The Deccan Traps shown as dark purple spot on the geologic map of India

Deccan Traps near Matheran, east of Mumbai

The Deccan Traps near Pune

The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India (between 17°–24°N, 73°–74°E) and one of the largest volcanic features on Earth. They consist of multiple layers of solidified flood basalt that together are more than 2,000 m (6,562 ft) thick and cover an area of 500,000 km² (193,051 sq mi) and a volume of 512,000 km³ (123,000 cu mi). The term "trap", used in geology for such rock formations, is derived from the Swedish word for stairs^[1] and refers to the step-like hills forming the landscape of the region.

History[link]

The Deccan Traps formed between 60 and 68 million years ago,^[2] at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 65 million years ago. This series of eruptions may have lasted less than 30,000 years in total.^[3]

The original area covered by the lava flows is estimated to have been as large as 1.5 million km², approximately half the size of modern India. The Deccan Traps region was reduced to its current size by erosion and plate tectonics; the present area of directly observable lava flows is around 512,000 km² (197,684 sq mi).

Effect on climate and contemporary life[link]

The release of volcanic gases, particularly sulfur dioxide, during the formation of the traps contributed to contemporary climate change. Data points to an average fall in temperature of 2 °C in this period.^[4]

Because of its magnitude, scientists formerly speculated that the gases released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene extinction event (also known as the K-Pg extinction), which included the extinction of the non-avian dinosaurs. Sudden cooling due to sulfurous volcanic gases released by the formation of the traps and localised gas concentrations may have contributed significantly to mass extinctions. However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in Central America (which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter).^[5]

Chemical composition[link]

Within the Deccan Traps at least 95% of the lavas are tholeiitic basalts, however other rock types do occur:

• Alkali basalts
• Nephelinites
• Lamprophyre
• Carbonatites

Mantle xenoliths have been described from Kachchh (northwestern India) and elsewhere in the western Deccan.

Fossils[link]

The Deccan Traps are famous for the beds of fossils that have been found between layers of traps lava. Particularly well known species include the frog Oxyglossus pusillus (Owen) of the Eocene of India and the toothed frog Indobatrachus, an early lineage of modern frogs, which is now placed in the Australian family Myobatrachidae.^[6][7] The infratrappean and intertrappean beds also contain fossil freshwater mollusks. ^[8]

Theories of formation[link]

It is postulated that the Deccan Traps eruption was associated with a deep mantle plume. The area of long-term eruption (the hotspot), known as the Réunion hotspot, is suspected of both causing the Deccan Traps eruption and opening the rift that once separated the Seychelles plateau from India. Seafloor spreading at the boundary between the Indian and African Plates subsequently pushed India north over the plume, which now lies under Réunion island in the Indian Ocean, southwest of India. The mantle plume model has, however, been challenged.^[2]

Data continues to emerge which supports the plume model. The motion of the Indian tectonic plate and the eruptive history of the Deccan traps show strong correlations. Based on data from marine magnetic profiles, a pulse of unusually rapid plate motion begins at the same time as the first pulse of Deccan flood basalts, which is dated at 67 Myr ago. The spreading rate rapidly increased and reached a maximum at the same time as the peak basaltic eruptions. The spreading rate then dropped off, with the decrease occurring around 63 Myr ago, by which time the main phase of Deccan volcanism ended. This correlation is seen as driven by plume dynamics.^[9]

The Indian and African plates motions have also been shown to be coupled, with the common element being the position of these plates relative to the location of the Réunion plume head. The onset of accelerated motion of India coincides with a large slowing of the rate of counterclockwise rotation of Africa. The close correlations between the plate motions suggest that they were both driven by the force of the Réunion plume.^[9]

Suggested link to Shiva Crater[link]

A geological structure exists in the sea floor off the west coast of India that has been suggested as a possible impact crater, in this context called the Shiva crater. It has also been dated at approximately sixty-five million years ago, potentially matching the Deccan traps. The researchers claiming that this feature is an impact crater suggest that the impact may have been the triggering event for the Deccan Traps as well as contributing to the acceleration of the Indian plate in the early Paleogene.^[10] However, the current consensus in the Earth science community is that this feature is unlikely to be an actual impact crater.^[11][12]

See also[link]

• List of volcanoes in India
• Geology of India
• Siberian Traps
• Emeishan Traps
• Lameta Formation

References[link]

External links[link]

• "Animated simulation by the Geodynamics group at the Geological Survey of Norway illustrating the Indian plate moving through the Indian Ocean". http://www.geodynamics.no/indexOld.htm. 

Coordinates: 18°51′N 73°43′E / 18.85°N 73.717°E / 18.85; 73.717

Deccan Plateau covers parts of central and southern India

The Deccan Plateau ^[1] is a large plateau in India, making up most of the southern part of the country. It rises a hundred meters high in the north, and more than a kilometer high in the south, forming a raised triangle within the familiar downward-pointing triangle of the Indian subcontinent's coastline.^[2]

It extends over eight Indian states and encompasses a wide range of habitats, covering most of central and southern India.^[3]

It is located between two mountain ranges: the Western Ghats form its western boundary, and the Eastern Ghats its eastern boundary. Each rises from their respective nearby coastal plains and nearly meet at the southern tip of India. It is separated from the Gangetic plain to the north by the Satpura and Vindhya Ranges, which form its northern boundary.

The name Deccan is an anglicised form of the Prakrit word dakkhin, itself derived from the Sanskrit word dákṣiṇa, meaning "south".^[4]

Geography[link]

Hogenakal Falls, Tamil Nadu

Near Hampi, Karnataka

The Deccan Plateau lies south of the Indo-Gangetic plain. The Western Ghats Mountain Range is tall and blocks the moisture from the southwest monsoon from reaching the Deccan Plateau, so the region receives very little rainfall.^[5][6] The eastern Deccan Plateau is at a lower elevation spanning the southeastern coast of India. Its forests are also relatively dry but serve to retain the rain to form streams that feed into rivers that flow into basins and then into the Bay of Bengal.^[2][7]

Most Deccan plateau rivers flow south. Most of the northern part of the plateau is drained by the Godavari River and its tributaries, including the Indravati River, starting from the Western Ghats and flowing east towards the Bay of Bengal. Most of the central plateau is drained by the Tungabhadra River, Krishna River and its tributaries, including the Bhima River, which also run east. The southernmost part of the plateau is drained by the Kaveri River, which rises in the Western Ghats of Karnataka and bends south to break through the Nilgiri Hills at Hogenakal Falls into Tamil Nadu, then forms the Shivanasamudra Falls at the island town of Shivanasamudra before flowing into the Stanley Reservoir and the Mettur Dam that created the reservoir, and finally emptying into the Bay of Bengal.

The two main rivers which do not flow into the Bay Of Bengal are the Narmada and Tapti. They start in the Eastern Ghats and flow into the Arabian Sea. All Deccan plateau rivers depend on rains and dry up in the summers.

The climate of the region varies from semi-arid in the north to tropical in most of the region with distinct wet and dry seasons. Rain falls during the monsoon season from about June to October. March to June can be very dry and hot, with temperatures regularly exceeding 40°C.

Geology[link]

This unreferenced section requires citations to ensure verifiability.

The volcanic basalt beds of the Deccan were laid down in the massive Deccan Traps eruption, which occurred towards the end of the Cretaceous period between 67 and 65 million years ago. Some paleontologists speculate that this eruption may have accelerated the extinction of the dinosaurs. Layer after layer was formed by the volcanic activity that lasted many thousands of years, and when the volcanoes became extinct, they left a region of highlands with typically vast stretches of flat areas on top like a table.The volcanic hotspot that produced the Deccan traps is hypothesized to lie under the present day island of Réunion in the Indian Ocean.

Typically the Deccan Plateau is made up of basalt extending up to Bhor Ghat near Karjat. This is an extrusive igneous rock. Also in certain sections of the region, we can find granite, which is an intrusive igneous rock. The difference between these two rock types is: basalt rock forms on eruption of lava, that is, on the surface (either out of a volcano, or through massive fissures—as in the Deccan basalts—in the ground), while granite forms deep within the Earth. Granite is a felsic rock, meaning it is rich in potassium feldspar and quartz. This composition is continental in origin (meaning it is the primary composition of the continental crust). Since it cooled relatively slowly, it has large visible crystals. Basalt, on the other hand, is mafic in composition—meaning it is rich in pyroxene and, in some cases, olivine, both of which are Mg-Fe rich minerals. Basalt is similar in composition to mantle rocks, indicating that it came from the mantle and did not mix with continental rocks. Basalt forms in areas that are spreading, whereas granite forms mostly in areas that are colliding. Since both rocks are found in the Deccan Plateau, it indicates two different environments of formation.

The Deccan is rich in minerals. Primary mineral ores found in this region are mica and iron ore in the Chhota Nagpur region, and diamonds, gold and other metals in the Golconda region.

People[link]

This unreferenced section requires citations to ensure verifiability.

The Deccan is home to many languages and people. Bhil and Gond people live in the hills along the northern and northeastern edges of the plateau, and speak various languages that belong to both the Indo-European and Dravidian families of languages. Marathi, an Indo-Aryan language, is the main language of the north-western Deccan in the state of Maharashtra. Speakers of Telugu and Kannada, the predominant languages of Andhra Pradesh and Karnataka respectively, occupy those states' portions of the plateau. Tamil is the main language of Tamil Nadu to the south of the plateau, and Malayalam that of the hills and coast to the south-west, in the state of Kerala. The city of Hyderabad is an important centre of Urdu language in the Deccan; its surrounding areas also host a notable population of Urdu speakers. The Urdu dialect spoken in this region is also known as Dakhini or as Deccani.

The chief crop is cotton; also common are sugarcane, rice, and other crops.

Apart from the states already mentioned, the state of Chhattisgarh is found in the northeast corner of the plateau. The three large cities in the Deccan are Chennai the capital of Tamil Nadu, Hyderabad the capital of Andhra Pradesh and Bangalore the capital of Karnataka. Other major cities include Mysore in Karnataka, Coimbatore and Salem in Tamil Nadu, Pune, Nagpur and Aurangabad (in Maharashtra).

History[link]

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2010)

Of the early history, the main facts established are the growth of the Mauryan empire (250 B.C.) and the invasion (A.D. 100) of the Scythic tribes known as the Sakas, Pahlavas and Yavanas, which led to the establishment of the power of the Kshaharata satraps in western India. Prominent dynasties of this time include the Cholas (3rd c. BC to 12th c. AD), Chalukyas (6th to 12th c.), Rashtrakutas (753–982), Hoysalas (10th to 14th c.), Kakatiya (1083 CE to 1323 CE) and Vijayanagara Empire (1336–1646). Ahir Kings once ruled over the Deccan. A cave inscription at Nasik refers to the reign of an Abhira prince named Ishwarsena, son of Shivadatta.^[8][9]

In 1294, Ala-ud-Din Khilji, emperor of Delhi, invaded the Deccan, stormed Devagiri, and reduced the Yadava rajas of Maharashtra to the position of tributary princes (see Daulatabad), then proceeding southward to conquer the Telangana and Carnatic. In 1307, a fresh series of Muslim incursions led by Malik Kafur began in response to unpaid tributes, resulting in the final ruin of the Yadava power; and in 1338 the conquest of the Deccan was completed by Sultan Muhammad bin Tughluq. The imperial hegemony was brief, as soon Telingana and Karnataka reverted to their former masters. These defections by the Hindu states was soon followed by a general revolt of the Muslim governors, resulting in the establishment in 1347 of the independent Muslim dynasty of Bahmani.^[10] The power of the Delhi sultanate evaporated south of the Narmada River.

Jahangir receives Prince Khurram on his return from the Deccan (10 October 1617)

In the power struggles which ensued, the Hindu kingdom of Telingana fell bit by bit to the Bahamani dynasty, who advanced their frontier to Golkonda in 1373, to Warangal in 1421, and to the Bay of Bengal in 1472. When the Bahmani empire dissolved in 1482, its dominions were distributed into the five Muslim states of Golkonda, Bijapur, Ahmednagar, Bidar and Berar, giving rise to the Deccan sultanates.^[10] South of these, the Hindu state of Carnatic or Vijayanagar still survived; but this, too, was destroyed, at the Battle of Talikota (1565) by a league of the Muslim powers. Berar had already been annexed by Ahmednagar in 1572, and Bidar was absorbed by Bijapur in 1609. Mughal interest in the Deccan also rose at this time; Ahmadnagar was partially incorporated in the Empire in 1598 and again in 1616, Bijapur in 1686, and Golkonda in 1688.

In 1674, Shivaji laid the foundation of the Maratha Empire which within 75 years of his death covered territory of over 250 million acres (1 million km²) or one-third of the Indian sub-continent. Marathas under Shivaji directly challenged the foreign rule of the Bijapur Sultanate and ultimately the mighty Mughal empire. Once the Bijapur Sultanate stopped being a threat to the Maratha Empire, Marathas became much more aggressive and began to frequently raid Mughal territory. The Marathas had conquered part of central and western India by Shivaji Maharaj's death in 1680. After Shivaji, Sambhaji defended the Maratha empire from the Mughal onslaught led by Aurangzeb. Aurangzeb did not win a single major victory against Sambhaji before he was deceitfully captured and executed. Thereafter, Peshwas began commanding Maratha armies. After 1707, the Marathas acquired the right to levy tribute in southern India. After the death of Chhatrapati Shahu, the Peshwas became the de facto leaders of the Empire from 1749 to 1761, while Shivaji's successors continued as nominal rulers from their base in Satara. The Marathas kept the British at bay during the 18th century. By 1760, with the defeat of the Nizam in the Deccan, Maratha power had reached its zenith. However, dissension between the Peshwa and their sardars (army commanders) saw a gradual downfall of the Empire leading to its eventual annexation by the British East India Company in 1818 after the three Anglo-Maratha wars.

A few years later, the Aurangzeb's viceroy in Ahmednagar, Nizam-ul-Mulk, established the seat of an independent government at Hyderabad in 1724. Mysore was ruled by Hyder Ali. During the contests for power which ensued from about the middle of the 18th century between the powers on the plateau, the French and British took opposite sides. After a brief course of triumph, the interests of France declined, and a new empire in India was established by the British. Mysore formed one of their earliest conquests in the Deccan. Tanjore and the Carnatic were soon annexed to their dominions, followed by the Peshwa territories in 1818.

In British India, the plateau was largely divided between the presidencies of Bombay and Madras. The two largest native states at that time were Hyderabad State and Mysore State; many smaller states existed at the time, including Kolhapur, Sawantwari, Travancore, and Cochin.

After independence in 1947, almost all native states were incorporated into the Republic of India. Hyderabad refused to join, and was annexed by the Indian Army in Operation Polo in 1948.^[11] In 1956, the States Reorganisation Act reorganized states along linguistic lines, leading to the states currently found on the plateau.

• 

  Deccan style

• 

  Calligraphic emblem of sculpted sandstone – 16th century

• 

  Nimmatnama-i Nasiruddin-Shahi (the Book of Recipes)

See also[link]

• Geography of India
• South India
• Mysore Plateau
• Vijayanagara Empire
• Kakatiya empire
• Bayaluseemae

Notes[link]

References[link]

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 

This file is in the public domain because its copyright has expired in the United States and those countries with a copyright term of no more than the life of the author plus 100 years.

External links[link]

Wikimedia Commons has media related to: Deccan Plateau

• Destruction along the Deccan plateau
• Photos of Deccan Plateau
• Dynasties of Deccan
• The Deccan Peninsula
• Central Deccan Plateau dry deciduous forests
• Geology of Deccan Plateau
• Deccan South Indian Online

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Coordinates: 17°N 77°E / 17°N 77°E / 17; 77