The rise of the dinosaurs was driven by major volcanic eruptions and ‘mega monsoons’ more than 230 million years ago, a new study claims.
Researchers at the University of Birmingham analysed sediment and fossil plant records from a lake in the Jiyuan Basin in northern China.
Chemical signatures in the records, suggestive of pulses of volcanism, correlated with environmental changes that made up the Carnian Pluvial Episode (CPE).
CPE was a global crisis that occurred 234 million to 232 million years ago, during the stage of the late Triassic period, prior to continental drift when the world’s continents were clumped together.
It consisted of ‘mega monsoons’ of intense rainfall, as well as increases in global temperature and humidity, caused by the release of greenhouse gases.
It was a time of major volcanic eruptions, sudden changes in global climate and mass extinctions for plant and animal life, but it paved the way for dinosaurs to become the dominant species, the researchers say.
Ecological changes following intense volcanic activity during the Carnian Pluvial Episode 230 million years ago paved the way for dinosaurs to become the dominant species
CPE also coincided with the establishment of modern conifers, the group of cone-bearing seed plants, which dominated the landscape when dinosaurs flourished.
THE CARNIAN PLUVIAL EPISODE
The Carnian Pluvial Episode (CPE) was a global environmental change and biotic crisis that occurred during the Late Triassic period, 234 million to 232 million years.
It was a time of major volcanic eruptions, sudden changes in global climate and extinctions.
It was accompanied by increases in global temperature and humidity, large-scale volcanism and the ascent of dinosaurs.
The new study has been led by Jason Hilton, a professor at the University of Birmingham’s School of Geography, Earth and Environmental Sciences.
‘During the CPE, environments became wetter and lakes got deeper and larger, with these conditions favouring wetland and aquatic species,’ he said.
‘After the CPE climates and environments returned to drier conditions that favoured terrestrial species adapted to drier environments.
‘We see widespread turnover in plant and animal species during and following the CPE as conditions changed, with dinosaurs and modern conifer families being groups that benefitted from the globally drier conditions that occurred after the CPE.’
As well as benefitting dinosaurs, CPE also helped the evolution of terrestrial ecosystems and animal and plant life – including ferns, crocodiles, turtles, insects and the first mammals.
Although the existence of the CPE is already known, this new paper ‘convincingly shows’ that the CPR was driven by massive-scale volcanism, divided into four distinct episodes and spread over a two million year period, Professor Hilton told MailOnline.
‘Each pulse of volcanism was accompanied by large-scale perturbations in the carbon cycle and changes in global climate and environments,’ he said.
Example pollen, spores, and algae from the Carnian Pluvial Episode in China that record climate and environmental change following massive volcanism
For the study, the research team investigated terrestrial sediments from the ZJ-1 borehole in the Jiyuan Basin of North China.
They used uranium-lead zircon dating and high-resolution chemostratigraphy – a technique to determine chemical variations within sedimentary rock – as well as palynological data (the study of particles such as pollen and spores).
They found a correlation between terrestrial conditions in the Jiyuan Basin with large-scale volcanic activity in North America at the same time.
The most likely source of this volcanic activity was major eruptions in the Wrangellia large igneous province in North America, which was at the time west of the ‘supercontinent’ Pangaea.
CPE was a global crisis that occurred 234 million to 232 million years ago, during the stage of the late Triassic period, prior to continental drift when the world’s continents were clumped together. Volcanic eruptions that caused the CPE were likely triggered at Wrangellia (labeled on the map as 1), west of supercontinent Pangaea
WHEN DID DINOSAURS APPEAR?
The origin of the dinosaurs is long-debated. What is agreed is the Triassic began ended with dinosaurs everywhere.
Although dinosaurs were around from the beginning of the Triassic Period, some 245 million years ago, they were relatively rare at this point in history.
About 232 million years ago, the dinosaurs diversified explosively, so the CPE essentially marks the beginning of the ‘age of dinosaurs’ and their 165-million-year rule of the Earth.
Source: The Geological Society
The results suggest that there were four distinct episodes of volcanism during the period – based on mercury concentration data used as a proxy for eruptions – each associated with enormous releases of carbon dioxide (CO2) into the atmosphere.
‘In the borehole core we studied, we sampled the rock to examine its chemistry and microfossils as evidence of environmental change,’ explained Professor Hilton.
‘Each pulse of volcanism is marked by a change in the carbon cycle and each has a peak in the concentration of the toxic metal mercury.
‘Mercury derives from volcanism and was deposited ultimately in the lake directly from the atmosphere or washed into the lake from surrounding land.
‘The microfossils include pollen and spores produced by plants living in and around the lake, as well as cysts from algae living in it.’
The microfossils revealed that each pulse of volcanism was marked by changes in the flora – specifically an increase in algae and spores from wetland plants including ferns, and decreases in pollen from plants living in drier conditions such as conifers.
‘The microfossils give us excellent information on the conditions in which the plants and algae lived changing over time,’ said Professor Hilton.
It was the enormous releases of carbon dioxide (CO2) into the atmosphere that triggered a major intensification of the hydrological cycle, causing mega monsoons, as well as lake acidification and eutrophication.
Eutrophication is overly-enriched waters leading to excessive growth of algae, due to increased levels of CO2 needed for photosynthesis.
About 232 million years ago, the dinosaurs diversified explosively, so the CPE essentially marks the beginning of the ‘age of dinosaurs’
Overall, increased rainfall from the mega monsoons resulted in widespread expansion of drainage basins converging into lakes or swamps, rather than rivers or oceans.
‘This relatively long period of volcanic activity and environmental change would have had considerable consequences for animals on land,’ said Dr Emma Dunne, a palaeobiologist at the University of Birmingham who was not involved in the study.
‘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.’
Dinosaurs dominated the landscape of both land, sea and air until their own mass extinction event 66 million years ago.
The new study has been published today in the journal Proceedings of the National Academy of Sciences.
HOW THE DINOSAURS WENT EXTINCT AROUND 66 MILLION YEARS AGO
Dinosaurs ruled and dominated Earth around 66 million years ago, before they suddenly went extinct.
The Cretaceous-Tertiary extinction event is the name given to this mass extinction.
It was believed for many years that the changing climate destroyed the food chain of the huge reptiles.
In the 1980s, paleontologists discovered a layer of iridium.
This is an element that is rare on Earth but is found in vast quantities in space.
When this was dated, it coincided precisely with when the dinosaurs disappeared from the fossil record.
A decade later, scientists uncovered the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, which dates to the period in question.
Scientific consensus now says that these two factors are linked and they were both probably caused by an enormous asteroid crashing to Earth.
With the projected size and impact velocity, the collision would have caused an enormous shock-wave and likely triggered seismic activity.
The fallout would have created plumes of ash that likely covered all of the planet and made it impossible for dinosaurs to survive.
Other animals and plant species had a shorter time-span between generations which allowed them to survive.
There are several other theories as to what caused the demise of the famous animals.
One early theory was that small mammals ate dinosaur eggs and another proposes that toxic angiosperms (flowering plants) killed them off.