Hazards when mountaineering:

• falling rocks
• falling ice
• snow avalanches
• the climber falling
  • falls from ice slopes
  • falls down snow slopes
  • falls into crevasses
• danger from altitude
• danger from weather
  
  
  
• tree wells
• cornices
• getting separated (because someone gets injured, because the team makes a decision to temporarily split up, because a team member falls down a slope, etc)
• snow blindness