The late Paleozoic usually spans from the beginning of the Devonian period (417 Ma) to the end of the Permian Period and the Great Dying (248 Ma). Since I talked about the Devonian and its mass extinction last week, in this post I’ll be focusing on the Carboniferous Period through the Permian and the Great Dying. For only covering a relatively short 100 million years, these periods experienced some of the greatest changes the Earth has ever seen. Ever wondered where all Earth’s coal comes from? How about how and when Pangea formed? And what is the worst mass extinction the Earth has ever seen? All of this and more was in the late Paleozoic!

The Carboniferous Period (359-299 Ma) is often broken down into the Mississippian (354-323 Ma) and Pennsylvanian (323-290 Ma) periods and was the time of the swamps. According to a USGS Paleozoic page, the Carboniferous was the time when most of the Earth’s coal formed because its climate was so swampy, allowing many plants, including a variety of ferns and even the first evergreen trees, to flourish. (To learn more about the Paleozoic’s plants, check out this detailed paper.) During this period, the climate swung between glacial and warmer periods, causing repeated sea level changes. Because of this, some shallow water organisms moved onto land, and the first reptiles and winged insects appeared. Some of these bugs had wingspans of up to 3 feet!

 

The Carboniferous didn’t just experience climate swings, it also saw the formation of Pangea, Earth’s most famous supercontinent. You might have heard of Pangea before because it was the supercontinent that formed the mountain ranges, glacial scars, and fossils that Alfred Wegner used to propose the theory of Plate Tectonics. Pangea formed in the Carboniferous over a few million years as Gondwana, which had been over the South Pole, moved upwards until it crashed into Laurussia/Euramerica.

 

 

The formation of Pangea began after the Iapetus Ocean, which separated Laurussia and Gondwana, started to close in the Ordovician, setting the stage for a major collision around 320 million years ago. When Gondwana and Laurussia collided to form Pangea, they also formed many of the mountain ranges that we know today, including the Appalachians in North America and the Alps in Europe. Pangea’s climate was largely very dry in the center of the continent with occasional devastating flash floods, and warm swamps in the equatorial region.

 

The Pangea supercontinent lasted until about 190 Ma, when it began to break apart over the course of 15 million years to form the continents we know today. (If you’d like to learn more about plate tectonics, check out this USGS website!)

After the Carboniferous ended with the formation of Pangea, the Permian Period (299-252 Ma) began. The Permian was largely defined by the conditions created by Pangea, so its climate was extremely dry as water from the oceans couldn’t reach the center of the continent because of the various mountain ranges created by the continental collisions. This led to a decrease in the number of amphibians and an increase in the number of reptiles wandering around. The early precursors to mammals evolved during this time, and the swamps of the Carboniferous became large evergreen forests. Unfortunately, the Permian is known less for the animals that lived during this period, and more for the mass extinction that followed.

The Great Dying was the worst mass extinction the Earth has ever seen. This mass extinction killed 90% of all species on Earth, including 96% of those in the oceans and 70% of those on land. Scientists are unsure what exactly caused this mass extinction, but it seems to be some combination of acid rain caused by volcanic eruptions, mercury produced by extensive basaltic magma plateaus, and global warming, which may have deprived the oceans of oxygen, causing the mass suffocation of oceanic organisms. The chain of events that started the Great Dying may have gone something like this. A series of volcanic eruptions known as the Siberian Traps produced enough lava to cover the entire US in up to a kilometer (0.6 mi) of basaltic plateaus. This eruption released greenhouse gases that caused surface and ocean temperatures to increase by about 10 degrees Celsius, decreasing the oxygen in the ocean by 76%.

I know I covered a lot today, so thanks for sticking with me! Here’s a quick summary of the late Paleozoic to wrap things up: a swampy Earth created the coal that fuels today’s industry, the Pangea supercontinent formed in the Carboniferous Period, and the Permian Period ended with the Great Dying. And just remember, it may not seem like it to us, but the Earth is an incredibly dynamic system. I hope to see you next time for an investigation into the Mesozoic and the dinosaurs!