South Asia's Physical Landscape

South Asia's Himalaya Mountains are the highest in the world, soaring to over 8,800 meters (29,000 feet). Yet, these are also some of the world's youngest mountains, reflecting a region that has experienced significant physical and cultural changes throughout its history. Here, we find one of the earliest and most widespread ancient civilizations, the hearth area for several of the world's great religions, and a region whose population will soon be the largest on Earth.

Figure 8.1: Map of South Asia (© Cacahuate, Wikimedia Commons, CC BY-SA 4.0)

South Asia is a well-defined region in terms of its physical landscape (see Figure 8.1). Formidable physical barriers separate the region from the rest of the Eurasian landmass. Much of the impressive physical geographic features of South Asia are the result of tectonic activity. Between 40 and 50 million years ago, the Indian Plate collided with the Eurasian plate (see Figure 8.2). Both the Indian Plate and the Eurasian plate were comprised of fairly low density material, and so when the collision occurred, the two landmasses folded like an accordion creating the mountain ranges we see today. The Indian Plate is still moving towards the Eurasian plate today and over the next 10 million years, will move an additional 1,500 km (932 mi) into Asia.

Figure 8.2: Indian Plate and Eurasian Plate Boundary (United States Geological Survey, Public Domain)

This massive tectonic collision resulted in perhaps the most well-known physical feature in South Asia: Mount Everest. Everest, located in the Himalaya Mountain range on the border of Nepal and China, is the highest mountain in the world. Because the India Plate continues to collide with the Eurasian Plate, this mountain range is still tectonically active and is rising at a rate of 5 mm each year. Thus, if you're planning on scaling Mount Everest in ten years, be prepared to climb an extra two inches.

Although the Himalaya Mountains are well-known for having the highest peak, the Karakoram Mountain range, passing through Pakistan, India, China, and Afghanistan, has the highest concentration of peaks above 8,000 meters (26,000 feet). Its highest peak, K2, is the second-highest mountain in the world and far fewer people have successfully made it to the top compared to Everest. One in four people die while attempting to summit.

Another key physical feature of South Asia, the Deccan Plateau, was also formed from the region's tectonic activity. Around 65 million years ago, there was an enormous fissure in Earth's crust which led to a massive eruption of lava. The entire Indian peninsula was buried in several thousand feet of basalt, a type of dense, volcanic rock.

South Asia's rivers, including the Indus, Ganges, and Brahmaputra form a lowland region that was home to several ancient civilizations. Today, these rivers provide for the water needs of many of this region's people, irrigation for agricultural lands, and an abundance of fish. However, these rivers have had significant environmental concerns in recent years and have supported increasing numbers of people along their banks. Most of the area along the Ganges River, for example, has been converted into urban or agricultural land and the wild species like elephants and tigers that used to be present along the river are now gone. Pollution in the Ganges River has reached unprecedented levels as industrial waste and sewage is dumped untreated into the river despite the fact that people frequently use the water for bathing, washing, and cooking. It is estimated that around 80 percent of all illnesses in India result from water-borne diseases. The World Bank has loaned India over $1 billion to clean up the river, but experts believe that larger scale infrastructure improvements are needed to improve the region's water quality.

Figure 8.3: Map of Monsoon Onset Dates (© Saravask, based on work by Planemad and Nichalp, Wikimedia Commons, CC BY-SA 3.0)

The most important climatic feature of South Asia is a dramatic weather cycle known as the monsoon (see Figure 8.3). The monsoon refers to seasonal shifts in wind that result in changes in precipitation. From October to April, winds typically come from the northeast in South Asia creating dry conditions. Beginning in April, however, winds shift to the southwest, picking up moisture over the Arabian Sea, Indian Ocean, and Bay of Bengal.

Most of the rain during the monsoon season results from orographic precipitation, caused when physical barriers form air masses to climb where they then cool, condense, and form precipitation (see Figure 8.4). India's Western Ghats, a mountain range on its western coast, for example, causes orographic precipitation on its windward side. The Himalaya Mountains similarly result in orographic precipitation. However, these impressive highland areas are so formidable that they cause a dry area on their leeward side, known as a rain shadow. On one side of the Himalayas are some of the wettest places on Earth with over 30 feet of rain each year. On the other side, the rain shadow from the mountains forms the arid Gobi Desert and Tibetan Plateau.

Figure 8.4: Orographic Precipitation (© Saperaud~commonswiki, Wikimedia Commons, CC BY-SA 3.0)

The monsoon rains, though extreme, provide significant benefits for South Asia's agriculture and economy. India gets more than 80 percent of its yearly rainfall from the monsoon and the rains are essential for both subsistence and commercial agriculture in the region. A good monsoon year will replenish the region's water supplies and increase crop yields, driving down food prices. Ample rainfall also contributes to the region's hydroelectricity potential. However, the torrential rains of the monsoon can also cause widespread flooding, destroying agricultural lands and transportation infrastructure, and can contribute to water-borne and insect-borne illnesses due to the significant amounts of standing water.

The monsoon is changing, though. Global changes in climate have made the monsoon harder to predict. In addition, rising numbers of automobiles across South Asia have increased air pollution, which can interfere with the mechanics of the monsoon. In the past, once the monsoon season starts, rains continue throughout the season. Recently, though, the monsoon rains have begun to stop and start throughout the rainy season. People in this region are generally unprepared for an unpredictable or variable monsoon season and rely heavily on the rains for agriculture. Local leaders are pushing for more research to better understand the shifting monsoon rains and for increased education on water conservation and sustainable agricultural management.

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Source: Caitlin Finlayson, https://worldgeo.pressbooks.com/chapter/south-asia/#chapter-293-section-4
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