Iceland's South Coast compresses 120 kilometres of volcanic drama into a corridor no wider than fifteen kilometres at its broadest point. The region's geology is young — the youngest landforms on Earth outside active volcanic zones — with Eyjafjallajökull's 2010 eruption depositing fresh tephra across basalt fields that themselves date back only 10,000 years. The coastal strip between Selfoss and Vík sits on the boundary of the North American and Eurasian tectonic plates, a seam that pulls apart by two centimetres each year and feeds the geothermal systems that power Reykjavík. Seljalandsfoss and Skógafoss anchor the western segment of the South Coast. Seljalandsfoss drops sixty metres from a cave-riddled cliff line; a footpath behind the curtain of water opened in 1987 after erosion widened the recess. Skógafoss, twenty-five kilometres east, falls from the edge of the Eyjafjallajökull ice cap and throws a permanent mist cloud that refracts light into doubled rainbows on clear mornings. Both waterfalls mark the retreat line of Iceland's coastline; the cliffs they tumble from were sea bluffs during the last interglacial period, and the lowland farms below occupy marine terraces exposed when isostatic rebound lifted the island. Reynisfjara, the black sand beach east of Vík, is built from basalt fragments eroded from the Reynisdrangar sea stacks. The columnar basalt formations at the beach's western edge — Garðar and Hálsanefshellir — cooled slowly enough to fracture into hexagonal prisms, a geometry that appears wherever lava meets seawater at controlled rates. The beach's undertow has claimed seventeen lives since 1995; sneaker waves arrive without warning when Atlantic swells refract around the headland. Sólheimajökull, a three-kilometre tongue of the Mýrdalsjökull ice cap, has receded 1,200 metres since 1930. The glacier's terminus sits above a subglacial lake fed by geothermal vents beneath Katla, a volcano that erupts on average every fifty years and last erupted in 1918. When Katla erupts, the jökulhlaup — glacial outburst flood — can discharge 300,000 cubic metres of meltwater per second, ten times the flow of the Amazon. The flood plain between the glacier and Route 1 is an exclusion zone during seismic alerts. Iceland south coast half day tour itineraries concentrate stops along the sixty-kilometre segment from Seljalandsfoss to Sólheimajökull, a route that the Ring Road completes in under ninety minutes. The density of landforms makes the South Coast Iceland's most-visited rural region outside the Golden Circle, with 1.8 million travellers passing through in 2025.