Editing North America (section)

==== Geologic history ====
[[Laurentia]] is an ancient [[craton]] which forms the geologic core of North America; it formed between 1.5 and 1.0 billion years ago during the [[Proterozoic]] eon.<ref>{{Cite journal |last=Dalziel |first=I. W. D. |year=1992 |title=On the organization of American Plates in the Neoproterozoic and the breakout of Laurentia |journal=GSA Today |volume=2 |issue=11 |pages=237–241}}</ref> The [[Canadian Shield]] is the largest exposure of this craton. From the Late [[Paleozoic]] to Early [[Mesozoic]] eras, North America was joined with the other modern-day continents as part of the supercontinent [[Pangaea]], with [[Eurasia]] to its east. One of the results of the formation of Pangaea was the [[Appalachian Mountains]], which [[Taconic orogeny|formed]] some 480 mya, making it among the oldest mountain ranges in the world. When Pangaea began to rift around 200 mya, North America became part of [[Laurasia]], before it separated from Eurasia as its own continent during the mid-[[Cretaceous]] period.<ref name="ReferenceA">{{cite book |last1=Merali |first1=Zeeya |title=Visualizing Earth Science |last2=Skinner |first2=Brian J. |date=9 January 2009 |publisher=Wiley |isbn=978-0-470-41847-5}}{{page needed|date=February 2014}}</ref> The Rockies and other western mountain ranges began forming around this time from a period of mountain building called the [[Laramide orogeny]], between 80 and 55 mya. The formation of the [[Isthmus of Panama]] that connected the continent to South America arguably occurred approximately 12 to 15 mya,<ref name="Origins">{{cite web |date=10 April 2015 |title=Land Bridge Linking Americas Rose Earlier Than Thought |url=http://www.livescience.com/50450-when-panama-land-bridge-appeared.html |url-status=live |archive-url=https://web.archive.org/web/20151004171848/http://www.livescience.com/50450-when-panama-land-bridge-appeared.html |archive-date=4 October 2015 |access-date=3 October 2015 |work=LiveScience.com}}</ref> and the [[Great Lakes]] (as well as many other northern freshwater lakes and rivers) were carved by receding [[glacier]]s about 10,000 years ago.

North America is the source of much of what humanity knows about [[geologic time]] periods.<ref name="dinopedia-american">{{cite book |last=Dodson |first=Peter |title=Encyclopedia of Dinosaurs |publisher=Academic Press |year=1997 |editor1-last=Currie |editor1-first=Phillip J. |pages=10–13 |chapter=American Dinosaurs |editor2-last=Padian |editor2-first=Kevin}}</ref> The geographic area that would later become the United States has been the source of more varieties of [[dinosaur]]s than any other modern country.<ref name="dinopedia-american" /> According to [[Paleontology|paleontologist]] Peter Dodson, this is primarily due to stratigraphy, climate and geography, human resources, and history.<ref name="dinopedia-american" /> Much of the Mesozoic Era is represented by exposed outcrops in the many arid regions of the continent.<ref name="dinopedia-american" /> The most significant [[Late Jurassic]] dinosaur-bearing fossil deposit in North America is the [[Morrison Formation]] of the western U.S.<ref name="jurassicdistribution">{{cite book |last=Weishampel |first=David B. |title=Dinosaur distribution (Late Jurassic, North America) |publisher=University of California Press |year=2004 |isbn=978-0-520-24209-8 |editor-last1=Weishampel |editor-first1=David B. |series=The Dinosauria |location=Berkeley |pages=543–545 |editor2-last=Dodson |editor2-first=Peter |editor3-last=Halszka |editor3-first=Osmólska}}</ref>