ARTS / Under the Volcano: James Turrell used to fly secret missions for the US Government. Now he is completing one of the most ambitious earthworks of modern times. He also has a new show at the Hayward. Mark Holborn met him

'MY ART has no object, no image, no point of focus.' I remembered James Turrell's words as we flew through the clouds and between the mountains. The electric grid of Phoenix glowed in the Arizona night, then the plane climbed to the high plateau of Flagstaff and dipped to the tiny airstrip. Instrument flying, when you see nothing but cloud beyond the cabin, requires great skill, Turrell later explained, or you might hit 'cumulo-granite'.

Bordered by the San Francisco Peaks, rising to nearly 15,000ft, Flagstaff lies on the edge of the Painted Desert and the Navaho reservations, just an hour or two from the Grand Canyon. Route 66 passes right through town, long freight trains whistle in the night, and cowboys still roam the streets. It is here that James Turrell, the artist, cartographer and pilot whose work went on show last week at the Hayward Gallery, has chosen to settle.

Like Max Ernst and the arcane photographer Frederick Sommer before him, Turrell was drawn to the space of northern Arizona. He is shaping and preparing tunnels through Roden Crater, the volcano which is the centre of his activity in the Painted Desert, in perhaps the most ambitious earthwork of modern times. His drawings of the crater project are included in the Hayward show, together with three light installations conceived from the meteorological phenomena of weather-fronts.

Turrell's studio is a hangar on the edge of the runway at Flagstaff. On the walls of his office are photographs of the aerial bombardment of Rotterdam and, surprisingly, of the Allied bombing of Paris, an action not widely publicised in history books. He says he admired the precision of the bombing patterns. His desk faces shelves of aeronautical literature. The adjacent studio space contains cartography instruments, tripods, wooden cabinets and rolls of elaborate drawings. An aesthetic of intricate design surrounds him, and he is clearly a man who understands the workings of sophisticated machinery. Downstairs his Helio plane, with its stripped fuselage of polished silver, is under going reconstruction.

With a fixed camera on the plane, he can manoeuvre and fly as if he were adjusting a lens, treating the aircraft itself as a camera. He proudly pulls out a flying helmet and puts it on for me. Then, out of a case, comes a military-issue, high-altitude helmet with an anti-nuclear flash visor - a relic of the days in the early Sixties when he flew secret missions over Tibet and the Himalayas for the United States government. He handles it very delicately, then places it on a bench for me to photograph. 'This was never really issued to me,' he says, alluding to the clandestine nature of the work, 'so I never had to return it.' Turrell is an exception to the land or light artists of his generation. He is not concerned with leaving his mark on the landscape, and he does not refer to his installations as 'light pieces'. It is clear by now that he was also no ordinary pilot. He turns to raise the vast hangar door. The famous Arizona light can be almost blinding.

Light is Turrell's medium. His installations are really no more than spaces where one's perception is transformed. They serve as a means or vehicle for seeing. 'Light is a powerful substance,' he has written, 'we have a primal connection to it. But, for something so powerful, situations for its felt presence are fragile. I form it as much as the material allows. I like to work with it so that you feel it physically, so you feel the presence of light inhabiting a space. My desire is to set up a situation to which I take you and let you see. It becomes your experience.'

In a totally white studio in Los Angeles in the Seventies he made 'sky-windows': simple squares through which one looked up to the sky and passing clouds. As the light changed, so did the colour of the sky, producing tones beyond the realm of normal perception. The neutrality of the space and the presence of the window-frame dramatically transformed viewers' perceptions, especially at the cusp between day and night. It is an effect now recreated on the roof of the Hayward with Sky Piece, a 24ft-high wooden structure which is open to the sky.

As Turrell's installations became more complex, he applied his knowledge of perception to projected light and immaculate surfaces with such effect that museum visitors leant against imaginary walls with catastrophic effect. His exploration of the outer realms of seeing was considered dangerous in certain conditions. Lawsuits followed. The scale of his spaces then changed from the simple chamber, suitable for the museum, to monumental constructions involving the curvature of the Earth itself.

Turrell's viewpoints are understandably more extreme than those of an amateur pilot; he can draw from high-altitude flying experience, from a sense of entering the space of the sky and observing the Earth from a great distance. His artistic allies and predecessors might have been the human kites of Tibet, or the classical garden designers of Japan, with their ability to imagine their designs as if seen from high above. He grew up in California in the Sixties, part of a generation whose members were used to enormous advances in technology, who were growing up with ideas of 'deep space', and whose Western views of art were being radically rearranged by Oriental attitudes.

Turrell was a pilot in his teens, but as the son of a Quaker aeronautical engineer he was deemed unsuitable for military service. While still in his teens he was sent on 'alternative service' to Laos, from where he flew more than a hundred missions over Tibet and was decorated by the Tibetans. He mapped the Himalayas and experienced extraordinary meteorological phenomena. Inspired by Antoine de Saint-Exupery's descriptions of flight, he realised that among the clouds or in the face of advancing weather-fronts, spaces were created in the sky - spaces within space. Weather phenomena had structures the pilot could enter, where astonishing visions could be experienced.

Flying over the jungle of Burma he gained a sense of the surface of the Earth as a sensitive emulsion, or as a 'holder of image'. The surface was active, opening up to reveal the sites of civilisations or closing in on them again. Rising from the jungle he saw the hemispherical domes of Buddhist 'stupas', symbolising heaven over their grounded square bases. The form of the stupa, repeated from the Himalayas to the great Indian Buddhist site of Sanchi, inspired him to think of enclosed spaces which one entered to be engulfed in light.

Of his return to California and his art studies in the mid-Sixties, Turrell says little, except that he studied art history under Walter Hopps, then a young and brilliant curator in Pasadena who had organised an important Duchamp retrospective. Hopps drove a limousine and took his students to Oldenburg 'happenings'. They were heady days. Turrell's knowledge of Western painting came from Hopps's slides. But when he eventually reached Europe, he was disappointed to find that the originals didn't possess the luminosity of the slides. It was as if canvas seemed dead after the light of the projector. He realised he could never become an artist in Europe, because European culture was already constructed. He was looking for a place to set his own agenda.

As part of an art and technology project, Turrell visited Japan to create an installation for the Osaka Expo in 1970, and was exposed to the intricacies and revelations of Japanese garden design for the first time. Vistas and motifs were repeated, echoing each other from different vantage points, but maintaining the appearance that there was no design at all. The moss of the garden could look like jungle from the air, and the stones like mountains. The vision was detailed and close-up, yet simultaneously vast and cosmic, as if sketched from the sky. Turrell's experience in Japan included an apprenticeship to a Living National Treasure, who made wooden boxes. Quaker austerity and Japanese discretion of design were perfectly matched.

South of Japan, between Kyushu and the island of Okinawa, lies a chain of active volcanic islands. Suwanose, a tiny volcano, became the base for the American writer Gary Snyder and a farming community which existed in almost prehistoric circumstances, like those faced by the original settlers in Japan, who had migrated up from the South Pacific using the islands as stepping stones. Turrell visited the island and again experienced the sense of the earth as an active emulsion, the same feeling he had when flying.

The ground shook with the constant rumble of the volcano. Stretching away from the island is an archipelago of conical shapes falling sheer into the ocean. The trip to Suwanose confirmed Turrell's desire to own a volcano, a desire planted by Saint-Exupery's book, The Little Prince. He wanted to combine his sensitivity to light and his sense of scale with the volatile implications of the conical volcanic shape.

When he became the first artist to receive the MacArthur award, the valuable and prestigious prize for 'genius', he spent the money on aircraft fuel. He began methodically to survey the western states of America, searching for a site that was large enough for a viewer to experience 'celestial vaulting', where space curved at the edges of one's perception. It was a phenomenon he had frequently experienced when flying close to the ground. An extinct volcano between 400 and 1,000ft above a high-altitude plain would provide him with the perfect disc shape and a brilliant blue sky. For seven months he flew six days a week, sleeping under the wing of his plane, until on the edge of the Painted Desert he found Roden Crater. He has been working there ever since.

'At Roden Crater I was interested in taking the cultural artifice of art out into the natural surround,' he wrote. 'I wanted the work to be enfolded in nature in such a way that light from the sun, moon and stars empowered the spaces. I wanted to bring culture to the natural surround as if one was designing a garden.' The physical presence of Roden Crater and its surrounding crater-field is so impressive that one might be fooled into believing that the crater itself, its cone levelled by Turrell, is the work.

If the colour of the landscape lives up to the title of Painted Desert, the construction within the volcano is equally magnificent in its ambition. Turrell, with no financial means of his own, acquired the site in 1979 by establishing a foundation. He inhabited the volcano alone for months, in order to understand the light qualities of the space, before recruiting a team of volunteers to aid him.

The tunnelling will, on its completion, take the viewer under the volcano then out into open sky. Spaces are being constructed within the volcano in positions which relate to the solstices and lunar alignments. Each space looks out on a different portion of sky. When the project is finished, you will be able to walk up to the lip of the crater, look out over the horizon, and see the Earth curve beneath you the wrong way. This is 'celestial vaulting' - at that point, as at the stupa, heaven and Earth will be in symbolic balance.

But for Turrell it is not the shaping of the crater, not the image, nor the endeavour, but the release of perception itself which is the key. From a pilot's view of the Earth, we will be able to gaze back out at the sky.

James Turrell's drawings of the Roden Crater project and three light installations are on show at the Hayward Gallery, SE1 (071-928 8800), until 27 June. 'Air Mass' by James Turrell is published by the South Bank Centre (pounds 25.95).

(Photographs omitted)