When did the seas rise and fall over north America?

The seas have risen and fallen over North America many times throughout geologic history. Some of the major periods of marine transgressions and regressions include:

- Ordovician Period (485-444 million years ago): During the Ordovician Period, much of North America was covered by a shallow sea. The sea level reached its highest point during the Middle Ordovician, when the continent was almost completely submerged.

- Silurian Period (444-419 million years ago): The sea level dropped significantly during the Silurian Period. The continent was mostly exposed, with only a few shallow seas covering the interior of the continent.

- Devonian Period (419-359 million years ago): The sea level rose again during the Devonian Period. The continent was once again almost completely submerged, with only a few islands remaining above sea level.

- Mississippian Period (359-318 million years ago): The sea level dropped again during the Mississippian Period. The continent was mostly exposed, with only a few shallow seas covering the interior of the continent.

- Pennsylvanian Period (318-299 million years ago): The sea level rose again during the Pennsylvanian Period. The continent was once again almost completely submerged, with only a few islands remaining above sea level.

- Permian Period (299-252 million years ago): The sea level dropped significantly during the Permian Period. The continent was mostly exposed, with only a few shallow seas covering the interior of the continent.

- Triassic Period (252-201 million years ago): The sea level rose again during the Triassic Period. The continent was once again almost completely submerged, with only a few islands remaining above sea level.

- Jurassic Period (201-145 million years ago): The sea level dropped significantly during the Jurassic Period. The continent was mostly exposed, with only a few shallow seas covering the interior of the continent.

- Cretaceous Period (145-66 million years ago): The sea level rose again during the Cretaceous Period. The continent was once again almost completely submerged, with only a few islands remaining above sea level.

- Cenozoic Era (66 million years ago-Present): The sea level has fluctuated significantly during the Cenozoic Era. The continent was mostly exposed during the early Cenozoic, but the sea level rose again during the middle and late Cenozoic. The continent is currently experiencing a period of relative sea level rise.