Does Earth have a memory?
With the park closed for much of 2020 due to COVID19 and later the Woodward Fire, the Point Reyes National Seashore Association began producing webinars with local experts to keep people connected to nature as part of their #ParkInPlace program.
Staying connected through these webinars was a lifeline. Of the many excellent webinars, the one I enjoyed most was local educator and naturalist Don Jolley’s Does Earth Have a Memory? (… and if it does, what does it remember?) He asks, “How do we make sense of a story extending 4.5 billion years into the past? And what events in that long history have left their marks most indelibly on the planet we call home?” He used simple but highly engaging tools — paper, a black marker, and a meter stick to vividly describe what has happened to the earth over deep geologic time to the very beginning of Earth’s formation. He provides a mini math lesson and makes complex concepts and processes easy to understand — semantic and episodic memory, the invention of sex, and much more. You don’t want to miss this one!
He begins by asking you to consider these 7 questions about your own history:
What’s your most memorable event since you woke up today?
What’s the most memorable event from the last 24 hours?
What’s the most memorable event from the last week?
What’s the most memorable event from the last month?
What’s the most memorable event from the last year?
What’s the most memorable event of the last decade?
What’s the most memorable event of your life?
Did you notice the farther back in time you go, the more significant your memories tend to be? The magnitude, duration and impact of the events that have left their mark is larger the farther back you go in time. And the memories are unevenly spaced.
Don explains that semantic memory is our knowledge of how to do things. It’s experiential knowledge. What does Earth know how to do? Earth knows how to regulate temperature, organize elements according to density, move materials, cycle rock. In contrast, episodic memory are the things that have happened to Earth over time. Earth’s episodic memory is the drift of continents, movement of oceans, formation and melting of ice caps, rise and fall of species.
He distinguishes between the abiotic factors that shape our world such as the formation of continents and oceans, change in chemical composition of atmosphere, periods of rapid vulcanism, and changes in climate versus the biotic or living components of our Earth’s ecosystem such as plants and animals and their affect on the world.
Don showed a simple black and white geologic time scale. He noted there’s no census on the geologic time scale — the names for periods of time and when they occurred varies widely. He demonstrated some basic math to help us comprehend how enormous a billion years is.
The Cryptozoic eon (sometimes called the Precambrian eon) is by far the largest period of time in Earth’s existence. It lasted two BILLION years from 4.5 billion years ago to 2.5 billion years ago. Crypto means hidden. It was the time of hidden life where biotic life had not yet emerged.
The Hadean era (4.5-4 bya) is when the Earth was formed. It took half a billion years for this to happen.
The Archean era (4 to 2.5 bya) marks the first life on earth, bacteria. For 1.5 billion years or three times the amount of time it took the Earth to form, cyanobacteria ruled the Earth — a rocky watery planet with pond scum. Bacteria were spewing oxygen into the atmosphere for 1.5 billion years.
The Proterozoic era (2.5 bya to 570 million years ago) marks the rise and proliferation of multi-cellular life and the invention of sexual reproduction.
We now move out of the hidden life and enter the Phanerozoic eon, meaning the time of visible life. The Cambrian period at 570 million years ago experienced a major explosion of life with incredible diversity, complexity, and variation. All major phylla emerged — life with limbs, shells, central nervous systems. Respiration and photo synthesis are present. The predator/prey relationship begins. Oxygen, which had been building for billions of years, fuels larger life forms.
An “aha” moment is understanding the geologic time scale is not proportionate. The time of the deep past is represented in a small portion of the scale at the bottom of the page since so little is known of that time, whereas more recent times are shown in a more detailed breakdown taking up the majority of the page. At about 30 minutes into the webinar, Don spread this arms and explained that a fathom is 6 feet, which is about the length of an arm span. The Crypotozoic eon extended from the tip of his right finger to his opposite wrist. Everything in the Phanerozoic (visible) eon is represented in the vastly smaller portion from his left wrist to finger tip. Don took out a pair of nail clippers and clipped off the top of a fingernail. That small sliver represented the sum total time humans have existed on earth. Don explained that “Earth is writing its autobiography and erasing it through erosion.“ I love that metaphor.
Earth remembers 5 major extinctions, from earliest to latest:
Ordovician - disruption of global temperatures; volcanic activity was largely the cause; 87% of species wiped out.
End of Devonian - a long duration extinction that lasted 20 million year! Plants moved onto land and changed the atmosphere; 75% of species were eliminated.
End of Permian - called the great dying; volcanic activity, ocean acidification, ozone depletion; possibly due to a meteor strike; lasted 50,000 years; 96% of species were eliminated.
Triassic - extinction event lasted 18 million years, half the length of the Triassic period; 80% of species wiped out.
End of Cretaceous — caused by a meteor strike; meteorite evidence still exists today; 76% of species wiped out.
Extinction is normal. The background rate of extinction is one species per million per year. This normal extinction rate amounts to about ten to one hundred species per year. However, since the 1990’s the extinction rate has skyrocketed — 27,000 species a year from habitat destruction alone. That’s hundreds of times the normal rate of extinction!
Don’s physical explanation of carbon dioxide in the atmosphere was another aha moment. He held up a meter stick and marked a line on 280 millimeters. It represented the carbon dioxide level in the atmosphere in the pre-industrial age. Then, he drew another line nearby at 417 millimeters — almost at the halfway point of the meter stick. That’s the amount of carbon dioxide in the atmosphere today. Carbon dioxide is one of four primary greenhouse gases that traps heat and affects climate, ocean levels, and the distribution of species. To measure parts per million (ppm), he explained that one million millimeters would be 1000 meter sticks lined up end to end. These 1000 meter sticks represent the sum total of earth’s atmosphere. The truth is, there’s almost no carbon dioxide in the atmosphere proportionally! That means it doesn’t require much human activity to change the levels. Don’s explanation made it clear to me how delicate the balance of carbon dioxide is in the atmosphere — a small elevation can have catastrophic effects. We are seeing evidence of this today with the affects of global warming: sea level rise, ocean acidification, droughts, wildfires, more severe weather events such as hurricanes and more.
The coming sixth extinction is being driven by human activity. We are at the dawn of a new memory for earth, the Anthropocene, where human activity is the dominant influence on climate and the environment. What’s different about this extinction? Most extinctions took tens of thousands or tens of millions of years to unfold. Compare that with the rapid rate of environmental change today. Don finished the webinar by reading some of his own thoughts on the current state of Earth. He concluded, “we’ve hitched a ride on a changing planet and it’s going to respond based on its working memory. No single thing abides.” Ever hopeful, he ended the webinar on a humorous note with the words from his favorite bumper sticker “Nature bats last”.