Flood Basalt

Initially, most scientists concluded that the asteroid killed the dinosaurs, but there was another candidate. Peter Vogt had proposed in 1972 that a massive flood volcanic event in India, which formed the Deccan Traps, emitted sulfur dioxide, which polluted the atmosphere and killed the dinosaurs (Figure 11‑35). Hot magma plumes periodically well up from the inner earth and release massive quantities of lava to earth’s surface, along with toxic gases.

The Deccan Traps is what remains of one of several flood basalt events that have left behind large igneous provinces on earth (Figure 11‑37).[1] The flood basalt event that caused the Great Permian left behind the Siberian Traps. The Central Atlantic Igneous Province corresponds with the End Triassic extinction. The Deccan Traps (Figure 11‑36) covered a huge region in India with extensive layers of lava during almost one million years. The Columbia River Basalt Group (CRBG) in the NW United States is comparable in size to the Deccan Traps and caused the extinction of many species between 17-14 Ma. This plume is now under Yellowstone.

The Chicxulub impact took place between North America and South America. The location of India at the time of the Deccan Traps was off the southeast coast of Africa in the location of what is now Madagascar.

In some amazing radiometric detective work, scientists precisely dated the Chicxulub impact and Deccan Traps volcanism and found that they overlapped in time. Paul Renne precisely dated the K-Pg boundary at Hell’s Creek and found that the asteroid impact took place at precisely 66.0 Ma.[2] Scientists have also precisely dated the period of Deccan Traps volcanism between 66.3 to 65.5 Ma. Renne stated,

“Based on our dating of the lavas, we can be pretty certain that the volcanism and the impact occurred within 50,000 years of the extinction, so it becomes somewhat artificial to distinguish between them as killing mechanisms: both phenomena were clearly at work at the same time,” [3]

Mark Richards stated,

“If our high-precision dates continue to pin these three events – the impact, the extinction and the major pulse of volcanism – closer and closer together, people are going to have to accept the likelihood of a connection among them,” [4]

The Deccan Traps emitted enough lava to cover the entire US with 200 m of lava. Now scientists know that the Chicxulub impact triggered most of the Deccan Traps magma flow. This triggering of Deccan Traps volcanism was recently confirmed by Sprain et al., who showed that most of the Deccan Traps volcanism took place after the asteroid impact.[5] Based on a plot of volcanic triggering by earthquakes vs. distance, Richards determined that the Chicxulub earthquake of magnitude 11 could have triggered increased volcanism in the Deccan Traps on the other side of the earth. [6] In addition, there may be a link between the impact and other volcanism. Based on anomalous seafloor lava flows, Byrnes proposed that the huge earthquake from the asteroid might have triggered volcanism in the ocean at the Mid Atlantic ridge and other locations.[7] The confusing aspect of the great majority of Deccan Traps volcanism coming after the impact is the climate change prior to the impact. There was a rise in temperature by 5 ⁰C during the period 450,000 and 100,000 years before the impact and a subsequent 5 ⁰C rise in the 100,000 years prior to the impact. Sprain et al. proposed that it is possible that sulfuric acid degassed and caused climate warming prior to the main part of the flood basalt event. A recent study indicates that the Deccan traps might have mitigated the effects of the asteroid by keeping the climate warmer than it would have been during the global winter that followed the asteroid.[8]

References

[1] Richards, Mark A., Robert A. Duncan, and Vincent E. Courtillot. "Flood basalts and hot-spot tracks: plume heads and tails." Science 246, no. 4926 (1989): 103-107.

[2] Renne, Paul R., Alan L. Deino, Frederik J. Hilgen, Klaudia F. Kuiper, Darren F. Mark, William S. Mitchell, Leah E. Morgan, Roland Mundil, and Jan Smit. "Time scales of critical events around the Cretaceous-Paleogene boundary." Science 339, no. 6120 (2013): 684-687.

[3] Renne, Time scales.

[4] http://www.sci-news.com/paleontology/science-deccan-traps-volcanism-chicxulub-impact-03299.html

[5] Sprain, Courtney J., Paul R. Renne, Loÿc Vanderkluysen, Kanchan Pande, Stephen Self, and Tushar Mittal. "The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary." Science 363, no. 6429 (2019): 866-870.

[6] Gauri Dole, Shilpa Patil Pillai, Devdutt Upasani, Vivek S. Kale; Triggering of the largest Deccan eruptions by the Chicxulub impact: Comment. GSA Bulletin ; 129 (1-2): 253–255. doi: https://doi.org/10.1130/B31520.1

[7] Byrnes, Joseph S., and Leif Karlstrom. "Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism." Science advances 4, no. 2 (2018): eaao2994.

[8] Chiarenza, Alfio Alessandro, Alexander Farnsworth, Philip D. Mannion, Daniel J. Lunt, Paul J. Valdes, Joanna V. Morgan, and Peter A. Allison. "Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction." Proceedings of the National Academy of Sciences 117, no. 29 (2020): 17084-17093.

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Western Ghats in India formed by the Deccan Traps flood basalt event. Credit Nichalp. Used here per CC BY-SA 2.5