His exploration below the Lhakpa La pass led him on 3 August 1921 to realise that the East Rongbuk Valley provided the key to a viable route to the summit of Everest.

[1] A few weeks later, a party consisting of George Mallory, Guy Bullock, and Oliver Wheeler explored the head of the valley via the Lhakpa La pass to become the first people to reach the North Col of Everest and set foot on the slopes of that mountain.

[4] Since 2007, American mountaineer and film-maker David Breashears has been chronicling the rapid disappearance of the Rongbuk glacier due to global climate change.

Breashears has retraced the steps of Mallory's 1921 expedition, revealing a significant loss of ice mass across the West, Main and East Rongbuk Glaciers.

In 80 years, the Rongbuk has shrunk by more than 300 vertical feet across the entire glacier, approximately the height of the Statue of Liberty.