Iceland is situated directly on the boundary between the North American and Eurasia tectonic plates. These plates move apart at around 2cm per year. As part of this spreading, giant fissures open up, and in some places fill with water. Silfra is one such place. Located in Thinvellir Lake in Thingvellir National Park, which was the first national park in Iceland and is also UNESCSO World Heritage Site. Silfra has remarkably clear water, which makes it an excellent diving location, with visibilities exceeding 100m. But the water is also very cold, ranging from 2°C to 4°C year-round.
The clarity of the water is a result of volcanic activity upstream of the lake. As water from Lángjökull glacier melts it trickles through the porous volcanic rock, taking between 30 to 100 years to travel the 50km from the glacier to the lake. This filters the water to a quality so pure that divers often drink right from the lake.
Despite the beauty divers must remember that this is area is tectonically very active, with large earthquakes occurring about every 10 years, the last one in 2008 measured 5.4 on the Richter scale.
Photo Credit: Alexander Mustard