The Mesozoic Begins
Published in the EarthSphere Blog. Feature Image: The Great Carnian Flood — No Arcs Available (©2022 Archean Enterprises, LLC; ArcheanArt)
Prologue
Our last article in the Forgotten Origins series chronicled a biological catastrophe at the end of the Permian Period, the Great Dying. The vast majority of all species on the planet disappeared in the geological blink of an eye. Those species remaining struggled forward into the Triassic.
Last article: Life Crashes as the Permian Ends
A New Era
Geological history drew a line in the sand 252 million years ago. The Permian Period ended, and the Triassic began. But it also marked the end of the Paleozoic Era and the beginning of the Mesozoic. As a society, we find the Mesozoic Era much more interesting than its predecessor. To my knowledge, there are no popular movies about Cambrian, Ordovician, Silurian, Devonian, Carboniferous, or Permian theme parks. But it seems we get a new movie or book every several months about Mesozoic attractions like Jurassic Park or Jurassic World. There is something about dinosaurs we find quite thrilling.
All dark clouds have a silver lining, and the mass extinction at the end of the Permian was no exception. The good news was that the fittest survived, and when the planet returned to a more livable state, life had a clean slate on which to work its magic and embark on a new beginning. Evolution had the opportunity to do what it does best, adapt and create.
The Triassic began in unusual circumstances with an underpopulated planet. Amongst the survivors of the “Great Dying” were the archosauriforms. They continued evolving during the Triassic, eventually starting the reign of the dinosaurs.
The earliest dinosaurs (Nyasasaurus parringtoni) appeared about 243 million years ago in the Middle Triassic during the Anisian age. But they were comparatively small creatures, and another 30 million years passed before a giant arose. Weighing in at 3 tons and up to 27 feet long, the Plateosaurus was a forerunner of the Jurassic monsters we love to see on the big screen.
New species inevitably arise after the biosphere collapses. So we can rest safely knowing that the Anthropocene extinction probably won’t be the end of all life. Perhaps Homo sapiens will be around after the party ends to help get the ball rolling again, or maybe not.
Carnian Pluvial Episode
The Triassic period lasted for about 50 million years, but it was not all peaches and roses. The period of the Upper Triassic from 237 to 227 million years ago is known as the Carnian. A two million-year stretch of the Carnian from 234 to 232 million years ago is known as the Carnian Pluvial Episode. It is famous for intense climate change, where global warming pushed temperatures up by over 4 degrees Celsius, creating a very wet planet.
Pluvial periods are characterized by a wet climate with intense rainfall and widespread flooding. Researchers have described the Carnian Pluvial Episode as “one of the most significant intervals of the past 250 My. Within the space of ∼2 My, the world’s biota underwent major changes with dinosaurs becoming the notable incumbents.”
Heat, humidity, and intense storms changed life on land, and the increased sedimentation from constant flooding wiped out coastal marine reefs and ecosystems. Climate change was in full swing, and species extinction rates climbed. The most likely culprit for global warming during the Carnian was massive quantities of carbon dioxide and other greenhouse gases emitted into the atmosphere from volcanic eruptions. Carbon isotope analysis of rocks from the Carnian Pluvial Episode supports this hypothesis.
The Wrangellia Large Igneous Province
Sometimes geological lingo becomes a bit obtuse, but in this case, a large igneous province is just what it says. It’s not just one volcano or a single fissure with magma flowing out, but a large geographical region with lots of these features actively spewing molten lava over Earth’s surface.
Today a visitor traveling the length of North America’s West Coast traverses mountain ranges from Vancouver, Canada, to Alaska. They might not realize they are traveling through the remains of an ancient geological province known as the Wrangellia Large Igneous Province. The rocks forming today’s mountains are part of a plateau formed deep beneath a long-gone Triassic ocean. Magma and flood basalts erupted onto the ancient ocean floor with accumulations up to 4,000 feet thick.
These thick basalt flows erupted for millions years and originally covered over half-a-million square miles of seafloor. As was the case with the Permian extinction, volcanic gases, not magma, served as the instigator for global climate change.
Some researchers link the Carnian Pluvial Episode with the formation of the Wrangellia basalts, but others believe the Wrangellia eruptions began at the end of the Pluvial Episode. Further work will be needed before Carnian global warming and Wrangellia volcanic emissions can be definitively tied together.
Our increasing awareness of today’s Anthropocene climate change makes the Triassic story uncomfortably familiar. True, the Carnian warming was not due to industrial activity, but global warming makes no distinction between greenhouse gas sources. Whether greenhouse gases are from volcanic activity, carbon feedback cycles, or fossil fuel burning is irrelevant because the warming and environmental consequences are the same. Earth only responds to the physics of more heat trapped in the atmosphere.
(Next: Dinosaurs get a kick start)
ArcheanArt
Sources:
Did a million years of rain jump-start dinosaur evolution? (Source: Nature)
Volcanically driven lacustrine ecosystem changes during the Carnian Pluvial Episode (Late Triassic); (Source PNAS)
Extinction and dawn of the modern world in the Carnian (Late Triassic) — (Source: Science Advances)
Scientists Discover Oldest Known Dinosaur (By Riley Black; Smithsonian)
Insights into climate change during origin of dinosaurs (Source: University of Utah; Phys Org)
A Climate Catastrophe Paved the Way for the Dinosaurs’ Reign (By Peter Brannen; The Atlantic)
The Accreted Late Triassic Wrangellia Oceanic Plateau in Alaska, Yukon, and British Columbia (By Andrew R. Greene, James S. Scoates, Dominique Weis; Large Igneous Provinces Commission)
