Many people mistakenly call the Santorini bay simply a "volcano crater," but in fact it is something much more grandiose. A caldera (translated from Spanish as "huge cauldron") forms when, after a catastrophic eruption, the magma chamber beneath the volcano empties and its roof collapses inward.
Imagine this: an ordinary volcano is a mountain with a crater on top. And the Santorini caldera is a giant basin (or depression) that forms when an entire mountain top collapses downward. In the case of Santorini, this "collapse" happened with such force that most of the ancient island sank beneath the sea.
Today we see the result of this ancient cataclysm: a crescent-shaped archipelago of several islands surrounding a deep sea lagoon. The main island (Fira, or Thira – which everyone calls Santorini), Thirassia, and Aspronissi are the surviving edges of the "collapsed roof" of the ancient volcano.
The history of birth: how an explosion 3600 years ago changed the world
Approximately 3600 years ago (around 1613 BC), an event occurred on Santorini that the Greeks call the Minoan Eruption. It was one of the most powerful volcanic events in human history.
What happened then:
First stage – the explosion. The volcano ejected tens of cubic kilometers of ash, pumice, and gases into the atmosphere. The height of the column reached tens of kilometers.
Second stage – the collapse. The emptied magma chamber could no longer support the weight of the island. The roof of the volcano collapsed into the void, forming a depression up to 400 meters deep below sea level.
Third stage – the tsunami. The collapse of the rock caused a giant wave (estimated to be up to 100 meters high), which swept across the entire eastern Mediterranean, destroying coastal cities.
Fourth stage – the death of a civilization. The eruption wiped out the thriving Minoan settlement of Akrotiri (often called the "Greek Pompeii") from the face of the earth, and perhaps also caused the decline of the entire Minoan culture on Crete.
After the eruption:
The huge "cauldron" quickly filled with the waters of the Aegean Sea. But the volcano did not die. Over the following thousands of years, it continued to erupt, creating new volcanic islands in the center of the flooded caldera.
Size and geology of the Santorini Caldera
So that you can imagine the scale of this place, here are a few facts.
• Shape and size: the caldera is an oval basin measuring approximately 12 by 7 kilometers (according to other sources, 8 by 4 kilometers for the inner depression).
• Depth: from 290 to 400 meters below sea level. This is higher than the height of most skyscrapers, only going downward.
• Height of the walls (cliffs): from 100 to 300 meters above sea level. It is on these sheer cliffs that the whitewashed villages are built.
The age of the first caldera began to form more than 100,000 years ago.
The islands inside the Santorini caldera are the youngest. In the center of the bay are two small black islands – these are the "children" of the volcano, which grew after the main basin had already collapsed.
• Palea Kameni ("Old Burnt") formed about 2000 years ago.
• Nea Kameni ("New Burnt") formed as a result of eruptions over the last 450 years. The last time the volcano awakened here was in 1950.
What makes the Santorini Caldera interesting for tourists: three ways to experience it
Getting to know the caldera is not just about gazing at the view from a hotel. It is a full-fledged adventure that can be experienced in three different ways.
First way: viewing from above – the "eyebrow of the caldera"
This is the classic for which people come to Santorini. The villages located right on the edge of the sheer cliffs are called the "eyebrow of the caldera."
• Fira is the bustling capital. Here are the best restaurants and shops, as well as the cable car that descends to the old port.
• Imerovigli is the highest point and the quietest place. Here is the famous Skaros Rock and the best sunset views without crowds.
• Oia is the most photographed village. It is from here that those "postcard" views with blue domes against the sunset are taken.
Tip: the best view is not from public viewing platforms, but from hotel pools or restaurant terraces. Sunset here is a sacred time for all photographers in the world.
Second way: walking along the edge – the Fira – Oia trail
This is the adventure for which it is worth wearing comfortable sneakers. The route from Fira to Oia (or vice versa) runs right along the ridge of the Santorini caldera and is considered one of the most beautiful hiking trails in the world.
• Characteristics of the route: the distance is about 10–11 kilometers. Difficulty is moderate (the route is suitable for prepared beginners and school-age children). Travel time is 3 to 5 hours depending on stops.
• Features of the route: the surface is mixed. About 6.5 kilometers are natural rocky paths, the rest are roads and asphalt.
• Direction: It is recommended to go from Fira to Oia, as there are more descents than ascents in this direction.
• Start: look for the beginning of the path near the Atlantis Hotel in Fira. Do not trust navigators that lead you into alleys – go straight to the cliff.
• What you will see: walking 10 kilometers, you will pass through all three main villages (Fira, Firostefani, Imerovigli), see volcanic rocks, ancient churches, and if you are lucky, meet locals treating tourists to watermelon on the hilltops.
Important tip: take at least 1.5–2 liters of water per person. The sun on the cliffs is merciless, and shops are not frequent. You also need comfortable closed-toe shoes – sandals will slip on the stones.
Third way: sailing inside – the boat excursion
This is the only way to find yourself inside an active volcano. Boats depart from the old ports of Fira or Oia.
The standard excursion route looks like this.
• First stop – landing at Nea Kameni. You walk across solidified lava fields towards the crater. This is about 20–30 minutes of climbing over black rock, as sharp as glass. The feeling is that you are on another planet.
• Second stop – swimming at Palea Kameni. The boat approaches the bay with hot springs. The water there is murky orange (due to iron) and warm. Attention: the color of your swimsuit may be ruined (become yellowish), and it smells of sulfur there.
• Third stop – dinner and sunset. Usually the program includes dinner on board with local wine and watching the sunset, which is especially beautiful on the open sea.
Flora and fauna of the Santorini Caldera: life on the ash
At first glance, it might seem that on the volcanic islands (especially on Nea Kameni) there is nothing but black rock. But that is not the case.
Rare plants: in summer, amazing plants emerge on the hot volcanic rock and in the cracks of the solidified lava. These are low-growing shrubs and grasses, resistant to heat and drought. Many of them are endemics – meaning they are found only on Santorini and nowhere else in the world.
Underwater volcano: the islands inside the caldera are only the tip of the iceberg. Near Santorini, underwater, is the active volcano Kolumbo. Its crater lies at a depth of 500 meters, and it also contributes to the geothermal activity of the region.
The Santorini Caldera is not just a "beautiful bay." It is a large and impressive geological monument of nature that can and should be explored from three different sides: from above (walking along the edge), from below (by boat on the water), and even from the inside (excursion to the volcano). If you want to truly explore Santorini, it would be great to dedicate at least a full day to getting to know the caldera: spend the morning on a hike, and after lunch go on a boat trip to see the sunset right from the sea.
