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Evolution 1
Nisyros was founded on a sea bed which currently is 300 metres deep. The sea bed consists of calcareous rock which was formed 150 million years ago from the activities and accumulation of sea organisms, such as corals and shells, in the shallow waters.
Around 150,000 years ago, shortly after the great explosion of Kos, the volcano emerges from the sea and forms a conical mountain. In the following years, violent explosions and mild volcanic activity succeed each other. The eruptions eject fragments of melted rock into the air that subsequently cool and fall back to the ground, forming thin and thick layers of volcanic ash. In other occasions, calm rivers of melted rock gush from the cracks, fill the valleys and cover the area forming solid thick streams of lava.
Thus, in the next 80,000 years, a succession of ash layers, lava streams and domes, form a typical stratovolcano, a large volcanic cone situated above the sea level. Its is approximately seven kilometres wide and 700 metres high; there is a main crater at the top which is filled with water thus forming a small lake. We are referring to a small island which resembles present Nisyros in its size and shape.
Video 1: Creation of Nisyros
Evolution 2
70,000 years ago, significant volcanic activity takes place in the southern and eastern slopes of the volcano, and viscous rhyolitic and dacitic lava spurts out creating the lava formations in Argos to the south and Pachia Ammos to the east.
Video 2: Lava Formations of Argos and Pachia Ammos
Evolution 3
As time passes and layers are added to the conical island of Nisyros, magma which is viscous and richer in gases starts to be stored in smaller depths, just a few kilometres under the earth’s surface. There is only one escape method for the enormous amount of energy accumulating: the large explosions. The first series of explosions occurred around 60,000 years ago.
The trapped magmatic gases blow the melted rock into the air pulverizing it and in turn producing tens of millions of tons of pumice. Saline water, water from underground aquifers, as well as water from small lakes in the volcano’s craters, is mixed with magma and turned into overheated steam multiplying the intensity of these eruptions, which are known as hydrovolcanic eruptions.
Volcanic ash ejects, reaching quite a few kilometres up to the sky, in many cases carrying along fragments from older rock, even limestone located at a great depth below the volcano. The tens of layers of gray ash, which currently cover the eastern slopes of the island, have been deposited following a respective number of eruptions during a period of a few thousand years, somewhere between 60,000 and 55,000 years ago.
The ash from these eruptions was carried by the wind for many kilometres and can now be detected in Pyrgoussa, Pachia and the northern valleys of Tilos. The geological formation resulting from these deposits was named “Kyra”, from the homonymous monastery at the eastern slopes of the island.
Video 3: First Eruptions
Evolution 4
Following these eruptions, new andesitic magma feeds the volcanic activity in the form of hydro-volcanic eruptions, where it comes into contact with water, and in the form of lava streams which cover the north-eastern and south-western part of the island, extending it to the northeast and creating cape Katsouni.
Video 4: Cape Katsouni Extension
Evolution 5
A mild outburst of large quantities of dacitic magma follows and creates the domes in the northern section of the island. Some of these domes collapsed and covered the northern and northwest slopes of the volcano with multiple layers of hot block and ash flows. Emborio is built on top of these layers of lava which is the reason they were called lava of Emborio.
Video 5: Dacitic Magma Outburst
Evolution 6
Following a dormant period of a few thousand years, around 40,000 years ago, the volcano in Nisyros displayed a violent and catastrophic eruption. Within a short period of time, 8 billion tonnes of molten rock ejected to the sky producing over 20 billion cubic metres of pumice stone and ash.
They reached 12 kilometres high, forming an enormous cloud and covering the entire island with layers of ash up to 15 metres thick. Thus the geological formation of the “Lower Pumice” was created. The volcano topples down, falling into the 3 cubic kilometre hole created under the island due to the ejection of magma, and the first caldera in Nisyros was created.
Video 6: First Large-scale Eruption
sEvolution 7
Following this explosion, the thick melted rock which lacks gases and energy, at this point, continues to calmly spurt out. It forms large lava domes near the eastern rim of the first caldera, and once it flows over the rim it covers the south eastern slopes of the volcano with thick rivers of lava, the lava of Nikia.
Video 7: Lava Creation of Nikia
Evolution 8
A dormant period follows and lasts a few thousand years. It is interrupted by the second destructive explosion of Nisyros, around 35,000 years ago. It resembles the previous large explosion. Twenty billion cubic metres of pumice and ash cover Nisyros once again, either falling like rain from the sky, or in the form of burning hot clouds of gas and ash covering the volcano’s slopes.
The void resulting from the ejection of magma is filled by the main section of the volcano which collapses forming the caldera of Nisyros which is still visible today. The eruption last only a few days and the ash deposited on the ground creates the geological formation of the “Upper Pumice”, the white pumice and ash which currently covers the northern section of the island.
Video 8: Second Large-scale Eruption
Evolution final
The viscous and poor in gases magma which remained in the lower layers of the magma chamber quietly spurts for thousands of years following the eruption, forming postcaldera domes, which include the hills of Boriatiko, Nifio, Profiti Ilia and Trapezina, filling approximately 2/3 of the caldera. Outside the caldera the dome of Karaviotis is formed. Nisyros takes on its current form, around 25 to 20,000 years ago.
Final Video: Current Form of Nisyros
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