It has been quiet for nearly 400 years, but Kolumbo, an underwater volcano just off the Greek island of Santorini, is not asleep. A previously undetected magma chamber is gradually filling with melt, prompting researchers to recommend real-time monitoring of the volcano.
The last time Kolumbo erupted, in 1650, it killed 70 people, but population growth and tourism on Santorini mean the impact of an equivalent eruption today could be far greater.
