A snowboarder is just about to start carving up a completely fresh slope in the GoPro video above, when the snow starts cracking right in front of him, cascading into a small avalanche.

The footage itself is pretty scary, but imagine being there and realising that if you slip a few metres downhill you're going to be caught up into a flood of snow. Suffice to say, this guy is very lucky.

Captured by YouTuber Sorin Radu, the video also provides a rare glimpse into how an avalanche actually starts.

Usually really big avalanches occur naturally, when the snowpack becomes unstable and starts to fall. All this really takes is a slope of more than 30 degrees and gravity, snow scientist Jordy Hendrikx from Montana State University in the US told Mike Tyburski from National Geographic.

But smaller avalanches can frequently be caused by skiers and snowboarders - as seems to be the case here.

"You have a layer of snow on a slope that can only bear so much of a load. When you exceed that load, it collapses," Hendrikx told Tyburski. "That is the simple cause of most snow avalanches."

But the amount of weight required to set off an avalanche varies almost constantly depending on temperature, snow density, humidity and a myriad of other factors.

As Karl Birkeland, Director of the US Forest Service National Avalanche Centre in Montana, US, told Tyburski: "A pinprick almost can set them off."

Frightening stuff.

Sources: SploidNational Geographic