During the Ecca period the Falklands Plateau collided and then fused with Southern Africa, forming a vast range of mountains to the south of the Cape Fold Belt. This new mountain range was comparable in size to the Himalayas. The northern slopes of these mountains generally dipped steeply into the Karoo Sea which was at its deepest at this point. The earthquakes that accompanied the formation of the Cape Mountains therefore initiated frequent underwater mud- and rock-slides, forming fan-shaped accumulations of turbidites, which can be seen in the south west corner of the Karoo today (see photograph lower down on the right). Turbidites have for some time been recognized as petroleum producing rocks, because the underwater avalanches that cause these deposits often carry organic matter from close to the coastline, especially near river estuaries and deltas, into the anoxic depths of adjoining troughs. Here it is buried in the turbidite and turns into hydrocarbons, particularly petroleum and gas. The turbidites in the Ecca formation of the Tanqua and Laingsburg Karoo regions have thus, recently, come under scrutiny by the petroleum industry and geologists, who have found them to have rich and readily accessible deposits of oil and gas. Thus the north-eastern Ecca basin is rich in coal, while its south-western corner is becoming renowned for its oils reserves.