Hiking at high altitude presents you with challenges that hikers at elevations ranging from sea level to about 3,500 feet rarely, if ever, confront. There's a reason boxes of commercial cake mixes and the like offer separate instructions for high-elevation bakers: As you ascend into Earth's atmosphere, air thins, which alters the dynamics of everything from baking to human metabolism. Thinner air holds less water, retains less heat, exerts less pressure and carries less oxygen. On an athletic level, your body functions less efficiently at high elevation until it adapts, and high-elevation terrain presents its own challenges for hikers.
Definition
"High" elevation is relative to that where you live. If you live at sea level and are reasonably fit, you probably won't notice elevation-related difficulties until you ascend to at least 5,000 feet, and more likely 8,500 feet or more, according to the authors of "Mountaineering: The Freedom of the Hills." If, however, you live at 7,000 feet most of the time, your body will have adapted to that elevation by producing additional red blood cells to carry more oxygen to your organs, among other changes. For you, it may take a trail at 12,000 feet to constitute a high-elevation hike.
Physical Challenges
Thinner air means the body can deliver less oxygen to the brain and muscles until it adapts, a process that usually takes several days. About 50 percent of those who ascend to 8,500 feet or higher will manifest symptoms of acute mountain sickness, or AMS, but those who do usually notice changes within 24 hours. Symptoms include shortness of breath, headache, weakness, nausea, insomnia, loss of appetite and muscle cramps. Your kidneys work harder at high elevations as well, so carry and drink extra fluids to prevent dehydration and associated muscle cramps. If you hike with a dog, the aforementioned considerations apply to it as well. If you're planning a day hike after which you immediately return to your usual elevation, you may notice no symptoms beyond feeling a bit more winded than usual due to the temporary shortage of available oxygen. Hikers who embark on multiday high-altitude excursions may manifest more severe symptoms. AMS can progress to pulmonary or cerebral edema during extended stays at high elevations -- descend immediately and seek medical help if you or a companion experiences severe headache, confusion, vomiting, fever, or bluish lips and fingernails.
Terrain
"All mountains are in a state of continuous collapse," writes Laurence Gonzales in "Deep Survival: Who Lives, Who Dies, and Why." As mountains erode, they produce fields of boulders, talus -- large scattered rocks -- and scree -- fields of flat, flaky rock. Lingering snow fields at high elevation present additional obstacles to both solid footing and navigation, particularly on steep slopes. As a result, high-elevation hikers should approach mountain terrain with respect. Wear appropriate footwear for clambering over rockfall and take care before hiking beneath precarious overhangs. Depending on the season, you may wish to carry crampons -- these are traction devices -- and a hiking pole or ice ax for more secure purchase on snowy slopes.
Weather
Temperatures range much more widely at high altitude, in part because thinner air provides less of an insulating effect; temperatures decrease on average by 3 degrees Fahrenheit for every 1,000 feet you ascend, and solar heat gained during the day dissipates rapidly as the sun goes down. Mountainous terrain also induces more turbulence and convection in the atmosphere, potentially producing thunderstorms during warmer months and sudden blizzard conditions in winter. Check the weather forecast before you go, and carry clothing to keep you warm and dry should you encounter inclement weather. If lightning threatens, descend to a lower elevation, discard metal objects such as hiking poles and seek shelter in a thickly forested area or low culvert until the storm passes. Avoid open terrain, ridges and caves.
Considerations
Take the same precautions for a high-elevation hike as you would for any other. Let someone know where you're going and when you plan to return. Carry a cell phone and/or GPS device, but don't count on a connection in the wilderness. Carry a map and a compass as well, and make sure you know how to use them. If you encounter wild predators such as bears or mountain lions, stay calm, make yourself "large" by lifting your arms or your gear, and back away slowly; don't run, or the animal may mistake you for prey. During spring runoff season, don't attempt to wade across rushing rivers or streams, particularly upstream of waterfalls.
References
- "Mountaineering: The Freedom of the Hills"; Steven M. Cox and Kris Fulsaas, Editors; 2003
- "Encyclopedia of Outdoor & Wilderness Skills"; Chris Townsend and Annie Aggens; 2003
- "Deep Survival: Who Lives, Who Dies, and Why"; Laurence Gonzales; 2004;
Member Comments