Red Gerard, born on June 29, 2000, celebrated a storming win in slopestyle, which also made him the second youngest individual winner in Games history.
"I'm super-psyched!" said Gerard, adding: "I cannot believe it. I'm shaking right now, maybe from the cold or the excitement, I don't know. But I'm ecstatic. I can't believe it."
Slopestyle was one of the events that did not fall victim to high winds on Sunday, when the showpiece men's downhill skiing was aborted until Thursday following a pre-dawn meeting of ski chiefs.
A day of extremes started with a surprise earthquake alert, after a 4.7-magnitude quake rattled eastern South Korea, with its epicentre about 260 kilometres (160 miles) from the Games.
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South Korea isn't known for deadly earthquakes, but organisers gave assurances that the Olympic venues had been built to stand up to a major tremor.
"All the facilities in the Games area are built so they can withstand strong earthquakes over 7.0... so I assure you there was no issue regarding these facilities," said Sung Baik-you, spokesman for the Pyeongchang organisers.
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The severe chill which has made Pyeongchang one of the coldest Games in history was set to worsen, with temperatures forecast to plunge to -14 degrees Celsius (7 Fahrenheit) on Monday -- with a real-feel of -25C.
"People are advised to dress warmly and wear hats and gloves to keep themselves warm," warned Sung.
On the second day of full competition, Simen Hegstad Krueger led a Norwegian sweep in the men's skiathlon after recovering from an early fall and breaking a pole.
"It is an indescribable feeling," Krueger said. "It is an amazing day but it started in the worst way with the fall after the first 100 metres and a broken pole.
Dutchman Sven Kramer roared to a third straight Olympic title in the men's 5,000m speed skating, and Germany's Arnd Peiffer upstaged French hope Martin Fourcade to win the men's 10km sprint biathlon.
In the slopestyle, Canada's Mark McMorris staked an early claim for the most inspirational story of the Games after taking bronze -- just 11 months after a near-fatal crash.
"I don't want to think too much about the past today, but I appreciate the fact I'm here on my snowboard," he smiled.