Okay, Laurentia is not a super-continent, although
it has been involved in those. It is today known as the North American Craton,
because it is a bit of crust that makes up about the eastern 2/3 of North
America. Originally, this craton included Greenland and a piece of Scotland,
but those have split off.
The base of Laurentia is composed of
metamorphic and igneous rocks formed 1.5 to 1 billion years ago. Above that are
younger sedimentary rocks that were deposited when most of the craton was
covered by a shallow (with a depth of no more than 200 feet) tropical sea where
much marine life lived and died, settled to the bottom and eventually became
rock such as limestone and dolomites.
During the Cretaceous Period, this type of
sea - known as the Western Interior Seaway - ran from today’s Gulf of Mexico to
the Arctic Ocean, diving North American into eastern and western land masses
The southwestern area of Laurentia has been
deformed by continental collisions and has been stretched up to 100% of its
original width. This area has experienced numerous large volcanic eruptions.
Laurentia sat on the equator some 458-444
million years ago.
About 1.82 billion years ago, Laurentia was
part of the supercontinent Columbia. But by 1.35-1.3 billion years ago,
Laurentia was an independent continent.
1.3 billion years ago, Laurentia joined other
bits to form the supercontinent Protorodinia, and by 1.07 billion years ago,
enough bits had joined to become the supercontinent Rodinia. This article
didn’t mention when Rodinia broke apart.
750 million years ago, Laurentia had again
joined others to form Protolaurasia, but Laurentia very nearly drifted away
from the others. Still, it stuck around at least until 600 million years ago,
when they formed the supercontinent Pannotia. (I’ve already written about
that.)
419.2 to 358.9 million years, Laurentia and
Baltica collided, forming Euramerica.
298.9 to 252.1 million years ago, all the
‘big boys’ got together to form the supercontinent Pangaea. That lasted until
201.3 to 145 million years ago, when Pangea broke into 2 supercontinents:
Laurasia and Gondwana. Laurentia was part of Laurasia.
145 to 66 million years ago, Laurentia was
again an independent continent. And about 23 million years ago, North America
(Laurentia) crashed against South America, forming the minor supercontinent
America.
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