A volcano dormant for decades erupted in south-central Chile on Saturday, belching an ash cloud more than 6 miles high that blew over the Andes and carpeted a popular ski resort in neighboring Argentina.

Fanned by winds, ash darkened the sky in San Carlos de Bariloche, Argentina, a government official there said, adding the city's airport had been closed.

The eruption in the Puyehue-Cordon C