Santorini, and the eruption that rewrote its skyline

Most islands acquire their shape slowly, worn down by weather over a very long time. Santorini got its current shape all at once. More than three and a half thousand years ago, in the Bronze Age, the volcano that had built the island up over millennia collapsed in on itself in one of the largest eruptions in recorded prehistory, blowing out the centre of what had been a roughly circular landmass and leaving the crescent of cliffs that visitors now photograph from every angle available. What looks like a beauty spot is, geologically speaking, a crime scene.

A town buried, and a civilisation in question

Before the eruption, Santorini, then known as Thera, was home to a prosperous settlement at Akrotiri, connected to the Minoan civilisation centred on Crete. Ash from the eruption sealed the town almost as thoroughly as Vesuvius later sealed Pompeii, and when Greek archaeologists began excavating it in the 1960s they found multi-storey buildings, drainage systems and wall paintings preserved in extraordinary detail, with no bodies among them: it seems the population had time to flee before the worst of it arrived. What the eruption's ash and tsunamis did to Crete and the wider Minoan world afterwards is less certain. It is one persistent theory, not a settled fact, that the disaster weakened Minoan civilisation enough to hasten its decline, and a related, older theory connects the event to Plato's account of Atlantis, written many centuries later and never claiming to be anything but a philosophical story.

The caldera is not finished yet

The flooded crater at the centre of the modern island, several hundred metres deep in places, is what most visitors mean when they say "the caldera view": white villages along the clifftop at Fira and Oia, looking out over water that fills what used to be the volcano's core. It is not, strictly, extinct scenery. A small dark islet near the centre of the caldera, Nea Kameni, has been built up by more recent eruptions, the most recent in the twentieth century, and the whole area remains monitored for volcanic activity. Santorini's famous view, in other words, is a live geological process paused mid-sentence, which is either unsettling or thrilling depending on how you like your scenery.

Away from the clifftop towns, the island's volcanic soil produces something more immediately enjoyable: vineyards planted in low, basket-shaped vines to withstand the wind, growing grapes in black volcanic ash that give Santorini's wines a mineral character found almost nowhere else in Greece.

Naxos, for contrast

An itinerary that pairs Santorini with Naxos gets the useful counter-example. Naxos is the largest of the Cyclades, green where Santorini is stark, and built on marble rather than ash: quarries here supplied stone for some of ancient Greece's finest sculpture, and the unfinished marble gateway standing near the harbour at Naxos town, intended for a temple to Apollo abandoned around the sixth century BC, has stood in that half-built state for roughly two and a half thousand years. Inland, villages like Apiranthos keep a slower, more agricultural character, and the local speciality, a citron liqueur distilled from the leaves of a fruit that grows almost nowhere else in Greece, says something about how different an island economy built on soil rather than volcanic ash can look.

Two islands, one sea

Seeing both in the same trip, whether on a tour that spends dedicated time in the Cyclades or as calls on a longer Mediterranean cruise, makes Santorini's drama easier to place in context. It is not simply that one island is prettier than the other; it is that they arrived at their present form by entirely different routes, one by catastrophe and one by four billion years of ordinary geology doing what it usually does. Santorini's cliffs are spectacular precisely because something went badly wrong there once. Naxos, mercifully, has no such story to tell, and is none the worse for it.