The glacial cycles find their rhythm
For a million and a half years the ice comes and goes every 41,000 years, in time with Earth's tilt.
- When
- —
- Duration
- 1.3 million years
- Known to
- ± 50 thousand years
- Era
- Early Pleistocene, Quaternary
Early Pleistocene glacial cycles are relatively small, symmetrical and reliably paced by the 41,000-year obliquity cycle, which governs how much summer sunlight reaches high latitudes. Ice sheets are thin and never reach the extent they later will. The deep-sea oxygen isotope record from this interval is close to a clean sine wave, and it is numbered into Marine Isotope Stages — odd for warm, even for cold — a scheme that becomes the master timescale for the whole Quaternary.