Deccan Traps

The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India (17°–24°N, 73°–74°E). They are 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 (6,600 ft) thick, cover an area of c. 500,000 km2 (200,000 sq mi), and have a volume of c. 1,000,000 km3 (200,000 cu mi). Originally, the Deccan Traps may have covered c. 1,500,000 km2 (600,000 sq mi), with a correspondingly larger original volume. The term 'trap' has been used in geology since 1785–1795 for such rock formations. It is derived from the Swedish word for stairs ('trappa') and refers to the step-like hills forming the landscape of the region. The Deccan Traps began forming 66.25 million years ago, at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats some 66 million years ago. This series of eruptions may have lasted fewer than 30,000 years. The original area covered by the lava flows is estimated to have been as large as 1.5 million km2 (0.58 million sq mi), 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 500,000 km2 (200,000 sq mi). The release of volcanic gases, particularly sulphur dioxide, during the formation of the traps contributed to climate change. Data point to an average drop in temperature of about 2 °C (3.6 °F) in this period. Because of its magnitude, scientists have speculated that the gases released during the formation of the Deccan Traps played a major role in the Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary or K–T extinction). It has been theorized that sudden cooling due to sulfurous volcanic gases released by the formation of the traps and toxic gas emissions may have contributed significantly to the K–Pg, as well as other, mass extinctions. However, the current consensus among the scientific community is that the extinction was primarily triggered by the Chicxulub impact event in North America, which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature (this cooling is called an impact winter). Work published in 2014 by geologist Gerta Keller and others on the timing of the Deccan volcanism suggests the extinction may have been caused by both the volcanism and the impact event. This was followed by a similar study in 2015, both of which consider the hypothesis that the impact exacerbated or induced the Deccan volcanism, since the events occur at antipodes. Within the Deccan Traps at least 95% of the lavas are tholeiitic basalts. Other rock types present include: alkali basalt, nephelinite, lamprophyre and carbonatite.