Iceland is unparalleled as a place to study glaciers and glacial landforms. About 11% of the land area of Iceland is covered by glaciers, or about 11,400 square kilometres (4,400 square miles). By far the largest of the glacier ice caps is Vatnajökull (Vatnajokull) glacier in south-eastern Iceland. Covering an area of 8,300 km2, up to c. 900 m thick, Vatnajökull is equal in size to all the glaciers on the European mainland put together.

Other large glacier caps are Langjökull (Langjokull) (953 km2) and Hofsjökull (Hofsjokull) (925 km2) - both in the Central Highlands; Mýrdalsjökull (Myrdalsjokull) (596 km2), Eyjafjallajökull (Eyjafjallajokull) (78 km2) and the small Tindfjallajökull (Tindfjallajokull) (19 km2) in the South, and Drangajökull (Drangajokull) (160 km2) in the Northwest. On the tip of Snæfellsnes (Snaefellsnes) peninsula, across the bay from Reykjavík (Reykjavik), one of the smaller glaciers, Snæfellsjökull (Snæfellsjokull) (11 km2), can be seen in clear weather - a fascinating sight at sundown. The main reason that most of the glaciers are located in the Southern Highlands of Iceland is the much greater precipitation in the South than in the North. At the time when the country was being settled, the glaciers were small, but they grew fast when it started getting colder during the latter part of the Middle Ages and up to the turn of the 19th century. Travelling across the glaciers was rare in earlier times, but nowadays it’s quite common when the weather is good. However, inexperienced hikers should not undertake glacier trips unless accompanied by professionals. You can join a glacier tour in a super-jeep, or go snowmobiling.

Types of glaciers in Iceland
Glaciers are classified based on their size and their relationship to topography. Almost all types of glaciers are found in Iceland, ranging from the small cirque glaciers (named for the bowl-like hollows they occupy, called cirques) to extensive dome-shaped glacier ice caps reminding one of the inland ice of Greenland. Most glaciers in Iceland classify as ice caps. Ice caps are miniature ice sheets, covering less than 50,000 km2, which form primarily in polar and sub-polar regions that are relatively flat and high in elevation. Ice caps may cover an entire mountain range or a volcano. Iceland´s Vatnajökull glacier (8,300 km2) is the largest ice cap in Europe; the area it covers is bigger than the state of Rhode Island, USA, and, hidden beneath its ice cap, there are no less than seven volcanoes, most of them active. The ice caps are drained by broad lobe-shaped outlets or by valley glaciers of the alpine type. Glacier tongues that drain an ice cap or ice sheet and outlet glaciers are also found in Iceland. Breiðamerkurjökull (Breidamerkurjokull), Skeiðarárjökull (Skeidararjokull), Skaftafellsjökull (Skaftafellsjokull), and Svínafellsjökull (Svinafellsjokull) are some of the larger outlet glaciers that drain the ice cap Vatnajökull.

Formation of glaciers
During the last Ice Age almost all of the country was covered by permanent snow and glacier ice. Glaciers form simply because more snow falls in the winter than can melt in the following summer. A glacier is a thick mass of ice that forms from the compaction and recrystallization of snow. When temperatures remain below freezing following a snowfall, a fluffy accumulation of new snow soon begins to change. Evaporation and recondensation of water causes recrystallization to form smaller, thicker and more spherical grains of ice. This recrystallized snow is called firn. As more snow is deposited and becomes firn, the pressure on underlying grains increases. When the thickness of the snow and ice exceeds tens of metres, the weight is sufficient to cause the firn to grow into even larger ice crystals. In glaciers where melting occurs in the zone of snow accumulation, snow may be transformed into ice very quickly by melting and refreezing (over several years).

Glacier features
The size and extent of glaciers are determined by the climate of a region. The balance between what accumulates high up on the upper part of the glacier, and what melts near the glacier's foot (terminus) is called the glacier mass balance. Accumulation occurs high up on the glacier (accumulation zone) where snow doesn't melt even during summer. The ice in a glacier is moving under the force of gravity and, as this material moves down the glacier, it eventually reaches the end of the glacier and melts in the ablation zone. The line that separates these two zones is called the equilibrium line. The elevation of this line varies each year depending on the temperatures that year and the amount of snowfall. If a glacier has more accumulation than ablation for several years, the glacier may advance. If more ablation occurs than accumulation, the glacier will retreat. At all times ice is continually moving down the glacier, even when the terminus is stable for several years. No matter what the size of the glacier, these basic principles determine glacier behaviour. The Icelandic ice caps, with their numerous outlet glaciers, are wet-based and temperate. This means that they are at the pressure melting point throughout the ice mass and during the whole year (except for the surface layers in winter).

The yearly average temperature in Iceland is around 5°C, so there would not have to be a great temperature drop for the glaciers to start growing and advancing again. The Icelandic glaciers are the so-called thaw-glaciers with temperatures around 0°C. Another characteristic of Icelandic glaciers is the great number of constantly moving glacier tongues. Sometimes they advance fast and then retreat gradually again, until the balance between the advance and the melting has been reached. The glaciers are an important source of water for the electrical production in the country. For that reason, they are being  constantly monitored and comprehensively researched.

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