FOCUS environmental science Mapping the Earth IMAGE COURTESY OF RYAN MCKENZIE ►Shown is a photo of Mt. Vesuvius in Italy. Data on sedimentary rocks in the area contributed to McKenzie’s analysis of volcanic activity. “In addition to the scientific literature, we did extensive work in India, Myanmar, and North China to fill in the existing gaps within zircon data sets,” McKenzie said. Compiling analyses of close to 120,000 zircons, McKenzie’s team found a promising pattern. The Cambrian, Jurassic, and Cretaceous periods, which saw high levels of CO 2 , had very high proportions of young zircons. In contrast, the Neoproterozoic, Carboniferous, early Permian, and Cenozoic periods, when CO 2 levels were low, had low proportions of young zircons. “We were able to establish a crucial link between the oscillations of volcanic gas activity and the flux of greenhouse gas levels,” McKenzie said. The findings of this study fit well into the geographic framework of continental shifts. Multiple times throughout Earth’s history, continents have rifted and amalgamated. Rifting periods—times when continents separate from each other—create extensive subduction zones, which in turn fuel continental volcanic activity, increasing zircon and CO 2 abundance. On the other hand, amalgamation periods—times when two continents combine—lead to a loss of subduction zones, reducing volcanic activity and therefore zircon and CO 2 abundance. Thus, the results of McKenzie’s study could be verified by existing knowledge about continental shifts. Ultimately, the techniques used in this project provide strong proof of the versatility of zircon as an indicator of volcanic CO 2 emissions. Thus, with this innovative zircon technique, McKenzie’s team has provided compelling evidence that volcanism has been an important driver of climate change over the past 700 million years. “Many of the specialists in this field were initially skeptical of this work, so we faced the challenge of revising popular opinion,” McKenzie said. While McKenzie and his group have primarily focused on volcanism as a key driver, they still recognize the importance of weathering in contributing to CO 2 changes. However, they argue that weathering can be interpreted simply as a secondary effect of volcanoes. Volcanoes contribute the primary influx of CO 2 into the atmosphere, so they exert the greatest first-order control over long-term climate change. However, volcanoes do not just act in one direction. Volcanoes result in both global warming and global cooling. According to other studies, a fuller consideration of the effect of volcanism on climate change must include the long-term effects of volcanic rocks. Indeed, volcanic activity can certainly lead to immediate increases in CO 2 emissions, leading to higher temperatures. However, during periods of volcanic dormancy, the volcanoes can be weathered. This weathering removes great quantities of CO 2 from the atmosphere, leading to a global cooling events. Thus, if considered on a long-term time scale, each volcano is both a carbon source and a carbon sink. Indeed, volcanism is a major force that regulates long-term climate change. Future digs Modern-day, human-driving global warming is a formidable challenge, especially given the jump in CO 2 emissions in such a short period of time. But placing ourselves in geological time, we would see that global warming has occurred multiple times since the formation of the Earth’s atmosphere as CO 2 levels oscillated with the rise and fall of continental volcanic activity. Global warming has defined the landscape of existing biodiversity and geography on Earth, notably during the Permian-Triassic extinction when 70 percent of land species and 90 percent of marine species went extinct. Importantly, global warming of the past educates us on the critical interactions that occur between carbon sources and carbon sinks, which is a part of present-day human-driven climate change as well as the climate variation of the past. Moving forward, McKenzie’s research group refuses to be constrained to one specific goal. “Up until now, the constraints of our data have been limited,” McKenzie said. “We hope to look at more high-resolution data sets and put more real numbers to this data.” Indeed, to fully uncover the Earth’s rich history, we must be willing to constantly dig deeper. ABOUT THE AUTHOR KEVIN BIJU KEVIN BIJU is a sophomore Molecular Biophysics and Biochemistry major in Morse College. He is the Alumni Outreach Coordinator of the Yale Scientific Magazine and is interested in the cross-talk between evolution and genetics in biomedical research. THE AUTHOR WOULD LIKE TO THANK Dr. Ryan McKenzie for his thoughtful interview, as well as his research team’s dedication. FURTHER READING M. R. Burton, G. M. Sawyer, D. Granieri Deep carbon emissions from volcanoes. Rev. Mineral. Geochem. 75, 323–354 (2013). 14 Yale Scientific Magazine December 2016 www.yalescientific.org
STICKING IT TO CANCER FIGHTING TUMORS WITH NANOPARTICLES BY JESSICA TRINH ART BY LAURIE WANG www.yalescientific.org December 2016 Yale Scientific Magazine 15
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