One of the things about science that puts many people off is the incredible number of words that you need to learn to be able to talk about (or listen to) scientific ideas. Really bad science teachers, in fact, stress the word aspects of science so much that their students begin to believe that science is just a list of odd (but picky and precise) terms and facts that need to be memorized. I apologize to everyone who has had such an ill-informed and ignorant teacher!
We do need, though, some precision of language and some terms that express ideas beyond our everyday experiences in order to explore many scientific ideas. Words like the terms in the hierarchy of the Geologic Time Scale, for example, allow us see and discuss things that go far beyond days of the week or months of the year. I am sorry, though, for having to introduce so many funny names!
I am writing this on Tuesday, July 24, 2018. This day, like all of my previous days and, I hope, all of my days to come are in the sub-division of Earth’s geologic existence called the Phanerzoic Eon. The Phanerzoic Eon started about 541 million years ago when living organisms “suddenly” became both more complex and more abundant! The Phanerzoic Eon, then, is defined as the span of time when the Earth has abundant plants and animals.
There were three eons before the Phanerzoic: the Hadeon, the Archean, and the Proterozoic Eons. Collectively these three eons are lumped into a phase called the Precambrium Super-eon which spans the first four billion years of the life of the Earth (or, to orient these numbers clearly, the first 90%, or so, of Earth’s existence).
The past 541 million years, this Eon of Life, then, is just a blink of the geologic eye in the span of “Earth time!”
The Phanerzoic Eon, like all eons, is divided up into eras. There are three eras named to express the stage development of life on Earth: Paleozoic (“early life”), Mesozoic (“middle life”) and Cenozoic (“new life”). Tuesday, July 24, 2018, of course, is in the Cenozoic Era (which has been going on for the past 66 million years (ever since something really bad happened to 75% of the species that had dominated the Mesozoic!).
The Cenozoic Era is divided up into three periods: the Paleogene, the Neogene, and the Quaternary. The Quaternary Period is the most recent of these periods and represents the past 2.6 million years. This is the time in which humans (defined as individuals of the genus Homo) have existed. This is also the time of the Ice Ages and the present day “warm” period (which, in fact, may be just a pause in the ice age cycle (we’re not absolutely sure about that)). These two events (Ice Ages and non-Ice Ages) serve as the basis for the two epochs of the Quaternary Period (epochs are, of course, divisions of periods): the Pleistocene (2.5 million years of ice advances and retreats across the face of the globe) and the Holocene (the past 12,000 years, or so, when the Earth has been warm and relatively ice-free (and during which humans developed agriculture and all of our other technologies!).
Epochs, by the way, are divided up into Ages. The 12,000 years of the Quaternary Epoch is divided pretty evenly (about 4000 years each) into three Ages: the Greelandian Age, the Northgrippian Age, and the Meghalayan Age. The onset of the Meghalayan Age began with the global climate shift that led to the end of the great, ancient human civilizations of North Africa, the Mediterranean, the Middle East, India and China. We, here on July 24, 2018 are in year #4,200 (possibly at the very end!) of the Meghalayan Age.
So what comes next? Is there a new Age in the wings waiting to come into definition?
There was a proposal a few years ago to call the “now” the Homogeocene to emphasize the influence of humans in the homogenization of the distribution of plants all around the world (see Signs of Spring 11, 2017). There have also been proposals to define the “now” in broader terms that emphasize more of the scope and magnitude of the human influence on the land, sea and air systems of the Earth. These proposals are all wrapped up in a geologic term called the Anthropocene.
The Carnegie Museum of Natural History in Pittsburgh has (until Sept. 3, 2018) an exhibition in which the characteristics of the proposed Anthropocene are displayed. Deborah and I had the chance to see this exhibition in May with our friends Patrick and Mardelle Kopnicky.
The exhibit illustrated human impacts on coral reefs, on plant flowering and leafing times, on domesticated and wild animals, on extinction rates, on habitats, on climate, and on the composition of the atmosphere itself. The astounding amounts of plastics produced, used, and then discarded into landfills, fresh water systems and the oceans were graphically and visually displayed. The wall-sized photograph of a surfer wrapped up in the curl of a wave that was densely packed with floating plastic debris is an image I cannot get out of my mind. These plastics represent the introduction into the systems of the Earth materials that have never existed before in Nature (see Signs of Fall #4, 2017). Their ultimate impacts on the Earth are still unclear.
The astounding (and growing) number of human beings on Earth (another feature of the Anthropocene) leaves one with the impression that none of the changes can ever be reversed (see Signs of Spring 3, 2016).
So what is the Anthropocene? Its name sounds like an Epoch. Something proposed to replace the Holocene? A committee of the International Commission on Stratigraphy (ICS) has proposed to make the Anthropocene the next geologic Age (i.e. the next subdivision of the Holocene). This proposal must then be voted on by the entire ICS and then approved by the International Union of Geological Science. The Anthropocene would not be a new Epoch (the Holocene still is incredibly new and appropriately defined), but it would be a logical continuation of the Ages of the Holocene emphasizing the prime force that is shaping our planet today: us.