Topographical Zonation
The state, Arunachal Pradesh can be described geographically in three distinct topographical zones: (1) the high mountainous region is in the north; (2) the intermediate hilly region is in the central part; and (3) the foothill plains are in the south.
The northernmost areas are characterized by rugged, snow-covered peaks of the Eastern Himalayas with heights often exceeding 4,500 meters. In this mountainous zone, there are several prominent ranges such as the Eastern Himalayas and the Assam Himalayas. In the high mountainous zone, the terrain is with steep slopes, enormous gorges, and permanent snow. This zone marks the international border with China and Bhutan, with significant historic strategic passes accounting for the steepness such as the Sela Pass and Bum La Pass.
South of the northernmost zone, in the central region, there are parallel hill ranges running mostly in the southwest-northeast direction in a series of moderate parallel ridges from 1,000 meters to 3,000 meters. In more detail, the topography consists of deep valleys, steep ridges, and forested slopes. The central zone has an exceptionally rich ecology, and it is the transition zone between the high mountains and the lowland plains.
The southernmost area extends into the flat lands of the plains bordering Assam. This area lies in the Brahmaputra Valley, situated at an elevation of about 100 to 300 meters. While occupying a small area as compared to the total area, it is crucial for human settlement, cultivation and communication. Instead, in the plains are floodplains, mild hillocks, and river beds.
Mountain Ranges
Arunachal is composed mostly of mountain systems, which form the dominant physical feature of the state's map. The Himalayan range extends into the state's boundaries, representative of some of the easternmost and geologically youngest features of the Himalayas. The Kangto Massif and Gorichen range dominate the horizons in the western and north-central sections of the state. Kangto is the highest peak in Arunachal Pradesh, at about 7,060 meters. Precursors to Kangto include Nyegi Kangsang and the mountain ranges and peaks that surrounded the Tawang district.
The eastern mountains in the Dibang Valley and Anjaw districts form the rest of the mountain ranges; these are the Mishmi Hills and the Dapha Bum range. These mountains have high biodiversity and features related to tectonic instability, such as landslides and erosion.
The Patkai Hills run along the eastern and southeastern border with Myanmar. It is less elevated than the main Himalayan chain and serves as a transition into the Southeast Asian hill system
River Systems
The landscape of Arunachal Pradesh is generally cut by numerous major river systems, the vast majority of which are tributaries of the Brahmaputra. These rivers all start either in glacial or partially glacial regions on the northern mountains and quickly cut large valleys in a southerly direction.
The Siang River, or what is now the upper section of the Brahmaputra as it enters India from Tibet (Yarlung Tsangpo), is probably the major river through the central areas, plunging into deep gorges and creating rich valleys before merging into the Brahmaputra in Assam.
The Subansiri River, through the western section, rises in the Indo-Tibetan border region and flows through the Upper Subansiri district where it is the lifeline of that territory. It also comprises a catchment area that in turn has many tributaries such as Kamla, Chayul and Rang.
To the east, the Lohit and Dibang rivers are also important. The Lohit rises in the eastern Himalayas of Tibet and flows eastwards through eastern Arunachal, where it merges with the Brahmaputra. The Dibang River, another large tributary, drains the Mishmi Hills and merges with the Lohit before entering the plains.
Other smaller, yet locally significant rivers that possess unique physical environments include the Kameng, Tawang Chu, and Noa-Dihing. These rivers have turbulent and rapidly flowing water due to steep gradients, which characterizes the suitability of the rivers for hydropower potential, as well as the hazards associated with seasonal flooding and landslides.
Valleys and Gorges
The rivers create several narrow and wider valleys, which provide the basis for habitation and agriculture. The Siang Valley, with its wider and fertile basin, can support a relatively larger population. The Subansiri and Dibang valleys are narrower but are river valleys with some agricultural importance.
A characteristic of the Himalayan foothills is deep gorges, with deep gorges occurring especially in the upper courses of the rivers. The Yarlung Tsangpo Grand Canyon, which is actually in Tibet but continues in the Siang River system in this region, is one of the deepest river gorges in the world. Deep gorges create dramatic landscapes that are not easy to travel through.
Climate Zones
The physical map displays a wide variety of climate zones from the north's alpine climate to the south's humid subtropical climate. The high altitudes in the north get long, cold winters, including snow cover, and temperatures in some areas drop below freezing for several months. Tundra-like vegetation is supported in the high altitudes with permafrost in some regions.
The mid-altitude regions are cooler with moderate to heavy rainfall. The rainfall increases heavily during the monsoons. This area predominantly supports temperate forests with a good variety of flora and fauna.
The southern plains and foothills have a humid subtropical climate with hot summers, lots of rainfall during the monsoon season, and relatively mild winters. These conditions support large amounts of tropical forests, bamboo forests, and agricultural production.
Soil Types and Landforms
The physical map also illustrates the types of soil and geological structure. There are rocky and skeletal soils in the northern highlands, which cannot be cultivated. The soils in the central hills are primarily loamy and sandy, where there is organic matter mixed in from the dense vegetation. The area practices shifting cultivation or "jhum".
In the plains of the south, there is plenty of fertile alluvial soil deposited by rivers, and wet rice and horticulture can be grown well in these areas. There is a downside to cultivating in these areas because they are also susceptible to soil erosion and siltation during the monsoon.
From a tectonic standpoint, the area is in the seismically active Himalayan belt. A very active area with frequent earthquakes, landslides, and flash floods that continually change and reform the physical space.
Natural Vegetation and Forest Cover
The diversity of topography and climatic conditions in the region has resulted in one of the richest forest covers in India. On physical maps, forest areas are typically shaded green, and over large areas, including tropical rainforests, subtropical pine forests, and alpine meadows.
The southern and later central belts are heavily forested and contain deciduous and evergreen trees, including sal, teak, bamboo, and cane. Higher up, coniferous forests contain pine, fir, and deodar. Higher than 4,000 m, only sparse vegetation, microorganisms, and hardy grasses are supported, with vegetation not even seen.
This rich forest cover provides the conditions for ecological stability as well as livelihoods through timber, non-timber forest products, and eco-tourism.
Glaciers and Snowfields
The extreme northern parts of the state, especially in the Tawang, West Kameng and upper Dibang Valley areas, have various small glaciers and snowfields of seasonal nature. Though limited in size when compared to the Himalayas in the western part of India, glaciers are significant to the river system and for the water table.
They are mainly located in places above 4500 meters. Most are melting, as a result of global warming. Glacial melt contributes to the flow of rivers throughout the year, but on the flip side adds to the probability of Glacial Lake Outburst Floods (GLOFs).
Strategic Passes and Border Geography
Many mountain passes connect the state with other borders and areas. They appear prominently on any physical map because of their altitude and strategic importance. Sela Pass (approximately 4170 metres), connects Tawang with other areas in the state thus improving access to the rest of Arunachal Pradesh and is snow-bound for several months out of the year.
Similarly, Bum La Pass lies near the Indo-China border and, like Sela, it has some historical significance, particularly during the 1962 Sino-Indian war. Most of the passes lead into India from other countries and, now that border areas are being developed, they have become all weather passes (if the climate is benign). Today, they are seen as gateways through the Himalayas and are being developed within the context of tourism and military supply issues.
Geological and Tectonic Setting
The geology of the region primarily consists of crystalline rock belonging to the Precambrian era, with portions overlain by sedimentary rock and metamorphic rock. Geologically, this complex mountainous region has the potential for seismicity to be common.
The area is located along significant thrusts, including two major features, the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT). These features indicate tectonic collision zones and tectonic movement. These features are critical in investigating the occurrence of earthquakes, mountain-building mechanisms, and shifts in river course.
FAQs
Q.1: What is shown on the physical map of Arunachal Pradesh?
It shows the state's natural features such as mountains, rivers, valleys, and elevation.
Q.2: Which mountain ranges are shown on the physical map?
The physical map displays the Eastern Himalayas, the Kangto and Patkai ranges.
Q.3: What is the highest peak in Arunachal Pradesh?
Kangto Peak, which is approximately 7,060 meters above sea level.
Last Updated on : June 11, 2025
