Sri Lanka is a continental island, separated from the Asian continent only by shallow Palk Strait. Sri Lanka was once a part of Gondwanaland, until the Cretaceous Period. Then as a part of the Indian Plate, it detached and drifted northward. The Indian Plate collided with the Asian mainland about 55 million years later. Therefore, there are many ancient Gondwana taxonomic groups present in Sri Lanka. Sri Lanka first became separated from the mainland Indian subcontinent during the late Miocene Epoch. Due to climatic changes, an intermittent drier region emerged between the moist forests in southwest Sri Lanka and the Western Ghats in India, the closest other moist forests. Although the island has been connected with the mainland repeatedly by land bridges since the initial separation, Sri Lanka's moist forests and its wet forest-adapted biota have been identified as being ecologically isolated.