Chloe Kim qualifies to defend her gold.

ZHANGJIAKOU, China — The icy halfpipe yawned on the mountainside, waiting to be awakened by the world’s best snowboarders on Wednesday at Genting Snow Park.

And with them came Chloe Kim, the defending gold medalist from the United States, soaring through the qualification round and into Thursday’s 12-women finals.

Kim had the best run of the day, an 87.75 on the first of her two runs, to snag the top spot in the next day’s final. She fell on her second run, under-rotating and slipping, but it did not matter. Her first run was more than enough to carry her to the finals as the favorite for the gold again.

“I feel really good,” she said afterward, through a U.S. Olympic official because Kim did not stop to speak to reporters gathered at the base of the halfpipe. “Obviously I’m going to have to bump it up tomorrow, so I’m looking forward to that. It’s going to be like a whole new competition.”

Another American with designs on a gold medal was Maddie Mastro, a California quietly riding in Kim’s shadow the past few years. But Mastro struggled through both her runs, and had to wait for the other competitors to go to see if she would squeak into the final.

She did not, finishing 13th, one spot out of the final.Snowboarding’s halfpipe competition is one of the showcase events for the Winter Olympics, at least for American audiences curious to see what Kim will do next, and what Shaun White might do last.

White, now 35, is competing in his fifth and final Winter Olympics, searching for his fourth gold medal. He and the other men were scheduled to go through their qualifications later on Wednesday.

The morning belonged to the women. Each of the 22 competitors were allowed two runs down the pipe, with its 22-foot walls. The best of their two scores, judged by an international panel, was used to rank them.

The top 12 advanced to ride for medals the next day. Among them were a pair of veteran Chinese riders, Liu Jiayu and Cai Xuetong. Japan’s Mitsuki Ono finished second in qualifications behind Kim.

Kim, 21, won the gold medal four years ago in Pyeongchang, South Korea. A year later, burned out and pondering retirement, she left the public eye and went to Princeton for a year of college. She went 22 months without stepping on a snowboard, the longest break since she began riding as a toddler.

She returned to competition a year ago, though, independent, refreshed and as dominant as ever. She arrives in China as the favorite to win again, though the competition appears to have crept closer to Kim’s level.

Liu was the silver medalist four years ago. Cai was fifth. Liu fell on her first run, the first run of the competition, catching an edge off a relatively easy maneuver.

Kim followed, a bit tentative, perhaps, from what she had witnessed from her rival, but still received a strong score.