Langjökull
Langjökull (, Icelandic for "long glacier") is the second largest ice cap in Iceland (953 km2), after Vatnajökull. It is situated in the west of the Icelandic interior or Highlands of Iceland and can be seen clearly from Haukadalur. Its volume is 195 km³ and the ice is up to thick. The highest point of the ice cap (at Baldjökull at the northern end of Langjökull) is about above sea level. In the past, the largest recorded surface area was in 1840. Situation and form The glacier is roughly parallel to the direction of the country's active volcanic zone: north-east to south-west. It is about long and wide, and has a slightly narrower point roughly between the lake Hvítárvatn on the Kjölur mountain road to the east and the Þrístapajökull glacier to the west, near another smaller glacier, Eiríksjökull, which is not quite connected to Langjökull. It is the nearest large glacier to Reykjavík. The area of the glacier includes some mountains, e.g. Jarlhettur (; "The earl's hat") on the east side of Langjökull, a palagonitic mountain range, which originated in a fissure vent under a glacier during the Ice Age. The mountain Skríðufell () is situated on the east, above lake Hvítárvatn. Other mountains on the eastern side of Langjökull are Fjallkirkja (), Þursaborg () and Péturshorn (). A little to the east of Fjallkirkja is the hut of the Icelandic Glacier Research Society (also called Jöklarannsóknarfélag in the ), which includes scientists as well as interested amateurs. Glaciers in the area A number of outlet glaciers reach down from Langjökull to the valleys and plains below. These include Norðurjökull and Suðurjökull to the east; Vestri-Hagafellsjökull and Eystri-Hagafellsjökull at the southern end of Langjökull which are separated by the mountain Hagafell ; and Þrístapajökull to the west. Geitlandsjökull (1395m) is an outpost to the southwest, a glacier covering a tuya which is connected to Langjökull. Research shows that the outlet glaciers Norður- and Suðurjökull reached as far as lake Hvítárvatn until about 1900 but have retreated rapidly since then. Water flow and development of the glacier Despite the size of Langjökull, not many rivers directly originate there. However research has shown that large quantities of water flow in sub-surface streams to lake Þingvallavatn (some 50 km to the south and easily accessible to tourists) and reappear in springs in and around the lake, while the same happens on the west side, giving rise to various tributaries of the Hvítá River as well as some rivers flowing north towards Húnaflói. Thus many of the hot springs in the Borgarfjörður region (near the estuary of the Hvítá on the west coast), such as Deildartunguhver, receive ground water from Langjökull. The same is true for the lake Hvítárvatn to the east: ⅔ of its waters appear to come from Langjökull by underwater channels. Langjökull is shrinking quite fast, and some researchers believe that it will disappear in about 150 years if climate change continues at its recent pace. Volcanism Under Langjökull there