Greenhouse Earth
No ice at the poles, and seaways cut continents in half
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Tropical sea surface temperatures were probably 5–10 degrees above today's, and the deep ocean around 15 degrees against today's 2. The driver was sustained high volcanic CO₂ input from unusually fast sea-floor spreading. Sea level stood up to 250 metres higher, and the Western Interior Seaway split North America. The oxygen-poor conditions in these warm seas buried great quantities of organic matter — much of the world's oil is Cretaceous. The period is the closest analogue we have to a high-CO₂ climate, and is actively used as a reference in climate modelling.
For children
The Cretaceous was the warmest period in a long while. There was no ice at the poles at all, and crocodile relatives lived north of the Arctic Circle. Sea level stood so high that a shallow sea split North America in two from the Gulf of Mexico to the Arctic Ocean.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org