The Zuidwal volcano is an extinct volcano in the Netherlands at more than 2 km below ground under the Wadden Sea, between Harlingen and Vlieland, just south west of the island Griend. The volcano was last active during the late Jurassic, (about 160 - 148 Ma ago) and has since been covered by about 2000 meters of sedimentary rock, most of it shale and sandstone from the Cretaceous. Read more