One million years of heavy rain triggered Earth's era of dinosaur dominance

Roughly 233 million years ago, Earth’s continents were fused into one massive landmass, and life as we know it was on the brink of transformation due to a one-million-year period of rain called the Carnian Pluvial Episode (CPE).

An international team of scientists has found evidence of this significant extinction event, which appears to have paved the way for dinosaurs to become the dominant creatures on Earth.

Involved in this important research are Dr. Jacopo Dal Corso from the China University of Geosciences at Wuhan and Professor Mike Benton from the University of Bristol.

Their collaborative efforts have pieced together a pivotal moment in our planet’s history that reshaped life both on land and in the oceans.

Carnian Pluvial Episode

Back in the Late Triassic period, all the continents were joined together in a supercontinent known as Pangea, surrounded by the vast Panthalassa Ocean. The interior of Pangea was mostly dry and arid, with rainfall occurring mainly near the coastal regions.

This dry spell took a dramatic turn when a layer of dark gray rock was discovered in Austria’s Northern Limestone Alps in the 1970s by geologists Schlager and Schollnberger.

This layer indicated wet conditions sandwiched between arid periods, suggesting a global climate event — the Carnian Pluvial Episode.

So, what caused this sudden shift to a wetter climate? The main culprit appears to be massive volcanic eruptions in the Wrangellia Province, an area that now includes parts of Alaska and British Columbia.

These eruptions released enormous amounts of carbon dioxide into the atmosphere.

“The eruptions peaked in the Carnian,” notes Dr. Jacopo Dal Corso. “They were so huge, they pumped vast amounts of greenhouse gases like carbon dioxide, leading to spikes of global warming.”

Pangea, biodiversity, and evolution

The supercontinent known as Pangea joined together almost all of Earth’s landmasses into one massive landmass.

Imagine all the continents we know today — North America, South America, Africa, Europe, Asia, Australia, and Antarctica — snapped together like pieces of a giant puzzle.

Pangea formed around 335 million years ago during the late Paleozoic era and dominated the planet until it began to break apart about 175 million years ago.

This massive gathering of land had a huge impact on the climate, sea levels, and the distribution of plants and animals across the globe.

As Pangea started to split apart, it set the stage for the continents to drift to their current positions through the process of plate tectonics.

This breakup led to the formation of the Atlantic Ocean and reshaped ecosystems, creating new environments for species to evolve and adapt.

Mass extinction and new beginnings

The surge in greenhouse gases caused global temperatures to rise by about 5 to 7 degrees Fahrenheit, amplifying evaporation from the seas and triggering increased rainfall worldwide.

This climate chaos led to significant biodiversity loss. Many species couldn’t adapt to the rapid environmental changes, resulting in a mass extinction event. But nature abhors a vacuum.

As some species disappeared, new ones emerged to fill the gaps, leading to ecosystems that began to resemble those we see today.

“The new floras probably provided slim pickings for the surviving herbivorous reptiles,” says Professor Mike Benton.

“We now know that dinosaurs originated some 20 million years before this event, but they remained quite rare and unimportant until the Carnian Pluvial Episode hit. It was the sudden arid conditions after the humid episode that gave dinosaurs their chance.”

Dinosaurs emerge from the Carnian Pluvial

As the climate shifted back to drier conditions, dinosaurs seized the opportunity to thrive. This period also saw the rise of the first turtles, crocodiles, lizards, and even the earliest mammals.

The expansion of conifer forests created new habitats, and these emerging animal groups diversified life on land in remarkable ways.

The oceans weren’t spared from the upheaval. The Carnian Pluvial Episode marks the beginning of modern coral reefs and the appearance of many groups of plankton.

These changes indicate significant shifts in ocean chemistry and the carbonate cycle, affecting the entire marine food chain and leading to new forms of marine life.

Recognizing a sixth mass extinction

Until now, scientists had identified five major mass extinctions over the past half-billion years. These events dramatically reshaped life’s trajectory on Earth.

“So far, paleontologists had identified five ‘big’ mass extinctions in the past 500 million years of the history of life,” says Dr. Dal Corso.

“We have identified another great extinction event, and it evidently had a major role in helping to reset life on land and in the oceans, marking the origins of modern ecosystems.”

Lessons from this Carnian Pluvial

The Carnian Pluvial Episode offers valuable insights into how massive volcanic eruptions and the resulting climate shifts can have far-reaching consequences.

The release of greenhouse gases like carbon dioxide led to global warming, increased rainfall, and environmental upheaval.

In our current era, human activities are raising greenhouse gas levels, leading to climate change. Studying events like the CPE can help us understand how ecosystems respond to rapid environmental changes.

Massive volcanic events

Dr. Dal Corso emphasizes the scale of these ancient volcanic events, saying, “The eruptions were so huge, they pumped vast amounts of greenhouse gases like carbon dioxide, and there were spikes of global warming.”

His observations highlight how natural events can dramatically alter our planet’s climate.

“I had noted a floral switch and ecological catastrophe among the herbivores back in 1983 when I completed my PhD,” Professor Benton notes.

His decades of work illustrate how scientific understanding evolves, building on clues from various fields to piece together Earth’s complex history.

Learning about events from millions of years ago requires collaboration across multiple scientific disciplines, including geology, paleontology, and climate science.

Discoveries like the Carnian Pluvial Episode showcase the importance of interdisciplinary research in deepening our understanding of Earth’s past.

Why does any of this matter?

As we face our own environmental challenges today, looking back at events like the Carnian Pluvial Episode can inform our actions.

If natural volcanic activity could cause such drastic changes, it raises questions about the impact of human-induced climate change.

How might life on Earth adapt — or struggle to adapt — in the face of current environmental shifts?

The story of the Carnian Pluvial Episode demonstrates Earth’s resilience and ability to recover and evolve after catastrophic events.

A period of massive volcanic eruptions and climate upheaval set the stage for the rise of dinosaurs and the formation of ecosystems that continue to influence life today.

As we continue to explore our planet’s history, each discovery offers a new perspective on the resilience and adaptability of life on Earth.

The full study was published in the journal PNAS.

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