Kolumbo (or Kolumbos, Colombo) volcano is an active submarine volcano located 8 km NE of Santorini Island
in the Aegean Sea. The volcano forms an elliptical SW-NE elongated 3 km wide cone with a 500 m deep and
1.5 km wide crater, whose rim's highest parts rise to 18-15 m beneath sea level.
The crater floor, in particular in its northern part, contains a large and very active high-temperature fumarole field.

The crater of Kolumbo volcano is a small caldera which could have (at least in parts) formed during the volcano's
only known, but very violent last eruption which occurred in 1650 AD.
http://www.volcanodiscovery.com/kolumbo.html

Extending from the northeast part of Santorini there is a line of about twenty submarine volcanic cones.
By far the largest one is the Kolumbo submarine crater (fig. 1), with a crater that is about 1.5 km in diameter.
Kolumbo was discovered in 1650 AD, when a major explosive eruption broke the ocean surface, sending
destructive pyroclastic surges across the sea to the coast of Santorini. Up to 70 people died on Santorini as a result.
The eruption built up a small white pumice island on the crater rim, but it was quickly destroyed by the ocean waves.
http://oceanexplorer.noaa.gov/explorations/06blacksea/logs/summary_thera/summary_thera.html

Wednesday, December 28th, 2011
The number of earthquakes beneath Santorini volcano remains at slightly elevated levels. The activity is concentrated
along the volcano-tectonic SW-NE alignment passing through the submarine volcano Kolumbo 8 km to the NE of the
island and the center of the caldera where most volcanic vents in the past hundreds of thousands years of activity at
Santorini were located.
http://www.volcanodiscovery.com

Wednesday, December 14th, 2011
At 19h22 GMT (21h22 local time), a 3.2 earthquake occurred at the little-known submarine volcano Kolumbos
ca. 8 km NE of Santorini, Island, Greece. This marks one of the largest events in recent months.

There is no reason to state that new activity from Santorini or Kolumbus is likely in a foreseeable future but on
the other hand, there are very few data available, unfortunately, to judge the situation.
We regret that the Greek monitoring institutes are not publishing more details about the ongoing activity.
Access to important earthquake details such as as their depth, are not published (they are available for earthquakes
in all the other regions in Greece, raising some suspect why not for Santorini...)

Why does this remind me of what is happening on El Hierro at present?



Above info from
http://www.volcanodiscovery.com/view_news/4206/Kolumbos-submarine-volcano-Santorini-Greece-32-magnitude-earthquake.html


From the Thera 2006 Expedition
by Haraldur Sigurdsson,. Steven Carey. Graduate School of Oceanography University of Rhode Island
When "Hercules" reached the bottom, it turned out that the crater floor was entirely covered by a thick blanket of a
bright reddish-orange bacterial mat, which is a good indicator of hydrothermal venting near-by. Further exploration
led to the discovery of a large hydrothermal vent field in the northern part of the crater floor. It consists of hundreds
of hydrothermal vents that are discharging hot fluids, and some are vigorously discharging gases and fluids at
temperatures up to 224°C (figure 3). The deposition of minerals in many of the hydrothermal vents has led to the
construction of chimneys up to 4 m in height. Samples of the vent chimneys were brought up to the surface, and
preliminary analyses show that they are composed of polymetallic sulfide/sulfate. Thus there is a mineral deposit that
is actively growing in the Kolumbo crater today, and it has probably grown entirely during the 356 years that have
passed since the 1650 AD eruption.
http://oceanexplorer.noaa.gov/explorations/06blacksea/logs/summary_thera/summary_thera.html