North America 77 million years ago, mapped

The Cretaceous is the third and last Period of the Mesozoic Era geological period that lasted from approximately 145 to 66 million years ago.

It was a geologic period with a relatively warm climate, culminating in high eustatic ocean levels that formed many shallow inland water bodies.

The Earth was without ice, and forests extended to the poles. Oceans and water bodies were inhabited by now-extinct aquatic reptiles, ammonites, and rudists, while dinosaurs dominated on land.

However, during this time, new groups of birds and mammals appeared. Birds became more typical and diverse. During the Early Cretaceous, flowering plants appeared and began to diversify speedily, becoming the leading group of plants across the planet by the end of the Cretaceous, coinciding with the decline and elimination of previously widespread gymnosperm groups.

By the late Cretaceous (100.5–66 million years ago), the Earth's continents were beginning to assume their broad current alignment. The Americas were moving westwards, making the Atlantic Ocean enlarge. India was still in the beginning phases of its northward voyage, connected alongside Madagascar. Australia was also still attached to the Antarctic portion of the ancient supercontinent of Gondwanaland. Manchuria and China were yet to crash with Siberia, and the continents of the northern hemisphere were, as yet, separated from their southern counterparts by a curved Tethys Ocean. Snaking up from Tethys, the Western Interior Seaway cut across the North American landmass.

During the Late Cretaceous, the climate was warmer than nowadays, although, throughout the Period, a cooling trend is clear. The tropics became reduced to equatorial regions, and northern latitudes experienced substantially more seasonal climatic conditions.

In the Late Cretaceous, the hadrosaurs, dromaeosaurs, ankylosaurs, therizinosaurs, spinosaurids, pachycephalosaurs, and ceratopsians experienced success in Western North America and eastern Asia. Tyrannosaurs conquered the large predator niche in North America. In the northern hemisphere, cimolodont, eutherians, multituberculates, and metatherians were the prevailing mammals.

Near the end of the Cretaceous Period, flowering plants diversified. In temperate regions, recognizable plants like magnolias, sassafras, roses, redwoods, and willows could be discovered in abundance.

The Cretaceous finished with the Cretaceous–Paleogene extinction crisis, a substantial mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and giant marine reptiles, died out.

Below is the map created by the team of North America 77 million years ago. According to this map, In the Late Cretaceous, the many modern U.S. states were underneath the waves of the Western Interior Seaway. It's fascinating that elevations and water levels have altered that much throughout millions of years.

North America 77 million years ago

Today, you can see many marine fossils in the mountains of Colorado and New Mexico that 77 million years ago were at the bottom of the Western Interior Seaway.

And here is an imaginary map of what the 2020 U.S. presidential election map would look like if the position of the Erth's continents had not changed in 77 million years.

America 77 millions years ago


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