HUNTSVILLE — The snow is light, deep and freshly fallen, and the slope untracked and irresistible to snowmobilers ... first one, then another and another.

Each time the tracks reach higher and higher until ...

A weak spot, a crack, a sudden whumphing noise and an avalanche breaks loose.

That's how they start — weak snow, steep slope and a snowmobiler, or even a cross country skier, snowboarder or snowshoer, pushing the limit.

How it ends depends on how well prepared the individual is and luck. One in four avalanche victims die from trauma and not from being buried.

The latest statistics nationally show that snowmobilers now top the list of those caught and killed in avalanches. Here in Utah, snowboarders venturing into avalanche-prone areas top the list, followed by snowshoers and snowmobilers.

On average, four deaths a year are a result of avalanches. In 2004-05 there were eight. This winter there have been two snowmobile fatalities and one close call.

But with heavier than normal snowfall so far this winter, the threat is there.

Craig Gordon, avalanche forecaster/educator with the Utah Avalanche Center, said "knowing" is the key to survival.

Roughly 90 percent of all avalanche accidents are caused by the victim or someone in his or her group.

That may not be the case in movies or commercials, but in real life "we are the ones who start the avalanches that kill us," said Gordon. "And the more we know the safer we will be when we go into the backcountry."

Knowing means being prepared. Standard winter equipment should be a shovel, probing pole and an avalanche transmitting beacon.

The two snowmobilers killed in December were not wearing a beacon. The snowmobiler who survived was wearing a beacon.

As Gordon pointed out, however, it is far better to simply avoid an avalanche. This means knowing where to ride and what not to do.

Slope steepness is the key factor when looking for avalanche terrain. And many of Utah's popular riding areas have steep mountain slopes.

Riders should never "high line" above another rider, and they should have only one rider at a time on an uphill climb. If there are three riders and all three are caught in an avalanche, who's there to initiate a rescue?

One thing that has increased avalanche danger is that snowmobilers have greater access to a lot more terrain. That's because new machines are faster, lighter and can travel in snow conditions that would bog down older machines.

There are also groomed trail systems that can take riders and machines into some of the most remote and scenic riding country in the state.