The Neugrund meteor crater in Estonia is a 8 km diameter submarine impact crater formed about 475 million years ago in the Ordovician period. The impact crater formed in a shallow epicontinental sea as the result of the impact of an extraterrestrial body with a diameter of about 400 m. The location of the crater is submerged, but the nearby island of Osmussaar contain shock metamorphosed rocks and impact blanket debris from the explosion. The structure was only discovered in 1997.