INDIAN OCEAN

What is the importance of Indian Ocean for India? (CSE 1999)

Mention the advantages which India enjoys being at the head of the Indian Ocean. (CSE 1996)

The Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by the Indian subcontinent; on the west by East Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean (or, depending on definition, by Antarctica). It is the only ocean to be named after a country, i.e., India.

1.The Indian Ocean

2.Bathymetric map of the Indian Ocean

India is situated at the North middle of the Indian Ocean. It makes three boundaries of India and delivers it many benefits in economic, climatic and strategic fields.

ECONOMIC AND COMMERCIAL ADVANTAGES · In the South Sri Lanka is neighboring the tip of the India. In the South-east, countries like Malaysia, Indonesia etc. are situated. India has developed sea-route trade along with these countries since historical period. · The major routes connecting east and west part of the world pass through Indian Ocean and India is a mid-destination for these routes. · After the opening of Suez-canal, the way to Europe has become more convenient through the Indian Ocean increasing to the benefits of India. · Trade routes to America, Africa and Europe pass through the Indian Ocean, this makes Indian position significant.

CLIMATE ADVANTAGE

· It keeps the climate of the southern India moderate and gives most of the rain India through the south-west monsoon.

· Providing a long sea coast, the Indian Ocean delivers, advantage of fishing, coastal vegetation etc.

STRATEGIC ADVANTAGE · It covers and protects three boundaries of India, reducing the huge cost of protection. · It prevents confrontation with neighboring countries which exist with land-boundary connected countries like Pakistan, China and Bangladesh.

Aravallis(Mewar/Marwar)

Why the Aravallis are called a divide between Mewar and Marwar? (CSE2004)

Mewar and Marwar are two socio-cultural regions which are located on either side of the Aravallis. While Mewar is located to the east of the Aravaliis, Marwar is located to the west. The Physical terrain on the either side of the Aravaliis is vastly different and this has given rise4 to the two different regions.

Marwar is largely an arid wasteland suitable only for the raising of goats and camels. The region has very low rainfall, in the range of 0-20cm. the whole region is covered with shifting sand dunes. The luni is the only river of some importance. In greater part of the area the ground water is impregnated with salt. There are numerous salt lakes of which Sambhar is largest. Gypsum and salt are mined, and cotton is raised.

Mewar is mostly an alluvial plain watered by ma by intermittent streams. Rainfall is in the region of 20-40cm. Grains, sugarcane and oilseeds are grown. There are also extensive mineral deposits of iron ore, lead and zinc.

THE ARAVALLI RANGES are one of the most ancient mountain ranges in India that lies in the north-western part of the country. It separates the sandy desert of west Rajasthan and the fertile tracts in the eastern parts of the State. The present Aravalli ranges comprise only a part of the gigantic system that existed in pre-historic times. The entire ranges once rose to stupendous heights nourishing glaciers which in turn fed many great rivers. The ranges are now crossed by many rivers including Luna and the Banas. Luna and its small tributaries flow westward and in due course merge with Rann of Kutch and the Banas and its streams flow from the eastern side of the ridge and join the Yamuna. Aravallis are also gifted with great mineral wealth. MARWAR In 1901 the region (Jodhpur state) had an area of 90,554 km² (34,963 square miles). Marwar is a sandy plain lying northwest of the Aravalli Range, which runs southwest-northeast through Rajasthan state. The Aravallis wring much of the moisture from the southwest monsoon, which provides most of India's rainfall. Annual rainfall is low, ranging from 10-40cms. Temperatures range from 48 to 50 degrees Celsius in the summer, to below freezing point in winter. The Northwestern thorn scrub forests lie next to the Aravalli Range, while the rest of the region lies in the Thar Desert. Marwar region of Rajasthan The Luni River is the principal feature of the Marwar plains. It originates in the sacred Pushkar Lake of Ajmer District, and the main river flows through Marwar in a south-westerly direction until it finally disappears into the seasonal wetland of the Rann of Kutch in Gujarat. It is fed by numerous tributaries that flow from the Aravallis. Irrigation from the river and from wells near the river, support crops of wheat and barley. The sandy tracts of Thar Desert in western Marwar are characterized by a harsh physical geography and a fragile ecology. High wind velocity, shifting sand dunes and very deep and saline water sources pose a challenge to sustained human habitation in the Thar. The area is also prone to devastating droughts. The Thar Desert is one of the most inhospitable landscapes on earth. Apart from the huge distances between hamlets and settlements here, the landscape is constantly shifting with the sand, as wind and sandstorms re-arrange the landscape at will. This added to the lack of water in such an arid region, means that the villagers of the area often find themselves migrating on foot across hundreds of miles towards neighboring states in search of water. MEWAR The northern part of Mewar is a gently sloping plain, drained by the Bedach & Banas River and its tributaries, which empty northwest into the Chambal River, a tributary of the Yamuna River. The southern part of the region is hilly, and marks the divide between the Banas and its tributaries and the headwaters of the Sabarmati and Mahi rivers and their tributaries, which drain south into the Gulf of Cambay through Gujarat state. The Aravalli Range forms the northwestern boundary of the region, composed mostly of sedimentary rocks, like marble and Kota Stone, which has traditionally been an important construction material. The region is part of the Kathiawar-Gir dry deciduous forests' ecoregion. Protected areas include the Jaisamand Wildlife Sanctuary, the Kumbhalgarh Wildlife Sanctuary, the Bassi Wildlife Sanctuary and the Sitamata Game Sanctuary. Mewar has a tropical climate. Rainfall averages 660 mm/year, and is generally higher in the southwest and lower in the northeast of the region. Over 90% of the rain typically falls in the period June to September every year, during the southwest monsoon

RIVER DELTA

Why do the rivers of west coast not form a delta? ( CSE 2006)

The west flowing rivers do not make delta, but estuaries. Many west flowing rivers like Narmada, Tapti, Periar etc passes through rift vallies. This river contains very few amounts of Slits and due to its fast speed it cannot make delta. When these fast flowing rivers reach to its mouth it become unable to deposit its slits, due to this reason slits falls in to the sea.

An ESTUARY is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea Estuaries form a transition zone between river environments and ocean environments and are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries among the most productive natural habitats in the world.

There are many small rivers which originate from the western Ghat Mountains and the fall in to the Arabian Sea. Due to the high gradient of Western Ghat these rivers flow with a very high speed and unable to deposits slits. They pass through the hard rocks, these rivers contain very little amount of silts. The estuaries made by these rivers are full of bio-diversity.

WHAT IS A RIVER DELTA? DELTAS Deltas are the result of interacting fluvial (river) and, usually, marine systems. However, they can form anywhere a stream flows into shallower open water. Whence the name Delta? Delta was coined by Herodotus (the father of history, 484-425 BC) after the Greek letter delta because of the deltoid-shape at the mouth of the Nile. Delta definition: Coastal accumulations, both subaqueous and Subaerial, of river-derived sediments adjacent to, or in close proximity to, the source stream, including the deposits that have been secondarily molded by various marine agents, such as waves, currents, or tides. [L. D. Wright, 1978] Deltas occur throughout the world, except at the poles (see slides). They all have three characteristics in common: 1. The presence of a large catchment, or drainage, basin (the area where all run-off water drains to the river). The top 30 river deltas all have catchment basins in excess of 1,000,000 sq km. 2. They all are at the mouth of large river systems that carry large quantities of clastic sediments (soils or portions of rocks that have been moved by water from where they formed). 3. They are not near geologically active coastlines. In order to have a large catchment basin, a very complex tributary system is necessary. These long, complex systems take a long time to develop, so they are very rarely situated on tectonically active coasts. ANATOMY OF A DELTA: Subaqueous (=under the water) delta - That part of the delta that is below the low-tide mark. Seaward, finer and finer soil particles are found. The seaward-most portion has the finest soils (clays) and is called the prodelta. II. Subaerial (=under the air, or, above water) delta - That part above the low-tide mark. A. Lower delta plain - That part governed by riverine/marine interaction. Extends landward to the limit of tidal influence. All salt and brackish flora and fauna are within this area. B. Upper delta plain - That part governed by riverine depositional processes. following two additional categories: 1. Active delta - That part that is still active and has water channeling through it carrying sediment. 2. Abandoned (or inactive) delta - That part that was once active, but now has reduced or no fluvial activity. TYPES OF DELTAS: 1. Arcuate (fan-shaped) delta - e.g., Nile River. Has many active, short distributaries taking sediment to their mouths. The receiving (ambient) waters are rather shallow and have relatively even wave action arriving perpendicular to the shore with minimal long shore current. As the sediment exits the many distributary mouths, the waves push it back, so the coastline is rather smooth. Bird-foot (shaped like a bird foot) delta - e.g., Mississippi River. Tend to have one or a very few major distributaries near their mouths. The receiving basin has currents that carry the sediment away as it exits the distributary mouth. There is a broad, shallow shelf that deepens abruptly, so the trend is to grow long and thin like a bird's toe. 3. Cuspate (tooth-shaped) delta - e.g., Tiber River of Italy. Usually has one distributary emptying into a flat coastline with wave action hitting it head-on. This tends to push the sediment back on both sides of the mouth, with a "tooth" growing out onto the shelf. 4. Estuarine delta - e.g., Seine River of France. This type of delta has a river that empties into a long, narrow estuary that eventually becomes filled with sediment (inside the coastline). DELTA TERMS: Progradation - The river deposits sediments faster than the sea is able to remove them, so the delta grows outward into the sea (=prograde). Aggradation - The river deposits build up (elevation) via overbank flooding, accumulation of biotic remains, etc., so the delta grows upward. Transgression - The retreat of the delta, usually by the loss of sediment caused by continued wave attack or the reduction of nourishment soils. It follows that deltas have four options: 1. They stagnate, i.e., remain in equilibrium. 2. They prograde. 3. They aggrade. 4. They transgress.