The Secret Caldera

On the night of 27th September 1650, the island is
shaken by the largest volcanic eruption of the last
millennium in the Eastern Mediterranean 6,5 kilometres
NE of Santorini. Seventy people and more
than a thousand animals lose their life due to the
released H2S. Tephra ash blackens the sky. A huge
10m high tsunami swamps the beaches of Santorini
and the Aegean. Pumice covers the sea surface and
makes it look like land. The church of Panaghia
Kalou will be later on built at the Koloumbo cape to
soften the memory of the nightmare.
The island has just acquired one more distinct feature
to its already exclusive profile : the submarine
volcano Koloumbo with a circular caldera 1,7km
in diameter, its shallowest part reaching 18m and
its deepest part 504m. The steep vertical inner walls
of the crater form a unique underwater relief of
thick pumice deposits, interrupted at times by
solid angular pieces of lava. A red-orange bacterial
mat colors the bottom and covers the flanks of the
volcano in 250m depth. Thermal fluids with temperatures
as high as 220o C and precious metals
form colorful “chimney-like” sculptures (vents) up
to 6m high, while gases are released up to even 10m
above the bottom. These bacteria live in dark toxic
environments of high pressures and temperatures
and use hydrothermal fluids and gases coming out
of the vents as their energy source (chemosynthesis)
instead of solar energy (photosynthesis). Many
scientists support that the first forms of life on
earth used to live in toxic environments similar to
those of hydrothermal vents; however, with the
lapse of centuries, they modified their metabolism
and entered the atmosphere. In addition, it is believed
that environmental conditions similar to
those of hydrothermal fields prevail also on other
planets of the solar system. Scientists are highly interested
in these geological and biological features
that occur nowhere else in the Mediterranean.
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