Zuidwal volcano

About

The Zuidwal volcano is an extinct volcano in the Netherlands at more than 2 km (6, 600 ft) 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 2,000 metres (6, 600 ft) of sedimentary rock, most of it shale and sandstone from the Cretaceous.

Adapted from Wikipedia (CC BY-SA). Photography via Wikimedia Commons.