Ice Ages
2.6 million – 11,700 years ago
Glacial cycles, sea-level change, and the landscapes early humans actually walked.
Every claim in this period carries its evidence with it.
Ice cores, deep-sea sediment cores, glacial landforms, and orbital mechanics calculated independently of the geological record.
- 01
The Quaternary contains repeated glacial and interglacial cycles, not one single ice age.
- 02
Cycle timing tracks predictable variations in Earth's orbit and axial tilt.
- 03
Sea level fell substantially during glacial maxima, exposing land bridges and continental shelves now underwater.
Each row states the method, what is actually measured, and — the part usually skipped — what the result does not settle.
| Method | Material | What it constrains |
|---|---|---|
| Oxygen isotope stratigraphy | Foraminifera shells in deep-sea sediment cores | Produces a continuous global ice-volume curve. Regional temperature must be inferred separately. |
| Ice core analysis | Annual layers, trapped air bubbles and dust in polar ice | Directly samples past atmosphere back several hundred thousand years. It does not reach earlier glaciations. |
| Orbital calculation | Computed eccentricity, obliquity and precession cycles | Predicts the pacing independently of any sediment. Amplitude of response still requires feedbacks. |
Why did cycles shift from roughly 41,000 to roughly 100,000 years?
The mid-Pleistocene transition is not fully explained by orbital forcing alone.
How abrupt were the warming events within glacial periods?
Ice core records show rapid shifts whose triggers and ocean-circulation role remain argued.
“The ice age was one continuous frozen world.”
It was a repeating cycle, with interglacials as warm as today. We are in one now.
“Ice sheets covered the whole planet in the Quaternary.”
Glaciation was concentrated at high latitudes and altitudes; the tropics remained unglaciated, though cooler and drier.
- What sets the amplitude of each cycle?
- How much of the coastline record of early humans is now on drowned shelves?
- How stable are the feedbacks that ended each glacial phase?
EPICA and Greenland ice core records
Nature / Climate of the Past
Marine isotope stage stratigraphy
Quaternary Science Reviews
Where Ice Ages connects to the rest of the ancient record — the worlds it belongs to, the chapters it sits in, the documents that record it, and the questions still open.
Evidence Files
All evidence files →Doggerland
North Sea · c. 18,000 – 6,000 BCE
How much human history is sitting under post-glacial sea level rise?
Open question in Ice Ages
Yonaguni Monument
Okinawa, Japan · Disputed
Is the Yonaguni formation carved, natural, or natural rock modified by people?
Open question in Ice Ages