In 1919, two Swedish students, Hakon Wadell and Erik Ygberg, set out to explore the possible causes of the jökulhlaups that frequently emerged from beneath Skeiðarárjökull, unaware that they were retracing the past. They found the glacier very difficult to traverse: they had four horses pulling the sledge, but this was hard going because of a 10-cm thick cover of tephra, which had come from the large eruption of Katla. Suddenly, the front horse stopped, refusing to budge or go any further forward no matter how hard the students beat it. A slight break in the fog appeared, and they found they were standing on the edge of a precipitous cliff. The horse had sensed the up-draught at Grímsfjall! ‘When we came to the head of the horse, there appeared below us a crater comparable to the side of hell in size, though even that would have been expanding in these recent and most difficult times.’ The crater welcomed them with ‘… the rumbling of ice rocks that continually crashed from the cliff walls, hundreds of metres high, down into the crater’s basin where they melted in warm, emerald green water.’ Typical students, they toasted their discovery with cognac and christened the caldera Svíagígur (‘Swedish crater’), a name that did not catch on.