] The Eastern Himalayas extend from eastern

Nepal Nepal (; ne, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne, सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in South Asia. It is ma ...

across

Northeast India , native_name_lang = mni , settlement_type = , image_skyline = , image_alt = , image_caption = , motto = , image_map = Northeast india.png , ...

Bhutan Bhutan (; dz, འབྲུག་ཡུལ་, Druk Yul ), officially the Kingdom of Bhutan,), is a landlocked country in South Asia. It is situated in the Eastern Himalayas, between China in the north and India in the south. A mountainou ...

, the

Tibet Autonomous Region The Tibet Autonomous Region or Xizang Autonomous Region, often shortened to Tibet or Xizang, is a province-level autonomous region of the People's Republic of China in Southwest China. It was overlayed on the traditional Tibetan regions ...

Yunnan Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

and northern

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

. The climate of this region is influenced by the

monsoon of South Asia The Monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year fro ...

from June to September. It is a

biodiversity hotspot A biodiversity hotspot is a biogeographic region with significant levels of biodiversity that is threatened by human habitation. Norman Myers wrote about the concept in two articles in ''The Environmentalist'' in 1988 and 1990, after which the c ...

, with notable biocultural diversity.

Geologic strata

The Eastern

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 10 ...

have a much more sophisticated geomorphic history and pervasive topographic features than the Central Himalayas. In the southwest of the Sub-Himalayas lies the

Singalila Ridge The Singalila Ridge is a north–south mountain ridge running from northwestern West Bengal through Sikkim in the Indian part of the Himalayas. The district of Ilam in Nepal falls on the western part of this ridge. The ridge separates mountain r ...

, the western end of a group of uplands in Nepal. Most of the Sub-Himalayas are in Nepal; a small portion reaches into Sikkim, India and a fragment is in the southern half of Bhutan. The region's topography, in part, has facilitated the region's rich biological diversity and ecosystem structure. The Buxa range of Indo-Bhutan is also a part of the ancient rocks of the Himalayas. The ancient folds, running mainly along an east-west axis, were worn down during a long period of

denudation Denudation is the geological processes in which moving water, ice, wind, and waves erode the Earth's surface, leading to a reduction in elevation and in relief of landforms and landscapes. Although the terms erosion and denudation are used interc ...

lasting into

cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

times, possibly over a hundred million years. During this time the

carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...

and

permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...

rocks disappeared from the surface, except in its north near Hatisar in Bhutan and in the long trench extending from

Jaldhaka River The Jaldhaka River (Pron:/ˌdʒælˈdɑːkə/) ( bn, জলঢাকা নদী), also known as Dichu, a tributary of Brahmaputra is a trans-boundary river flowing through India, Bhutan and Bangladesh with a length of 233 kilometres. It ori ...

to Torsa River, where

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

deposits are preserved in discontinuous basins. Limestone deposits also appear in Bhutan on the southern flanks of the Lower Himalayas. The rocks of the highlands are mainly

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

of the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

age, with limestones and shales of the same period in places. The core of the mountain is exposed across the centre, where

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...

rocks, mainly

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

and

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...

slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. ...

s and Takhstasang gneiss outcrops are visible in the northwest and northeast, the latter extending to western

Arunachal Pradesh Arunachal Pradesh (, ) is a state in Northeastern India. It was formed from the erstwhile North-East Frontier Agency (NEFA) region, and became a state on 20 February 1987. It borders the states of Assam and Nagaland to the south. It shares ...

in India. In the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

era the whole of the worn-down plateau was under sea. In this expansive shallow sea, which covered most of

Assam Assam (; ) is a state in northeastern India, south of the eastern Himalayas along the Brahmaputra and Barak River valleys. Assam covers an area of . The state is bordered by Bhutan and Arunachal Pradesh to the north; Nagaland and Manipur ...

and Bhutan,

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. C ...

deposits formed from seawater tides oscillating between land and sea levels. During subsequent periods, tertiary rocks were laid down. The Paro metamorphic belt may be found overlying Chasilakha-Soraya gneiss in some places. Silurian metamorphics in other places suggest long denudation of the surface. This was the time of

Alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National P ...

mountain and large number of "active volcanoes" formation which act as backbone of the Himalayas and much of the movement in the

palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and '' ...

region was probably connected with it. The Chomolhari tourmaline granites of Bhutan, stretching westwards from the Paro Chu and adds much depth below the present surface, were formed during this period of uplift, fracture and subsidence.

Climate

The climate of the Eastern Himalayas is of a tropical

montane ecosystem Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial f ...

. The tropical rainforest climate is hot and wet all year round, with no dry season in the foothills in Köppen Climate Classification System ( Af), and chilly winters mainly on higher elevations. The hot season commences around the middle of April reaching its maximum temperature in June, and finishing by the end of August. The average summer temperature is generally . The average annual rainfall is 10,000 mm (390 inches). A significantly large amount of snowfall is rare, and it is uncommon even at higher elevations. This belt of Himalayas is wetter as it receive more rain than the drier Western Himalayas. In the valleys of

Rangeet The Rangeet or Rangit is a tributary of the Teesta river, which is the largest river in the Indian state of Sikkim. The Rangeet river originates in the Himalayan mountains in West Sikkim district. The river also forms the boundary between ...

Teesta Teesta River is a long river that rises in the Pauhunri Mountain of eastern Himalayas, flows through the Indian states of Sikkim and West Bengal through Rangpur, and enters the Bay of Bengal. It drains an area of . In India, it flows th ...

, and Chumbi most precipitation during winter takes the form of snowfall. Snow accumulation in the valleys greatly reduces the area's wintertime temperature. The northeast monsoon is the predominant feature of the Eastern Himalayan region's weather, while on the southern slopes cold season precipitation is more important.

Agriculture

Agricultural conditions vary throughout the region. In the highlands the soil is

morainic A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice she ...

, and the hill slopes are cut by the locals into successive steps or terraces only a few meters broad, thus preventing water run-off and allowing spring crops to thrive. The region's economy relied mostly on

shifting cultivation Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned while post-disturbance fallow vegetation is allowed to freely grow while the cultivator moves on to another plot. The period of cu ...

agriculture, supplemented by hunting, fishing and barter trade. Agricultural does not produce sufficient yields to meet local needs. The region's economy remained stagnant and at

subsistence A subsistence economy is an economy directed to basic subsistence (the provision of food, clothing, shelter) rather than to the market. Henceforth, "subsistence" is understood as supporting oneself at a minimum level. Often, the subsistence econo ...

levels for centuries due to the lack of capital, investor access, or entrepreneurial knowledge. Inhabitants also relied heavily on wild and semi-cultivated species for food and herbal medicines.

Political divisions

The Eastern Himalayas consist of 6 distinct political/national territories: *

i Himalaya (central, eastern and southern Nepal) * Darjeeling Sub-Himalaya * Sikkim (Indian) Himalaya *

Sub-Himalaya *

Himalaya *

Himalaya * Garhwal/Kumaon Himalaya

Wildlife

The Eastern Himalayas sustain a diverse array of wildlife, including many rare species of fauna and flora. Wildlife in Nepal includes

snow leopard The snow leopard (''Panthera uncia''), also known as the ounce, is a felid in the genus '' Panthera'' native to the mountain ranges of Central and South Asia. It is listed as Vulnerable on the IUCN Red List because the global population is es ...

in its Himalayan region, and

Indian rhinoceros } The Indian rhinoceros (''Rhinoceros unicornis''), also called the Indian rhino, greater one-horned rhinoceros or great Indian rhinoceros, is a rhinoceros species native to the Indian subcontinent. It is listed as Vulnerable on the IUCN Red Li ...

Asian elephant The Asian elephant (''Elephas maximus''), also known as the Asiatic elephant, is the only living species of the genus '' Elephas'' and is distributed throughout the Indian subcontinent and Southeast Asia, from India in the west, Nepal in t ...

and

water buffalo The water buffalo (''Bubalus bubalis''), also called the domestic water buffalo or Asian water buffalo, is a large bovid originating in the Indian subcontinent and Southeast Asia. Today, it is also found in Europe, Australia, North America, So ...

in the foothills of the Himalayas, making the country one of the world's greatest

s. Three major river basins of Nepal, namely the

Ghaghara Ghaghara, also called Karnali, is a perennial trans-boundary river originating on the Tibetan Plateau near Lake Manasarovar. The Karnali cuts through the Himalayas in Nepal and joins the Sharda River at Brahmaghat in India. Together they f ...

Gandaki River The Gandaki River, also known as the Narayani and the Gandak, is one of the major rivers in Nepal and a left bank tributary of the Ganges in India. Its total catchment area amounts to , most of it in Nepal. In the Nepal Himalayas, it is notab ...

and

Koshi River The Kosi or Koshi ( ne, कोशी, , hi, कोसी, ) is a transboundary river which flows through China, Nepal and India. It drains the northern slopes of the Himalayas in Tibet and the southern slopes in Nepal. From a major conflue ...

basins, feature dense forests and provide habitat for

butterfly Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group compris ...

species and 8% of the world's bird species. Preserving this diverse wilderness is essential for the area's and the world's biodiversity. The area has many ecological projects intended to ensure the survival and growth of many species. The most diverse

cloud forest A cloud forest, also called a water forest, primas forest, or tropical montane cloud forest (TMCF), is a generally tropical or subtropical, evergreen, montane, moist forest characterized by a persistent, frequent or seasonal low-level cloud ...

is in India and China at , and

tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equator ...

on the lower slopes up to in the foothills. At higher elevations, wet

páramo Páramo () can refer to a variety of alpine tundra ecosystems located in the Andes Mountain Range, South America. Some ecologists describe the páramo broadly as "all high, tropical, montane vegetation above the continuous timberline". A narrowe ...

grasslands occur up to ), and above this elevation snow and ice occupies the space.

Asian black bear The Asian black bear (''Ursus thibetanus''), also known as the Asiatic black bear, moon bear and white-chested bear, is a medium-sized bear species native to Asia that is largely adapted to an arboreal lifestyle. It lives in the Himalayas, so ...

Himalayan vulture The Himalayan vulture (''Gyps himalayensis'') or Himalayan griffon vulture is an Old World vulture native to the Himalayas and the adjoining Tibetan Plateau. It is one of the two largest Old World vultures and true raptors. It is listed as Near T ...

, and

pika A pika ( or ; archaically spelled pica) is a small, mountain-dwelling mammal found in Asia and North America. With short limbs, very round body, an even coat of fur, and no external tail, they resemble their close relative, the rabbit, but wi ...

s are common around higher elevations, and also on the Tibetan plateau.

Arunachal macaque The Arunachal macaque (''Macaca munzala'') is a macaque native to Eastern Himalayas of Bhutan, China and India. It is listed as Endangered on the IUCN Red List. It was scientifically described in 2005. It is a relatively large brown pr ...

(''Macaca arunachalensis'') and

Rhesus macaque The rhesus macaque (''Macaca mulatta''), colloquially rhesus monkey, is a species of Old World monkey. There are between six and nine recognised subspecies that are split between two groups, the Chinese-derived and the Indian-derived. Generally ...

(''M. mulatta'') live in the tropical cloud forests, alongside various

sunbird Sunbirds and spiderhunters make up the family Nectariniidae of passerine birds. They are small, slender passerines from the Old World, usually with downward-curved bills. Many are brightly coloured, often with iridescent feathers, particularly ...

and

pheasant Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera native range is restricted to Eurasia ...

species. Himalayan high-elevation wetlands are also notable for their biodiversity. The picture seen right is of the national flower of Bhutan ''

Meconopsis ''Meconopsis'' is a genus of flowering plants in the poppy family Papaveraceae. It was created by French botanist Viguier in 1814 for the species known by the common name Welsh poppy, which Carl Linnaeus had described as ''Papaver cambricum''. ...

gakyidiana'', commonly called the blue poppy. This flower was the source of an ecological mystery for nearly a century, due to its misclassification as ''Meconopsis grandis''. In 2017, after three years of field work and taxonomic studies, its classification was corrected by Bhutanese and Japanese researchers. It was theorised this misclassification may have arisen due to the finding that some Himalayan flora readily hybridize with each other and produce viable seeds, causing wider morphological diversity.

References

External links

{{commons category, East Himalaya
Eastern Himalayas
– World Wildlife Fund projects . 01 Mountain ranges of Asia Mountain ranges of India Mountain ranges of Myanmar Mountain ranges of Nepal Mountain ranges of Pakistan Mountain ranges of Tibet East Asia Regions of India Regions of Myanmar Regions of Nepal Physiographic divisions