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The caves of Lesvos
Lesbos Island - which lies in the North of the Aegean Sea - is the third largest island in Greece in terms of area (1672 km2) and seventh in the Mediterranean area.

A cave is a natural cavity in the earth that either communicates with the surface through an opening or is completely hidden beneath the ground. There are three main ways in which caves are formed:

1. By shifts that occur in the solid surface of the Earth, which sometimes result in the formation of cracks.
2. By the constant action of water against the rocks lining the shores.
3. By the action of ground water that dissolves and carries off portions of rock. Rainwater (H2O) that combines chemically with carbon dioxide (CO2), forms a solution with increased solubility toward the impervious limestone. The CO2 combining with the barely soluble calcite (calcium carbonate (CaCO3) of the limestone, forms a carbonic acid solution Ca(HCO3)2.
CO2 + CaCo3 <---> Ca(HCO3)2

Water then carries off the resulting soluble carbonic acid solution that is formed. This water seeps into the small cracks in the rocks, dissolving portions of rock as it passes. The effect of time and the corrosive and cleansing power of the groundwater leads to the cracks becoming deeper. Eventually, the water forms a huge cavity, i.e. a cave.

Cave walls often contain calcium deposits called calcite curtains or drapery. Caves may also contain icicle-like lime deposits called stalagmites, stalactites, columns, steps, streams, rivers, even waterfalls and lakes. Stalactites are lime deposits that hang downward from the ceiling or walls of caves, measuring merely a few centimeters or up to several meters. They are usually formed as follows: The water, containing a carbonic acid solution, rises until it reaches the level of the ceiling of the cave. Drops of water begin dripping. Some of the water evaporates or carbon dioxide gas escapes from the water and some of the carbonic acid becomes barely soluble calcite (calcium carbonate).

Successive drops dripping from the ceiling form a small lime tube. As water continues to drip through the tube’s hollow center its diameter and length increases. Some of the water containing carbonic acid (carbonate of lime) may drip from the overhanging stalactite, thereby resulting in a vertical icicle-like deposit which grows upward from the floor of the cave. This lime deposit is called a stalagmite. With the passing of time, the stalactite and stalagmite grow until they join, forming a column, the diameter of which constantly increases.

A large part of the island is made of limestone, which accounts for the large number of caves, most of which are small. Nonetheless, many of these caves were once used as places of worship of the Christian faith.

The Cave of the Commune of Alifanta is the longest cave on the island, extending approx. 120 meters. Many relics and fragments of broken decorated pottery, were found at the above site, indicating that the area was inhabited as early as the Roman and Byzantine Era. Although it does not contain decorative dripstone features called speleothems due to small size of its passages, this cave is particularly interesting, and should be the subject of an archaeological survey (Figure 1)

The St John’s cave, otherwise known as Fousa in the Commune of Mychou is 95 meters long and consists of two passages with marble walls. Like the previous cave mentioned, this cave does not contain any speleothems either, but it does contain beautiful structures on on its vault. Tombs dating from the 5th century b.c., containing various relics, were found inside the cave. These findings are now kept at the K’ Archaeological Board of Lesbos, and should be part of an in-depth archaeological study, which I hope will soon be initiated. (Figure 2).

The St.Vartholomeo’s cave of in the Commune of Taxiarchis (Kayiani) is approx. 60 meters long. In earlier times it contained beautiful stalactites; unfortunately, however, visitors destroyed most of them. Prehistoric vessels were found inside the cave and are now kept at the Archaeological Museum of Mytilene. The archaeological study of this cave is almost complete.

Other caves that are of local interest are:

The cave at the Glastra or Castelli site in the Municipality of Agiasos,

Liakas Cave in the Commune of Asomatos,

Kourtzis cave in the Municipality of Mytilene,

St.John’s Cave (the sanctuary) in the Municipality of Thermi,

St.Iridoros Cave and Anidros Cave in the Municipality of Plomari.

We would like to point out that many of the 192 small caves on Lesbos Island are of particular interest because of the indications that they were inhabited from the Neolithic time.

29 karst pits called Fouses, were found on Lesbos. Investigation of these pits has not been made possible due to lack of the special equipment required for this purpose. The wells are extremely interesting and once research work is initiated they will reveal the massive labrinthic system which lies beneath the surface of Lesbos.

During the years between 1981 to 1992 my brother and I explored most of the caves on Lesbos, with limited financial support provided by the Prefecture of Lesbos. We can only hope that our work will benefit the generations to come. However we are proud of the beautiful moments we experienced in the sublime stillness of those caves. This experience was a unique opportunity to do some soul-searching and be overwhelmed by these wonders of nature.

This text was written exclusively by:
George M. Houtzaiou
Associate Professor at the Pedagogic Institute of Athens