While the Sierra Nevada is an incredibly beautiful mountain range, travellers should never ignore safety and should be aware of the many hazards one might face while travelling through the Sierra.
Elevation - The Sierra span a range of altitude from several thousand feet to over fourteen thousand feet. Higher altitudes can pose a risk to travellers who are not acclimated appropriately. Altitude sickness can affect many people not properly acclimated, and at its worst can result in the life threatening condition known as high altitude pulminary edema (HAPE). Altitude sickness often affects travellers above 8000ft, and comes with symtoms such as headaches, dizziness, fatigue, loss of apetite, and nausea. Those entering high elevation areas should be aware of methods to prevent sickness (acclimation, hydration), what the symptoms are, and how to treat symptoms at their onset (descend).
Creak and River Crossings - while mostly an early season hazard, travellers should be careful in all seasons. Spring runoff, especially in high snow years, can cause dangerous conditions due to swollen creaks and rivers. Extra care should be taken when crossing these hazards, and travellers should be prepared to turn back should the conditions not allow a safe crossing.
Avalanches - while avalanches are mainly a winter hazard, rock fall can be a hazard in the summer.
Summer - travellers in areas with high instability should travel quickly and avoid stopping in slide prone areas. These areas are often but not always indicated by recent slide tailings.
Snow and Ice - snow and ice is not always a winter hazard. Oftentimes snow and ice can persist on northfacing slopes well into the late summer, and can make travelling quite hazardous. If one expects to travel on steep snow or icefields, one should carry an ice axe and crampons and know how to use them. When snow covers much of the terrain, even gentler terrain can be hazardous: postholing (sinking deep into the snow) can cause injury, week snow bridges can mask fast and deep running water, cornices can break off onto steep snow and ice, and much more. Should one be travelling in areas with possible snow and ice, one should be prepared for the conditions.
Hypothermia - Weather can change rapidly in the wilderness, and travellers should be prepoared for a quick and unexpected drop in temperature. Cotton should be avoided, as its insulative power is severly reduced when wet, and extra clothes/insulative gear should be carried regardless of the daytime or expected temperatures.
Lightning - Thunderstorms and be exciting and fun to watch, but are also a hazard to those travelling outdoors. Monsoonal moisture often hits the sierra in the summertime, bringing with it rain and lightning. Travellers should avoid exposed areas, and climbing in these conditions is extremely dangerous.
Mosquitos - while more of an annoyance than a hazard, mosquitos can at best not be present and at worst swarm so severly it can be virtually claustrophobic. Repellants, headnets, and long sleeve shirts and pants can help make the worst conditions bearable. Mosquitos peak in early to mid-summer, depending upon the previous winter's snowfall and location, and travelling outside this time one can avoid mosquitos entirely.
Wildlife - Seeing wildlife in the Sierra can be a rare treat, but should also be respected. Bears, deer, coyote, bobcats, and mountain lions should always be given their distance, and under no circumstances should any wildlife be fed.
This article is only an introduction to the many hazards that a backcountry traveller can experience. It is ultimately the responsibility of the traveller to be knowledgeable and prepared of the dangers within the High Sierra.
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