Dinosaur Extinction Discovery

The last one million years of the nearly 180-million reign of dinosaurs was a tumultuous time that witnessed some of the largest volcanic eruptions in Earth’s history. Over this time, the Earth experienced large-scale fluctuations in the climate, and eventually a six-mile-wide meteorite impact that led to the extinction of more than 75% of life on Earth, including dinosaurs.  

Determining the ultimate cause — or causes — of the massive extinction has been fiercely debated by scientists over the past several decades. Although the Chicxulub meteorite impact is widely recognized as the main cause of the dinosaurs suddenly dying off, massive volcanic eruptions, known as the Deccan Traps, were going off at roughly the same time in present-day India and have also been proposed as a contributing factor. A new study published by an international team of scientists, including Denver Museum of Nature & Science paleontologist Dr. Tyler Lyson, on rocks in North America helps disentangle the impact, volcanic eruptions and climate and suggests the asteroid impact was the primary driver of the extinction that wiped out the dinosaurs 66 million years ago.  

"Over the past several decades, there’s been a big question about what contributed to the extinction of the dinosaurs. Was it a one-two punch, with volcanic activity weakening the dinosaur dominated ecosystems before the asteroid delivered the knockout blow? Or was it the asteroid alone, in a singular knockout punch?" said Dr. Lyson.  

Read more: Recorded in Stone: Single Worst Day for Multicellular Life on Earth 

The study led by scientists from The University of Manchester, with contributions from scientists at Plymouth University and Utrecht University, examined fossil records from ancient swamps that once existed here in Colorado and in North Dakota. These fossil swamps contain specialized cell-membrane molecules produced by bacteria. By analyzing the composition of these molecules, the researchers could estimate past temperatures.  

The team reconstructed the mean annual air temperatures for the 100,000 years leading up to the major extinction event. Their goal was to determine whether the volcanic activity played a decisive role in the mass extinction. The findings revealed that volcanic CO2 emissions caused a gradual warming over this period. However, a brief cold “snap” occurred 30,000 years before the extinction event, likely triggered by volcanic sulfur emissions that blocked out that light from the sun.  

Dr. Lauren O’Connor, lead scientist and now Research Fellow at Utrecht University: “These volcanic eruptions and associated CO2 emissions drove warming across the globe and the [sulfur] would have had drastic consequences for life on earth. But these events happened tens of thousands of years before the mass extinction and played only a small part in the extinction of the dinosaurs.”  

The field work took place at two of Tyler’s primary field areas in the Western United States. In Colorado, the paleontologists’ sampling took place just an hour away from Denver, along West Bijou Creek near the town of Strasburg. Discovered by Kirk Johnson, former Curator of Paleobotany and Vice President of Science at the Denver Museum of Nature & Science and current Sant Director of the Smithsonian Institution, this West Bijou site holds an excellent fossil record for studying the end of the age of dinosaurs and the dawn of the mammalian dominated Cenozoic Era.  

Read more: Uncovering the Mysteries of Mammals 

The North Dakota site is just north of the town of Marmarth, a tiny town of less than one hundred people, where Tyler grew up. The site is famous for preserving Earth’s last dinosaur ecosystem and was recently in the worldwide press this past summer with the discovery of the “Teen Rex” fossil by two brothers, their dad and their cousin in the nearby hills. 

Read more: Teen Rex Discovery Roars into the Denver Museum of Nature & Science 

During the time of the Deccan eruptions and end of the age of the dinosaurs, the planet was much warmer than today, with no permanent ice caps. Colorado was covered in a lush, diverse forest, roaring rivers, and dinosaurs such as T. rex and Triceratops roamed the landscape. At the time, vast inland seas split North America in two, even covering eastern Colorado. 

The next step for this research, according to Tyler, includes testing these findings at other sites worldwide. Future studies will help determine whether the volcanic cooling effects had played any role in the mass extinctions. 

"The study is a step toward better understanding the reasons behind why the dinosaurs went extinct, but I’d like to see high-resolution sampling studies take place at other sites around the world to further test our hypothesis,” said Dr. Lyson. “Science is a cumulative process, and much more data are needed before we’re going to have a closed case on the Deccan Traps involvement, or lack thereof, in the extinction of the dinosaurs.” 

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