Strait of Gibraltar

clockwise around the Mediterranean

Diatomite Mines (Diatomite Pit North), Quincy, Grant County, Washington, USA(mindat.org) Diatomite - middle Miocene (∼15 Ma) freshwater lacustrine deposit located between flows of the Columbia River Basalt Group.

Strait of Gibraltar (Wikipedia) The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa. The two continents are separated by 13 kilometres (8.1 miles; 7.0 nautical miles) of ocean at the Strait’s narrowest point between Punta de Tarifa in Spain and Point Cires in Morocco. Ferries cross between the two continents every day in as little as 35 minutes. The Strait’s depth ranges between 300 and 900 metres (980 and 2,950 feet; 160 and 490 fathoms).