Aspronisi, the white islet on Santorini's caldera rim
0.1 km² of rock in the south-west gap of the caldera. Dark lava at the base, pale eruption ash on top. It is the clearest thing on the whole cruise to point at and say: that is what happened here.
€100 per person · 10:00 - 15:00 · Shared seats
Aspronisi is the small white islet in the south-west gap of the Santorini caldera, between Cape Akrotiri and Thirassia. It is uninhabited, about 0.1 km², and it is a piece of the island that stood here before the eruption. The pale rock on top is the ash the eruption dropped on it.
Aspronisi means white island, and the name is a description rather than a flourish. Everything else inside the caldera is dark. This one is not, and there is a reason for it.
The five islands of the caldera
Three on the rim, two in the middle. The rim is what was left standing when the caldera collapsed. The two in the middle grew back afterwards, inside the hole.
| Island | Size | What it is | How old |
|---|---|---|---|
| Thira (Santorini) | 75.8 km² | The main rim island. Cliffs up to about 300 m, with Fira, Imerovigli and Oia along the top. | Older than the caldera. The cliff face is the rock that stood before, capped by the eruption's ash. |
| Thirassia | 9.3 km² | The north-west rim, cut off from Santorini by the collapse. 249 people at the 2021 census. | The same age as Thira. It is the same island, on the far side of the water. |
| Aspronisi | 0.1 km² | An uninhabited islet in the south-west gap. Steep cliffs, two gravel beaches, no landing. | The same age again, and the smallest surviving fragment of the old rim. |
| Nea Kameni | 3.4 km² | Black lava island at the centre, 114 m at its highest. The crater walk is here. | New. Built by eruptions from 1707 onward; the most recent was in 1950. |
| Palea Kameni | 0.5 km² | The hot springs island, at Agios Nikolaos bay. | Built between 197 BC and AD 47, with a submarine eruption in AD 726. |
The present caldera formed about 3,600 years ago in the Minoan eruption. The dating is disputed: radiocarbon gives roughly 1619–1560 BC, conventional archaeology 1550–1480 BC. We use the round figure.
Why it is white when everything else is black
Read the island in section as the boat goes past. The base is dark lava: the old island, the ground people lived on. Above it sit thick pale beds of pumice and ash, dropped by the Minoan eruption and hardened since into cliffs.
Black is before. White is the eruption itself.
Nea Kameni and Palea Kameni, in the middle of the caldera, carry no white cap at all. They are made only of what came up afterwards, which is why they are dark to the top. Aspronisi and the Kameni islands are the before and the after of the same event, half an hour apart on the same boat.
What a pass looks like
Nobody lands on Aspronisi. There is a small anchorage and two gravel beaches, but no water, no shade and nothing to go ashore for. Our cruises pass it.
It sits in the break on the south-west side of the ring, which is the door the boats use. Round the Akrotiri lighthouse, turn north, and the caldera opens up with Aspronisi to one side and the volcano ahead.
Low sun rakes across the white beds and separates them from the dark base. At midday the island flattens out and reads as one grey lump. On the full-day private cruise there is time to slow down for it, and time for Thirassia after.
Into the caldera the way the boats go
Round the lighthouse, past Aspronisi, on to the volcano and the hot springs. Five hours, €100 per person, lunch cooked on deck.
Call the harbour office+30 698 977 1888
Common questions
What is Aspronisi?
The smallest of the three islands that form the rim of the Santorini caldera, alongside Santorini itself and Thirassia. It is uninhabited, roughly 0.1 km², and sits in the south-west gap between Cape Akrotiri and Thirassia. Nobody lands there. Boats pass it, which is how most people see it.
Why is Aspronisi white?
Because it is capped by pumice and ash from the Minoan eruption, which consolidated into pale cliffs over the dark lava base underneath. The base is the pre-eruption island; the white is the eruption's own debris sitting on top of it. That stacking is visible from a passing boat.
Can you land on Aspronisi?
Not on our cruises. The islet is uninhabited with no facilities, no fresh water and no shade, and there is nothing ashore to visit. Sources describe a small anchorage and two gravel beaches, but we treat it as a pass-by. If landing anywhere matters to you, tell us before you book.
How many islands make up Santorini?
Five. Three form the rim: Thira, which is Santorini itself, Thirassia and Aspronisi. Two sit inside it: Nea Kameni and Palea Kameni, both built by eruptions after the collapse. A caldera cruise shows you all five in an afternoon, and only the first two have people living on them.
Santorini Boat Tour - Water Taxi is a catamaran cruise and water taxi operator based in Fira, Santorini.
Updated August 2026