3 PHYSIOGRAPHIC REGIONS [3 regions]
As was discussed in the previous lesson, South Asia is a physically [ssphys] well defined realm with the Himalayan mountains to the north, the Karakoam and Hindu Kush mountains to the northwest deserts to the west, and dense forest and hills along the Burmese (Myanmar) border to the east. South Asia spans a large area and contains great physical variety.
Much of the subcontinent is tropical [wwtropic] [ssclimat]; only at higher elevations in the north and northwest is frost common. The main climatic variable is the amount of precipitation [ssprecip] and its seasonally.
The landforms of the subcontinent are divided into three major physical regions [ssphyreg]:
The Northern Mountains [ssphyreg]
Several mountain ranges comprise the northern margins of the subcontinent, forming a mountain barrier that is one of the most formidable barriers in the world. The height and magnitude of these mountains exceed that of others and its geology indicates massive compressional and stress forces at work. The Himalayas are a result of plate tectonics; the Indian subcontinent once was connected to Africa [fit] ; eventually it split apart and this continental crust slammed into the Eurasian continent producing the Himalayas [india] [ssphys]. The Pamirs and the Hindu Kush are major ranges that are a part of this mountain chain. These mountains have been an effective barrier between Indian and Chinese realms. India has long exchanged ideas and goods more with Middle Eastern civilizations than with East Asia.
[TOP]
The River Lowlands [ssphyreg]
The neighboring plains [ssphys] of the Indus, Ganges, and Brahmaputra Rivers are among the most significant physical features of South Asia. They form the heartland of ancient Hindu civilizations [wwhearth]. The drainage systems comprise the largest continuous alluvial plain on Earth covering over 300,000 square miles. Today the Indo-Gangetic Plain supports roughly half of the population of South Asia. The Ganges and Brahmaputra form a physiographic region called the North Indian Plain [ssphyreg], while the Indus River lowlands are called the Punjab [sspak]. Precipitation [ssprecip] declines from east to west with the Indus River crossing essentially a desert (Thar) [ssphys].
[top]
Southern Plateaus [physical regions]
Peninsular India is a plateau tilted up on the west to elevations [sselev] that exceed 6,000 feet and sloping gently eastward. Coastal plains are narrow and abrupt escarpments [ssphys] fringe both coasts (Eastern and Western Ghats). The Deccan Plateau contains most of the mineral wealth of India: copper, iron, gold least, manganese and coal. Poor soils and water shortages are an intermittent problems.
[The text of the above was written by Scott Girhard, San Antonio College from his online course GEOG 1301 World Geography. Used with permission.]
[TOP]
At the risk of being redundant, we know that geography not only studies WHERE things are but also WHY they are THERE, and WHY DO WE CARE. The basic structure of the physically well-defined Indian subcontinent can be understood using the theory of plate tectonics that we discussed in the Introduction and again in the chapter on Sub-Saharan Africa
We mentioned how at one time, about 250 million years ago, all the world's landmasses were joined in one huge supercontinent named Pangaea [fit]. Much of the unique physical geography of Africa is the result of all the other land masses breaking off and moving away from the African continent while it remained almost stationary. Much of the physical geography of South Asia is also a consequence of plate tectonics.
The Indian subcontinent was at one time joined to southeast Africa [fit] . It broke off and drifted northeast [india] until it ran into the Eurasian plate [eurasplt]. This collision of the Indian plate with the Eurasian plate crumpled the plates along the collision line creating the Himalayan mountains and the Xizang (Tibetan) plateau [eaphys] of southwest China. Furthermore,the Western Ghats [ssphys] and the narrow coastal plain of western India are analogous to the escarpments of southwestern, southern, and southeastern Africa [afescarp] [afelevpc]. The Western Ghats were at one time connected to the southern African plateau [india]. Just as Africa is a "plateau continent", the Deccan Plateau of southern India has the same origin.
FROM THE USGS (United States Geological Survey):
Continental-Continental Convergence
The Himalayan mountain range dramatically demonstrates one of the most visible and spectacular consequences of plate tectonics [tectibet]. When two continents meet head-on, neither is subducted [oceancont] because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. (Because both these continental landmasses have about the same rock density, one plate could not be subducted under the other.) Instead, the crust tends to buckle [tectibet] and be pushed upward or sideways. The collision of India into Asia [india] 50 million years ago caused the Eurasian Plate to crumple up and override the Indian Plate. After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan (Xizang) Plateau [eaphys] to their present heights. Most of this growth occurred during the past 10 million years. OPTIONAL ANIMATION: http://www.scotese.com/indianim.htm
Map/drawing [tectibet]: The collision between the Indian and Eurasian plates has pushed up the Himalayas and the Tibetan Plateau.
The Himalayas, towering as high as 8,854 m above sea level, form the highest continental mountains in the world. Moreover, the neighboring Tibetan Plateau, at an average elevation of about 4,600 m, is higher than all the peaks in the Alps except for Mont Blanc and Monte Rosa, and is well above the summits of most mountains in the United States.
Drawing [indeuaspl]: Cartoon cross sections showing the meeting of these two plates before and after their collision. The reference points (small squares) show the amount of uplift of an imaginary point in the Earth's crust during this mountain-building process.
For more on this continent-continent plate collisions from the United States Geological Survey see: http://pubs.usgs.gov/publications/text/himalaya.html
[top]