Spain’s Civil Protection for Volcanic Risk has closed two beaches on the island of El Hierro in the Canary Islands because of potentially toxic gasses emanating from an underwater volcano off the island’s shore.
The island has experienced hundreds of low intensity earthquakes due to volcanic activity. Witnesses say that explosions from the underwater volcano sometimes blasted 25 metres above sea level.
Video of erupting gas
A few things struck me (a geologist) when I heard this news and saw this footage. First, if a boat had been in or around this bubble, the crew could have died. I wonder if such events have happened in the past and account for some unsolved mysteries (as is suspected with methane eruptions from underwater that make a boat sink). Second, the Canary Islands have had massive undersea landslides that can cause tsunamis that pose a hazard to the UK and American (east) coasts. See this Science Daily article for more on that.