South Asia or Southern Asia is the southern region of Asia, which is defined in both geographical and ethno-cultural terms. The region consists of Afghanistan, Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka. Topographically, it is dominated by the Indian Plate and defined largely by the Indian Ocean on the south, and the Himalayas, Karakoram, and Pamir mountains on the north. The Amu Darya, which rises north of the Hindu Kush, forms part of the northwestern border. On land (clockwise), South Asia is bounded by Western Asia, Central Asia, East Asia, and Southeast Asia.