Iceland

For a long time, it was impossible to drive all the way around Iceland, because a plain of sand stood in the way.

The ring road is meant to circle the whole island, but a stretch on the south coast was missing. A black sand plain lies there, roughly the size of the city of Los Angeles.

Meltwater from a glacier flows across the plain in rivers that keep moving. Beneath the ice are volcanoes, and when they erupt, the ice melts and huge floods surge out across the sand.

In the mid-1970s, Iceland’s longest bridge was finally finished, almost a kilometre long. Some twenty years later, a flood carrying blocks of ice the size of houses tore parts of it apart. The bridge was repaired.

Then the glacier retreated, and the river changed course. Iceland’s longest bridge suddenly stood over dry sand. Today the road crosses a new bridge next to it, and two twisted girders from the old one remain as a monument.

Geologists all over the world call plains like this sandur, after the Icelandic word for sand.