Did you know that for thousands of years, earthworms were almost nonexistent in a large part of North America? This wasn’t because of predators but due to glaciers. Around 10,000 years ago, during the last ice age, glaciers covered the northern part of the continent, making it impossible for earthworms to survive. It wasn’t until European settlers arrived that earthworms were reintroduced to the area.
Hi, I’m Erin McCarthy, and welcome to The List Show. Today, we’re diving into fascinating facts about the ice age, from Antarctic palm trees to how carbon dioxide might cool the planet under certain conditions. Let’s get started!
An ice age is a long period when global temperatures are cold, and large parts of the Earth are covered by ice sheets and glaciers. According to the Utah Geological Survey, a brief cold spell doesn’t count as an ice age; it takes millions of years of chilly temperatures and extensive ice coverage.
Throughout Earth’s 4.5-billion-year history, it has swung between extreme heat and cold. At one point, crocodile-like reptiles lived at the North Pole, and palm trees grew in Antarctica!
Several factors can trigger an ice age, and some might surprise you. While high carbon dioxide levels usually warm the planet, they can also cool it under certain conditions. About 460 million years ago, volcanic eruptions released CO2, leading to acid rain. This rain reacted with rocks, turning CO2 into limestone and removing it from the atmosphere, which may have cooled the Earth.
This process is part of the slow carbon cycle, where carbon moves between rocks, soil, the ocean, and the atmosphere over millions of years. Scientists are interested in how weathering processes, like those involving mountain ranges, can sequester carbon and potentially cool the planet.
Changes in Earth’s orbit and tilt can also lead to ice ages. These variations affect how much sunlight reaches different parts of the planet, influencing temperatures. When Earth’s tilt decreases, summers cool, allowing snow to accumulate and form glaciers, which reflect sunlight and further cool the planet.
Ice ages consist of cycles of freezing and thawing, known as glacial and interglacial periods. During interglacial periods, glaciers retreat but don’t disappear entirely. These cycles unfold over tens of thousands of years, so an instant freeze, like in movies, isn’t realistic.
The first major ice age, the Huronian glaciation, began about 2 billion years ago and may have been triggered by a long pause in volcanic activity. This ice age was so severe that the entire planet froze, creating a “snowball Earth.”
The Karoo ice age, starting around 360 million years ago, was influenced by land plants absorbing CO2 and releasing oxygen, which cooled the planet. When people talk about “the ice age,” they usually mean the most recent one during the Pleistocene epoch, from about 120,000 to 11,500 years ago.
Tectonic activity, like the formation of the Isthmus of Panama, played a role in the Quaternary Glaciation by altering ocean currents and increasing snowfall in the Northern Hemisphere. This snow formed glaciers, which reflected sunlight and cooled the planet further.
The ice age peaked around 20,000 years ago, with ice covering 8% of Earth’s surface and a quarter of its land area. Ice sheets up to a mile thick blanketed North America, and sea levels were 400 feet lower than today.
Despite the cold, wildlife thrived. Animals like shrews, mice, and lemmings survived, while megafauna like woolly mammoths and saber-toothed cats roamed the land.
Many iconic ice age animals went extinct after the ice age ended. Theories suggest climate shifts, intense cold snaps, or even human activity contributed to these extinctions.
Humans thrived during the ice age. Modern Homo sapiens evolved around 300,000 years ago and began migrating out of Africa during the last glaciation period. Our large brains and advanced tools helped us survive harsh conditions.
Other human species, like Neanderthals, went extinct during the ice age. Changes in climate and landscape may have contributed to their disappearance.
The last glacial period ended over 10,000 years ago due to changes in Earth’s orbit and tilt, leading to warmer summers and melting ice. Sea levels rose, and global temperatures increased.
You can still see evidence of the ice age today. The La Brea Tar Pits in California contain bones of ice age animals, and Ireland’s Killarney shad fish are remnants of the ice age. Glacial striations and erratics are common sights in many landscapes.
Interestingly, we’re still technically in an ice age, known as the Holocene interglacial period. While much of the Northern Hemisphere is ice-free, glaciers and ice sheets remain in places like Antarctica and Greenland.
Stay tuned for our next episode, where we’ll explore the history of television. Feel free to share your favorite show in the comments. I’m your host, Erin McCarthy—thanks for watching!
Create a detailed timeline of the major ice ages discussed in the article. Include key events such as the Huronian glaciation, the Karoo ice age, and the Pleistocene epoch. Use visuals like drawings or digital graphics to represent different periods and their characteristics.
Engage in a role-playing debate where you represent different theories about the extinction of megafauna after the ice age. Prepare arguments for climate shifts, human activity, and other factors. Present your case to the class and discuss the most convincing theories.
Construct a physical or digital model to demonstrate how changes in Earth’s orbit and tilt can lead to ice ages. Use this model to explain how these variations affect sunlight distribution and contribute to glacial and interglacial periods.
Conduct a research project to identify and present evidence of the ice age in today’s world. Focus on sites like the La Brea Tar Pits or glacial striations. Present your findings through a multimedia presentation or a detailed report.
Write a creative story or diary entry from the perspective of a human living during the last glacial period. Incorporate details about the environment, survival strategies, and interactions with megafauna. Share your story with the class to explore different experiences during the ice age.
Here’s a sanitized version of the provided YouTube transcript:
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Did you know that for thousands of years, there were very few earthworms across a large part of North America? These creatures largely disappeared from the northern part of the continent around 10,000 years ago, not due to predation by prehistoric animals, but because of glaciers.
During Earth’s most recent glaciation period, which peaked around 20,000 years ago, glaciers advanced across the northern latitudes, grinding and scouring everything in their path. Earthworms were unable to survive the heavy ice. For thousands of years, much of the continent’s soil was devoid of earthworms—until European colonists inadvertently introduced them to the landscape.
Hi, I’m Erin McCarthy, and this is The List Show. A virtual worm wipeout is just the first fact about the ice age I’ll share with you today, along with topics ranging from Antarctic palm trees to a theory on how carbon dioxide can actually cool the planet under certain conditions. Let’s get started.
Before we go any further, let’s clarify what an ice age actually is. The Utah Geological Survey defines an ice age as “a long interval of time when global temperatures are relatively cold and large areas of the Earth are covered by continental ice sheets and alpine glaciers.” Essentially, a brief cold spell wouldn’t qualify as an ice age, but millions of years of chilly temperatures with ice sheets and glaciers would.
Throughout its 4.5-billion-year history, Earth has alternated between periods of extreme heat and extreme cold. Crocodile-like reptiles once inhabited the lakes of the North Pole, and palm trees thrived in Antarctica.
Several factors can contribute to the onset of an ice age, and some explanations may not be immediately obvious. While increased carbon dioxide levels in the atmosphere are known to warm the planet, they might also have a cooling effect under the right conditions. Around 460 million years ago, volcanic eruptions that helped form parts of the northern Appalachian Mountains released significant amounts of CO2 into the atmosphere, leading to acid rain. As geochemist Lee Kump explained, when acid rain interacts with silicate rocks, a chemical reaction can incorporate CO2 into limestone, effectively removing it from the atmosphere. This process may have contributed to the Earth’s cooling.
This volcanic example is a faster version of what’s sometimes called the slow carbon cycle, where carbon moves between rocks, soil, the ocean, and the atmosphere over hundreds of millions of years.
Because rocks can sequester carbon—removing it from the atmosphere and storing it in a form that doesn’t contribute to the greenhouse effect—scientists are interested in factors that might influence the weathering processes that break down rocks and lead to this sequestration. The formation of large mountain ranges, like the Himalayas, is often central to these investigations. Some believe that mountain formation increases weathering, allowing more carbon from the air to be stored in rocks.
Recent research complicates this view; it may be that mountain formation doesn’t necessarily increase overall weathering but instead exposes more reactive rocky material that is more efficient at sequestering carbon. Anything that exposes new rocky material could lead to increased carbon sequestration.
This area is of great interest to geologists and climate scientists. At the very least, the slow carbon cycle could provide insights into how the planet regulates its temperature. More ambitiously, some believe that humans could eventually harness certain rocks’ carbon-sequestering abilities to help combat climate change.
The planet’s orbit and axial tilt are not as constant as one might think, and variations in these can contribute to ice ages. These changes occur regularly over hundreds of thousands of years, affecting the amount of sunlight different latitudes receive, and consequently, the planet’s temperature. When the angle of Earth’s tilt decreases, summers cool, allowing snow to accumulate. As layers of snow condense into glaciers and ice sheets, they reflect more sunlight—and therefore heat—resulting in lower global temperatures.
Each major ice age went through cycles of freezing and thawing, known as glacial and interglacial periods. During an interglacial period, glaciers recede toward the poles but do not completely disappear. This ebb and flow of ice and heat is a long process that unfolds over tens of thousands of years, so an instant planetary freeze, like depicted in movies, is not a realistic concern.
The first of Earth’s five major ice ages was the Huronian glaciation, which began about 2 billion years ago, possibly aided by a 250-million-year pause in volcanic activity. This ice age was so severe that the entire planet froze over, creating the first of several “snowball Earths.” (Many geologists argue that “slushball Earth” would be a more accurate term, as the planet may not have been entirely frozen.)
It’s believed that land plants contributed to the Karoo, or Late Paleozoic, ice age, which started around 360 million years ago. As plants spread across the planet, they absorbed carbon dioxide from the atmosphere and released oxygen, causing temperatures to drop again. When people refer to the ice age, they typically mean the most recent glaciation during the Pleistocene epoch of the Quaternary period. This timeframe lasted from about 120,000 to 11,500 years ago.
Tectonic activity is thought to have played a significant role in triggering the Quaternary Glaciation, particularly the formation of the Isthmus of Panama, which connects North and South America. This land bridge altered ocean currents, preventing warm tropical water from flowing between the Atlantic and Pacific Oceans. The warmer water moved north, leading to increased precipitation in the Northern Hemisphere’s high latitudes. This precipitation, which fell as snow in those regions, accumulated and froze, forming glaciers and ice sheets. The ice reflected more sunlight and absorbed less heat than the darker oceans, creating a feedback loop that further lowered the planet’s temperature.
The ice age reached its peak, known as the Last Glacial Maximum, around 20,000 years ago. At that time, 8 percent of the Earth’s surface and a quarter of its total land area were covered by ice. Ice sheets up to a mile thick blanketed North America, covering 97 percent of Canada, as well as large parts of Northern Europe, Asia, and Patagonia. Other areas of Northern Europe transformed into tundra, eliminating the warm-weather plants that had previously thrived there. Steppes, which are flat, unforested grasslands, expanded across the planet, and sub-Saharan Africa became more arid. Due to the water locked in frozen ice sheets, sea levels were 400 feet lower than they are today.
During the Last Glacial Maximum, the planet’s average temperature was around 46 degrees Fahrenheit, which is 11 degrees colder than the 20th century’s average global temperature. Average Arctic temperatures were 25 degrees cooler than today.
Despite the cooler temperatures, wildlife thrived. Animals we still see today, like shrews, mice, and lemmings, survived despite the changing landscape.
Megafauna dominated during the ice age. The reasons for the size of prehistoric animals are not fully understood. One theory suggests that larger prey animals were less likely to be hunted, while another theory, based on a contested principle known as Bergmann’s Rule, posits that larger animals are more common in colder climates and higher latitudes.
Regardless of the cause, there were some impressive animals roaming those cold regions. Woolly mammoths stood up to 11 feet tall at the shoulder. The largest saber-toothed cats, often incorrectly referred to as saber-tooth tigers, weighed nearly 1,000 pounds—more than double the size of modern tigers. Bear-sized beavers roamed North America, and 12-foot-tall giant ground sloths inhabited South America. The Irish elk, one of the largest deer species ever recorded, stood 7 feet tall at the shoulder and had antlers that spanned up to 12 feet—double the size of a moose’s antlers.
Many iconic ice age megafauna went extinct after the ice age ended. There are several theories regarding this. One suggests that the end of the last glacial period and the resulting climate shift altered the vegetation that certain animals relied on, negatively impacting large herbivores and, consequently, the large carnivores that depended on them. Another theory proposes that an intense cold snap caused the extinctions. A more speculative idea suggests that meteorites or comets impacted Earth, shifting the climate and leading to the extinction of various species. Additionally, there is a popular theory that attributes these mass extinctions to humans.
Humans thrived during the ice age. Modern Homo sapiens evolved around 300,000 years ago. It was during the last glaciation period that Homo sapiens began migrating out of Africa in large numbers.
Modern humans were already present in Europe, interacting with Neanderthals and creating intricate cave art, tens of thousands of years before the ice age reached its peak. It’s believed that our relatively large brains—and the tools and weapons Homo sapiens developed over millennia—enabled people to survive and expand their range during the harsh conditions of the Last Glacial Maximum.
The last of the other human species scattered around the world went extinct during the ice age. The latest known evidence of Homo erectus dates to between 117,000 and 108,000 years ago. Neanderthals disappeared roughly 30,000 years ago, and some believe that the cooling climate in the years leading up to the Last Glacial Maximum may have contributed to their extinction. Although Neanderthals had adapted to Europe’s colder climate for hundreds of thousands of years, the changing landscape may not have suited their hunting styles.
The last glacial period ended over 10,000 years ago. Changes in Earth’s orbit and an increase in the planet’s axial tilt led to longer, more intense summers in the Northern Hemisphere. Ice melted, and sea levels rose. The exposed water absorbed rather than reflected light, causing global temperatures to rise.
You can still see traces of the ice age today. Visit Southern California’s La Brea Tar Pits, where you’ll find bubbling tar full of ice age animal bones, including dire wolves and saber-toothed cats. Or head to Kerry, Ireland, where a single lake is home to the only population of Killarney shad, a type of fish whose ancestors split their time between the ocean and freshwater but became trapped in an Irish lake after ice sheets altered the landscape. On Canada’s Calvert Island, you’ll find human footprints from 13,000 years ago, left by the people who migrated to North America during the ice age. When ice sheets moved across the land, they left deep scars, and melting glaciers filled those depressions, creating famous bodies of water like the Great Lakes and Scotland’s Loch Ness. Norway’s famous fjords are valleys carved by glaciers that later filled with seawater. However, you don’t need to travel far to find evidence of the ice age. If you’re hiking in the woods and come across a large, scratched rock, you’re likely looking at glacial striations caused by debris dragged against the rock by moving ice. Or, if you see a massive boulder seemingly dropped from nowhere, it’s likely a glacial erratic, a rock left behind by a glacier.
We’ll leave you with a fact about the current ice age. The ice age ended a long time ago, but we are still technically in an ice age. We are currently in the Holocene interglacial period of the Quaternary ice age. Large portions of the Northern Hemisphere are no longer covered by ice, but we still have some glaciers and ice sheets. Despite rapidly increasing global temperatures, our glaciers and the Antarctic and Greenland ice sheets are still present—for now.
Our next episode will explore the history of television. Feel free to share your favorite show in the comments. All answers are welcome, as long as it’s either Buffy, Lost, or What We Do In the Shadows. I’m your host, Erin McCarthy—thanks for watching.
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This version maintains the informative content while ensuring clarity and appropriateness.
Ice Age – A period of long-term reduction in the temperature of Earth’s surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. – During the last Ice Age, vast areas of North America and Europe were covered by thick ice sheets.
Glaciers – Large masses of ice that form on land by the compaction and recrystallization of snow, moving slowly due to their own weight. – The retreat of glaciers in the Himalayas is a significant indicator of climate change.
Carbon – A chemical element that is the fundamental building block of life, found in all organic compounds and a key component of Earth’s atmosphere and biosphere. – Carbon cycles through the atmosphere, oceans, and living organisms in a process known as the carbon cycle.
Extinction – The permanent loss of a species from Earth, often due to environmental changes or human activities. – The extinction of the dodo bird is a classic example of how human interference can lead to the loss of a species.
Climate – The long-term pattern of weather conditions in a region, including temperature, precipitation, and wind. – Scientists study climate patterns to understand how global warming affects different ecosystems.
Temperatures – The degree of heat present in a substance or object, often measured in degrees Celsius or Fahrenheit. – Rising global temperatures are causing polar ice caps to melt at an alarming rate.
Wildlife – Animals, birds, and other living organisms that are not domesticated and live in their natural habitats. – Conservation efforts are crucial to protect the diverse wildlife found in the Amazon rainforest.
Orbit – The curved path of a celestial object or spacecraft around a star, planet, or moon, especially a periodic elliptical revolution. – Earth’s orbit around the Sun affects the seasonal climate changes experienced by different regions.
Megafauna – Large or giant animals, especially those from the Pleistocene epoch, such as mammoths and saber-toothed cats. – The extinction of megafauna in North America is often attributed to a combination of climate change and overhunting by humans.
Interglacial – A period of warmer global temperatures between two ice ages, characterized by the retreat of ice sheets and glaciers. – We are currently living in an interglacial period, which has allowed for the development of human civilization.
