Carnian Pluvial Episode: That time when it rained for 1-2 million years

The Carnian Pluvial Episode (CPE) was an event on earth that took place at some point between 232 and 234 million years ago, when the earth’s climate changed radically.

During that time, the earth’s surface was still divided into the Pangea and the Panthalassa, where all the continents were joined together, forming one massive supercontinent surrounded by one vast ocean.

The Pangea was surrounded by mountains and consequently, all its central area was under a long dry spell, and some rainfall was present only at its edges near the vast ocean.

At some point in the 1970s, geologists Schlager and Schollnberger were investigating Austria’s Northern Limestone Alps when they discovered a layer of dark grey siliciclastic rock, which indicated very wet conditions within the era’s dry carbonate rock layer.

Following this discovery, the same layer was later uncovered by geologists in England, Israel, Italy and the U.S.A., solidifying the base for the occurrence of the Carnian Pluvial Episode.

During the CPE, the earth was receiving very frequent intervals of very heavy, continuous rain.

The main theory for the causes of CPE is that a series of very powerful volcanic eruptions took place in the Wrangellia Terrane, today’s Alaska and British Columbia, which filled the atmosphere with massive amounts of carbon dioxide.

It is worth noting that another theory exists, supporting that the emergence of a new mountain range, the Cimmerian orogen, created a strong pressure gradient between the ocean and the continent, creating a monsoon phenomenon deep withinin the Pangea. However, the volcanic eruption theory is believed to be more plausible.

In their turn, the massive amounts of carbon dioxide that were released into the atmosphere would have contributed to a global warming phenomenon.

Namely, it is believed that the planet’s average temperature before CPE was already 10 °C higher than today and was further raised by 3-4 °C due to the volcanic activity, while a change in the ocean’s salinity might also have taken place.

The Carnian Pluvial Episode was the cause for mass extinction of species inhabiting the earth at the time and played a major role in reshaping the environment for the next couple of millions of years.