Seventh.

This recent posts have focused on the adaptability of dinosaurs to survive climate change; this one will examine how it could have wiped them out. The Deccan Traps, India, was an area of intense volcanism towards the end of the Cretaceous, caused by the northward movement of India over the Reunion hotspot. Covering over 512000 km² today after erosion, the original lava flows would have spanned nearly three times as much (Keller, 2011). Operating over one million years, three distinct phases of volcanicity can be attributed to the flow, the largest being the second phase, right at the K/T boundary (Keller, 2011) 

The problem with associating the Deccan Traps to the end Cretaceous mass extinction is the fact that there are recovery periods between each phase, as well as the lack of significant marine microfossils interbedded within the traps, as they are a good indicator of mass extinction events (Keller, 2011).  However, comprehensive data collection at the volcanism site by Keller et al. (2011) has yielded more information on the exact nature of the event.

Microfossils were found in quarries along the K/T boundary, and showed the devastating impact of the volcanism of these tiny marine organisms:

 

The fossils found here were concordant with fossils found at other localities with known volcanicity, showing a high-stress low-diversity assemblage (Keller, 2011), in what is known as the "Lilliput effect". In addition, gas concentrations were calculated, after being preserved in rare bubbles within the rock. The concentrations of carbon and sulphur dioxide was beyond any anthropogenic induced change seen today, whilst evidence of a 'cooling' stage would have increased weathering, thus compounding the adverse effect of the gases. Keller (2011) writes:

Relating to dinosaurs, Keller (2009) wrote in an earlier paper how the last known remains of the reptiles are found before the significant lava flows at the K/T boundary, between the first and second phase, and show no signs of recovery after. It is plausible, therefore, that the Deccan traps had some effect on the giant reptiles. The theory of mass volcanism should not be disregarded in favour for the Meteor Impact theory, rather the meteor was the final straw in an already stressed environment, thanks to the volcanism. 

  

http://filebox.vt.edu/artsci/geology/mclean/Dinosaur_Volcano_Extinction/media/cretdawS.gif

http://www.science-story.com/images/deccan-traps.jpg

Keller G, Sahni A and Bajpai S 2009 Deccan volcanism, the KT mass extinction and dinosaurs; J. Biosci. 34 709–728

Keller et al. 2011.Deccan Volcanism Linked to the Cretaceous-Tertiary Boundary Mass Extinction: New Evidence from ONGC Wells in the Krishna-Godavari Basin. JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.78, November 2011, pp.399-428