wunder beta❄️ The Ice Ages
The truth about ice ages: we're living in one right now, and Earth's orbit is the clock that runs the deep freeze.
What you’ll learn
- What an Ice Age Really IsUnderstand what geologists mean by an ice age and the difference between glacial and interglacial periods.An ice age is any long period with permanent ice sheets, and we are in one that began 2.6 million years ago. Within it, climate swings between cold glacials and warm interglacials like today's Holocene. The last glacial peaked 20,000 years ago, and its moving ice carved the Great Lakes, fjords, and much of the northern landscape.
- The Evidence TrailLearn the physical evidence, erratics, striations, and moraines, that established the reality of past ice ages.Louis Agassiz proposed the Ice Age in 1837, reading glacial features far from any modern ice. Erratic boulders reveal how far ice carried rock, striations record its direction of flow, and moraines mark where it stopped. Together these clues gave overwhelming proof of repeated glaciations across the northern continents.
- The Orbital PacemakerExplain the three Milankovitch cycles and how they pace the advance and retreat of the ice.Milutin Milankovitch calculated how eccentricity, axial tilt, and precession change the summer sunlight reaching high latitudes, pacing the glacial cycles. Cool summers let snow survive and ice grow. Long dismissed, his theory was confirmed in 1976 when deep-sea sediment cores showed exactly the orbital rhythms he predicted.
- The Ice-Age WorldPicture the physical world of the last glacial period, from drowned lands to the rebounding crust.At the last glacial maximum, seas were about 120 metres lower, exposing Doggerland between Britain and Europe and the Bering land bridge between Siberia and Alaska. The climate was colder, drier, and dustier, with lower carbon dioxide. The crust, pressed down by ice, is still slowly rebounding today.
- Megafauna, Cores, and the FutureExamine the ice-age megafauna and their extinction, and how ice cores reveal the past and reframe the future.The Pleistocene megafauna thrived in the cold, open glacial world, then most went extinct, likely through a mix of climate change and human impact. Ice cores preserve 800,000 years of ancient air. Orbital math suggests the next glacial was naturally far off, and human emissions are likely to delay it further.
Questions this course answers
According to geologists, why are we currently living in an ice age?
An ice age is defined by the presence of permanent continental ice sheets. Greenland and Antarctica still have them, so we remain in an ice age, currently in a warm interglacial phase called the Holocene.
What is the difference between a glacial period and an interglacial?
Within a long ice age, the climate swings between colder glacial periods when ice sheets grow, and warmer interglacials like today when ice retreats and seas rise.
The Great Lakes of North America were formed mainly by what?
The Great Lakes sit in basins gouged out by the advancing and retreating Laurentide Ice Sheet, one of many landforms inherited from the last glacial period.
What idea did Louis Agassiz propose in 1837?
Agassiz argued that features far from any modern glacier were left by vanished ice, giving science the concept of the Ice Age, published in his 1840 Studies on Glaciers.
What is a glacial erratic?
An erratic is a boulder transported by ice and stranded on foreign bedrock. Because only moving ice can do this, erratics are strong evidence of past glaciation.
What do glacial striations reveal?
Striations are parallel scratches gouged into bedrock by rock dragged under a glacier. Their alignment records the direction of ice flow, helping map vanished ice sheets.
Grounded in trusted sources
- NOAA National Centers for Environmental Information
- British Geological Survey
- NASA Earth Observatory
- United States Geological Survey
Every Wunder lesson is built from real, reputable sources — never invented.
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