Route 1, Iceland's ring road, was completed in 1974, but the South Coast section between Selfoss and Höfn remains the country's most geologically volatile corridor. The 180-kilometre stretch traverses active glacial tongues, jökulhlaup flood plains, and basalt columns shaped by Holocene eruptions. Skógafoss and Seljalandsfoss, the two waterfalls most visitors encounter first, drop from cliffs that once marked Iceland's southern coastline before post-glacial rebound pushed the shore five kilometres seaward. Extended South Coast itineraries unlock landscapes inaccessible on single-day loops from Reykjavík. Vatnajökull, Europe's largest ice cap at 8,100 square kilometres, calves directly into Jökulsárlón glacial lagoon, where icebergs drift toward the Atlantic under the watch of Arctic terns and grey seals. The lagoon formed only in the 1930s as Breiðamerkurjökull glacier retreated; by 2026, thermal expansion and ablation have deepened it to over 250 metres. Nearby Reynisfjara black sand beach, composed of basaltic tephra from Katla's subsurface magma chamber, extends beneath Reynisdrangar sea stacks — hexagonal basalt formations that Icelandic folklore attributes to petrified trolls caught by dawn. Overnight tours along the South Coast allow time for blue ice cave exploration beneath Vatnajökull's outlet glaciers, a phenomenon available only between November and March when meltwater channels freeze into accessible tunnels. The caves shift annually; what existed in 2025 may collapse or reform by the following winter. Sólheimajökull glacier tongue, a southern extension of Mýrdalsjökull, remains a stable site for guided glacier walks, though its terminus has receded 1.2 kilometres since 2000. The South Coast's weather systems, driven by North Atlantic depressions, shift within hours — morning sun at Vík can turn to coastal fog by afternoon, a volatility that makes two-day itineraries more adaptable than single-day rushes. The region's 24-hour daylight in June and four-hour winter days shape the rhythm of South Coast tours. Summer itineraries favour midnight drives under low sun angles that illuminate glacial crevasses and coastal cliffs in amber light. Winter departures prioritize ice cave access and northern lights potential, though aurora visibility depends on solar activity and cloud cover, neither guaranteed.