LAKE BAIKAL, Russia — The ice rumbled and then shook underfoot. No one had warned Véronique Messina about that.

Ms. Messina, a French speech therapist working in Cambodia, came to Lake Baikal in distant Siberia to run a marathon across its frozen surface. She ventured onto the ice for her first trial run just a day before the race.

“I am afraid of water to begin with, and you can see that you are running on water,” she said.

The booms and tremors rippling across the ice as it shifts, sometimes called the “Baikal Symphony,” proved an even worse surprise.