Kolumbo is an active submarine volcano in the Aegean Sea, about
300 7 km northeast of Cape Kolumbo, Santorini Island. It is the largest of a line of about twenty submarine volcanic cones extending to the northeast from Santorini. It is about 3 km in diameter with a crater 1.5 km across. Previous to the newly discovered Tamu Massif volcano in the northern Pacific Ocean, Kolumbo was considered the largest underwater volcano.
In 1650 a very explosive eruption took place that ejected pumice and ash as far away as Turkey, and produced pyroclastic flows. A tsunami occurred as well, probably during the collapse of the cone. Up to 70 people died on Santorini as a result.
During the eruption, it constructed a temporary island (hence its name Kolumbo, in Greece “swimming”). It caused damage on nearby islands up to 150 km and invaded the flat coastal areas, especially on the eastern side of Santorini, where ruins from Roman times were uncovered. The eruption also killed a great number of livestock because of poisonous gasses, mainly H2S.
For the next 356 years that is about all the anyone knew about Kolumbo. Then in 2006, in collaboration with the Hellenic Centre for Marine Research in Greece (HCMR), oceanographers from the University of Rhode Island carried out two research cruises to this area from April to July, on the ships R/V Aegaeo and R/V Endeavor. It is known as the “Thera 2006 Expedition”. In researching articles for this post, I found that nearly every one referenced this expedition for their information.
Today, underwater mapping and remotely operated vehicles with high definition cameras and sample collection devices are the research tools that allow these kinds of expeditions. What the expedition found is that the crater of Kolumbo is 505 m in depth with the shallowest point of only 10 m below the surface on the south-west crater rim.
When the ROV Hercules reached the bottom of the crater they found the entire crater floor covered by a thick blanket of a bright reddish-orange bacterial mat. In the northern part of the crater are hundreds of hydrothermal vents discharging gasses and fluids at temperatures up to 224 C (435 F) and chimneys up to 4 m in height.
Samples of the chimneys were taken and show minerals of pyrite, sphalerite, galena and barite. Abundant metals include iron, zinc, lead, and significant quantities of copper and silver occur.
So Kolumbo is very much alive. I encourage everyone to read this summary of the expedition which includes exploration of the Minoan pyroclastic deposits and possible avalanche blocks.