In a terrible eruption, 3.600 years ago,the Strongyli volcano collapsed,creating the huge cauldron of the caldera we see today. The Santorini island complex, the island of Thira, Thirasia, and Aspronisi, are the fragments tha remained above the surface of the sea after the collapse, while the rest,the greatest portion of the island, dissapeared under the water. Not long after the caldera was formed, molten rock, viscous magma with few gases, again began to flow up in the center of it, solidifying in contact with the seawater and thus slowly building up a submarine volcanic structure which would eventually become the foundation of the Kameni islets. This activity was not recorded by the ancient historians, and was very likely not observed by the people then living on the island.

THE ERUPTION OF 46-47 A.D
About 200 years later, towards the end of the year 46 and the beginning of the year 47 A.D., the volcano re- awakened. Huge quantities of viscous molten rock (magma) spouted out of the sea two kilometers southwest of lera, creating the islet of Palea Kameni. At that time the islet, which was known as Thia, had a circumference of 5,550 meters, as the Roman historian Aurelius Victor registers in his work Historia Romana. It gradually acquired its present shape through fragmentation by great cracks and faults and the collapse of its shoreline in many places.

THE ERUPTION OF 726
During the next seven centuries the volcano remained quiescent. It became active again in the year 726, this time extremely violently. Several explosive events spewed pumice and volcanic ash several kilometers into the air, sending it drifting across the Aegean and into Asia Minor, as Theophanes the chronicler recorded:

"In the summer of that same year of the eighth "Indiction"', steam as from a fiery furnace bubbled up from the depths of the sea between the islands of Thira and Thirasia for several days, and in a short while, after it had increased and hardened by the furious heat of the blazing fire, the smoke began itself to seem like fire, and on account of the thickness of this solid matter, large pumice stones were spewed out all over Asia Minor and Lesbos and Abydos and towards those parts of Macedonia which overlook the sea".

This eruption seriously disrupted the economic and social life of the Aegean, and was interpreted as an indication of the wrath of God caused by the Iconoclastic Controversy which was then lacerating the Byzantine Empire. Great quantities of volcanic tephra spewed out in this eruption can still be seen on Palea Kameni. The viscous magma which later filled the crater now appears as a black tongue of lava with a rough scoriaceous surface on the northeastern shore of Palea Kameni, forming the north side of the bay of Aghios Nikolaos.

THE FIRST ERUPTION (1570-1573)

After the violent explosive eruption of 726, no further sub-aerial volcanic activity was recorded for more than 800 years. But the volcano struck again in 1570. From an area near the "Bankos" reef (the remnant of the islet of lera), flowed viscous magma punctuated by numerous explosions. This activity continued for approximately three years, creating a small dome-shaped island with a diameter of about 400 m. and a height of 70 m.,which was called "Mikri Kameni" (Litle Burnt Island).The summit of the dome is occupied by a crater about 20 meters deep.

THE ERUPTION OF 1707-1711

One hundred and thirty-tive years ot quiescence followed before the volcano next showed signs of activity. The initial signals took the form of minor seismic events on May 18 and 21, 1707. Two days later the inhabitants of Santorini watched the sea floor to the west of Mikri Kameni slowly rise to the surface and become an islet, bringing with it great quantities of shells, which the more daring among them gathered. The new islet was called Aspronisi (White Island), because the land that had arisen from the bottom of the sea was white with pumice. A week later, the viscous magma made its appearance to the north of Aspronisi. This new islet, formed of black chilled lava, was called Mavronisi (Black Island). A few days later there began a series of explosive eruptions, spewing tephra and lava fragments to a height of up to two kilometers. This volcanic activity continued for more than four years, and, by September 1711 had created alongside Mikri Kameni a new island which became known as Nea Kameni (New Burnt Island). The northeastern shore of the islet, and parti- cularly the shores of a little bay known as Vulcanos Cove, quickly became dotted with tiny churches and small buildings for the use of the people of Santorini who came to the island to soak in the thermal springs with which the coast abounded. They were also used by the fishermen who used to bring their boats into the warm water to clean their bottoms, for the ferrous and sulphurous hydrothermal solutions kill the accumulated parasites.

THE ERUPTION OF 1866-1870

The dormant stage which followed lasted for 155 years. It was finally interrupted on January 14, 1866 by a series of seismic events which continued over a period of two weeks. The waters of the eastern shore of Nea Kameni became noticeably warmer, and the sea was coloured by fluids seeping from the magma which had begun to rise. The buildings around Vulcanos Cove slowly began to sink into the sea. On February 4, the first lavas appeared in the middle of the cove, and two days later the eruptions began. They gradually increased in number and intensity, sending lava fragments to a distance of more than 700 meters. These ejecta frequently caused damage to the fishing boats that dotted the waters around the islands, while the volcanic gases and the ash that were ejected from the volcano caused problems for the inhabitants of Santorini and the neighbouring island of Anafi. The volcanic activity continued until October 15, 1870, mainly in the form of effusion of fluid and extrusion of viscous lava. Besides the center in Vulcanos Cove (which was named Georgios, in honour of the reigning King of Greece, George I), two other centers produced lava flows and domes: these were Aphroessa, 400 meters to the southwest of Georgios, and the two Islets of May, which rose to the surface between Palea and Nea Kameni in May of 1866. These two islets later subsided, and today are about one meter below the surface of the sea. The quantities of lava that were produced during this period (140 million cubic meters) tripled the size of Nea Kameni. A small strip of sea continued to separate Mikri from Nea Kameni. This area became known as Kokkina Nera (Red Waters) because the waters of the thermal springs that abounded there left deposits of red oxidised iron on the shore, just as they still do around Nea and Palea Kameni.

THE ERUPTION OF 1925-1928

A series of minor seismic events on July 28, 1925 warned the inhabitants of Santorini that the volcano was waking after a dormant period of 55 years. The sea around Kokkina Nera changed colour and became noticeably warmer, and the eastern shore of Nea Kameni once again began to subside. The eruption, heralded by tremendous fountains of steam and water in the area of Kokkina Nera, began on August 11, 1925. The fountains rapidiy became explosive columns ejecting lava and volcanic ash. A few days later the center of volcanic activity moved 200 meters to the southwest to a site which today has several (at least 5) craters grouped together. These craters and the pyroclastic cones of lava fragments which made them were created by the volcanic activity of 1925. During that period, volcanic ash was spewed to a height of more than 3,200 meters and lava fragments rained over an area with a radius of more than 850 meters. Victor Akylas describes one of these eruptions in his book entitled "The Volcanoes and the Island of Thira".

"Nothing can compare with the superb eruption of August 19th,when at about 3 o'clock in the afternoon there was a tremendous roar; a huge cloud of steam darkened the whole surrounding area, volcanic ash spewed with terrific force several kilometers into the air, while glowing fragments of lava rained over an area 3,000 meters in diameter all around the Dafni crater. This was followed by heavy showers of volcanic ash."

The explosive activity was accompanied by the ejection of huge quantities of lava - an estimated 100 million cubic meters – which flowed in two broad branches, one to each side of Mikri Kameni, filling the channel separating it from Nea Kameni and adding substantially to the land surface of the isiand which had now become a single mass. The name Daphni was given to the lava flows and the craters in honour of the first war ship to arrive on the scene immediately after the eruption. This period of activity lasted for two years, until May 1926. The volcano did reawaken briefly during the first three months of 1928, creating a small lava dome to the east of the Daphni craters which was baptised Nautilus. This dome, however, is no longer visibie for it was covered by lava produced during the next stage of activity.

THE ERUPTION OF 1939-1941

After a period of quiesence of only 11 years, the volcano awoke once again. Early in May 1939, it was observed that the waters in the little bay of Aghios Georgios with its chapel dedicated to St George, were heating up, and the coastiine was subsiding. A submarine explosion at the harbour entrance on August 20, cleared the vent for the new magma which began to appear, creating a small dome which the volcanologists of the time promptly baptised "Triton" after the mythological merman who used to rise up out of the sea. One month later, the focus of volcanic activity shifted a few hundred meters to the northeast where it created lava flows and a dome which were given the name of "Ktenas" after a geologist who studied the Kameni eruptions. This lava filled the little harbour of Aghios Georgios and covered the Triton dome. Between November 1939 and July 1940, the volcanic activity shifted even farther to the northeast, creating the Fouque lava flows and dome, named after the distinguished French naturalist who studied Santorini and the eruptions of Kameni up until 1866. In July 1940, two new centers of activity appeared to the south of the Fouque center. The first was called Smith, after an American; and the second Reck, after a German, voicanologist, both of whom had studied the 1925 eruptions. These centers produced lava domes and flows which covered the western slopes of the now single island of Nea Kameni and flowed into the sea. The explosive activity of this period was not severe, and the height to which volcanic ash was ejected did not exceed 1,200 meters. Late in August 1940, two major explosions from the summit of the island blew the old rock plug from 1866 into the air, opening two large craters each 50 meters across. These are the craters which visitors to the isiand go to see today. There was no magma outflow from these craters. Towards the end of November of that same year, viscous lava began to flow from a vent a bare 100 meters to the east, creating the lava fields named "Niki" (Victory), in honour of the Greek victories in Albania. The lava covered the eastern slopes of the isiand, stopping just short of the sea. This period of activity lasted until July 1941.

THE LAST ERUPTION ON SANTORINI (1950)

The most recent volcanic eruption in Greece was that which shook Santorini early in January, 1950. There had been advance warning in the form of seismic events since the previous August. On January 10, 1950, an explosion blew the oid rock plug to the southern foot of the Niki dome, opening a vent for the new magma which began to pour out. This was punctuated by intense explosive activity which spewed tephra 1000 meters into the air, and dropped lava fragments within a range of 850 meters ali around. The explosions and the effusion of magma continued untii February 2, creating the youngest volcanic rocks in Greece, the "Liatsikas lavas", named in honour of another eminent geologist who studied the Kamenis.

The Volcano of Santorini