Carnian pluvial episode

The Carnian pluvial episode (CPE), often called the Carnian pluvial event, was a time when Earth's global climate changed a lot. This change happened during the Carnian Stage, part of the Late Triassic Epoch, about 234–232 million years ago. Volcanoes near what is now North America caused the Earth to get warmer and rains to increase. Pluvial means "related to rain."

During the CPE, many types of plants and animals changed and grew in new ways. The first dinosaurs appeared, along with the ancestors of today's lizards, snakes, and the tuatara. Also, the first tiny ocean plants called coccoliths and dinoflagellates showed up. Some sea animals, like ammonoids, bryozoans, and crinoids, went extinct.

We can see signs of the CPE in rocks from that time all around the world. On land, the dry climate of the big landmass Pangea became hotter and wetter with more rain. In the oceans, layers of mud formed instead of limestone because fewer animals made carbonate shells.

Changes in chemicals in these rocks show that the Earth's temperature rose a lot. This warming was probably caused by big volcanic eruptions that put lots of CO2 into the air.

History and nomenclature

Scientists noticed changes in rocks from the Carnian stage before they thought about global climate changes. They saw dark layers in the Northern Limestone Alps that showed a break from long, sunny weather. These layers were called the Reingrabener Wende, or the Reingraben event. Other places, like Germany and the United Kingdom, also showed signs of more rain and rivers, even though the weather was usually dry.

In 1989, two scientists, Michael J. Simms and Alastair H. Ruffell, put these clues together. They suggested that a time of heavy rain changed many plants and animals in the middle of the Carnian. They called this time the Carnian pluvial episode. At first, many scientists did not agree with them. But in the late 2000s, more evidence from places like Italy started to support their idea. Today, scientists are still learning more about what caused this big change in the weather.

Environmental disruption

The Carnian pluvial episode made the world much wetter, changing the dry weather of the Late Triassic period. This extra wetness caused more rainfall. We can see this from things like siliciclastic sediments and special fossil soils that grow in humid places.

The world also got warmer during this time, likely because of big volcanic eruptions. This warmth changed the oceans and the air, making everything hotter. The extra rain and warmth caused rocks and soil to wear away faster. This sent more dirt and sand into the seas. These changes affected special ocean areas made of calcium carbonate, changing the shapes of these areas and the tiny sea creatures that lived there.

Effect on life

During the Carnian pluvial episode, many plants and animals changed. In the oceans, creatures like conodonts, ammonoids, crinoids, bryozoa, and green algae died out. But other groups, such as dinosaurs, calcareous nannofossils, corals, and conifers, grew and spread.

On land, the climate changes helped some animals do well while others had trouble. For example, some reptiles called rhynchosaurs that were common before mostly disappeared. Other animals, like aetosaurs and early sauropodomorph dinosaurs, became more diverse. Plants such as conifers, ferns, and bennettitaleans also spread widely, and large lakes and peat swamps began to form again.

Possible causes and influences

The Carnian Pluvial Episode was likely caused by the activity of the Wrangellia Large Igneous Province, a large area of volcanic activity in the Panthalassan Ocean. This volcanic activity put a lot of CO₂ into the atmosphere. This caused the Earth to get warmer and led to more rain on land. The warming also changed the oceans and hurt some areas that made carbonate.

Other things might have helped cause these changes, like the rising of a new mountain range, the Cimmerian orogen. This could have brought strong rains, like modern monsoons. Earth's orbit might have also played a part in when and how bad these changes were.