Sumatra consists of the region of Aceh and the provinces of Riau, Jambi, Bengkulu, Lampung, and North, South, and West Sumatra. The chief cities include Palembang and Padang. A great volcanic mountain chain, known as the Barisan Mountains and including several parallel ranges, traverses Sumatra, following the western coast. Along the eastern coast is a broad, gently sloping plain where all the main rivers flow, including the Musi, Hari, Indragiri, and Kampar, of much importance for interior navigation. Earthquakes and destructive storms, often causing injury and loss of life, are common.
Mineral deposits are large and include bauxite and petroleum.
Agriculture, the predominant activity, is pursued on small farms or on large plantations. The principal indigenous food crops are rice, by far the largest, and corn. Estate cultivation is primarily of rubber, tea, coffee, coconuts, and spices, principally for export. The indigenous Sumatrans belong, linguistically and culturally, to the Malayan peoples and are sometimes grouped as Indonesians. Among the most important ethnic groups are the Acehnese and Gayos in the north, the Bataks in the interior, the Lampongs in the south, and the Malays throughout Sumatra.