What is the True Altitude of Mount Everest?
How the Height of the Loftiest Mountain in the World is Shifting
Jun 3, 2009
Mount Everest, otherwise known as “Chomolungma” or “Sagarmatha”, which translate as “Mother Goddess of the Earth” and “Head of the Sky,” certainly earns these titles, when one considers its huge dimensions. A peak that scrapes the ceiling of the troposphere will create strange effects, most notably upon the instruments surveyors use.
Chomolungma of the Himalayas, the Mountain that Bobs up and Down
Everest will always be the tallest mountain in the world, but its exact height cannot be fixed. Officially, this has been set at 8,848 metres (29,028 feet), but this measurement is under review due to the collation of more recent measurements. The Asian continent is always colliding with the outcrop of India, forcing the Himalayas upwards. This means the heights of the Himalayan peaks are growing. But it does not end there. Attempts to measure the height of Everest has been going on since the Great Trigonometric survey of India was commissioned in 1808 and it is still being reviewed.
The History of Measuring Sagarmatha
For decades, Nepal would not allow the British to enter Everest’s territory, but when the restrictions were finally lifted, Andrew Waugh, the British Surveyor-General of India, made his first attempt to get a fix on Everest’s height in 1852. He found that Everest’s huge bulk generated its own gravitational pull, affecting the theodolites he used. Theodolites measure vertical and horizontal angles and require spirit levels to ensure the theodolites are level. However, the gravitational pull of the mountain and atmospheric refraction made it impossible for the surveyors to know if the spirit levels were true, and therefore giving an accurate reading.
Measuring Everest’s Peak
After taking six readings, the surveyors came to six different results. They decided to take an average, which came to 29,000 feet. However, Waugh considered this figure to be too neat for nature, so he and his team settled for a height of 29,002 feet. Waugh named this tallest peak after his predecessor, George Everest, but although the name has remained the same, its official height has not. Chinese and Indian surveyors took their own readings and came to a different measurement of 29,030 feet. These variations were put down to the shifting ice on the peak of the mountain.
The Official Height of Mount Everest
The official height of 29,028 feet was established in 1954 by B L Gulatee. Again, the theodolites he used were subject to the forces of the mountain, so even this figure could not be assured of absolute accuracy. The 1998 American expedition sponsored by the National Geographic Society, was the first to use GPS, which is not affected by gravity. Their leader, Wally Berg, drilled into Everest's highest outcrop, known as Barry Bishop’s Ledge, upon which to fix a GPS reader. After two hours of work, the expedition reached the conclusion that the official height of the mountain needed to be revised (How High is Everest?by Peter Potterfield: Mountain Zone, 1999). Charles Corfield, science manager of the expedition and Dave Mencin, the onsite scientist, reviewed the data, which suggest it is 8,810 metres (28,904 feet).
Establishing the Height of Everest
The gravitational forces of the mountain, atmospheric refraction and shifting ice, not to mention political restrictions, have balked attempts to measure Everest's exact height. Officially, this still stands at 29,028 feet, but according to a recent American expedition, this may need to be revised again. Everest is still rising, due to continental forces. Nick Estcourt, one of the 1975 British Expedition put it succinctly, “If Everest is bobbing up and down, we must hope to catch it on a low day.” (Reader's Digest Book of Facts by Magnus Magnusson et al., Reader's Digest 1985)
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