(Photograph) - Iceland is chilly by name and chilly by nature. About this time of the year thermometers start their steady descent and it gets so cold in winter that even waterfalls freeze. But, beneath all those glaciers and frozen tundra, Iceland is centrally heated.
This north Atlantic nation of just 250,000 people sits on top of a volcanic hot spot where the continental plates of North America and Europe grind against each other. The earth tremors and eruptions that shaped this island are still a regular occurrence.
Engineers have found a way of harnessing this power by sinking boreholes into subterranean reservoirs of volcanically superheated vapour, bringing it to the surface and piping it into people's homes. Eighty five per cent of the population keeps warm in this way.
Uncontrolled, this pent-up energy bursts out from underground in spectacular columns of boiling water ("Geysirs") or bubbles in hundreds of steaming pools.
The best known of these is the Blue Lagoon (left), near Reykjav!k. It is probably the most photographed too, not just for its colour but for the backdrop of silver cylinders shrouded in mist provided by the geothermal Svartsengi power station next door. The lagoon was formed in the 1970s when the power station began discharging hot water that was too salty to be used for domestic heating. In Iceland, alfresco bathing in thermal pools is an all-year-round pastime, so it wasn't long before people started stopping off for a bone-thawing soak.
The lagoon's soft white silica mud was found to have beneficial effects for psoriasis sufferers and its inviting turquoise waters - turned that colour by a high concentration of mineral salts and algae - have made it a major tourist attraction. It's an oasis of warmth in a country of cold.
This picture appears in "The Earth From The Air" by Yann Arthus-Bertrand (Thames and Hudson). Picture by Yann arthus-Bertrand.