What is the atmospheric pressure at the top of Elbrus?

The main difficulty encountered by climbers while climbing Mount Elbrus, regardless of the route, weather, experience or season - it is the altitude. The influence of the altitude factor on the human body is due to an unusually low level of atmospheric pressure and, accordingly, a low level of oxygen in the air. The material presented below is rough explanation about how the level of atmospheric pressure affects the oxygen content in the air, as well as about the peculiarities of the effect of altitude on the human body at various geographical latitudes.

Let's find out how it works right from the start. What is atmospheric pressure? Imagine that we live at the bottom of the air ocean, and the thickness of the atmosphere above us is about 1000 km. The entire air cover of the earth is subject to the universal law of gravitation and, therefore, has a mass. The closer to the surface of the earth - the denser and “heavier” the atmosphere becomes - the greater the mass of the air column. Since our habitual environment is precisely the surface of the earth, atmospheric pressure at this level is familiar and comfortable to us. A proportional amount of oxygen, which is approximately 21% of the total volume, is directly related to air pressure. Oxygen is vital for all the processes taking place in our body - therefore, when gaining altitude during climbing mountains, it is the lack of oxygen that causes many difficulties and problems.

To control the change in pressure, several conventional measurement systems have been adopted – one of the usual scales for us is millimeters of mercury. The norm for 99% of the world's population is a pressure of 760 mm, which corresponds to the altitudes of 0-100 meters above sea level. As you climb up above the surface of the earth, atmospheric pressure decreases - so, at an altitude of 1000 meters, atmospheric pressure will be 675 mm, and at the height of the summit of Mount Elbrus it will be 389 mm, which is almost half of the usual norm, including the proportional oxygen content. Atmospheric pressure at the highest peak of the Earth – Mount Everest is 265 mm (30% of normal) - this is far beyond the limits of normal human capabilities of surviving. The facts of oxygen-free ascents of Mount Everest tell us that the real possibilities of our body are much wider than is commonly believed.

The capabilities of the human body in terms of adaptation to external conditions, including the oxygen content in the air, are quite extensive. For example, it is claimed that the height of approximately 5,500 meters is the upper limit of a person’s living sphere - at this level some highland peoples live and even keep their household in Himalayas and Andes. Altitudes of more than 6500 meters with atmospheric pressure below 350 mm and an oxygen content of less than 40% of the norm are considered unsuitable for life. A person, without special means of supporting life, can stay at such altitude for a very limited time. This altitude level is called the "Death Zone" - full acclimatization is impossible at this altitude, and the body undergoes rapid irreversible changes - depending on the preliminary preparation and acclimatization, a person can survive at this altitude from several hours to several days.

All the figures and calculations described above illustrate only the general principle of the relationship between altitude, atmospheric pressure and oxygen content in the air. This rule cannot be applied universally to all the mountains of the earth, since the oxygen content at the same altitudes above sea level in different geographical latitudes will be significantly different. The fact is that the air shell of the earth does not correspond to the shape of the globe - the largest thickness of the air layer corresponds to equatorial latitudes, the atmosphere thickness decreases to the poles. Accordingly, the influence of altitude will be more noticeable the further north or south we move from the equator. For example, climbing Mount Kilimanjaro - the peak with a height of 5895 m in Africa, located just 342 km south from the equator - can be done much more comfortable than climbing Mount Elbrus (5642 m high and 4810 km north from the equator) - lack of oxygen and effect of altitude on Mount Elbrus will be felt much stronger. The general rule in mountaineering - at equal altitudes, the summits become harder to climb as you move away from the equator - this factor should be taken into account when choosing a mountain and acclimatization schedule for those who plan to start climbing and choose their first truly high mountain.

Based on this rule, the complexity of the alpine climbing programs in our collection is determined not only by the physical altitude of the mountain, but, to a greater extent, by its geographical location. In accordance with these features, an appropriate acclimatization schedule is built up, which is necessary for a safe ascent to the summit - in order to maximize the chances of a success and reduce the risk of possible health problems.

Text — Alexey Trubachev, founder of the MCS AlexClimb mountaineering and climbing school.

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