To climb the face, the 3 kilometer (2 mi) wide base of the wall must be surpassed by climbing up either the deep gashes of avalanche-swept gullies or the vertical, overhanging rock buttresses, full of deadly ice towers and unsteady snow. Since the crux of the route is near the bottom, retreat is more difficult, making the climb more committing; the relative isolation of the face and probable lack of other climbers also add to the commitment factor. The hanging glaciers and snow slopes pose a large risk of avalanches, especially in the case of a storm, adding to the objective danger of the route. Taking into account these challenges, George Mallory noted in his expedition book: "Other men, less wise, might attempt this way if they would, but, emphatically, it was not for us."Stephen Venables, Everest: Alone at the Summit, p. 8.
