Earth 500 Million Years Ago: The Cambrian Seas

Events of the time

• Ediacara fossils

  555 million years ago · Ediacara Hills, Australia

  Imprints of soft-bodied animals such as Dickinsonia, now known to be an animal from the fats preserved in it.

• Chengjiang fossils

  518 million years ago · Yunnan, China

  Soft-bodied animals preserved in fine mud, including some of the earliest relatives of vertebrates: a snapshot of the Cambrian explosion.

• Burgess Shale

  508 million years ago · British Columbia, Canada

  A Cambrian sea floor with strange animals such as five-eyed Opabinia and the predator Anomalocaris, then near the equator.

• Ice sheet over the Sahara

  445 million years ago · North Africa

  Scratched rock and glacial deposits in the Sahara show that ice covered North Africa when it lay over the South Pole. The cold and falling seas killed about 85% of marine species.

Which land was under the sea 500 million years ago?

On the map nearest this age (500 million years ago, late Middle Cambrian), about 39% of today’s land was under the sea at some point, some 55.7 million km². That makes it number 18 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.

• Sauk Sea

  Cambrian to Early Ordovician (approximate) · The centre of North America: the Great Plains, the Midwest and the Great Lakes

  The first great flood over North America’s interior, named after the Sauk sequence of rock layers. Its sandstones and limestones lie under much of the Midwest, and trilobites were its best-known animals.

Was it under the sea? 23 of 42 cities

1,303 marine fossil sites in the Paleobiology Database are dated closely enough to this map. Of those on today’s land, 99% fall in its shaded sea.

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