UNDERWATER WONDERS

Take a deep dive into some of the world's most curious submerged sites

- SCOTT DUTFIELD

SWIMMING BETWEEN CONTINENTS

Off the coast of Iceland's Thingvellir National Park is a place where divers can touch two different continental plates at the same time, called the Silfra fissure. After an earthquake rumbled along part of the North Atlantic in 1789, cracks appeared along the border between the Mid-Atlantic Ridge, where the North American plate and the Eurasian plate are moving away from one another. As the continents drift apart, the fissure is expanding at a rate of around two centimetres per year.

After the fissure formed, 'meltwater' from the nearby Langjökull glacier filled in the rift. The water travels from the glacier, some 30 miles away, to the fissure through porous rock. The journey of this water can take anywhere from 30 to 100 years to reach the fissure.

WATERFALLS BELOW THE WATER

The idea of a waterfall beneath the waves might seem ludicrous. However, they do exist. The largest example can be found between Iceland and Greenland in the Denmark Strait. At the bottom of the Denmark Strait is a seafloor filled with undulating geological formations called cataracts. The underwater waterfall is created when warm water from the Irminger Sea hits the cold water of the Nordic Seas. When water cools, it becomes denser than warmer water. This means the cold water sinks below warm water and cascades over the largest cataracts in the strait.