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Physical Geography of Myanmar

phy-geo-myan.htm

by U Kyaw Tun, et. al. based on Physical Geography of Southeast Asia edited by Avijit Gupta, Oxford Univ. Press, 2005, ISBN 0199248028, 9780199248025, 440 pages. Downloaded from: http://books.google.ca/books?Physical+geography+of+Southeast+Asia  080922.
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Burmese-Myanmar (Bur-Myan) spellings in both Myanmar script and in Romabama and are included. Romabama spellings are within { }, and words within < > are regular English words. You'll need only Arial Unicode MS font to read these files. Any other Unicode font may not display the characters correctly.

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geo-indx.htm

Contents of this page

Introduction
Getting your bearings
Geological Framework
Landforms of Southeast Asia

UKT notes
Paungsau Pass - an invasion route
• Proto-Irrawaddy River entering the Gulf of Martaban

Contents of this page

Introduction

UKT: The most prominent geological feature is Mount Popa, and to get your bearings in a map of Myanmar look for it. If it is not marked, figure out where it should be: 20.92 deg. N., 95.25 deg. E.

In the East such a prominent feature must have a guardian spirit or Nat {nût}. Do not confuse {nût} with {dé-wa.}. {nût} is Bur-Myan, and is the spirit of a dead ancestor who still guards his children. It is akin to the ancient Roman idea of Manes - the good ones. The bad ones are the Lemures - something like the modern poltergeist. See: Roman Household Spirits, Ancient History Encyclopediahttp://ancient.eu.com/article/34/ 111112. The {dé-wa.} on the other hand, is a Buddhist idea. Of course, the man on the street - the common man - and the foreign news writer who usually speaks with him during a hasty trip to Myanmar to write an "authoritative report to the world press" would be confused when the two words are put together: {nût dé-wa}.

The guardian spirits of Mt. Popa are the Lord of the Great Mountain, who was a blacksmith in his worldly life, and his sister. That even the guardian Nat was a blacksmith is a testimony to the abundance of metal deposits, particularly copper and zinc, in the land. My paternal great-grandfather, U Yan Shin, and his father Hpo Tagaung, and his uncle Hpo Mintha had worshiped the Brother and Sister Nats, and I still regard them as my ancestors and I still have a shrine to them in my home in Yangon, 35 Thantada St., Sanchaung. Do not think, the Brother Nat had six hands. No! He had only two, but he was a blacksmith so the artist must show one hand holding a hammer. He was appointed a minister by the king, and so the artist added another to hold the official fan.

Mt. Popa is not shown on the map below. But we could imagine that the area was a low lying area through which the old Irrawaddy (Proto-Irrawaddy) river had flowed, until the volcano arose raising the land around it cutting the old Irrawaddy into two: the Samon {sa.moan hkyaung:} flowing to the north, and Sittang {sic-taung:mric} river to the south to empty into the Gulf of Martaban. The modern administrative capital, Naypyitaw, lies to the east of the old Proto-Irrawaddy river.

 

UKT: Pushing into the history of Myanmar as far back as possible, I have landed myself in the geological ages when presumably there were no humans as we know of them today. The present work is mainly from Physical Geography of Southeast Asia edited by Avijit Gupta, Oxford Univ. Press, 2005, ISBN 0199248028, 9780199248025, 440 pages. Of course, there are my additions, and since I intend this to be a seamless narrative, the portions that have been added would get lost in the original text. However, I must emphatically add, I have no intention of masquerading my additions as those authenticated by the authors of the original text. The same goes for the pictures and maps from which I have taken only the part that is of interest. Some of these have been linked to the originals. Try clicking on them and you may come up with the original.

Note: Since, Ma = million years ago, the time frame of formation of what we now know as Myanmar is 1 to 100 million years ago - roughly the Cenozoic. For time-frame see permian.htm

Contents of this page

Getting your bearings

To appreciate the maps given, I always refer to the latitude 20°N where we find the most prominent landmark of the region, Mount Popa {poap~pa:taung}, 20.92°N 95.25°E, summit elevation 4,980 feet (1518 m).  The name is a combination of two words {poap~pa:} + {taung} 'mountain'. It is an extinct volcano, which according to local legends last erupted in 442 BC. -- info from: http://www.volcano.si.edu/world/volcano.cfm?vnum=0705-08- 080923.  Seismic activity is rare. In my almost 80years of life, I have known only two major earthquakes, the first one locally known as the Pegu earthquake of 1935, and the second the Pagan earthquake of 1975. There was only a single loss of life during the Pegu earthquake and not a single one during the Pagan earthquake.

UKT personal note: It was reported in New York Times to the effect that "Rangoon, the capital and largest city of Burma, in the southern part was heavily damaged with heavy loss of life by an earthquake and tsunami on May 5 1930,". The fact was at that time, my parents U Tun Pe and Daw Hla May, were in Kungyangon, now incorporated into Greater Rangoon (aka Yangon). My wife Daw Thanthan Tun was born that year in 31 Thantada St., Kemmendine (now Sanchaung), Rangoon. Yet, no one in both my family and my wife's has ever told me such "news" as reported in New York Times. I have read the reprint of that article, but as of today (2011 Nov 12), I could not get hold of it. However, you can see on the Internet reports such as : http://jtic.org/index.php?view=details&id=3052&pop=1&tmpl=component&option=com_eventlist&Itemid=523&lang=en

Mount Popa, {poap~pa:taung}, has stood like a sentinel overlooking the land of Myanmarpré for about 2500 years. Of course, as is common in the East such a prominent feature must have a guardian spirit or nat {nût}. The guardian spirits are the Lord of the Great Mountain, who was a blacksmith in his worldly life, and his sister. That even the guardian nat was a blacksmith is a testimony to the abundance of metal deposits, particularly copper and zinc, in the land.

The nearest major town to Mt. Popa is Meiktila {mait~hti-la mro.}, 20°53'N, 95°53' E. ( http://en.wikipedia.org/wiki/Meiktila 080923). You may also use its coordinates instead of those of Mt. Popa in studying the maps.

The second mountain to fix your position is Mount Victoria 21°14'N, 93°54'E, elevation: 3053m or 10,016ft, in the Chin Hills. --  http://www.peakbagger.com/peak.aspx?pid=10950 100802.

Mt. Vitoria is also known as NatMa Taung {nût-ma. taung}, also as Khaw-nu-soum or Khonuamthung in Chin. It is the highest mountain in the Chin State of western Myanmarpré. Located in Kanpalet Township,Mindat District, Mount Victoria is part of the Chin Hills range, and rises to 3,053 metres (10,016 ft) above sea level. Nat Ma Taung lies in the Chin Hills-Arakan Yoma montane forests ecoregion.

Surrounded at lower elevations by tropical and subtropical moist forests, Nat Ma Taung's higher elevations form a sky island, home to many temperate and alpine species typical of the Himalaya further north, as well as many endemic species. The mountain is now protected within Nat Ma Taung National Park, established in 1994. - http://en.wikipedia.org/wiki/Nat_Ma_Taung 100802.

Nat Ma Taung {nût-ma. taung} aka Mt. Victoria is an ultra prominent peak, or Ultra for short, is a mountain with a topographic prominence of 1,500 metres (4,921 ft) or more. There are a total of roughly 1,515 such peaks in the world. [1] Some are famous even to non-climbers, such as Mount Everest, Aconcagua (Andes Mountain range) and Denali (aka Mt. McKinley, Alaska) (the top three by prominence), while others are much more obscure. Not all famous peaks, such as the Matterhorn and Eiger, are not Ultras because they are connected to higher mountains by high passes and therefore do not achieve enough topographic prominence. - http://en.wikipedia.org/wiki/Ultra_prominent_peak 130102

Another location you can use to fix your coordinates is [from: http://en.wikipedia.org/wiki/Mandalay 100723] Mandalay {mûn~ta.lé: mro.}, 21°59'N, 96°5'E. (Though commonly referred to as Mandalay {mûn~ta.lé:}, it is better to specify if its the {mro.} 'city' or {taung} 'hill or mountain' you are referring to.) lies along the Sagaing Fault, a tectonic plate boundary between the India and Sunda plates. (The biggest earthquake in its history, with a magnitude of 7, occurred in 1956. [Wiki info from: Christophe Vigny et al.. "Present-day crustal deformation around Sagaing fault, Myanmar" (PDF). Journal of Geophysical Research, vol 108, 19 November, 2003. pp. 2–4. http://www.geologie.ens.fr/~vigny/articles/2002JB001999.pdf. Retrieved 2009-01-25. I, in Rangoon, have but a faint recollection of it. Presumably there was no loss of life. UKT100723]. The devastation however was greatest in nearby Sagaing, and it came to be known as the Great Sagaing Quake.)

Contents of this page

Chapter 1. The Geological Framework by Charles S. Hutchison

General Plate Tectonics, p.003: The Indo-Australian Plate is converging at an average rate of 70 mm a-1 in a 003° direction, pushed from the active South Indian Ocean spreading axis. For the most part, it is composed of the Indian Ocean, formed of oceanic sea-floor basalt overlain by deep water. It forms a convergent plate margin with the continental Eurasian Plate, beneath which it subducts at the Sunda or Java Trench.

The Eurasian continental plate protrudes as a peninsular extension (Sundaland) southwards as far as Singapore, continuing beneath the shallow Straits of Malaca and the Sunda Shelf as the island of Sumatra and the northwestern part of Borneo (Figure 1.1 - UKT: I have taken the part related to Myanmar, the reader is adviced to consult the original map.)

Indian Ocean, p.003: Based on magnetic anomaly identification, calibrated by drill site data, three distinct episodes of sea-floor spreading can be discerned (Curry et al. 1982).

1. Anomalies M10 to M25 (Neocomian-Oxfordian) have been identified (Heirtzler et.a. 1978) in the Argo Abyssal Plain, beneath the Sunda (Java) Trench and western Australia (Fig.1.3. UKT: I have left out this figure because it is not relevant to Myanmar). ... [{p003end - p007begin}]

2. The spreading pattern was completely reorganized between magnetic anomalies M0 and 34, which is the Cretaceous magnetic quiet period (110-80 Ma ago). From anomaly 34 to 19 (84-44 Ma ago) India made its spectacular rapid northwards flight with rates of 15 to 17 cm a-1: the anomalies are aligned east-west, offset by major north-south transform faults. One of the faults is the Investigator Ridge; others lie close to and parallel to the Ninety-East Ridge.

The prominent Nine-East Ridge is the trace of a single mantle hotspot, which now lies under the Kerguelen Plateau in the south Indian Ocean. The furthest end of it is the Rajmahal Traps, 200 km north-northwest of Calcutta, where the basalt has an age of 105 Ma. The average rate of relative motion of the hotspot trace was about 11 cm a -1 (Curray et. al. 1982).

3. Around magnetic anomaly 19 time (44 Ma ago), spreading completely ceased at the Wharton Ridge in the northern Indian Ocean (Curray and Munasinghe 1989). This striking event in Southeast Asia coincides with the prominent widespread unconformity within the Bengal Fan and with the unconformable continental beginning of many Southeast Asian Cenozoic basins (e.g. Central Sumatra.) ...


[UKT: It is interesting to note that the above map shows at least eight extinct volcanoes in Myanmarpré, however only three extinct volcanoes are listed in Wikipedia.].

Bengal and Nicobar Fans, p007: The Bay of Bengal contains the largest subaerial delta in the world, the Ganga-Brahmaputra [UKT: roughly the area of present day Bangladesh], filling the Bengal Basin, grading outwards into the Bay of Bengal and  Nicobar Deep Sea Fans, the largest turbidity complex in the world. ... Most of the fan sediments have been derived by erosion of the Himalaya Mountains and transported by the two great rivers.

Active Plate Margins, p007: A nearly continuous arc-trench convergent plate margin extends throughout the region. The correct terminology of the direction is that an observer, standing on the volcanic arc and facing the related trench, has the fore-arc in front of him and the back-arc behind. Fore-arc sedimentary basins lie between the volcanic arc and the accretionary prism. All the deep marginal basins and the oil- and gas-producing sedimentary basins, characterized by shallow-water sediments, lie in the back-arc. Hence the term 'back-arc basin' is of such diversity as to be useless for the petroleum industry [Hutchison 1996b]. In Myanmar the plate margin has been uplifted to form the Indo-Burman Ranges because of the collision of India to the west and the volcanic arc [{p007end}] through Mount Popa is extinct. However, an active plate margin continues southwards west of the Andaman Sea, west of Sumatra, and south of Java, curving northwards in the Banda Sea (Figure 1.4). ...

Myanmar, p009: Cratonic India began its collision with Asia around 50 Ma ago and rotated anticlockwise to cause a major indentation at the Assam-Yunnan syntaxis. Subduction was converted to collision, and the acretionary prism active along the length of Sumatra was strongly uplifted to form the Indo-Burman Ranges, immediately west of which Precambrian India outcrops in the Shillong Plateau and Mikir Hills of Assam (Fig.1.5). Accretionary prism and trenches (subduction systems) are known to be regions of low geothermal gradient. Accordingly an uplifted and eroding accretionary prism should contain outcrops of glaucophane shist (low-temperature-high-pressure metamorphism) and they have been described from several locations in the Naga Hills (Hutchison 1989). Discontinuous bodies of ophiolite, representing dismembered oceanic basement, also occur along the eastern margin of the ranges. The Indo-Burman Ranges accordingly have all the characteristics of a suture, or uplifted plate margin, formed between India and the Burma Plate (Hutchison 1975).

UKT: Fig.1.5. shows the presence of two north-south troughs in Myanmar through which the Chindwin and Irrawaddy rivers flow. Originally, the Irrawaddy flowed due south and became the Sittang and emptied into the Gulf of Martaban. However, at one time, the land rose about the area north of Pyinmana due to which the Irrawaddy turned west (near Mandalay) and combines with Chindwin, and finally empties into the sea forming a large delta.
   From the area north of Pyinmana, a relatively small stream known as the Samoan flows northwards and empties into the Irrawaddy near Mandalay. The Sittang, now reduced to a minor river continues to flow southwards and empties into the Gulf of Martaban. (These statements of mine still to be checked my peers.)

The volcanic rocks lie on three distinct lines (Chhibber 1934; Stephenson and Marshall 1984). The Western Line, through Narcondam and Barren Islands is tholeitic and still active. The Central Line, through Mount Popa [UKT: Mount Popa, 20°52'N 95°14'E, is the most prominent landmark], is calc-alkaline and high-K calc-alkaline and extinct in the Pleistoncene. The volcanoes of this line are subduction-related and the Benioff zone was easterly dipping. An Eastern Line, through Thaton and Madaw Island, is alkaline and probably related to continental rifting in the back-arc area related to the Sagaing-Namyin Fault system. A broad zone of earthquakes, wedge-shaped in east-west cross-section, extends eastwards from the western margin of the Indo-Burman Ranges, but there is no longer any well-defined Benioff zone. A formerly eastwardly dipping is inferred because the earthquakes become deeper eastwards.

The Burma or West Burma Plate is bounded on the west by the Indo-Burman Ranges suture, and on the east by the Sagaing right-lateral wrench fault, beyond which the terrain of the Shan Highlands belongs to the Sinoburmalaya or Sibumasu Plate, a northward continuation of western Thailand, western Penninsular Malaysia, and part Sumatra. Most of the Burma Plate is covered by Cenozoic strata, deposited in basins formed in the fore-arc (the Interdeep or Western Trough) and the back-arc (the Back Deep or Eastern Trough), but these terminologies are not useful because the collision of India on the west has caused a change from a convergent plate margin to a collison zone from the [{p009end-p011begin}] Eocene onwards. The sediments were from the proto-Irrawaddy River, confined to a southerly course towards the sea in the Gulf of Martaban, where the strata contain significant productive gas deposits.

Contents of this page

Chapter 3. Landforms of Southeast Asia by Avijit Gupta

 
Note: The above Gupta-fig3-4-w500.jpg is to be converted to .gif and edited. -- UKT130216

Introduction, p038 : ... This assemblage of landforms has resulted from a combination of plate tectonics, Pleistocene history, Holocene geomorphic processes, and anthropogenic modifications of the landscape. Most of the world has been shaped by such a combination, but unlike the rest of the world, in Southeast Asia all four are important. The conventional wisdom of a primarily climate-driven tropical geomorphology is untenable here. The first two factors, plate tectonics and the Pleistocene history, have been discussed in Chapters 1 and 2 respectively. In the Holocene, Southeast Asia has been affected by the following phenomena:

• The sea rose to its present level several thousand years ago

• The present natural vegetation, a major part of which includes a set of rainforest formations, achieved its distribution

• A hot and humid climate became the norm, except in the high altitudes and the extreme northern parts.

• The dual monsoon systems blowing from the northeast hemispheric winter which is dry making the trees shed their leaves] and from the southwest in the summer (and in general producing a large volume of precipitation)  became strongly developed.

UKT 130216:
The monsoons are marked by general changes in the wind directions. During what to us is winter, we get "North wind" {mrauk-lé} -- which is not the cold polar wind. This brings us what we call the Himalayan Rasi. Temperatures can drop to 10 deg C. even in a place like Mandalay. During such times we can get ground frost in Pyin-U-lwin (formerly Maymyo) and Taunggyi. In summer, the wind usually enters the country from the south-west. But once inland it changes direction due to the mountain ranges. We call it the "South wind" {taung-lé} which brings in heavy rains - the rice growing season in the Irrawaddy delta.

 

 

• Countries away from the equator (Myanmar, VietNam, and the Philippines) became prone to tropical storms, which could reach hurricane force.
• Anthropogenic alteration of vegetation, slopes, and river systems intensified over the last 200 years.

UKT: Myanmar (but not VietNam nor the Philippines) is protected from the cold north winds by the high mountain ranges. These rugged  mountains also protect the country from alien armies coming in from China and India. Thus chariot warfare (used in India as vividly described in the Mahabharata Epic) was unknown in the country. Bows and arrows (used extensively both in India and China) were generally ineffective because of dense vegetation. The form of warfare known in the country was the use of elephant calvary and the main weapon used was the hand-thrown spear. Also used was the single edged sword. The vegetation in these mountain ranges harbour a very virulent form of malaria which can kill a victim overnight and a form of diarrhea which attacks all those who come into these parts from the lowlands. See Tertian malaria - the sentinel of Myanmar - malaria.htm.

Of course such sudden deaths give rise the stories of powerful guardian Nats who must be appropriated by people coming into the regions. The word for malaria in Bur-Myan is {nghak-hpya:}.

The northern part of the country was well protected from armies crossing over from India or China as the British and Americans came to know during World War II. The is an excerpt from Wikipedia http://en.wikipedia.org/wiki/Ledo_Road 100722:
   "In the nineteenth century British railway builders had surveyed the Pangsau Pass, which is 3,727 feet (1,136 meters) high on the India-Burma border, on the Patkai crest, above Nampong, Arunachal Pradesh (then part of Assam). They concluded that a track could be pushed through to Burma and down the Hukawng Valley. Although the proposal was dropped, the British prospected the Patkai Range for a road from Assam into northern Burma. British engineers had surveyed the route for a road for the first eighty miles. After the British had been pushed back out of most of Burma by the Japanese, building this road became a priority for the United States. After Rangoon was captured by the Japanese and before the Ledo Road was finished, the majority of supplies to the Chinese were delivered via airlift over the eastern end of the Himalayan Mountains known as the Hump." 


UKT: The area known as the Hump is the topmost part of Myanmarpré. Myitkyina is the capital of Kachin State in the far north of the country located 1480 km from Yangon or 780 km from Mandalay. It is just less than 42 km of Myit_Sone, the confluence of two headstreams (MaiKha and MaliKha). It is the northernmost of the river port and rail terminal in Myanmar.

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UKT notes

Paungsau Pass - an invasion route

From: http://en.wikipedia.org/wiki/Pangsau_Pass 090929

Pangsau Pass, 3727 feet in altitude, lies on the crest of the Patkai Hills on the India-Burma (Myanmarpré) border. The reputed route of the 13th century invasion of [northern] Assam in India by the Ahoms, a Shan tribe, the pass offers one of the easiest routes into Burma from the Assam plains. Prospected by the British in the late 19th Century as a possible railway route from India to Myitkyina in north Burma through the Hukawng Valley, the pass became famous during World War II for being the initial obstacle encountered by American General "Vinegar Joe" Stilwell's forces in their effort to build a land route to isolated China after the fall of Burma to the Japanese. The Ledo Road began at Ledo, the railhead, and passed through Lekhapani, Jagun, Jairampur (the Assam- Arunachal Pradesh boundary and beginning of Inner Line), and Nampong before switchbacking [using hairpin turns] steeply upwards through densely forested hills to the pass, 12km away. The distance from Ledo to Pangsau Pass is 61 km (38 miles). Because of the fierce gradients and the mud which made getting up to the pass difficult, it was nicknamed "Hell Pass" during the war. The first Burmese village, Pangsau, lies 2 km beyond the pass to the east.

Go back Paungsau-pass-note-b

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