What did Earth look like during the Cretaceous?
The Cretaceous began 143.1 million years ago and ended 66 million years ago, with the extinction that finished the dinosaurs. Its shallow seas are the reason there is chalk under southern England.
AI reconstruction — not a photograph · Shutterstock AI/Shutterstock.com · Shutterstock Standard License
At the start
About 145 million years ago, near the start of the Cretaceous. The source calls this map the Jurassic-Cretaceous Boundary.
- Land
- Shallow sea
- Deep ocean
Yellow is land, mid-blue is shallow sea, dark blue is deep ocean. The map is drawn flat, so places near the poles look wider than they really are.
This is one model’s answer, not a photograph. It shows the world about 145 million years ago — the age of the map itself, which is the closest the source gets to the ages on this site.
Map data: Scotese, C. R., & Wright, N. M. (2018). PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5460860 Licensed CC BY 4.0. Grid 361×181 at 1° — about 111 km per cell at the equator, so nothing the size of a town can be read from it.
And near the end
About 70 million years ago, near the end of the Cretaceous. The source calls this map the Late Cretaceous.
- Land
- Shallow sea
- Deep ocean
Yellow is land, mid-blue is shallow sea, dark blue is deep ocean. The map is drawn flat, so places near the poles look wider than they really are.
This is one model’s answer, not a photograph. It shows the world about 70 million years ago — the age of the map itself, which is the closest the source gets to the ages on this site.
Map data: Scotese, C. R., & Wright, N. M. (2018). PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5460860 Licensed CC BY 4.0. Grid 361×181 at 1° — about 111 km per cell at the equator, so nothing the size of a town can be read from it.
The share of the world below sea level went from 66% to 63.4% between these two maps. The continents are recognisable now — you can find Africa, and South America has pulled away from it, opening an ocean that is still opening today.
Why this page shows 70 and not 66
The Cretaceous ends at 66 million years ago, and that is the age four town pages on this site ask about. But the maps come in steps of five million years, so there is no map at 66. The nearest are 65 and 70.
So this page shows 70 million years ago and tells you it is 70, rather than labelling it 66 and hoping nobody checks. A four million year gap sounds small next to seventy — it is longer than there have been people.
That habit is the point. When a source cannot answer exactly the question you asked, the honest move is to say what it can answer and how far off that is.
Real photograph · Sven Hansche/Shutterstock.com · Shutterstock Standard License
The chalk
The white cliffs of southern England are Cretaceous. So is the rock the geological map names under Brighton, Hull and Norwich. Chalk is made of the shells of things too small to see, which means it took an unhurried, shallow sea and a very long time.
What that chalk means about any one of those towns is on the town’s own page, from the rock and the fossils that were actually dug up there. This map is a different source answering a wider question.
Map built from data
The world about 70 million years ago, near the end of the Cretaceous — the same map as above, as a picture you can save and use in class, with its credit underneath.
- Land
- Shallow sea
- Deep ocean
Yellow is land, mid-blue is shallow sea, dark blue is deep ocean. The map is drawn flat, so places near the poles look wider than they really are.
This is one model’s answer, not a photograph. It shows the world about 70 million years ago — the age of the map itself, which is the closest the source gets to the ages on this site.
Map data: Scotese & Wright (2018), PALEOMAP PaleoDEMs — rendered by triassicwater.com · CC BY 4.0
Map data: Scotese, C. R., & Wright, N. M. (2018). PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5460860 Licensed CC BY 4.0. Grid 361×181 at 1° — about 111 km per cell at the equator, so nothing the size of a town can be read from it.
For teachers
For school
- The Cretaceous ends at 66 million years ago, and that is the age four town pages on this site ask about.
- But the maps come in steps of five million years, so there is no map at 66.
- Chalk is made of the shells of things too small to see, which means it took an unhurried, shallow sea and a very long time.
Classroom prompt
Chalk is built from shells too small to see. What does a tall white cliff of it tell you about the sea that laid it down, and about how long that sea stayed?
Extension: this page shows 70 million years ago rather than 66. When a source cannot answer the exact age you asked about, what should you say about the answer it can give?
Ages: the chalk and the two maps work from about seven; why the page will not label its map with the wrong age suits pupils of about ten upwards. That range is our teaching choice for this page, not a curriculum claim.
Where this comes from
- The maps
- PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic, version 2. Scotese, C. R., & Wright, N. M. (2018). PALEOMAP Paleodigital Elevation Models (PaleoDEMS) for the Phanerozoic (Version 2) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5460860 Licensed CC BY 4.0. Read from a copy whose checksum is recorded in this repository, so the numbers on this page can be checked against the exact file they came from.
- How sure is this?
- Every map here is a reconstruction — an estimate built from evidence, not a photograph. Its authors call each one the “best guess” or average geography for the time it represents, which is a fair description and worth repeating. 1° cells — roughly 111 km at the equator. Nothing at the scale of a town can be read from this grid. The source grid is 5 million years. An age between two maps is NOT interpolated: the nearest map is used and its own age is what gets published.
One reconstruction among several. PALEOMAP draws the world here; MULLER2019 places individual points elsewhere on this site. They are different models and are never composited or averaged.
Read from the source archive on .
Where next
The middle of this period has a map of its own at 100 million years ago. The sea that split North America in two during it is the Western Interior Seaway, read from the rock under one city. For the chalk under a particular town, start from the places page.