The Long Glacier (1355m, 4460 ft) is the second largest in Iceland. It has an area of about 950 km² and most of it rises between 1200 and 1300 m above sea level. It rests on a massif of hyaloclastite mountains. They rise highest under its southern and northern parts, but have not yet been researched thoroughly.
Four counties meet in Langjokull, Árnessýsla, Borgarfjarðarsýsla, Mýrarsýsla og Húnavatnssýsla. The Glaciological Society owns a hut at the foot of the nunatak Fjallkirkjan (1228m). Many glacier snouts crawl down to the lower lying areas and each of them has a name.
There are three smaller glaciers around the big one, to the northwest is Eiriksjokull, to the south is Thorisjokull and to the east is Hrutfell.
Two of the bigger highland tracks are leading alongside this glacier: Kaldidalur Highland road and Kjölur Highland road. Kaldidalur is between Langjokull and the glacier Ok in the west, whereas Kjölur lies between Langjokull and Hofsjokull in the east.
Very little water runs from The Long Glacier on the surface. It, however, supplies the largest natural lake of the country and the lakes to the north and geothermal areas in the West and the Geysir area as well.
The Langjokull central volcano lies at the northern end of an active volcanic zone that extends to the NE from the Reykjanes Penisula. Langjokull volcano occupies the NE half of the massive Langjokull icecap, east of the prominent Pleistocene table mountain, Eriksjokull. A summit caldera lies beneath the ice. Several shield volcanoes have been constructed along flank fissure zones, and postglacial lava flows flank Langjokull on the northern, western, and eastern sides. One of the most prominent of these is a small shield volcano that was formed at the site of the massive Hallmundahraun lava flow, which covers 200 sq km, and was erupted shortly after 900 AD. The Geysir thermal area, containing Iceland's largest geyser, lies in the Haukadalur basin, near the southern end of the lengthy fissure system extending from Langjokull central volcano.
Icecave at Langjokull.