The Paleozoic Period began about 542 mya and ended around 251 mya. It was a time of great changes on planet Earth. As this geological period began a super-continent began to breakup as another one began to form. Plants started to become more widespread and this period saw the first emergence of vertebrae animals on land.
The Paleozoic Period was the earliest geologic period and is normally divided into 6 smaller geologic periods (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and the Permian. It was during the Cambrian Period that our planet saw a great explosion of life known as the “Cambrian Explosion.” Fish, arthropods, amphibians, anapsids, synapsids, euryapsids, and diaspids evolved during the Paleozoic Period.
Evolutionary theory holds that life began in the oceans and transformed onto land. Vast forests with primitive plants began to cover the land masses and in time many of these began to form the great coal beds we see in Europe and eastern North America today. It was towards the end of this period that we see the first modern plants emerge. But the Paleozoic was not a complete “Paradise” as the end of this period brought about the largest extinction event in Earth’s history! This has come to be known as the “Permian-Triassic Extinction Event.”
The Permian-Triassic Extinction Event was a big deal! The effects of it were so devastating that it took land life 30 million years to recover and it’s believed that it took sea life even longer to recover!!
Within the Paleozoic is a smaller geologic period known as the Carboniferous Period which began about 359 mya and ended about 299 mya. It was during this time that average global temperatures were high. In the early part of this period global average temps averaged around 20 degrees Celcius (68 Fahrenheit) but had cooled to around 10 degrees Celsius (50 Fahrenheit) by the middle of the period.
The graph below shows oxygen concentrations in the Earth’s atmosphere with the Carboniferous Period being inbetween the blue lines.
Historically there has been much more CO2 in our planet’s atmosphere that there is today. The highest CO2 levels occurred during the Cambrian Period with close to 7000 ppm which is about 18 times higher than today. In terms of average global temperatures the Carboniferous and Ordovician Periods were the only periods during the Paleozoic in which global average temps were as low as they are today.
The Late Ordovician Period was also a period of glaciation (Ice Age) during which CO2 levels were about 12 times higher than today (4400 ppm).
Tropical swamps dominated many areas and trees stiffened by lignin grew taller and more in number. Bacteria capable of eating the lignin had not yet evolved so the remains of these trees were left buried and much of this is what created much of the carbon that became today’s coal deposits. Throughout this period there was a cooling trend which finally lead to the Permo-Carboniferous Glaciation (Ice Age) aka the “Carboniferous Rainforest Collapse.” The Gondwana super-continent was glaciated as most of it was located near the South Pole.
The Permo-Carboniferous Glaciation (aka: Carboniferous Rainforest Collapse) was marked by two conditions. For one there was a continuous landmass stretching from pole to pole which restricted the free circulation of polar and tropical water. Secondly, the existence of a large south polar landmass was present and it was capable of supporting thick ice accumulations. These same conditions exist today in our own Quaternary Period (Holocene). During the Carboniferous Ice Age glacial ice accumulated, melted, and then reaccumulated. Some of the glaciers during this period were 8000 feet thick at the South Pole! As these ice sheets moved they destroyed everything in their pathway and scraped the land to bare rock. Mountains, valleys, and river courses were dramatically altered by the moving ice sheets. Bedrock found in Africa, Australia, India, and South America show scratches and gouges from these very ice sheets! Of course, it is very important to keep in mind that during the Carboniferous Period the Continents were arranged differently than they are today. South America, Africa, India, Australia, Antarctica, and smaller land masses were joined together near the South Pole comprising a super-continent known as “Gondwanaland.”
As I’ve mentioned before on this blog we are currently in an Ice Age era known as the Quaternary Period. For about the past 10,000 to 12,000 years we’ve been in a warming period known as an “interglacial.” Geological records obtained from ocean sediments and ice cores show us that for the last 750,000 years interglacial periods happen about every 100,000 years and last between 15,000 to 20,000 years before the glacial periods return. WE ARE PRESENTLY AROUND 18,000 YEARS INTO THE PRESENT WARMING (INTERGLACIAL) PERIOD.
Regarding humans….ancient human ancestors or species such as Ardipithecus wasn’t around in the Paleozoic Period. They weren’t around until about 5.6 mya but some form of ancient human ancestor was around in this period otherwise we would not be here today.
The Mesozoic Era (251 mya) followed the Paleozoic Era and that in turn was followed by the Cenozoic Era. The Cenozoic Era began about 66 mya and continues into the present day. It is this period we will look at next from a climate point of view and an ancient human ancestor point of view.