A sandur is a desert made up of the volcanic debris that results from the erosion of mountains or the explosion of sub-glacial volcanoes, and transported there by glacial rivers. In the southeast of the country is Skeiðarársandur, the largest sandur in the world (1 000km2), fed by the Skeiðarárjökull Glacier. In the sights of this dark and flat expanse, home to a population of skuas, enormous brown birds that terrorise other birds, the gigantesque Vatnajökull ice cap.