Most of us are familiar with the story of the dinosaurs. They once ruled the Earth but were made extinct after an asteroid crashed into the Earth around 66 million years ago. The mass extinction that followed wiped out almost all of the dinosaurs and made way for the rise of mammals. Scientists from the China University of Geosciences at Wuhan and the University of Bristol have now discovered another extinction that occurred around 233 million years ago. This was the extinction that paved the way for dinosaurs to take over the world. Their findings are reported in the publication Science Advances.
There were 17 researchers involved and they studied paleontological and geological evidence to make the discovery. In the 1980s geologists Mike Simms and Alastair Ruffell discovered a warm, humid, wet period that lasted about 1 million years. This period has been known as the Carnian Pluvial Episode (CPE). The team from Bristol and Wuhan now say they have discovered the cause. They say that large volcanoes erupted along the western coast of Canada, pouring out volcanic basalt. This now forms part of the coast of North America. This area is today known as Wrangellia Province.
These volcanoes pumped out vast volumes of greenhouse gases such as carbon dioxide. As we are coming to realise today, when large quantities of greenhouse gasses accumulate in the atmosphere, it results in global warming. This research suggests this happened in a significant way during the CPE. The global warming eventually led to a major change in the biodiversity on Earth, both in the land and oceans. This created an opportunity for the coniferous forests to expand and other plants to develop. The Earth would have started to become more like it does today.
Due to the change in plants, existing herbivores, which are animals that eat plants, had very little food. The dinosaurs had already started to evolve before this event but they would have been quite rare. After the CPE, dinosaur populations began to expand rapidly. It is thought that the dry conditions after the warm humid period suited the dinosaurs and allowed them to prosper. Other animals such as crocodiles, lizards, turtles and even some mammals also appeared around the same time.
Before this discovery, we knew about 5 mass extinctions. This now brings the number to 6. Each of these extinctions was a turning point in evolution. They reset life, allowing different species to take over and dominate the world. They show just how resilient the Earth, life and nature are.
If you would like to read the paper in full you can get it at the link below. https://advances.sciencemag.org/content/6/38/eaba0099
Paul Smith 