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The land and the people

The land: The glaciers

Despite the name of the country, Iceland's ice–caps and glaciers only cover 11% of the surface area (about 11,000km²). The beginning of the twentieth century saw the end of the "little ice age" (c.1600–1900), a period during which Iceland's glaciers had grown, devouring farmlands and making communications more difficult. Since the turn of the century, however, the glaciers have been in retreat (perhaps by as much as 3km), due to a warming of the climate.

The largest expanse is Vatnajökull (8,400km²) which is the biggest ice–cap in the world after Antarctica and Greenland. Its central region is a plateau 1300–1700m high with isolated summits, though most of its surface is fairly flat or undulating. The ice thickness is on average 420m, up to a maximum of about 1,000m. To its south is the ice–cap Öræfajökull, within which is the country`s highest mountain, Hvannadalshnúkur (2,119m). To the south and east of the Vatnajökull–Öræfajökull ice–mass there are valley glaciers, sending rivers of ice down towards the coast while to the north and west, where the slope of the ground is not so great, wide lobes of ice spread out.

The other important glaciers are Langjökull and Höfsjökull (both in the central highlands), and two in the south, Mýrdalsjökull and Eyjafjallajökull, which were joined together by a thin neck of ice until recently. There are other smaller glaciers that cap high mountains such as Snæfellsjökull, Snæfell and Drangajökull. But it is Vatnajökull, and the many glaciers that flow from it, that is the most important and impressive example of glaciation in the country, and at Skaftafell National Park the visitor will have a good opportunity to look at some of Vatnajökull`s outflow glaciers at close hand.

The ice–caps are basically mountains on which snow (later to become ice) gathers and then travels slowly downwards via the glaciers. During winter (the main, but not the only, season for snow), snow collects as layers of crystals on the surface of the ice–cap. With continual melting and freezing, ice layers form in between the snow layers; rain or meltwater that percolates downwards and later freezes also changes the structure of the now-compressed snow and over a period of years the gradual process of snow crystals becoming (denser) ice crystals takes place. So long as the yearly addition of snow is greater than the amount melted, then the glacier will grow. The ice–cap may increase its thickness by up to 10 metres each year, and the additional weight will push the ice downhill.

Glaciers often start their downward journey from an ice–cap by following a steep V–shaped valley cut by a stream. In many ways a glacier behaves like a river of water, but the main difference is that the ice is frozen to the sides of the valley and as it moves down the valley it rips stones and boulders from the walls, widening its path considerably. At its base, too, it rips up the floor of the valley, deepening it as it travels. In this way the glacier transports vast quantities of material downhill, from large boulders to the finest of sand, the latter coming from the scraping of rocks frozen in the ice against other rocks still in the ground.

Along the edge of the glacier, the ice has a pile of rubble on it and frozen within it; this is the rock that has been taken off the valley wall and is called the "lateral moraine". When two glaciers meet and travel down the valley beside each other, the region where their lateral moraines meet and join together is called the "medial moraine". This is often a long ridge of black ice standing above the rest of the ice and is one of the most noticeable features of a glacier.

The glacier's speed (perhaps less than a few metres a day) is not constant all the way from the ice–cap to its snout: if the steepness of the slope increases then it will travel faster. Its speed across the glacier is not constant either: beside the valley walls it moves very slowly while at the centre of the glacier it moves much more quickly. All these changes in speed crack the ice and form crevasses, which are most obvious in the summer when there is little fresh snow on the glacier. If the glacier changes its direction then the crevasses will be curved, and if the glacier slows down then the crevasses may close up again. They may also appear at the valley walls and at the snout (the front of the glacier) when the glacier is spreading out.

If a glacier is retreating (or is "stagnant") then its snout will be jet black since it will contain a higher proportion of black sand to ice (which is melting). In front of the snout are the moraines, glacial lakes, glacial rivers and sand. Right at the front of the snout is the material that has most recently been dropped by the ice. This is usually a mixture of pebbles and sand and is called the "end moraine". If the glacier is advancing then it will push this material in front of it and begin to ride above some of it. However, if it is receding, then the old moraines will mark the position of the glacier's snout in previous years. At the side of the glacier the lateral moraine will contain much larger boulders that have been torn away from the valley wall.

The space between the moraines may often be filled by small lakes that gather water from the melting snout and the subglacial streams. While only a few meltwater channels may flow out of the lakes and past the moraines, they soon break up and form a myriad of interwoven streams, heavy with suspended material. Many of the pebbles in these streams are well-rounded as a result of the grinding down that takes place at the edges and the base of the glacier; the smaller pebbles and, finally, the sand, are washed away quite far from the snout and huge expanses of sand ("sandur") are formed. These often stretch into the open sea and around much of the south coast long sandbars have built up.

While the valley glaciers of the south produce these expanses of sand and sandbars, the rivers that carry Vatnajökull`s meltwater to the north have to carry their load a greater distance to the sea. Great rivers like Jökulsá á Fjöllum and Jökulsá á Brú dump huge piles of grey gravel by their banks as they make their way through the surrounding lavafields.

In a number of places beneath the ice there are volcanoes which can erupt, melting vast quantities of ice and causing jökulhlaups ("glacier bursts"). Eruptions in Öræfajökull and Katla (in Mýrdalsjökull) have produced such bursts. Similarly, far up in the Vatnajökull ice–cap, the subglacial solfatara area of Grímsvötn melts ice, the water from which then accumulates in lake Grímsvötn, which is formed in a depression in the mountains. About every five or six years, the water level rises sufficiently to lift up the surface ice, enabling the water to escape from the depression. A massive flood pours down, ending when the lake has dropped its level by as much as 200m. Another area prone to jökulhlaups is Grænalón, an ice–dammed lake to the west of Skeiðarárjökull. No volcanic or solfataric activity is involved here: it fills up with the meltwater of another small glacier and when its water level is more than nine–tenths of the thickness of the edge of the glacier, it lifts it up and sends a torrent of water into the river Súla.

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