilet because of the sometimes dangerously strong flow of waters that can flush divers through a narrow vertical drop, spitting them out at around 16 metres deep. Before restrictions stopped people entering the toilet, the daredevil divers that ventured through this tunnel did so headfirst.  

The Silfra cave – also off limits because of its potentially dangerous nature – is more than 60 metres deep in some parts.

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But tourists can visit other sections – the Big Crack, Silfra Hall, Silfra Cathedral and Silfra Lagoon – before wrapping up their tour. 

There aren’t many animals living in these waters (I don’t blame them – it’s bloomin’ freezing) but there are lots of microscopic organisms and neon green algae delightfully named ‘troll hair’. 

The most famous resident is an amphipod (a tiny crustacean) called Crymostygius thingvallensis. These animals are only found in Silfra and the other fissures around Lake Þingvallavatn. 

The lake is full of fish but most don’t swim into the fissure because there aren’t enough nutrients in the filtered waters. Arctic char sometimes make a trip to the fissure during mating season (August and September) and while dwarf char live in these waters year-round, they’re shy and not commonly seen by swimmers. 

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