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Iceland is an excellent place to study glaciers and glacial landforms.. About 10,9% of the land area of Iceland is covered by glaciers or about 11,260 square km (4328 sq. miles). By far the largest of the glacier caps is Vatnajokull in Southeast Iceland with an area of 8,086 square km, equal in size to all the glaciers on the European mainland put together. Vatnjokull glacier is up to about 800m thick. Other large glacier caps are Langjokull (953 sq. km) and Hofsjokull (925 sq. km), both in the central highlands, Myrdalsjokull (596 sq. km), Eyjafjallajokull and the small Tindfjallajokull (19 sq. km) in the south, and Drangajökull (160 sq. km) in the northwest. On the tip of Snæfellsnes, across the bay from Reykjavík, one of the smaller glaciers, Snæfellsjökull (11 sq. km) may be seen in clear weather and affords a fascinating sight at sundown. The main reason why most of the glaciers are located in the Southern Highlands 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 the turn of the 19th century. Travelling across the glaciers was rare in earlier times, but nowadays it´squite common when the weather is good. Such trips should not be undertaken unaccompanied by the inexperienced unless accompanied by professionals – you can buy a glacier tour with a Super-Jeep or go snowmobiling.
Almost all types of glaciers are found in Iceland, ranging from the small cirque glaciers to extensive glacier caps reminding one of the inland ice of Greenland. The latter are drained by broad lobe-shaped outlets or by valley glaciers of the alpine type. Glaciers are classified based on their size and their relationship to topography. The smallest glaciers are confined to mountain valleys. These are called valley glaciers or alpine glaciers. Larger masses of ice may cover an entire mountain range or volcano. These glaciers are called ice caps and most glaciers in Iceland classify as ice caps. Ice caps may cover several thousand square kilometers. Vatnajökull is the largest ice cap in Europe and covers an area of about 8086 km2. This is an area bigger than the state of Rhode Island, USA. Glacier tongues that drain an ice cap or ice sheet are called outlet glaciers. Breiðamerkurjokull, Skeidararjokull, Skaftafellsjokull, and Svinafellsjokull are some of the larger outlet glaciers that drain the ice cap Vatnajokull.
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 (in several years).
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 glaciers 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 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 glacier, even when the terminus is stable for several years. No matter what the size of the glacier these basic principles determine glacier behavior. 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).
Now the yearly average temperature in Iceland is around 5°C, so there would not have to be a great 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 characteristics 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. Therefore they have been and are still being researched and monitored thoroughly.
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