On Saturday, a 43-year-old woman on ski vacation with her family died in what was described as a fall into a tree well. Tuesday, Mono Sheriff officials confirmed the cause of death in this tragic case.

There had been rumors that the woman had died from breathing the volcanically produced carbon dioxide that is known to exist in the Mammoth Mountain area. The tree kill at Horseshoe Lake is one example, and few in the Eastern Sierra can forget the three ski patrollers who died after falling into a volcanic vent in 2006.

Mammoth Mountain officials reported that the woman had last been seen snowboarding near Chair 12 near a run called Secret Spot. The search started immediately, but it was close to three hours after the victim was reported missing that Ski Patrollers probing the snow located the woman in a tree well. A tree well is the protected area found underneath the boughs of trees, where the snow is soft and seemingly bottomless. People who fall into a tree well head first cant easily get themselves out and often suffocate on snow. Tree well fatalities are not unheard of at ski resorts in North America.

Mono Sheriff Lt. Robert Weber reported that the victim was found with her head facing downhill and completely covered by as much as two feet of snow. Lt. Weber explained that there were CO2 readings taken at the accident site on Saturday, but after further investigation the cause of death in this case was listed as asphyxiation on fresh snow secondary to a snowboard accident.