Kathmandu, April 23 -- A massive wall of ice-millions of tonnes suspended high above the Khumbu Icefall-has brought Nepal's Everest climbing season to an uneasy impasse, forcing expedition leaders, Sherpa guides and government officials into a tense waiting game.

For the past two weeks, the highly skilled "icefall doctors"-the Sherpa team tasked with fixing ropes and ladders through the most dangerous section of the world's tallest peak-have held back. Their hesitation is not routine caution. It is driven by a looming threat: a giant, unstable serac hanging precariously near the route to Camp I, which could collapse without warning and unleash a deadly avalanche.

"This is not something you can fix or move," said Himal Gautam, spokespers...