Cambrian Climate (posted 11/7/2019)
Mass demonstrations across America were in the news recently. Thousands of children, given the day off from school, flooded city streets with signs of “climate change” slogans. Their passion was driven by fear; teachers and politicians had been telling them the planet would die within just a few years from atmospheric carbon dioxide pollution, unless immediate, radical steps were taken to reverse the trend. America was to blame and only they could prevent the pending catastrophe and preserve their futures.
So is climate change such a new, man-made phenomenon? Let’s look at an ancient time period when no humans roamed the earth – the Cambrian.
View of the Grand Canyon with a man standing on the Cambrian-age (542 million years old) Tapeats Sandstone, the bottommost strata within the Paleozoic Era. The Tapeats rests upon the Great Unconformity, below which are the Precambrian rocks of the Vishnu Formation. Image source: rocdoctravel.com
Climate change is not a recent man-caused phenomenon; it has been the norm from the very beginning of our planet some 4.56 billion years ago. From 542 to 485.4 million-years-ago, in a geologic period known as the Cambrian, earth’s climate was quite different than today. Compare Today with the Cambrian:
Length of a day: 24 hours vs 21 hours; days in a year: 365 days vs 418 days; average global temperature: 56 degrees vs 70 degrees; polar ice caps: absent in most of the Cambrian; sea level: 100 to 300 feet higher during the Cambrian; carbon dioxide in the air: 405 ppm today vs 4500 ppm in Cambrian; atmospheric oxygen: 21% vs between 15% and 30%; location of continents: 95% of land south of the equator in Cambrian; land plants and animals: absent in the Cambrian; trilobites: extinct today and abundant in the Cambrian; Sun’s luminosity: 5% colder than today; number of animal phyla: approximately 36 – the same number today as during the Cambrian.
It is important to note that the Cambrian is a geologic period lasting nearly 58 million years, very long by today’s standards. Within that time span were a multitude of different climates. If you had lived during Cambrian times, your days would be three hours shorter, you would have a birthday every 418 days, you’d constantly need air conditioning, you would never experience ice and snow, and all your food would have to come from the ocean (no soil yet). On the positive side, you wouldn’t have to deal with insects, snakes, poison ivy and other nasties.
Cambrian Supercontinent Pannotia (Image credit: Daily Kos)
580 million years ago, during early Cambrian times, the earth looked much different than today. At that time, 95 percent of all land was located south of the equator, clustered in a supercontinent named Pannotia (also called Vendian or Greater Gondwana). The above view, looking down at the South Pole, shows only a little of Antarctica and Siberia extending north of the equator. Note: Amazonia = South America; Laurentia = North America; Baltica = Eurasia.
The Cambrian age officially began about 541.5 million years ago, marking the end of a six-million-year ice age known as Baykonurian. This ice age ended a 40-million-year span known as the “Ediacaran Biota”, a period filled with a myriad of weird-looking, complex, soft-bodied life forms. The global land mass was much smaller than today, and sea level was about 100 feet higher. Earth began to heat up early in the Cambrian (without the assistance of mankind), gradually melting the massive Baykonurian ice sheet, raising sea level an additional 200 feet while shrinking (by flooding) the exposed land masses.
Carbon dioxide in the Cambrian was over 10 times higher than the 405-ppm level of today. Of course, such a high level of this greenhouse gas helped keep global temperatures high, but no humans were around to blame - strictly nature. To support life on the planet, more greenhouse gas was needed to offset the cooling trend of the much-reduced luminosity of the Sun. Side note: the average human breaths out 3 pounds of CO2 per day; 4500 ppm = ½ percent of CO2 in the Cambrian atmosphere – humans can withstand more than ten times that level.
Oxygen levels in the sea is the lead story of the Cambrian climate; atmospheric oxygen would have mattered little since there were not yet land animals to breath it. Scientists believe that a rise in oxygen lead to what is commonly known as the “Cambrian Explosion”, a period when trillions of diverse fossils appeared in the strata. Pannotia, the super-continent near the south pole began to break up and move northward to the equator (due to plate tectonics). This opened the polar ocean currents, helping to distribute oxygen-rich waters for life to feed on. The first 20 million years of Cambrian (541mya to 521mya) the main evidence of life was from fossilized tracks called “Cruziana”. The first fossil trilobites appeared 521mya (see artist’s conception below – image credit: Tumbir).
There are 36 known Phyla of fauna (animal kingdom). In today’s world we see nine Phyla which dominate: Annelida (worms); Arthropoda (insects, extinct trilobites); Chordata (humans); Cnidaria (corals, jellyfish); Echinodermata (starfish, extinct crinoids); Mollusca (clams, squid); Nematoda (roundworms); Platyhelminthes (flatworms); and Porifera (sponges). Astonishingly, all 36 Phyla first appeared, in abundance, in the Cambrian; no new Phyla has evolved since then! Later in the Cambrian, 506mya, in a geologic rock bed known as the Burgess Shale, an entirely new suite of fossils appeared, presumed to have evolved from the former (see artist’s conception below – image credit: evidenceunseen.com).
Finally, toward the end of the Cambrian, another major change of climate occurred (500mya to 496mya); this change was labeled the SPICE Event (Steptoean Positive Carbon Isotype Excursion). Prior to SPICE, the oceans were buzzing with life, but the climate was changing, resulting in oxygen-deficient (anoxic) oceans. Then suddenly the climate took a drastic turn due to an event called a True Polar Wander (TPW). In a period of 4 million years, the seas filled with oxygen and atmospheric oxygen rose to 30 percent (compared to today’s 21%). Sea level dropped 75 feet, the earth cooled significantly, and huge amounts of carbon organic matter was buried in sediments thousands of feet thick. The result was mass extinctions of the creatures pictured above. But this opened wide the door for an explosion of biodiversity, which would appear in the next geologic period, the Ordovician.
The mega-climate changes observed in the Cambrian make our current changes seem minimal. It is obvious the Creator, without the help of mankind, was about the business of finetuning earth’s climate to accommodate his living creatures. The record shows that he continued to tweak the climate over the next 500 million years in preparation for the “just right” world that we thrive in. I think our concern over another couple hundred parts per million of carbon dioxide is a little over-rated; our Creator has everything under control.
