The Isthmus of Panama closes
Two continents join, two oceans are separated, and both the land and the sea are reorganised.
- When
- —
- Duration
- 200 thousand years
- Known to
- ± 300 thousand years
- Era
- Pliocene, Cenozoic
Around 2.8 million years ago the last shallow straits through Central America close and North and South America become one landmass. The Atlantic and Pacific are separated at the surface for the first time in over a hundred million years. Atlantic surface water, no longer able to escape westward, becomes saltier and the Gulf Stream strengthens, carrying more heat and moisture north — which has been argued both to have warmed Europe and to have supplied the snowfall that built the northern ice sheets. The date is contested, with some molecular evidence favouring a much earlier effective barrier.