Few birds wheel above the Atacama Desert, the driest place on earth, and you see no hint of green from the one paved road that crosses it, the Pan American Highway. An empty landscape of sunbaked rock, gravel and shifting dunes, the desert stretches for some 600 miles (1000km) beside the coast of northern Chile. And, with changes of name, it continues for another 1400 miles (2250km) both north and south. About 60 miles (96km) inland, the desert gives way to the bleak and windswept foothills of the Andes.
Empty and silent though it may be, the desert is not inert. Where there is sand, crescent dunes ripple across the Landscape, formed and reformed by the wind. In rocky areas, scudding dust devils of wind-whipped sand, and the infrequent downpour, have scoured the hills into soft curves. In the evening light, the mineral-rich rocks glow with colour – browns, reds, purples, greens.
As deserts go, the Atacama is cool. Summer temperatures are generally around 18°C (65°F ), but at midday, the ground can be as hot as 50°C (122°F ). At night the temperature can drop by 40°C (70°F ) in little more than an hour. A sound like a pistol shot at twilight may be a rock splitting, distorted by the swift temperature change.
Only one permanent river, the Loa, winds through the heart of the desert from the Andean foothills, its course cut so deep that desert travellers barely see it until they are on top of it. There are said to be areas of desert where it never rains – no one knows for sure.
In the ports of Iquique and Antofagasta, it rains no more than four times in a century – and when it does rain the results are devastating. Most moisture comes from the mist that often shades the sun in the northern and southern fringes of the desert, where a few cacti survive.
The Atacama is starved of rain by the circumstances of its surroundings. Rain cannot reach it from the Amazon basin because easterly winds drop all their rain on the eastern slopes of the Andes. In the Pacific to the west, the cool Humboldt Current sweeps north from the Antarctic. Whereas onshore winds are normally warm and moist. Bringing rain, here they are cooled by the chilly current, so on passing over the warmer land they take up moisture and form a mist.
Known locally as camanchaca, the mist clings to the coast below 1000ft (300m). It does not reach the heart of the desert above the cliffs. Its dry air makes the Atacama a place where traces of human activity are long preserved.
Cart tracks made about 100 years ago can still be seen in the crust of soft ‘costra’ formed from sun-baked rock fragments and salt crystals. Most intriguing are the earth pictures (or geoglyphs) of patterns and stylised figures outlined in stones.
The 400ft (120m) long Giant of the Atacama on a hill near Iquique is the largest. Although the earth pictures look as fresh as new, they were created maybe 1000 years ago by a long-vanished people.
The Atacamenos, the area’s original inhabitants, were conquered by the Incas of Peru not long before the 16th century when the Spaniards came. Prospectors followed in the Spaniards’ wake, seeking gold and silver – even, maybe, in the many well-preserved ancient graves.
They told tales of being guided by the Alicante, a legendary bird that glowed with the colour of the precious metal it devoured. But the Alicante vanished if threatened, leaving the prospector lost, starving, sweltering by day and shivering by night.
For the next 30 years, Chile’s wealth came almost entirely from sodium nitrate, but after World War I the industry collapsed as artificial chemicals replaced the natural ones. Now the desert winds blow round the skeletal remains of buildings, smokestacks and railways, and the innumerable crosses that poke up through the shifting veils of dust and sand and mark the graves of dead miners. But there is still mining in the area – one of the largest – known copper deposits is now being mined in the foothills around Chuquicamata.