Explanation:

• Eastern Hills or The Purvanchal are the southward extension of Himalayas running along the north-eastern edge of India.
• At the Dihang gorge, the Himalayas take a sudden southward bend and form a series of comparatively low hills which are collectively called as the Purvanchal.
• Purvanchal hills are convex to the west.
• They run along the India-Myanmar Border extending from Arunachal Pradesh in the north to Mizoram in the south.
• Patkai Bum hills are made up of strong sandstone; elevation varying from 2,000 m to 3,000 m; merges into Naga Hills where Saramati (3,826 m) is the highest peak.
• Patkai Bum and Naga Hills form the watershed between India and Myanmar.
• South of Naga Hills are the Manipur hills which are generally less than 2,500 metres in elevation.
• The Barail range separates Naga Hills from Manipur Hills.
• Further south the Barail Range swings to west into Jaintia, Khasi and Garo hills which are an eastward continuation of the Indian peninsular block. They are separated from the main block by Ganga and Brahmaputra rivers.
• South of the Manipur Hills are the Mizo Hills (previously known as the Lushai hills) which have an elevation of less than 1,500 metres. The highest point is the Blue Mountain (2,157 m) in the south.