Eastern Himalaya
Encyclopedia
Eastern Himalaya is situated between Central Nepal
in the west to Myanmar
in the east, occupying southeast Tibet
in China, Sikkim
, North Bengal
, Bhutan
and North-East India
. The area has been declared a biodiversity hotspot
by Conservation International
.
are the Singalila Ridge
, the western end of a group of uplands as in Nepal known as the sub-Himalaya of the Bhutan. Most of the Sub-Himalayas are in Nepal
, a small range reaches into Sikkim, and a fragment comprises the southern half of the Bhutan
. The Buxa range of Indo-Bhutan belongs to the ancient rocks of the Himalaya. The ancient folds mainly along east-west axes were worn down, during a long period of denudation
lasting to cretaceous
times, possibly a hundred million years. During this time the carboniferous and Permian
rocks disappeared from the surface, except in the north near Hatisar in Bhutan and in the long trench extending from Jaldhaka River
to Torsa River
, where limestone
and coal
deposits are preserved in discontinuous basins. Limestones appear also in Bhutan on the southern flanks of lower Himalayas. The rocks of the highlands are mainly sandstones of the Devonian
age, with limestones and shales of the same period in places. The core of the mountain is exposed across the centre, where Paleozoic
rocks, mainly Cambrian
and Silurian
slate
s and Takhstasang gneiss, outcrop in the north-west and north-east, in the later extending into western region of Arunachal Pradesh
. In the Mesozoic
era the whole of the worn-down plateau was under sea. In this sea, which covered most of Assam
, Bhutan, chalk
was deposited as a result of oscillations between land and sea levels, during subsequent periods of the tertiary rocks were laid down. Paro
metamorphic belt may be found overlying Chasilakha-Soraya gneiss in some places. Silurian metamorphics in others shows that that there must be long denudation of the surface. This was the time of the Alpine
mountain building, and much of the movement in the palaeozoic region was probably connected with it. The Chomolhari tourmaline granites of Bhutan stretching westwards from the Paro chu, but at a greater depth below the present surface belong to this period of uplift, fracture and subsidence.
The effect of snow accumulation in the valleys of Rangeet
, Teesta
, Chumbi
is very remarkable in reducing the temperature. In winter, most of the precipitation falls in the form of snowfall. Thus the North-East monsoon is the predominant feature in Eastern Himalayan region, while on the southern slopes the cold season precipitation is more important.
, supplemented by hunting, fishing and barter trade are characteristics of the region. Agricultural produce is not sufficient for local feed. Economy remained stagnant for centuries due to lack of capital market, entrepreneurship and avenues of investment.
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
in the west to Myanmar
Myanmar
Burma , officially the Republic of the Union of Myanmar , is a country in Southeast Asia. Burma is bordered by China on the northeast, Laos on the east, Thailand on the southeast, Bangladesh on the west, India on the northwest, the Bay of Bengal to the southwest, and the Andaman Sea on the south....
in the east, occupying southeast Tibet
Tibet Autonomous Region
The Tibet Autonomous Region , Tibet or Xizang for short, also called the Xizang Autonomous Region is a province-level autonomous region of the People's Republic of China , created in 1965....
in China, Sikkim
Sikkim
Sikkim is a landlocked Indian state nestled in the Himalayan mountains...
, North Bengal
North Bengal
North Bengal is a term used for the northern parts of Bangladesh and West Bengal. The Bangladesh part denotes the Rajshahi Division. Generally it is the area lying west of Jamuna River and north of Padma River, and includes the Barind Tract. The West Bengal part denotes Cooch Behar, Darjeeling,...
, Bhutan
Bhutan
Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
and North-East India
North-East India
Northeast India refers to the easternmost region of India consisting of the contiguous Seven Sister States, Sikkim, and parts of North Bengal...
. The area has been declared a biodiversity hotspot
Biodiversity hotspot
A biodiversity hotspot is a biogeographic region with a significant reservoir of biodiversity that is under threat from humans.The concept of biodiversity hotspots was originated by Norman Myers in two articles in “The Environmentalist” , revised after thorough analysis by Myers and others in...
by Conservation International
Conservation International
Conservation International is a nonprofit organization headquartered in Arlington, Virginia, which seeks to ensure the health of humanity by protecting Earth's ecosystems and biodiversity. CI’s work focuses on six key initiatives that affect human well-being: climate, food security, freshwater...
.
Structure and relief
Eastern Himalaya has a more complex geographical history than the Central Himalaya and has a more varied relief. In the south west of the SikkimSikkim
Sikkim is a landlocked Indian state nestled in the Himalayan mountains...
are the Singalila Ridge
Singalila Ridge
The Singalila Ridge is a North - South running mountain ridge in Northwestern West Bengal, India.The district of Ilam falls on the western part of this ridge and the northern ridge ends up in Sikkim Part of the Himalayas, it separates other mountain ranges of West Bengal from other Himalayan...
, the western end of a group of uplands as in Nepal known as the sub-Himalaya of the Bhutan. Most of the Sub-Himalayas are in Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
, a small range reaches into Sikkim, and a fragment comprises the southern half of the Bhutan
Bhutan
Bhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
. The Buxa range of Indo-Bhutan belongs to the ancient rocks of the Himalaya. The ancient folds mainly along east-west axes were worn down, during a long period of denudation
Denudation
In geology, denudation is the long-term sum of processes that cause the wearing away of the earth’s surface leading to a reduction in elevation and relief of landforms and landscapes...
lasting to cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
times, possibly a hundred million years. During this time the carboniferous and Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
rocks disappeared from the surface, except in the north near Hatisar in Bhutan and in the long trench extending from Jaldhaka River
Jaldhaka River
The Jaldhaka River is a trans-boundary river with a length of 192 kilometres that originates in southeastern Sikkim in the eastern Himalayas and flows through Bhutan and the Darjeeling, Jalpaiguri and Cooch Behar districts of West Bengal, India...
to Torsa River
Torsa river
Torsa River rises from the Chumbi Valley in Tibet, China, where it is known as Machu. It flows into Bhutan, where it is known as the Amo Chu...
, where limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
and coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
deposits are preserved in discontinuous basins. Limestones appear also in Bhutan on the southern flanks of lower Himalayas. The rocks of the highlands are mainly sandstones of the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
age, with limestones and shales of the same period in places. The core of the mountain is exposed across the centre, where Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
rocks, mainly Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
and Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
slate
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. The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering...
s and Takhstasang gneiss, outcrop in the north-west and north-east, in the later extending into western region of Arunachal Pradesh
Arunachal Pradesh
Arunachal Pradesh is a state of India, located in the far northeast. It borders the states of Assam and Nagaland to the south, and shares international borders with Burma in the east, Bhutan in the west, and the People's Republic of China in the north. The majority of the territory is claimed by...
. In the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
era the whole of the worn-down plateau was under sea. In this sea, which covered most of Assam
Assam
Assam , also, rarely, Assam Valley and formerly the Assam Province , is a northeastern state of India and is one of the most culturally and geographically distinct regions of the country...
, Bhutan, chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
was deposited as a result of oscillations between land and sea levels, during subsequent periods of the tertiary rocks were laid down. Paro
Paro, Bhutan
-History:Rinpung Dzong a fortress-monastery overlooking the Paro valley has a long history. A monastery was first built on the site by Padma Sambhava at the beginning of the tenth century, but it wasn't until 1646 that Ngawang Namgyal built a larger monastery on the old foundations, and for...
metamorphic belt may be found overlying Chasilakha-Soraya gneiss in some places. Silurian metamorphics in others shows that that there must be long denudation of the surface. This was the time of the Alpine
Alpine orogeny
The Alpine orogeny is an orogenic phase in the Late Mesozoic and Tertiary that formed the mountain ranges of the Alpide belt...
mountain building, and much of the movement in the palaeozoic region was probably connected with it. The Chomolhari tourmaline granites of Bhutan stretching westwards from the Paro chu, but at a greater depth below the present surface belong to this period of uplift, fracture and subsidence.
Climate
The climate of Eastern Himalaya is characterized by cool summer and chilly winter. The hot season commences about the middle of April, reaches its maximum in the month of June and lasts till the end of August. The average temperature generally recorded is 20 C. The average rainfall in the area is about 500mm. Snowfall is a usual phenomenon in the higher altitudes.The effect of snow accumulation in the valleys of Rangeet
Rangeet River
Rangeet or Rangit is a tributary of the Teesta river, the largest river in the Indian state of Sikkim. The Rangeet river originates in the Himalayan mountains in West Sikkim district. A perennial river, it is fed by the melting snow of the Himalayas in early summer and the monsoon rains in...
, Teesta
Teesta River
River Teesta or Tista is said to be the lifeline of the Indian state of Sikkim, flowing for almost the entire length of the state and carving out verdant Himalayan temperate and tropical river valleys. The emerald-coloured river then forms the border between Sikkim and West Bengal before joining...
, Chumbi
Chumbi Valley
Chumbi Valley is a valley in Tibet at the intersection of India , Bhutan and China in the Himalayas. Two main passes between India and China open up here: the Nathu La Pass and Jelep La Pass....
is very remarkable in reducing the temperature. In winter, most of the precipitation falls in the form of snowfall. Thus the North-East monsoon is the predominant feature in Eastern Himalayan region, while on the southern slopes the cold season precipitation is more important.
Agriculture
Agriculture conditions vary in different parts of the region. In the highlands of Eastern Himalaya the soil is morainic, and the hill slopes are embanked into successive steps or terraces, only a few meters broad, on which spring crops are grown abundantly. Agriculture predominated by shifting cultivationShifting cultivation
Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned. This system often involves clearing of a piece of land followed by several years of wood harvesting or farming, until the soil loses fertility...
, supplemented by hunting, fishing and barter trade are characteristics of the region. Agricultural produce is not sufficient for local feed. Economy remained stagnant for centuries due to lack of capital market, entrepreneurship and avenues of investment.
Political divisions
Eastern Himalaya can be divided into four distinguished regions;- Darjeeling Himalaya
- Sikkim Himalaya
- Bhutan Himalaya
- Arunachal Himalaya
External links
- Eastern Himalayas – World Wildlife Fund projects