Þjórsárhraun, a great lava–field that came about 8,000 years ago from cracks near the Veiðivötn lakes and flowed along Þjórsárdalur, Landsveit, Skeið and Flói to reach the sea between the rivers Ölfusá and Þjórsá, a distance of 130 km and covering some 800 km2. One of the largest known lava–flows anywhere on Earth.