500 million years ago a chunk of the supercontinent Pannotia drifted north and split into three masses, forming Laurentia (present-day North America), Baltica (present-day northern Europe), and Siberia. In shallow waters, the first multicellular animals with exoskeletons appeared, and an explosion of life began. Map courtesy of CR Scotese, PALEOMAP Project
      • multicellular organisms gradually became more common, produced the first representatives of all modern animal phyla;
      • mean surface temperature 7 °C above modern level;
      • sea level 30m above present day, rising steadily to 90m;
      • Pannotia splits up into masses that will become Laurentia and Gondwana;
      • Panthalassic Ocean forms with wide shallow seas;
      • Climate very warm with high oxygen content;
      • All land is barren, lifeless desert;
      • First vertebrates appear;
      • Many strange “experimental” forms appear, but many
        die out in mass extinction at the end of the period.


Name Diameter (km) Age (megayears) Dating method Morphological type Notes
Touchwood Hills, Saskatchewan >200 >541 Post Williston Basin deposit IMPROBABLE Multi-ring Basin?
Can-Am, Lake Huron 100 ~500 Geological dating PROBABLE Complex Underwater in Lake Huron
Glover Bluff, Wisconsin 8 <500 Geological dating CONFIRMED Complex
Presqu’ile, Quebec 24 <500 Geological dating CONFIRMED Complex High level erosion
Newporte, North Dakota 3.2 <500 Geological biostratigraphic dating CONFIRMED Simple No surface evidence