The Deccan Traps are one of the largest volcanic provinces in the world. It consists of more than 6,500 feet (>2,000 m) of flat-lying basalt lava flows and covers an area of nearly 200,000 square miles (500,000 square km) (roughly the size of the states of Washington and Oregon combined) in west-central India. Estimates of the original area covered by the lava flows are as high as 600,000 square miles (1.5 million square km). The volume of basalt is estimated to be 12,275 cubic miles (512,000 cubic km)(the 1980 eruption of Mount St. Helens produced 1 cubic km of volcanic material). The Deccan Traps are flood basalts similar to the Columbia River basalts of the northwestern United States. This photo shows a thick stack of basalt lava flows north of Mahabaleshwar. Photograph by Lazlo Keszthelyi, January 28, 1996.
The Deccan basalts may have played a role in the extinction of the dinosaurs. Most of the basalt was erupted between 65 and 60 million years ago. Gases released by the eruption may have changed the global climate and lead to the demise of the dinosaurs 65 million years ago. This photo shows the Deccan Tarps between Mambai and Mahabaleshwar. Photograph by Lazlo Keszthelyi, January 27, 1996.
Vocanologists are also trying to understand how such great volumes of lava are erupted. Early models proposed that lava flooded across large areas at extremely rapid rates. Recently proposed models suggested that at least some of the flows are emplaced at gradual rates, lasting months to years. This photo shows the Ajunta Caves, temples carved into the basalts. Note the school group for scale. Photograph by Lazlo Keszthelyi, January 31, 1996.
The ironic part is that Lonar Crater is an impact on the Deccan Trap volcanism, but is a very recent impact.
Excerpted from: http://freerepublic.com/focus/f-chat/1501131/posts
Figure 4a,b,c,d. Views of the Sahyadri (Western Ghats) escarpment at Mahabaleshwar, showing the 1200-m-thick, horizontally disposed Deccan flood basalt lava pile. The top of the lava pile is a heavily lateritized late Cretaceous planation surface. (d) The extensive, lateritized, heavily forested Mahabaleshwar plateau surface. Photos by Hetu Sheth, December 2005.
The great heights of the charnockite massifs may reflect both the original topography and the greater weathering resistance of charnockite than basalt (Gunnell & Louchet, 2000). Most importantly, the entire youthful Sahyadri is the precipitous western edge of an uplifted plateau that has been tilted eastward, and the plateau surface has an aged character – it is an ancient flat land surface rejuvenated relatively recently (Neogene) by major tectonic uplift (Radhakrishna, 1952, 1993; Vaidyanadhan, 1977), the uplift continuing during the Quaternary (e.g., Powar, 1993; Valdiya, 2001). Mahabaleshwar sits atop a spectacular, ~1200-m-thick exposed Deccan basalt sequence (Figure 4a,b,c), and the top of the Mahabaleshwar plateau represents a regional, low-relief, late Cretaceous palaeosurface or peneplain developed on the uppermost basalts after the cessation of the eruptions, represented by 25-50 m thick laterite (Widdowson, 1997a). In southern India, laterites or bauxites cap the high-elevation summits built of Precambrian rocks. Sahyadri uplift, extending well beyond the Deccan lava cover, is evidently not related to Deccan volcanism, but is more appropriately considered “rift-shoulder uplift”. Along with the Sahyadri, the Konkan Plain to the west of it has also been rising during the Tertiary (e.g., Powar, 1993). (Excerpted from http://www.mantleplumes.org/DeccanUplift.html
The Deccan Traps is located in central west India and dates from 66 million years ago.
The lava flows are some of the largest on earth covering 900 km and meet the coast at the Arabian Sea.
Deccan volcanism coincided with the decline of the dinosaurs raising the possibility
that the Indian volcanoes were involved with their decline.
Deccan lava meets the Arabian Sea at Goa. The lava flows cover 900 km throughout central and western India.
The Reunion mantle plume was responsible for the lava flows which covered 500 000 sq km.
Copyright John Seach
Labels: volcanoes-ancient vulcanism
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