What is the tallest mountain on Earth above sea level?

Everest, at 8,848.86 metres, a figure agreed in 2020 by a joint Chinese and Nepali survey after decades of competing numbers. It is still rising a few millimetres a year as India continues to drive into Asia, and the summit rock is marine limestone - it formed on a seabed, full of the shells of animals that lived in an ocean that no longer exists.

Above about 8,000 metres is the death zone, where there is not enough oxygen to sustain human life at all. The body deteriorates continuously however well acclimatised: digestion effectively shuts down, judgement degrades, and every hour spent there costs something that cannot be recovered by resting. Most deaths happen on the descent, after the summit has been reached and the decision-making has already gone.

The name is a colonial accident that its own namesake objected to. The Survey of India named it for George Everest, a former Surveyor-General who argued against it on the grounds that it could not be written in Hindi or pronounced by local people. It already had names - Chomolungma in Tibetan, Sagarmatha in Nepali - and the surveyors were aware of at least one of them.