The south side of Vatnajökull is characterised by many high, majestic mountain ridges, with outlet glaciers descending between them onto the lowlands. The southernmost part of the glacier envelops the central volcano Öræfajökull and Iceland's highest peak, Hvannadalshnjúkur. Sheltered by the high ice, the vegetated oasis of Skaftafell overlooks the black sands deposited to its west by the river Skeiðará. These sands are mostly composed of ash which stems from the frequent eruptions at Grímsvötn and is brought to the coast by jökulhlaups, or glacial floods.