Its narrowest point is at its southern opening, with a width of only 18 km, but at the northern opening it is 40 km across. Total length is about 60 km. Because it is 250 m deep1 — much deeper than the Strait of Malacca — ships that draw too much water to pass through Malacca (so-called "post Malaccamax" vessels) often use the Lombok Strait, instead.
The Lombok Strait is notable as one of the main passages for the Indonesian throughflow that exchanges water between the Indian Ocean and the Pacific Ocean.
It is also part of the biogeographical boundary between the fauna of Indo-Malaysia and the distinctly different fauna of Australasia. The boundary is known as the Wallace Line, for Alfred Russel Wallace, who first remarked upon the striking difference between animals of Indo-Malaysia from those of Australasia and how abrupt the boundary was between the two biomes.
Biologists believe it was the depth of the Lombok Strait itself that kept the animals on either side isolated from one another. When sea levels dropped during the Pleistoceneice age, the islands of Bali, Java and Sumatra were all connected to one another and to the mainland of Asia. They shared the Asian fauna. The Lombok Strait's deep water kept Lombok and the Lesser Sunda archipelago isolated from the Asian mainland. These islands were, instead, colonized by Australasian fauna.
References
van Oosterzee, Penny (1997). Where Worlds Collide: the Wallace Line.
