Going Up: Life in the Death Zone

The New Zealander struggled up the final snowy ridge. His companion soon joined him on the mountaintop, gasping for breath. Edmund Hillary offered his hand to Tenzing Norgay, but Norgay gave him a bear hug instead.

Fifty years ago, Hillary and Norgay became the first to reach the summit of Mt. Everest. Since 1953, the mountain has been climbed many times. The death toll is 175 for those who didn't make it to the top. Many were killed not by falls or avalanches, but by the effects of low pressure at extreme altitudes.

The weight of the atmosphere creates air pressure. At higher altitudes, there is less air above you. This means that the density and pressure of air decreases as altitude increases. Each intake of air on Mt. Everest has only one-third of the gas molecules—including oxygen—that would be present at sea level.

Mt. Everest is in Nepal, a small country sandwiched between India and China. Nepal's capital, Katmandu, is at 1,340 meters—not much higher than Salt Lake City, UT. Unless exercising hard, a person in Katmandu probably wouldn't notice the slightly thinner air.

However, as you move higher, the body reacts to the decreasing pressure. On their way to Everest, Hillary and Norgay stayed at Namche Bazaar, a trading town at 3,440 meters. With each breath at Namche Bazaar, the body takes in only 70 percent of the oxygen it would get at sea level.

In response, the body makes more red blood cells that carry oxygen throughout the body. More red blood cells mean that more oxygen can be pulled from the thin atmosphere. Breathing automatically speeds up, and the heart beats faster as the body tries to get the oxygen it needs.

It takes many days for the body to make the extra red blood cells. Allowing the body to adjust slowly to the lower air pressure at high altitudes is called acclimatization. Hillary and Norgay spent many weeks acclimatizing to higher altitudes. Rushing up and down Mt. Everest isn't an option. A person taken directly from sea level to the summit would die of oxygen starvation within minutes due to a lack of enough red blood cells to pull oxygen from the thin atmosphere.

From Namche Bazaar, Hillary, Norgay, and their team trekked to the Mt. Everest base camp at 5,364 meters, where most of their supplies were kept. At this altitude, air pressure is half that of sea level. Even with acclimatization, some people show signs of mountain sickness, which is caused by too little oxygen. It can result in headaches, dizziness, and fatigue.

Fluid buildup in the lungs and brain is also a threat. For reasons not well understood, lower air pressure causes fluid to leak from tiny blood vessels, called capillaries, in the body. Fluid in the lungs, known as pulmonary edema, keeps desperately needed oxygen from getting to the muscles and brain, causing weakness and confusion. Fluid leaking into the brain, or cerebral edema, causes dangerous swelling, hallucinations, and irrational behavior. Both pulmonary and cerebral edema can kill. The only cure is retreating to a lower altitude.

Hillary and Norgay helped move loads of supplies from the base camp to camps higher on the mountain, breathing bottled oxygen to help offset the thin air. “As the oxygen flowed into my lungs, my load seemed to lose half its weight,” wrote Hillary. After 44 days of acclimatizing on Everest's slopes, Hillary and Norgay climbed above 8,000 meters into the Death Zone.

Above 8,000 meters, the human body “hits the wall.” Bottled oxygen can hold off acute mountain sickness, pulmonary edema, and cerebral edema, but only temporarily. If a climber stays above 8,000 meters too long, death is inevitable. It's a brutal race against time. Can the climber get to the top and back before the body falls apart?

When Hillary was in the Death Zone, it took “three hours to do what I could have done in half an hour at sea level…every step became…[a] major task that was going to require a maximum of effort.” On the last climb to the summit, “I seemed clumsy and unstable, and my breath was hurried and uneven.”

Hillary and Norgay reached the top and took off their oxygen masks for a few moments. They were too tired to do more than hug and take photographs. When Hillary tried to put the camera away, he realized that a lack of oxygen to his brain was causing his slow, fumbling movements. Hillary and Norgay strapped on their oxygen masks and started their journey down.

As Hillary and Norgay descended the mountain, they were joined along the way by expedition members who had stayed at lower camps. As they neared one camp, they could see the question on the members' faces: Had they reached the top?

A companion walking down with Hillary and Norgay joyfully pointed toward the summit. Their faces “lighting up with unbelieving joy,” the men in camp rushed towards Hillary and Norgay.

It was a long, tiring, triumphant walk home.


  • atmosphere: The mixture of gases that surrounds Earth.

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  1. What kind of landform is described in this article?
    [anno: The landform is a mountain.]
  2. What are some of the features of this landform?
    [anno: Answers should include some of the following facts: the top of the mountain, or Mt. Everest, is the highest spot on Earth; the air is much thinner at the top of Mt. Everest than it is at sea level; there is snow and ice on the mountain.]
  3. Why would it be difficult for someone to settle and live at the top of this landform?
    [anno: Answers should include that because the air pressure is so much lower at the summit of Mt. Everest, it makes breathing difficult for people. People would need to have a constant supply of bottled oxygen to help prevent them from getting pulmonary or cerebral edema.]
  4. How are the conditions of this similar to those found in a deep trench in the ocean?
    [anno: Both Mt. Everest and a deep trench in the ocean have air pressure that is much different than that found at sea level. On Mt. Everest, the air pressure is greatly decreased. In an ocean trench, the air pressure is greatly increased. Answers may include that organisms living in either area may need special adaptations to survive.]