Greenland freezes over
Ephemeral northern ice becomes a permanent continental sheet for the first time in tens of millions of years.
- When
- —
- Duration
- 1 million years
- Known to
- ± 300 thousand years
- Era
- Pliocene, Cenozoic
Ice-rafted debris in North Atlantic sediment cores — stones dropped by melting icebergs, far from any shore that could have delivered them — increases sharply through the late Pliocene, recording the growth of a real Greenland ice sheet. Before this, northern ice had come and gone with orbital cycles; afterwards it persists. The Earth acquires a second permanent ice cap, having had only one since the Eocene, and the bipolar cryosphere that defines the modern world is complete.