Skeidararsandur is a vast sand plain, formed from alluvial deposits. It covers 1300 km², making it the largest sand in the world.
There is little vegitation in general to be found at Skeidararsandur. It is very rocky near the glacier, becoming more muddy and gravelly further on and made up of of sand and clay where it reaches the sea. Carex does however grow to a degree at Skeidararsandur and it is one of the largest nesting places for the Great Skua. There is also an abundance of seals by the shore.
Eruptions under the Vatnajokull glacier have caused many glacial bursts, the latest one being in 1996. They start at the Grimsvotn volcanic area and are known as Skeidararhlaup.