young caucasian woman trekker resting on chola pass in himalayas high altitude feeling low oxygen level affects of dizziness and

altitude sickness gokyo ri chola pass woman trekker himalayas flora fauna caucasian sagarmatha mountains nature wildlife nepal animal bird mountain species snow cock beak feather countryside himalaya close khumbu scenery tourism creature unique background high rural peak sick weak tibetan tibetian cold sunny ebc everest base camp track rocky alpine zone dizziness exhaustion top