Punjab's geography mostly consists of the alluvial plain of the Indus River and its four major tributaries in Pakistan, the Jhelum, Chenab, Ravi, and Sutlej rivers. There are several mountainous regions, including the Sulaiman Mountains in the southwest part of the province, and Margalla Hills, Salt Range, and Pothohar Plateau in the north. Agriculture is the chief source of income and employment in Punjab; wheat and cotton are the principal crops