The Brahmaputra River marks the eastern boundary of the Himalayas. Beyond the Dihang gorge, the Himalayas bend sharply towards south and form the Eastern hills or The Purvachal.
Following are the characteristics of Purvachal:
(a) These hills run through the north eastern states of India.
(b) They are mostly composed of sandstones (i.e. Sedimentary rocks).
(c) These hills are covered with dense forest.
(d) These hills are composed of the Patkai Hills, Naga Hills, Manipuri Hills and Mizo Hills.

The Brahmaputra river marks the eastern most boundary of the Himalayas .Beyond the dihang gorge, the Himalayas bend sharply to the south and spread along the eastern boundary of india .They are known as the Purvanchal or the eastern hills and mountains.

Introduction:
The eastern-most boundary of the Himalayas is marked by the Brahmaputra River. The Himalayas, the world's highest mountain range, spans across several countries including India, Nepal, Bhutan, and China. It is important to understand the geographical features and rivers that demarcate the boundaries of this massive mountain range.

Explanation:
The Brahmaputra River, also known as the Yarlung Tsangpo in Tibet, is one of the major rivers in Asia. It originates from the Chemayungdung Glacier in western Tibet and flows eastwards for about 2,900 kilometers before merging with the Ganges River in Bangladesh and eventually draining into the Bay of Bengal.

Eastern Boundary of the Himalayas:
The Himalayas extend from the Indus River in the west to the Brahmaputra River in the east. It forms a natural boundary between the Indian subcontinent and the Tibetan Plateau. The eastern boundary of the Himalayas is defined by the Brahmaputra River, which flows parallel to the mountain range, forming a deep gorge known as the Brahmaputra Valley. The river cuts through the easternmost part of the Himalayas, separating it from the hills of Assam and Arunachal Pradesh in India.

Importance of the Brahmaputra:
The Brahmaputra River plays a crucial role in the economy and livelihoods of the regions it traverses. It provides water for irrigation, supports diverse ecosystems, and is a major transportation route. The river also has significant hydropower potential, with several dams and hydroelectric projects being developed along its course.

Conclusion:
In conclusion, the Brahmaputra River marks the eastern-most boundary of the Himalayas. Its flow through the eastern Himalayan region has shaped the landscape, influenced the local ecology, and played a vital role in the lives of people in the region. Understanding the geographical features and boundaries of the Himalayas is essential to comprehend the broader context of the mountain range and its impact on the surrounding areas.