Roughly 234 million years ago, during the Late Triassic period, Earth’s continents were fused into the supercontinent Pangaea. This vast landmass was largely arid, with limited rainfall. However, a dramatic shift occurred: a period of incessant rain began, lasting approximately two million years. This event, known as the Carnian Pluvial Episode (CPE), appears to have fundamentally reshaped life on Earth, paving the way for the rise of the dinosaurs.
The evidence for this prolonged wet period was first identified in the 1970s by geologists Schlager and Schollnberger, who discovered a layer of dark gray rock within the Northern Limestone Alps of Austria. This layer indicated sustained wet conditions sandwiched between drier periods, suggesting a significant global climate event. “In the space of about 2 million years, the world’s fauna and flora underwent major transformations, with the emergence of dinosaurs,” explains a recent study published in the journal PNAS.
An international team of scientists has now pinpointed the cause of this dramatic climate shift. New analyses conducted in China reveal that the CPE can be broken down into four distinct events, each triggered by intense volcanic activity and massive releases of carbon dioxide into the atmosphere. These eruptions originated in the Wrangellia Province, an area now encompassing parts of Alaska and British Columbia.
The volcanic activity released enormous quantities of CO2, a greenhouse gas, into the atmosphere. This led to a natural warming of the planet, with temperatures rising by an average of 3 to 4 °C globally. As temperatures increased, evaporation from the oceans also rose, adding more moisture to the atmosphere and intensifying rainfall patterns.
The CPE wasn’t simply a period of increased rainfall; it was a period of significant ecological upheaval. The existing biodiversity largely collapsed as many species were unable to adapt to the rapidly changing conditions. However, new species emerged, including herbivorous reptiles that thrived in the newly abundant vegetation. Dinosaurs, already present at the time, were relatively few in number, but their population exploded following this extended period of rainfall, marking a pivotal moment in their evolutionary history.
The CPE demonstrates the profound impact that changes in CO2 emissions – whether from natural sources like volcanism or, as is the case today, from human activity – can have on the planet and all life it supports. The event highlights how alterations to the global carbon cycle can fundamentally reshape ecosystems and drive major evolutionary shifts. The increased humidity, a direct consequence of the warming, further exacerbated the situation, leading to more frequent and intense rainfall events.
The study highlights a crucial link between volcanic eruptions, climate change, and the rise of dinosaurs. Previous research had noted the temperature increases, humidity, and rainfall during this period, as well as the changes in both terrestrial and marine life. However, this new research provides a more detailed understanding of the causal mechanisms behind these changes. Scientists analyzed a several-hundred-meter core of lake-bottom sediments from the Jiyuan Basin in China, identifying four distinct layers of volcanic ash dating back to between 234 and 232 million years ago, coinciding with the CPE.
The implications of the CPE extend beyond understanding the distant past. The event serves as a stark reminder of the potential consequences of rapid climate change. Just as the massive volcanic eruptions of the Late Triassic triggered a cascade of environmental effects, the current anthropogenic increase in CO2 emissions is driving a similar, albeit faster, warming trend. The CPE underscores the interconnectedness of Earth’s systems and the potential for relatively small changes in atmospheric composition to have far-reaching and transformative consequences.
The research team, including Dr. Jacopo Dal Corso from the China University of Geosciences at Wuhan and Professor Mike Benton from the University of Bristol, emphasizes the importance of understanding past climate events to better predict and mitigate the impacts of future climate change. The CPE provides a natural experiment, demonstrating how ecosystems respond to significant shifts in temperature and precipitation, offering valuable insights for navigating the challenges of a rapidly changing world.