TELLURIDE — The foot-wide trail on loose rock above sheer cliffs is disconcerting, requiring deliberate steps. But when the footpath disappears, the Telluride Via Ferrata becomes a little more than thrilling. “I had a little sinking spell heading up there for sure,” said Justin Settle, a dentist from Illinois who last month dabbled in the fabled via ferrata’s adrenalized adventure above the valley floor. The roughly 2-mile traverse delivers on electrified elation without the challenging risks that typically accompany technical rock climbing.