Sri Lanka has 45 estuaries and 40 lagoons. Sri Lanka's mangrove ecosystem spans over 7,000 hectares and played a vital role in buffering the force of the waves in the 2004 Indian Ocean tsunami. The island is rich in minerals such as ilmenite, feldspar, graphite, silica, kaolin, mica and thorium. Existence of petroleum and gas in the Gulf of Mannar has also been confirmed, and the extraction of recoverable quantities is underway.