(also known as the North
), like all craton
land, was created as continents
about the surface of the Earth
bumping into other continents and drifting away.
Many times in its past, Laurentia has been a separate continent
as it is now in the form of North
America. During other times in its past, Laurentia has been part of
. It is named after the
Laurentian Shield, which in turn
is named after the St. Lawrence River.
Laurentia owes its existence to a network of Early Proterozoic orogenic
belts. Small microcontinents
oceanic islands collided with the ever-growing Laurentia, and
together formed the stable Archean
we see today.
In eastern and central Canada, much of the stable craton is exposed
at the surface as the Canadian
. In the United States the craton bedrock is covered with sedimentary
rocks of the interior platform except in northern Minnesota and
Wisconsin and the Upper Peninsula of Michigan.
of rocks varies from approximately 1,000 to in excess of 6,100
) in thickness. The cratonic rocks are
while the overlying sedimentary rocks
are composed mostly of
, and shales
sedimentary rocks were deposited from 650 to 290 million years
The metamorphic and igneous rocks of the "basement complex
" were created 1.5 to 1.0
billion years ago in a tectonically active setting. It was a
setting of great pressure and temperature. The younger sedimentary
rocks that were deposited on top of this basement complex were
formed in a setting of quiet marine and river waters. During much
of Mississippian time, the craton was the site of an extensive
marine carbonate platform on which mainly limestones and some
dolostones and evaporites were deposited. This platform extended
either from the present Appalachian Mountains or Mississippi Valley
to the present Great Basin. The craton was covered by shallow,
warm, tropical epicontinental or epicratonic sea
(meaning literally "on the
craton") that had maximum depths of only about 60 metres (200 ft)
at the shelf edge. Sometimes land masses or mountain
chains rose up on the distant edges of the
craton and then eroded down, shedding their sand across the
Geological history of Laurentian craton in chronological
- ~2.5 billion years ago, Arctica formed
as an independent continent.
- ~2.45 billion years ago, Arctica was part of the major
- ~2.1 billion years ago, when Kenorland shattered, the Arctican
craton was part of the minor supercontinent Nena along with Baltica and Eastern Antarctica.
- ~1.8 billion years ago, Laurentia was part of the major
- ~1.5 billion years ago, Laurentia was an independent
- ~1.1 billion years ago, Laurentia was part of the major
- ~750 million years ago, Laurentia was part of the minor
Laurentia nearly rifted apart.
- ~600 million years ago, Laurentia was part of the major
- ~Cambrian, Laurentia was an independent
- ~Ordovician, Laurentia was shrinking
and Baltica got bigger.
- ~Devonian, Laurentia collided against
Baltica, forming the minor supercontinent Euramerica.
- ~Permian, all major continents collide
against each other for forming the major supercontinent Pangaea.
- ~Jurassic, Pangaea rifted into two
minor supercontinents: Laurasia and
Gondwana. Laurentia was part of the minor
- ~Cretaceous, Laurentia was an
independent continent called North America.
- ~Neogene, Laurentia, in the form of
North America, crashed into South
America, forming the minor supercontinent America.
- ~250 million years from now, all continents may crash together,
forming the major supercontinent Pangaea
Ultima. Laurentia will be part of Pangaea Ultima.
- Geology - Definitions and images to illustrate geological
terms, links to images and website articles. See:
- Geology of the North American Craton during the Phanerozoic.
- See article by Michael Anissimov
- Dalziel, I.W.D., 1992 On the organization of American Plates in
the Neoproterozoic and the breakout of Laurentia: GSA_Today, 2, 11,
- Fisher, J.H. et al., 1988 Michigan basin, Chapter 13: The
Geology of North America, Vol D-2, Sedimentary cover - North
American Craton 361-382
- Sloss, L.L. , 1988 Conclusions, Chapter 17: The Geology of
North America, Vol D-2, Sedimentary cover - North American Craton
- Burgess, P.M. Gurnis, M., and Moresi, L., 1997 Formation of
sequences in the cratonic interior of North America by interaction
between mantle, eustatic, and stratigraphic processes: BGSA, 109,
- Arlo B. Weil, Rob Van der Voo, Conall Mac Niocaill, Joseph G.
Meert, 1998 The Proterozoic supercontinent Rodinia:
paleomagnetically derived reconstructions for 1100 to 800 Ma: EPSL,
154, 1-2, 13-24.
- Parker, Sybil P. (Ed.). 1997. McGraw-Hill Dictionary of Geology
and Mineralogy. New York: McGraw-Hill.
- Bates, Robert L. and Julia A. Jackson (Eds.) 1994. Dictionary
of Geological Terms. American Geological Instutute. New york:
Anchor Books, Doubleday Dell Publishing.
- Sloss, L.L. , 1988 Tectonic evolution of the craton in
Phanerozoic time: The Geology of North America, Vol D-2,
Sedimentary cover - North American Craton 25-51
- The Dynamic Earth @ Natural Museum of Natural History - United
Plate - shows an overview of this process - online at: