Robert Bruce, a doctor from Winchester, Hampshire, was attending a seminar last month in the French resort of Val d’Isère when he decided to take a break. He strapped on his snowboard and headed for the slopes before venturing off piste to a spot known as Face Bellevarde.

Nobody knows what happened next, but investigators say a disturbance in the snow surface, possibly caused by another boarder or skier, triggered a small avalanche that pushed Bruce down the slope and off a 260ft cliff.

About 30 people have died in avalanches on the Alps this season: the 39-year-old was among the latest. The 2005-6 season is regarded as one of the worst with 57 deaths in the French Alps alone, and this season is looking like surpassing that.

A combination of inexperience and thirst for adventure, as well as the lure of pristine powder, means more and more people are heading into areas that are dangerous but accessible.

“People are pushing their limits, looking for the fresh powder runs that they see in videos,” says Fabrice Jolly, a mountain rescue patroller at the resort. “But their ability to ski powder far outweighs their knowledge of avalanche safety.”

At 6.30am every day Jolly loads up with 66lb of dynamite in a backpack, and with his fellow patroller begins the job of pacifying the mountain by identifying areas of snow that look unstable and blasting them to create a controlled avalanche.

It’s risky, says Jolly. “You can’t know exactly where the snow slab that you are detonating extends to and where it is going to break. You could be standing on it when it goes.”

Down below, the ski resort waits expectantly. “You have all the chairlift companies, 600 ski instructors and thousands of guests relying on you and only two hours to get the mountain ready,” Jolly says. “There is a big commercial pressure. But if you let that get to you, if you cut corners hurrying to the next hotspot, you are playing Russian roulette with the mountain.”

In 2005 two of Jolly’s colleagues were caught out second guessing the mountain. Having twice detonated a hotspot that didn’t slide, they deemed it safe and skied across it to save time. As they did so, their weight triggered an avalanche, killing one of them.

In seconds, a small slide can grow into a thundering cascade of epic proportions, travelling at up to 60mph and carrying with it thousands of tons of snow. The chances of survival depend on several factors. Between 55% and 65% of victims buried are killed, while 80% of the victims remaining on the surface survive.

If the path of an avalanche forces you into a “terrain trap” such as thick trees, rocks, cliffs, crevasses or lakes, your chances of survival diminish further. A few years ago, Jolly lost one of his closest friends – a ski instructor – this way. Jolly found his body smashed against a tree trunk. He was recognisable only by his clothing.

“The force can be like a blast,” Jolly says. “It is like being in a car crash but without a metal frame to protect you. One problem is that people who have safety equipment often take extra risks. But equipment is no substitute for avalanche awareness and caution.”

The most destructive avalanches occur when slabs of snow break loose and race downhill, breaking into smaller pieces. They are most common in the 24 hours after a deep snowfall. The quick pile-up can overload the underlying snowpack, causing a weak layer beneath the slab to fracture.

The likelihood of an avalanche is dependent on many things including temperature, wind, slope steepness and terrain. Last year about 90% of avalanche fatalities occurred between December 1 and April 30.

Digging yourself out of an avalanche is all but impossible. “The compacted snow from an avalanche is like concrete,” Jolly says. “If there is snow in your mouth, you won’t even be able to free your hand to remove it. When someone is buried with their head under only 5cm or 10cm of snow, you can be walking on top of them but you can’t hear them shouting.”

Fully buried, an avalanche victim has an average of 15 minutes’ survival time. Their breath melts the surrounding snow, which, at a certain distance refreezes, forming an impermeable air pocket that quickly becomes filled with expired carbon dioxide, suffocating them.

The best chance of survival is to ensure you have the right safety equipment. “If they have a transceiver they can be located within minutes,” says Jolly. “Without one, it takes hours, even with 100 people searching.”

Research suggests that victims found within 15 minutes have a 92% chance of survival, after 35 minutes the rate falls to just 30% and to near zero after two hours.

The overall rate of deaths caused by avalanches in France remains stable at about 30 per year since 1970. This can be put down to better safety training and equipment (see panel) and mountain rescue tools – France recently replaced its ageing Alouette III helicopters with the EC145, which has a higher payload and can fly twice as fast. These improvements have more than compensated for the greater number of people getting into trouble.

Jolly’s radio crackles into life and he clips back into his skis to leave. “Remember,” he says, “the most important thing to put into your backpack each morning is humility.”

Lifesavers

Ortovox S1 Transceiver, £299 www.noblecustom.co.uk

If you are going off piste, take a transceiver, which will transmit your location on a given bandwidth. This version also allows you to search for fellow skiers

Ortovox Grizzly 1 Shovel, £49 www.noblecustom.co.uk You won’t be getting anyone out of compacted snow in a hurry without a shovel. This model is made of light, tough aluminium and folds to fit into a backpack

Black Diamond Quickdraw Carbon Fibre Probe, £60 www.bdel.com

A tool used for locating a companion buried in the snow. This 7.5ft probe fits in a backpack

ABS Airbag 15L, £556 www.absairbag.com

This emergency airbag can be fully deployed within two seconds. The buoyancy makes you far more likely to remain on or near the surface of a snow slide

Black Diamond Avalung II, £99 www.avalung.com

In the event of burial, this breathing apparatus can divert exhaled air behind you, reducing the build-up of carbon dioxide in front of your face