Aegean Before the Islands

A continent of edges

The Aegean is a deep and broken basin crossed by shallow shelves. That combination made its transformation especially dramatic. Deep channels ensured that Crete, Kythira, Rhodes, Karpathos and several western islands remained offshore even at the lowest stand. Elsewhere, a fall of more than a hundred metres joined islands to one another, tied eastern islands to Anatolia and pushed the northern Greek coast far south across exposed plain. The Ice Age Aegean was not dry land from Greece to Turkey. It was a different sea, partitioned by land bridges and enormous islands.

The central change was Cycladia. At 21,000 BP, Andros, Tinos, Mykonos, Naxos, Paros, Antiparos, Syros, Ios and many smaller modern islands stood within a single landmass. Lambeck’s reconstruction describes a broad, comparatively level interior fifteen to twenty metres above the contemporary sea, broken by the mountains that survive as islands today. Shallow freshwater ground may have occupied hollows between Naxos and Mykonos. The landmass divided the northern Aegean from the Myrtoan Sea and the Sea of Crete, leaving narrow marine passages at its margins.

Even Cycladia had limits. Milos, Kimolos and Polyaigos formed their own western island. Kythnos, Serifos, Sifnos, Amorgos, Anafi, Astypalaia and Thera remained separate from the mega-island in the newer regional reconstruction. Crete stayed across deep water. Low sea level shortened passages; it did not abolish the maritime Aegean. At the glacial minimum, the shortest route between Milos and the mainland world was about eight kilometres. A person could stand on one shore and see the next land, but still needed a boat.

The sea surface itself did not hold one height everywhere. Ice sheets pulled ocean water toward them, their weight bent the solid Earth, and newly flooded shelves depressed the crust beneath the water. Around 21,000 BP, relative sea level stood approximately −120 metres in the north and −145 metres near Crete. That difference changed when particular saddles flooded.

Cycladia breaks apart

For several millennia after 21,000 BP, Cycladia remained near its greatest extent. Then water entered its lowest ground. In the separation sequence modelled by Stylianos Simaiakis and colleagues, Gyaros pulled away around 17,000 BP. Kea separated from the Greek mainland around 16,000 BP. At about 15,000 BP, Mykonos, Syros and Donousa became distinct, while Andros and Tinos survived together as one island and Folegandros remained joined to Sikinos. Ios separated around 14,000 BP.

The large central body lasted longer. At about 11,000 BP, Naxos became separate from the Paros–Antiparos–Despotiko landmass and from the Koufonisia group. Around 9,000 BP, the Andros–Tinos connection drowned. Paros remained joined to Antiparos and Despotiko, and Milos to Kimolos, until roughly 4,000 BP. The present archipelago did not arrive as a single finished picture. Its outlines accumulated.

Those changes multiplied coast. A plain did not merely shrink around its rim; salt water crossed saddles and cut one ecological world into several. Freshwater catchments contracted. Plant and animal populations that had occupied continuous ground became island populations. Distances to a larger source of animals and plants grew. The Aegean’s extraordinary modern endemism belongs partly to this rhythm of union and isolation repeated across glacial cycles, with the last fragmentation still visible in the genetic relationships among island species.

The central island also organized movement. Before fragmentation, its plains connected resources now assigned to separate islands. After fragmentation, the same high ground became a network of visible destinations. A ridge changed from route to shoreline; a valley became a channel; the mountain across the plain became the island across the water. Geography trained travel to change form without ending it.

The Anatolian peninsulas become islands

Along the eastern Aegean, modern islands were the outer heights of Anatolia’s glacial-age coast. Their separations ran from south and centre toward a nearly modern configuration. Ikaria became isolated around 18,000 BP. Patmos and Fournoi followed around 15,000 BP; Leipsoi around 14,000 BP; the Kalymnos–Leros landmass around 13,000 BP. Lesbos separated from Asia Minor around 12,000 BP, Kos around 11,000 BP and Chios around 10,000 BP. Samos remained connected beyond 5,000 BP.

In the north, the Thracian plain reached more than sixty kilometres beyond parts of the modern shore at the low stand. Limnos and Imbros were joined to Anatolia before separating around 14,000 BP and then from one another about a millennium later. Marine water entered the Marmara basin through a changing northern gateway, altering the Aegean’s circulation as well as its shoreline. The water’s route onward through the Dardanelles, Marmara and Bosporus continues in The Gates of the Black Sea.

Farther west, the Euboean Gulf became marine in stages. The southern entrance opened around 9,000 BP and the northern connection through the Dhiavlos Strait before 8,000 BP in Lambeck’s reconstruction. Euboea became an island because the sea found two doors. The Saronic Gulf underwent its own transgression after about 14,000 BP, turning an enclosed depression and embayments into an arm of the Aegean.

Each threshold made a categorical change: one shore became two. Currents began, salinity changed, routes lengthened and formerly continuous populations acquired water between their parts.

People on the moving shore

The drowned Aegean was inhabited country. At Stelida on Naxos, people repeatedly worked a chert source from at least the Middle Palaeolithic through the Upper Palaeolithic and Mesolithic. During the Last Glacial Maximum the hill belonged to Cycladia, yet the central landmass itself remained separated from the Greek mainland by water. The archaeological sequence therefore does more than populate a lost island. It places stone-working, movement and recurring return inside a geography that alternated between shorter sea crossings and longer ones.

Franchthi Cave, on the southern Argolid coast of mainland Greece, preserves another edge of the story. At the glacial maximum its coast lay at least six kilometres away. The cave overlooked a coastal plain rather than the small modern bay. As the sea advanced, marine foods appeared in its deposits, and obsidian from Milos arrived by the late Palaeolithic or early Mesolithic. The cave survived above water; much of the activity outside it did not. An offshore Neolithic site later showed that the sea was still at least eleven metres below its modern position during part of the seventh millennium BP.

At Maroulas on Kythnos, an open-air Mesolithic settlement of the ninth millennium BC contained circular structures, stone industries and burials. Kythnos never joined Cycladia or the mainland during this window. Its inhabitants were islanders in the strongest geographic sense. In the Northern Sporades, the Cave of the Cyclops on Youra preserves fishing and occupation through the Mesolithic and Neolithic. At nearby Agios Petros, a Neolithic village begun in the late sixth millennium BC now extends beneath about ten metres of water. These sites do not describe refugees pushed passively uphill. They show people making durable island lives while shorelines continued to move.

Saliagos supplies a late transformation. During the Late Neolithic, when sea level remained several metres lower, the settlement stood on a low peninsula in the isthmus joining Paros and Antiparos. Its people fished, kept livestock, grew barley and made ceramics whose connections crossed the southern Balkans and eastern Aegean. Today Saliagos is a tiny islet and Paros and Antiparos are separate. A place positioned within a neck of land became the remnant between two islands.

The missing record lies seaward. Camps on open plains, estuaries at drowned river mouths, landing places and the coastal portions of settlements are precisely the sites most likely to have been flooded. Modern archaeology samples surviving high ground and the few submerged contexts discovered by survey. The blank seabed on an archaeological map is not evidence of an empty landscape.

A rising sea and sudden disasters

Most of the Aegean’s transformation came from cumulative sea-level rise as continental ice sheets melted. It was not uniform or gentle in every century. Meltwater Pulse 1A around 14,500–14,000 BP sent global sea level upward rapidly, and the regional rise accelerated after about 14,000 BP. Yet even a fast deglacial interval was not a single wave washing across the basin. Its land loss unfolded through tides, storms, erosion, marsh expansion and the repeated inland movement of ordinary shorelines.

The Aegean also produces true catastrophes. It sits above active faults and a subduction zone; volcanic centres line the South Aegean arc. Earthquakes can lift one coast, drop another or launch a tsunami in minutes. A tsunami may devastate a coast without permanently raising the sea. An earthquake may shift one tectonic block while the wider basin continues its longer inundation.

Ios preserves the distinction. Researchers have identified a high-runup tsunami deposit containing reworked pumice from the approximately 22,000-year-old Cape Riva eruption of Santorini. They place the tsunami broadly in the Neolithic, but its exact date and whether an earthquake, landslide or eruption generated it are unresolved. The deposit records a catastrophe without turning all Aegean flooding into catastrophe.

The famous Minoan eruption and tsunami at Thera came around 3,600 years ago. The great postglacial remaking of the archipelago was already largely accomplished before the event most often summoned as an Aegean apocalypse. Long inundation made the islands; local catastrophes periodically struck the people living on them.

A sea that rose unevenly

Relative sea level at the Last Glacial Maximum differed by about twenty-five metres from the northern Aegean to Crete. Gravity, the deformation of the Earth beneath ice and water, and the changing coastline all contributed. Faulting, uplift, subsidence, sediment and erosion then altered individual shores. Regional dates for drowned saddles are therefore more reliable than assigning one global water level to the entire basin.

By about 5,000–4,000 BP, the great ice-sheet contribution to sea-level rise had largely ceased. Local tectonics, sedimentation and smaller late changes became progressively more important. The great shelves and land bridges were already gone, but individual Aegean shores kept moving.

The archipelago made by water

The modern Aegean presents islands as fixed facts: one named object here, another across the channel. Their history restores the verbs. Cycladia fragments. Lesbos leaves Anatolia. The Euboean Gulf opens from both ends. A Saliagos isthmus narrows into an islet. Every change creates new coast and reorders what can be reached on foot, by a short crossing or only through open water.

People lived through the sequence. They worked Stelida’s stone, watched Franchthi’s distant shore approach, crossed to Milos for obsidian, built at Maroulas and fished from Youra. Rising water removed land while maritime knowledge made the remaining high ground into a connected human world. The Aegean became more insular without becoming less travelled.

Rising seas broke the Aegean mainland into the islands and straits of the modern archipelago.