"The Icefall is a frozen river. Gravity drags the ice downward. The pull is constant. The slow, steady flow of ice is imperceptible, but not all of the Icefall's movements are slow, some are sudden. The sudden shifts are the ones to fear; they are the ones that will kill you."
- Greg Wilson, Mountain Zone feature

Here the glacier separates from the steeper wall immediately above, leaving a gap where it pulls away from the rock. In the relatively gentle valley of the Cwm the moving ice creates crevasses, or deep fissures, which are relatively easy to negotiate. These obstacles are nothing compared to the steeper icefall beneath the Cwm.

"…the icefall could move at any moment and knock you off balance and you could fall into a crevasse, or a block of ice could come tumbling down at any moment. The icefall is a place where you want to move quickly and efficiently not stopping in areas that could collapse at any moment."
- Byron Smith, 1998 diaries

The Khumbu Icefall is the most technically demanding part of the southern route up Everest. The climbers ascend about 700 m during the three hours it takes to make it safely to the other side.

"No part of the South Col route was feared more by climbers," Jon Krakauer said in his 1996 book Into Thin Air. The fear comes from the shifting ice and the unpredictable nature of giant ice towers that could easily crush a passing climber.

"I know firsthand the terror, the confusion, the panic, and disbelief that reigns when all hell, in the form of an ice block, breaks loose. I've had my nostrils packed with snow and my glacier glasses ripped from my face in the collapse of an icefall. I've had to swim for my life in the white wave of icefall debris. I've watched helplessly as 11 climbers vanished in a cloud of white, buried alive, in the collapse of ice. And I've experienced the futility of the fruitless rescue attempts that follow."
- Greg Wilson, Mountain Zone feature

This is what happened April 17, 2000 when Byron's team was crossing through the icefall. Near the lip of the icefall, a giant serac (as high as four ladders end-to-end) collapsed, destroying the route in this section. Byron, his teammate Tim Rippel and their Sherpa sirdar Lhakpa Tshering were about an hour beneath this area but a group of nine Sherpas from Byron's team was already above the fallen serac, having passed by without trouble just a little while before hand. No one was injured in the collapse but it delayed any passage through the icefall by a day.

The route looks kind of like a three-dimensional game of Snakes and Ladders with fixed ropes snaking down from ice slopes and extra long aluminum ladders leaning precariously against ice blocks. Expeditions climbing via the South Col route depend on a professional team of guides and Sherpas to scout and fix the route through the labyrinth. Every group pays to cover the Sherpas' fee. Maintaining the route is a full-time job because every time a crevasse widens, an iceblock shifts or a serac tumbles, new ladders and ropes have to be installed.

The Sherpas lash together several aluminum ladders end to end, creating a bridge that may be two or three ladders long. It can take up to four ladders lashed together to get over an ice wall. Fixed ropes are used in tandem with the ladders to secure a climber should they slip from the ladder. The ropes are fixed to pitons in the ice at the top and bottom of a wall ladder or on either side of a wide crevasse. If something collapses or shifts suddenly, the careful route ends up as a mess of mangled ladders and torn ropes.

"Because the climbing route wove under, around, and between hundreds of these unstable towers, each trip through the Icefall was like playing a round of Russian roulette: sooner or later any given serac was going to fall over without warning, and you could only hope you weren't beneath it when it toppled."
- Jon Krakauer, Into Thin Air

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