The idea that huge volcanic eruptions on the Indian subcontinent may have contributed to the extinction of dinosaurs has been a subject of discussion for a long time. This volcanic activity occurred just before a meteorite struck the Earth, 66 million years ago. The impact of these eruptions on the climate has sparked intense scientific debates for many years. Recent findings from climate scientists at Utrecht University and the University of Manchester reveal that, although volcanism caused a brief period of cooling, its effects had faded thousands of years before the meteorite hit. Consequently, these scientists assert that the meteorite impact was the primary driver of the extinction event affecting the dinosaurs.
What led to the extinction of the dinosaurs? Was it the Chicxulub meteorite, or did the massive volcanic activity also play a part? Many contemporary children’s literature on dinosaur history explores these two competing theories.
The meteorite impact in the Gulf of Mexico around 66 million years ago is well-established and acknowledged as the pivotal moment marking the end of the dinosaur era. However, geologists have debated for decades whether the extensive lava flows in the Indian region, occurring both before and after the meteorite strike, also influenced the decline of dinosaur populations. These volcanic events released substantial quantities of CO2, dust, and sulfur, which changed Earth’s climate in various ways and over different time periods compared to the meteorite collision.
Ancient peats
A fresh study published in the scientific journal Science Advances by researchers from Utrecht University and the University of Manchester provides strong evidence indicating that while volcanic eruptions in India had a significant impact on global climate, they most likely had a minimal effect on the dinosaurs’ mass extinction.
By examining fossil molecules in ancient peats from the USA, this research team reconstructed air temperatures from the time surrounding both the volcanic eruptions and the meteorite impact. Their findings revealed that a major volcanic eruption occurred roughly 30,000 years before the meteor impact, corresponding with a temperature drop of at least 5° Celsius. This cooling trend was likely caused by sulfur emissions from the volcanoes obstructing sunlight from reaching Earth’s surface.
Crucially, the scientists found that by around 20,000 years before the meteorite struck, Earth’s temperatures had already stabilized and returned to levels similar to those before the volcanic activity began. This warming period was likely facilitated by CO2 emissions from the volcanoes, according to Lauren O’Connor from Utrecht University: “These volcanic eruptions and their associated emissions of CO2 and sulfur would have had severe effects on life on Earth. However, these events occurred thousands of years prior to the meteorite impact and were probably only a minor factor in the dinosaurs’ extinction.”
Impact winter
With the impact of volcanism largely dismissed, the Chicxulub meteorite impact remains the leading cause of the dinosaur mass extinction. “In contrast, the asteroid’s impact triggered a series of catastrophic events, including wildfires, earthquakes, tsunamis, and an ‘impact winter’ that blocked sunlight and wreaked havoc on ecosystems. We believe that the asteroid ultimately delivered the decisive blow,” asserts Rhodri Jerrett from the University of Manchester.
The fossil peats analyzed by the researchers contain unique membrane-spanning molecules created by bacteria, whose structures vary according to their environmental temperatures. By studying the composition of these molecules found in ancient sediments, scientists can reconstruct historical temperatures. O’Connor states: “In this way, we established a detailed ‘temperature timeline’ leading up to the dinosaur extinction, allowing us to compare it with the fossil record to better understand the sequence of events.”
The researchers from Utrecht University, the University of Manchester, Plymouth University, and the Denver Museum of Nature & Science are now using the same methodology to explore past climates during other crucial periods in Earth’s history.
