Emergence of dinosaurs was driven by volcanoes powering ancient climate change

The rise of the dinosaurs during the middle to late Triassic period, more than 230 million years ago, coincided with significant environmental changes powered by major volcanic eruptions, new research has revealed.

The volcanoes drove an increase in global temperatures and humidity, which had a considerable impact on the development and evolution of animals and plants, and also coincided with the emergence of modern coniferous trees.

These changes are known as the Late Triassic Carnian Pluvial Episode (CPE), and the intense rainfall conditions that arose are known as a “mega-monsoon” climate, affecting the planet some 234 million to 232 million years ago.

The changes led to selective collapses in biodiversity in the world’s oceans, but on land both plants and animals underwent a period of rapid diversification.

To study the environmental changes, researchers led by academics at the UK’s University of Birmingham analysed sediment and fossil plant records from a lake in northern China’s Jiyuan Basin.

They found that pulses of volcanic activity aligned with the significant environmental changes that defined the creation of the mega-monsoon climate.

The research team said their work revealed “four distinct episodes of volcanic activity” during this period, with the most likely source being major volcanic eruptions from the Wrangellia Large Igneous Province, the remnants of which are preserved in western North America.

Co-author Jason Hilton, professor of palaeobotany and palaeoenvironments at the University of Birmingham’s School of Geography, Earth and Environmental Sciences, said: “Within the space of two million years the world’s animal and plant life underwent major changes including selective extinctions in the marine realm and diversification of plant and animal groups on land.

“These events coincide with a remarkable interval of intense rainfall known as the Carnian Pluvial Episode.

“Our research shows, in a detailed record from a lake in North China, that this period can actually be resolved into four distinct events, each one driven by discrete pulses of powerful volcanic activity associated with enormous releases of carbon dioxide into the atmosphere. These triggered an increase in global temperature and humidity.”

Professor Hilton also said that as well as driving the diversification of dinosaurs, “this remarkable period in Earth history was also important for the rise of modern conifer groups and had a major impact on the evolution of terrestrial ecosystems and animal and plant life – including ferns, crocodiles, turtles, insects and the first mammals”.

The study, published in Proceedings of the National Academy of Sciences, found that each phase of volcanic eruption coincided with large disturbances of the global carbon cycle, resulting in major climatic changes to more humid conditions, and also found that as a result the lake had deepened, while oxygen and animal life decreased.

Geological events over the same period in central Europe, east Greenland, Morocco, North America and Argentina, among other locations, indicate that higher rainfall led to widespread expansion of drainage basins converging into lakes or swamps, rather than rivers or oceans, the team said.

“Our results show that large volcanic eruptions can occur in multiple, discrete pulses demonstrating their powerful ability to alter the global carbon cycle, cause climate and hydrological disruption and drive evolutionary processes,” said co-author Dr Sarah Greene, senior lecturer also in the School of Geography, Earth and Environmental Sciences at the University of Birmingham.

Dr Emma Dunne, a palaeobiologist also at the the University of Birmingham, who was not involved in the study, said: “This relatively long period of volcanic activity and environmental change would have had considerable consequences for animals on land.

“At this time, the dinosaurs had just begun to diversify, and it’s likely that without this event, they would never have reached their ecological dominance we see over the next 150 million years”.