The biggest beasts to walk the Earth had humble beginnings. The first dinosaurs were cat-sized, lurking in the shadows, just waiting for their moment. That moment came when four major pulses of volcanic activity changed the climate in a geologic blink of an eye, causing a 2-million-year-long rainy spell that coincided with dinos rising to dominance, a new study suggests.
During this geologically brief rainy period 234 million to 232 million years ago, called the Carnian Pluvial Episode, dinosaurs started evolving into the hulking and diverse creatures that would dominate the landscape for the next 166 million years.
Previous research has noted the jump in global temperatures, humidity and rainfall during this time period, as well as a changeover in land and sea life. But these studies lacked detail on what caused these changes, says Jason Hilton, a paleobotanist at the University of Birmingham in England.
So Hilton and his colleagues turned to a several-hundred-meter-long core of lake-bottom sediments drawn from the Jiyuan Basin for answers. The core contained four distinct layers of sediments that included volcanic ash that the team dated to between 234 million and 232 million years ago, matching the timing of the Carnian Pluvial Episode. Within those layers, the team also found mercury, a proxy for volcanic eruptions. “Mercury entered the lake from a mix of atmospheric pollution, volcanic ash and also being washed in from surrounding land that had elevated levels of mercury from volcanism,” Hilton says.
During this geologically brief rainy period 234 million to 232 million years ago, called the Carnian Pluvial Episode, dinosaurs started evolving into the hulking and diverse creatures that would dominate the landscape for the next 166 million years.
Previous research has noted the jump in global temperatures, humidity and rainfall during this time period, as well as a changeover in land and sea life. But these studies lacked detail on what caused these changes, says Jason Hilton, a paleobotanist at the University of Birmingham in England.
So Hilton and his colleagues turned to a several-hundred-meter-long core of lake-bottom sediments drawn from the Jiyuan Basin for answers. The core contained four distinct layers of sediments that included volcanic ash that the team dated to between 234 million and 232 million years ago, matching the timing of the Carnian Pluvial Episode. Within those layers, the team also found mercury, a proxy for volcanic eruptions. “Mercury entered the lake from a mix of atmospheric pollution, volcanic ash and also being washed in from surrounding land that had elevated levels of mercury from volcanism,” Hilton says.
