Earth 100 Million Years Ago: The Cretaceous Hothouse

Which land was under the sea 100 million years ago?

On the map nearest this age (95 million years ago, Mid-Cretaceous), about 26% of today’s land was under the sea at some point, some 36.6 million km². That makes it number 38 of the 80 maps from 535 to 5 million years ago, which run from 2% to 50%. Each map shows the greatest flooding of its stage, so no single moment had quite this much sea.

• Tethys Ocean

  Permian to Miocene · Southern Europe, North Africa, the Middle East, Iran, the Himalaya and South-East Asia

  The ocean between the northern and southern continents. As Africa, Arabia and India moved north it closed, raising the Alps and the Himalaya; the Mediterranean is what is left of it.

• Turgai Strait

  Jurassic to Oligocene, on and off · Western Siberia and Kazakhstan, east of the Urals

  A sea east of the Ural Mountains that linked the Arctic to the Tethys and kept Europe apart from Asia for animals that could not swim. The map under-draws it.

• Western Interior Seaway

  Late Cretaceous · The Great Plains of the United States and Canada, from the Gulf of Mexico to the Arctic

  A shallow sea that split North America in two, from the Arctic to the Gulf of Mexico. The chalk of western Kansas formed on its floor.

• Trans-Saharan Seaway

  Late Cretaceous to Eocene · Niger, Mali, Nigeria and Algeria

  A shallow sea that crossed the Sahara from the Gulf of Guinea to the Tethys. Rocks it laid down in Mali hold fossils of giant sea snakes and large catfish. The map under-draws it.

• Mississippi Embayment

  Late Cretaceous to Eocene · The lower Mississippi valley, from the Gulf of Mexico north to southern Illinois

  A long bay of the Gulf of Mexico that reached up the Mississippi valley. It left the sands and clays under Mississippi, Arkansas and Tennessee.

Was it under the sea? 21 of 42 cities

3,246 marine fossil sites in the Paleobiology Database are dated closely enough to this map. Of those on today’s land, 93% fall in its shaded sea.

Seas: Ancient seas: PaleoCoastlines v7 (Kocsis & Scotese 2021), CC BY 4.0 · Fossils: Paleobiology Database.