The vibrating mass of strangely sculptured ice is 30km long and 10km wide. It borders the moonscape-like area of Laka Gigar, a training ground for US astronauts. Here, in 1783, a great catastrophe took place. Gas belched from a 50km volcanic fissure and poisoned 80 per cent of the livestock. Most people who survived the gas starved to death. The Icelandic race was nearly wiped out. The flattened land seems a fitting epitaph, with gigantic cinders and contorted black lava rising from sparkling snowfields.
From Reykjavik I hitchhiked to the almost unpronounceable village of Kirkjubaejarklaustur and then walked 30km to a farmer's hut where I spent the night. There are many different types of huts and shelters in Iceland in which hikers can usually stay for free, although it is best to check this at the nearest farmhouse. My hut was large, built as a temporary shelter for livestock. Better equipped than a Scottish bothy, it had bunks, heating and cooking facilities. It was insulated with turf and almost buried in snow.
The glacier was about a 25km walk from the hut. My first attempt even to reach it was unsuccessful. Fear of lakes being insufficiently frozen kept me to the ridges. At the end of my first day I retreated to the hut and, as the aurora faded over the volcanoes to the north, I studied the map, looking at a more northerly approach.
Satisfied, I went outside for a midnight stroll. It seemed a moonlit fairyland, but my sense of tranquillity was broken when I saw a dozen pairs of headlights moving across the landscape in my direction.
I remembered the mess behind me. The hut was littered with parts of my tent, waterproof clothing, two sleeping bags, and numerous pairs of my socks, which were among the more mentionable items hanging up to dry. By the time I had the place presentable the convoy was at the door.
It consisted of those strange cross-country vehicles beloved by the Icelanders, land cruisers on huge wheels. I welcomed about 30 people who had come to share the hut for the night. They were teachers, factory workers and market gardeners, and they, too, were bound for the glacier. I showed them the route I proposed to walk. Nonsense, they said, you come in the vehicles with us.
We set out at 6am next day, with an orange glow on one horizon and the full moon on the other. Our headlights swathed the hillsides, picking out now a twisted outcrop, now a hidden ravine. Old volcanoes loomed in the darkness, their snows showing the first pink of day.
The drivers of our team raced up the hillocks, played chicken at the snow bridges and dodged round the boulders. Jokes crackled over the radios, faces glowed with delight, the laughter was infectious.
There was no set route. We just tried one way after another until one proved passable. It took a lot for a route to be impassable. On foot later that day I saw tyre tracks where I was having to use my crampons and ice axe.
The technique is just like walking over suspect ground. When you come to a dodgy-looking bit, try it, delicately, with one wheel, then two and, having decided to go, go fast and do not stop.
After two hours I became aware that the shadow across our path was gaining depth and height. This was the glacier. A chaos of broken ice 30m high gradually took shape. A turgid brown stream oozed from its base. Frost vapour wreathed the fantastic shapes of the ice. And as the sun edged above the horizon, the translucent pillars became turquoise prisms refracting the low light.
As we approached the glacier on foot, at first I thought one of the car engines was coughing. But they were more than a kilometre away. There it was again - a repetitive raking thump. Then I realised. This was the sound of a mountain in motion. From the depths of the glacier came a muffled hammering with 100 different rhythms - now slow and echoing, now in double time like the frantic hammering of 1,000 trolls struggling to escape their icy prison. The ice throbbed wherever I touched it. Even 10m from the edge of the glacier the vibrations came up through my boots and shook my knees.
Back in our vehicles, we drove along the side of the glacier to its source high on Vatnajokull, an ice mass the size of Wales and one of the largest outside Antarctica. Other weekenders were arriving, and vehicles dotted the horizon. We passed the end of the ridge I had walked the day before, where it seemed I had been the only person for miles. Here I said goodbye to my friends. They were driving to the road; I returned to the hut.
Next day I started back to Reykjavik. Half of Iceland seemed to be out for a day at the glacier. The four-wheel drives with bristling antennae alternated with gleaming saloons and old bangers.
As the track eased down from the plateau, streams danced from under the ice and moss-green lava shed the shroud of snow. I passed a dump of snow scooters for hire, completely unattended. I was 50km from the nearest cafe and 1,500km from the nearest motorway. It certainly felt like it.
MARTIN HOUSDEN has had a great deal of experience in techniques of cold- weather survival. No one without similar experience should attempt his walk unless accompanied by a guide. Driving in the area should also be undertaken with caution. Snow scooters and four-wheel- drive vehicles can be hired at Kirkjubaejarklaustur from Hannes Jonsson (010 354 8 74785). For organised walking holidays and Jeep safaris contact Arctic Experience, 29 Nork Way, Banstead, Surrey SM7 1PB (0737 362321). Prices start at about pounds 400 inclusive of flights, three nights' accommodation in Reykjavik, meals and excursions. Further information from Icelandair, 172 Tottenham Court Road, London W1P 9LG (071-388 5599).