The Eons of Earth are long and diverse, I’ll be showing some of the unique events happening in each eon and try to explain where Severson would be in this time period. The image to the right shows how long each Eon is in compared to how long the Earth has been a part of this universe. If you look extra closely you can see the tiny little sliver of light blue where the modern humans first came into existence showing truly how our time on this planet has been infinitesimally small so far.
FIELD NOTES BLOG
Severson Through Billions of Years
Alex Lunde
June 19, 2024
How Old is the Earth?
The Earth is extremely, unimaginably old- even now it's hard for me to truly comprehend given I have only been around this planet for a very short amount of time (25 years give or take a few). On the contrary the Earth is about 4.543 billion years old (± 0.05 billion years). That means the Earth is almost two hundred million times older than me, but to be honest that still barely makes any sense, so let's try to rectify that. From there we will develop a better understanding of each of the different eons that exist and view where Severson Dells might be in this situation.
Visualizing Absurdly Large Numbers
There are a couple ways to visualize big numbers. Let's start off with the ‘smaller’ number of 1 million. If you were able to count one number per second without stopping (a herculean feat that is impossible for a human but oh well). It would take 11 days, 13 hours, 46 minutes, and 40 seconds to count from 1 to 1,000,000. So that is with optimal conditions. Someone has actually counted to the number 1,000,000 and it was recorded all online for the history books. His name is Jeremy Harper and he counted to one million to raise money for charity (Jeremy Harper Counting). Averaging about 16 hours a day it took him 89 days to count from one to one million. Now let's look at that pesky billion number. There are a thousand millions in a billion, so with optimal conditions of one number a second it would take about 32 YEARS to count to one billion. If you were as dedicated as Jeremy Harper (who might I remind you spent 16 hours A DAY counting) it would only take you 243 YEARS to count to one billion…. Then just do that 4 and a half more times to get to the age of the earth at a simple 1103 years of counting non stop for 16 hours a day.
How do we know how old the Earth is?
There are a lot of techniques that people have used to determine the age of the Earth (some more unreliable than others but all similarly fascinating). One of the more consistent ways to determine the age of something is looking at some isotopes of radioactive elements because they decay over time at a predictable rate. This means we can calculate how old certain rocks are by measuring this rate of decay. The issue is rocks go through a process called the rock cycle which is the method of transformation from one type of rock to another, so there likely are not any rocks that still exist in their original form from the first moment on the Earth. The oldest minerals found on Earth were found in Western Australia and these little Zircon are measured to be as old as 4.404 billion years old. This tells us the Earth is at least 4.4 billion years old but for more information we need to look elsewhere away from Earth itself. Other aspects of our solar system likely formed at the same time as the Earth itself. The moon has rocks as old as 4.5 billion years old and there have been asteroids that have ages that range between 4.4 and 4.5 billion years. These are more clues that aid in confirming this theory of earth being 4.54 billion years old (± 0.05 billion years). Now, lets visualize how old that really is. If you shrank down the 4.54 billion years old that the Earth is into a single calendar year there are a lot of things that are happening in that year but lets just focus on some special ‘holidays’.
Eons of Earth
Severson's Timeline
Utilize the graphic below to travel through the timeline of Severson...Click on the 'Eon' listed to learn more!
4.54 to 4.03 billion years ago (11.2% of Earth)
To tell the lifespan of the Earth humans use a couple different ways to explain the passage of time. Let us start at the beginning then! There are four major eons that make up the history of the Earth and it starts with the Hadean. This was the beginning of Earth where orbiting dust, gas, and rocky material coalesced together creating the foundation of the planet which we all call home. Early Earth was not a comforting place, it was a liquid ball of superheated rock for millions of years. On top of that a giant object the size of Mars smashed into the Earth tilting its axis knocking a large amount of debris out into space. This debris orbited around the Earth and slowly formed into the moon. While the moon began to orbit the Earth it also slowed down and balanced its rotation allowing Earth to eventually develop the seasons we are more familiar with. The lava began to cool and liquid water began to form on Earth leading to the potential of a more unique future. Our whole preserve of Severson would likely be superheated lava at the beginning then slowly be exposed to the surface during mid-Hadean and then disappear under a thick ocean by the end (like almost every other piece of land).
4 to 2.5 bya (33.81% of Earth)
The Archean Eon began when the Earth’s crust cooled enough that our continental plates began to form and liquid water covered most of the planet. The earliest signs of life began to form as simple single-celled organisms called prokaryotes. These prokaryotes survived in the shallow waters for hundreds of millions of years until a new microbe came around to work towards making the Earth much different. Cyanobacteria developed oxygenic photosynthesis, taking light and water and turning it into energy with a simple byproduct called oxygen (this is very important… obviously). It took hundreds of millions of years before this did much, but then the Great Oxygenation Event happened. This event killed off almost all the anaerobic life but then life adapted. It discovered the great potential oxygen gives for creating energy. Severson Dells would be underwater for most of this time.
2.5 to 0.541 bya (43.14% of Earth)
The Proterozoic Eon started with the beginning of an oxygenated atmosphere. This timespan also developed the first oxygen-dependent animals called Ediacara fauna. The Earth during this time also went through a number of glaciations that took place during this eon. The crust also developed and broke into many supercontinents starting with the supercontinent of Columbia between 2.1 billion and 1.8 billion years ago and then Rodinia which was about 1.0 billion years ago. This eon ended with the Cambrian explosion. During both of these supercontinents Severson Dells nature center would probably be on a landmass called Laurentia and it might have been rotated about 90° clockwise from its current position.
538 mya (million years ago) to current day (11.85% of Earth)
Now we reach the Eon that includes the modern day! The Phanerozoic Eon began 538 million years ago when plants and animals proliferated across all of Earth's surface. This expansion of animal and plant life is called the Cambrian explosion and was the beginning of complex life forming quickly on the Earth. This is the eon where we are all much more familiar with many things that happen like the dinosaurs, ice age, and the modern era. Even now with how close we are getting to the modern era, Severson is unrecognizable from its modern day form but now we get to view some influential parts that built our land into what it is today.
When Severson was an Ocean (543 to 323 mya) (4.85% of Earth)
At this time Severson Dells started to sink slowly down allowing a shallow, tropical ocean from the South that covered the land. Little bits of sand and marine organisms (such as shells, algae, and coral) would sink to the bottom of the ocean and slowly over many years compact together with the weight of everything over them and transform into sedimentary rock. This rock became different types of sandstone and limestone. It was around this time the Dells at Severson Dells began to form as well (but they weren’t the Dells yet because they were just part of the ocean floor slowly being formed)!
Pangea (335 to 200 mya) (2.97% of Earth’s life)
Around this time was the formation of the third major supercontinent called Pangea. As the land masses came together, the ocean retreated from the future land of Severson Dells, and large river systems flowed across all of Illinois. At this point Severson was actually much closer to the equator than it is now so much more consistently warm weather. Hills and valleys formed all around Severson for hundreds of millions of years and DINOSAURS ROAMED the land. Unfortunately all evidence of dinosaurs in Illinois was erased for reasons that will be explained later. The odds of large scaled beasts roaming the Illinois landscape are very high, though, given they all lived on one major landmass that had many parts connecting them together. Around 200 million years ago Pangea started to break apart and slowly move towards the continental places that are likely much more familiar to us on a world map. The Dinosaurs lasted longer than Pangea but after about 200 million years being around they went extinct. Practically a blink of an eye when compared to the age of the Earth (3.68% of Earth's life so far had dinosaurs existing).
Ice Age (1.6 mya to 10,000 years ago) (0.003% of Earth’s life)
The Ice Age was directly responsible for shaping the land that Severson Dells has been developed on. During this time large swaths of land were covered by glaciers including Severson Dells. The first glacial period was called pre-Illinoian and it carved over Severson taking away the hills and valleys and flattening it. Then the next glacial period called the Illinoian took away more land, carving away at the millions of years of rock that formed before it. This left the landscape very flat (which is why Illinois is the second flattest state in the United States). From this land, massive prairies covered much of Illinois. The millions of years worth of rock dragged away included many fossils (like all the dinosaur fossils) that were likely in the rocks. Over 400 million years worth of rock was torn out from Illinois exposing the rocks that formed when it was a warm sea. So the fossils that you can find at the dells include crinoids, corals, and Brachiopods (which are all water creatures that live in oceans). Once the glaciers left and water began to flow, it carved out our little nook of the woods and the dells were formed showing the beauty of time passing.
Holocene Epoch (10,000 years ago - right now) (0.0002% of Earth’s Life) (That's us!)
Now we come to the Holocene, this was when the ice age began to fade and the Earth became warmer. This is the current time period we live in and it only covers the last 10,000 years. So much has happened in 10,000 years, this is the era where humans have truly taken over and expanded worldwide. Every bit of our written history is included in this Epoch. The civilizations that have risen and fallen, the wonders we have built, the wars we have waged. All in just a fraction of a fraction of the Earth’s total life. Even though Severson Dells Nature Center has existed for less than 50 years- an incomprehensibly small portion of Earth’s time- we are thankful to have you as a part of our story. Each moment we share together betters this beautiful Earth and ensures that humans will continue to enjoy it for millennia ahead.
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“Once you see it you can’t unsee it”
From the rugged peaks of the Rocky Mountains to golden desert canyons, the rolling prairies to the ancient, mist-shrouded Appalachian mountains — America is a land rich in many beauties. We are home to the towering redwoods of the west coast, sun-drenched coastlines in the south, and the deep blues of the Great Lakes that collectively hold the largest volume of freshwater on Earth. These wild places offer a kind of quiet that stirs the soul. This vast, varied land is what we proudly call “America the Beautiful.” And on Earth Day, this is the America we celebrate. We scroll through snapshots of National Parks, photos of mountain trails, canyon vistas, tidepools, and wildflower filled prairies. Maybe we've seen these places with our own eyes — maybe we carry them like a dream we hope to one day reach. We’ve all, in some way, been struck by the beauty of this land. As I write these words, I’m sitting at my desk looking out the window into the woodland of Severson Dells, watching the first green buds emerge, listening to the fluting whistles of returning songbirds. How lucky are we to live among such beauty? But that beauty is in danger. Today, mountaintops in Appalachia are being blown apart for coal, their peaks stripped and valleys buried in rubble. Ancient forests in the Pacific Northwest are leveled for lumber, their centuries-old trees felled in minutes. Oil rigs rise like metal skeletons in Alaska’s fragile tundra, while pipelines thread through sacred Indigenous lands and important wildlife corridors. Wetlands that once buffered our coastlines from hurricanes are drained and filled. Prairies, once stretching unbroken across the heart of the continent like an ocean of grass, are disappearing under pavement and plow. Our coastlines are receding. Our coral reefs, once vibrant, are dying, bleaching bone-white. Even here, outside my window, invasive honeysuckle strangles the understory where spring ephemerals once bloomed, and the chorus of birds is quieter than it used to be — a stark reminder that nearly one-third of North American bird populations have vanished in the past fifty years. But this isn’t a new story. Ours is not the first generation to witness the cost of ‘progress’. The tension between beauty and destruction has shaped this nation since the Industrial Revolution. And while the challenges we face today are daunting, they are not insurmountable. Every year, on April 22nd, we celebrate Earth Day – a day that itself was born from a moment not unlike our own. America of the 1950’s and 60’s is almost unrecognizable from the America we know today. In 1943, Los Angeles residents awoke one morning to skies so dark and chemical-laden they feared they were under a gas attack . It was smog. Just 5 years later, a lethal blanket of smog from zinc smelters in Pennsylvania killed 20 people in just three days . The Merrimack River in New Hampshire ran a different color each day , depending on what the local mills were dumping. And in 1969, Cleveland's Cuyahoga River — thick with oil and industrial waste — burst into flames , its smoke billowing four stories high. These weren’t isolated incidents. They were the symptoms of a larger crisis—one brought on by decades of industrial expansion with few, if any, environmental safeguards. At the same time that America was enjoying unprecedented prosperity, it was also polluting its air, poisoning its rivers, and sickening its people. The economy boomed, but the environmental consequences were growing harder to ignore. In 1962, a marine biologist named Rachel Carson published Silent Spring, a book that would become a cornerstone of the modern environmental movement. Carson’s work focused on the effects of chemical pesticides—especially DDT—on ecosystems and human health. She warned of a future without birdsong, where toxins accumulated in the food chain and sickened both wildlife and people. Silent Spring struck a chord. It didn’t just present scientific facts, it gave voice to a deep, growing unease. People were already noticing the changes around them: the absence of fireflies in summer, the increasing number of fish kills in local lakes, the haze that lingered over cities for days. Carson’s words helped connect the dots, and it didn’t just inform, it inspired, and from it spurred the beginning of the environmental movement. By the late 1960s, a wave of activism was sweeping the country. Young people were leading protests against the Vietnam War, civil rights leaders were marching for justice, and college campuses had become hotbeds of political energy. Watching this cultural shift with inspiration was Senator Gaylord Nelson of Wisconsin. A long-time advocate for environmental protection, Nelson saw how the antiwar movement had galvanized young people—and he wondered whether that same passion could be channeled into fighting a different kind of crisis: the growing threat to America’s air, water, and land. His sense of urgency only deepened in early 1969, when tragedy struck the California coast. A blowout at a Union Oil drilling platform off the coast of Santa Barbara spilled nearly 100,000 barrels of crude oil into the Pacific Ocean . Black sludge washed up on miles of pristine beaches. Seabirds lay dying under slicks of oil. Dolphins and seals washed ashore. The air reeked of petroleum for weeks. The images were devastating—and they were broadcast into homes across the nation. Senator Nelson knew the time to act was now. In November of that year, he announced plans for a "National Teach-In on the Crisis of the Environment" —a day when Americans would come together to learn, protest, and push for meaningful environmental change. This name was later changed to Earth Day, and the date chosen was April 22, 1970—strategically placed between spring break and final exams to ensure strong participation on college campuses.  To bring this ambitious vision to life, Nelson turned to Denis Hayes, a 25-year-old student activist. With Hayes’ help, a 7 month timeline, and a shoestring budget of just $124,000, Earth Day sparked an unprecedented nationwide movement. College campuses began planning teach-ins and events. Newspapers picked up the story. Civic groups, churches, and schools joined in. The momentum built quickly—and organically. Within a few months, the Earth Day idea had become a nationwide grassroots event supported by millions of people. Colleges campuses across the country organized “teach- ins”, and major newspapers were writing about Senator Nelson's ideas. Earth Day may have been Gaylord Nelson’s idea, but American citizens made it happen. “Earth Day worked because of the spontaneous response at the grassroots level,” reflected Gaylord Nelson. “It organized itself.” Historian Adam Rome would later call it “the most famous unknown event in modern American history.” On April 22, 1970, an estimated 20 million Americans—nearly 10% of the U.S. population at the time —participated in what remains the largest single-day political demonstration in the nation’s history. People from all walks of life gathered for marches, cleanups, rallies, and teach-ins. The message was clear: the environment mattered, and the public was ready to fight for it. What made Earth Day so powerful was not just its scale, but its unity. The movement crossed ideological lines. It was bipartisan, supported by both Democrats and Republicans. At a time of deep national division, Earth Day reminded Americans that the health of our planet is a shared responsibility—and a common cause. Even more remarkable is that this enormous, coordinated event was pulled off without the tools we rely on today. No social media. No email. No cell phones. Just passionate people, printed flyers, rotary phones, and the belief that change was possible. The success of Earth Day didn’t just move the public—it resonated with leaders in Washington, and led to real change. In just a few years, the United States went from having almost no federal environmental policy to enacting an environmental policy infrastructure strong enough to slow down the era of unregulated industrial sprawl to protect our planet and public health. The success of the first Earth Day led to the passage of some of the most important environmental legislation in American history, including: The Clean Air Act (1970) The Clean Water Act (1972) The Endangered Species Act (1973) President Richard Nixon oversaw the establishment of the Environmental Protection Agency and signed the above landmark environmental laws into effect. In a 1970 speech, Nixon captured the spirit of the moment with a message that still rings true today: “The great question of the seventies is, shall we surrender to our surroundings, or shall we make our peace with nature and begin to make reparations for the damage we have done to our air, to our land, and to our water? Restoring nature to its natural state is a cause beyond party and beyond factions. It has become a common cause of all the people of this country. It is a cause of particular concern to young Americans, because they, more than we, will reap the grim consequences of our failure to act on programs which are needed now if we are to prevent disaster later. Clean air, clean water, open spaces—these should once again be the birthright of every American. If we act now, they can be. We still think of air as free. But clean air is not free, and neither is clean water. The price tag on pollution control is high. Through our years of past carelessness we incurred a debt to nature, and now that debt is being called. ” In the years that followed the first Earth Day, America made progress—rivers stopped catching fire, cities began to breathe a little easier, and wildlife rebounded. But the work was never meant to end in the 1970s. Earth Day is a reminder that the environment is not a limitless resource, and that protecting it requires action, accountability, and cooperation. Fifty five years later we face new environmental challenges, but Earth day is a reminder of what we can accomplish when we come together, regardless of party or background, to protect the natural world we all share. Today, the landmark pieces of legislation that were established in the 1970’s are under threat. The first hit to the Clean Water Act was the U.S. Supreme Court’s 2023 decision in Sackett v. EPA, which significantly narrowed the Act's scope, limiting protections for wetlands and many streams. This ruling has led to a significant weakening of federal oversight. More recently, the EPA has announced significant changes to the Clean Water Act that potentially puts the drinking water sources for tens of millions of Americans at risk. As for the Endangered Species Act, there is a proposed rule change that would limit violations of the Act only to actions that hurt or kill animals. Harming the habitats the endangered animals need to survive would no longer be a violation of the Endangered Species Act, which would open large swaths of land to logging, mining and development that were previously protected. As we all know, if a species doesn’t have the habitat to survive and breed in then it will eventually go extinct. This proposed rule change is open for public comment until May 19 in the Federal Register, so please consider sharing your opinion . Additionally, there is the Zero-Based Regulatory Budgeting To Unleash American Energy Executive Order. The legal community is still trying to figure out just how far reaching this EO is, but it is likely to have a significant impact on a wide range of environmental regulations. These threats to the health of our environment put “America the Beautiful” at risk. The spacious skies, amber waves of grain, purple mountain majesties, and the fruited plain from sea to shining sea are left vulnerable. Now more than ever, Earth Day calls on all of us to act to protect our beautiful environment. Earth Day is now celebrated in over 190 countries. But its roots lie in a time when people refused to accept the destruction of the world around them as inevitable. So, what will you do this Earth Day? Because history has shown us: when people care, when they act together, the world changes. The debt to nature is still being called—and we still have the power to answer. This Earth Day, don’t just celebrate – participate. Plant a tree. Call your representatives. Learn the name of the bird outside your window. Donate to organizations that support our natural lands, our water, and our future. Vote. Teach your children not just to love the Earth, but to fight for it. Talk about climate change, even when it’s hard. Especially when it’s hard. Use your voice, use your art, use your science. Join a local cleanup, start a compost bin, reduce your plastic use. Talk to your neighbors. Talk to your parents. Talk to your children. You can’t wait for someone else to take action. You don’t need to be perfect. You don’t need to do everything. But you do need to begin. Because the Earth doesn’t need more perfect people, it needs millions of imperfect people who care enough to act with intention everyday. Sources: Klein, Ezra, and Thompson, Derek. Abundance . Simon & Schuster, 18 March 2025 “Gaylord Nelson & Earth Day Origins.” Nelson Earth Day , https://nelsonearthday.net/gaylord-nelson-earth-day-origins/ . Accessed 18 Apr. 2025. Gammon, Katharine. “The Deadly Donora Smog of 1948 Spurred Environmental Protection—But Have We Forgotten the Lesson?” Smithsonian Magazine , 26 Oct. 2018, https://www.smithsonianmag.com/history/deadly-donora-smog-1948-spurred-environmental-protection-have-we-forgotten-lesson-180970533/ . Accessed 18 Apr. 2025. Lamoreaux, Naomi. “The 1943 Hellish Cloud Was the Most Vivid Warning of L.A.'s Smog Problems to Come.” Smithsonian Magazine , 15 Jan. 2018, https://www.smithsonianmag.com/smart-news/1943-hellish-cloud-was-most-vivid-warning-las-smog-problems-come-180964119/ . Accessed 18 Apr. 2025. “The Merrimack River: How Revisiting Its History Helps Renew Action.” Forest Society Blog , Society for the Protection of New Hampshire Forests, 26 Sept. 2022, https://www.forestsociety.org/blog-post/merrimack-river-how-revisiting-its-history-helps-renew-action . Accessed 18 Apr. 2025. Pyne, Stephen J. “The Cuyahoga River Caught Fire at Least a Dozen Times, but No One Cared Until 1969.” Smithsonian Magazine , 22 June 2019, https://www.smithsonianmag.com/history/cuyahoga-river-caught-fire-least-dozen-times-no-one-cared-until-1969-180972444/ . Accessed 18 Apr. 2025. Westervelt, Eric. “How California’s Worst Oil Spill Turned Beaches Black and the Nation Green.” NPR , 28 Jan. 2019, https://www.npr.org/2019/01/28/688219307/how-californias-worst-oil-spill-turned-beaches-black-and-the-nation-green . Accessed 18 Apr. 2025.
