Geologic events that occur today, such as volcanism and earthquakes, are a direct result of the varied and dynamic history of our continent. Tectonic Structure of North America; View Political North America Map with countries boundaries of all independent nations as well as some dependent territories. The Nain province had already collided obliquely with the eastern Churchill province about 1.82 billion years ago, forming the Torngat Mountains, which parallel the coast of northern Labrador. "Plate tectonic history of the northeast Pacific and western North America", The Eastern Pacific Ocean and Hawaii, E. L. Winterer, Donald M. Hussong, Robert W. Decker. The Slave province (300 miles [480 km] wide) and the Nain province (500 miles [800 km] wide) are located in the northwestern and northeastern parts of the shield, respectively. Geological Formation of North America Through the Eons / Orogeny 600 Million Years Ago To Present. There are many occurrences of rocks between 3.5 and 3.0 billion years old, but, like the older rocks, none are known to be more than a few tens of square miles in extent. The Juan de Fuca Plate is still actively subducting beneath N. America. The interval between about 3.0 and 2.6 billion years ago was one of rapid crustal growth in North America, during which most of the Canadian Shield and the crust beneath the northern Great Plains was formed. Extended selected references also available. The North American Cordillera extends up and down the coast of North America and roughly from the Great Plains westward to the Pacific Ocean, narrowing somewhat from north to south. While the North American plate in the east moves in the southwest direction, the Pacific plate in the west moves northwest. But the central part of the old Farallon plate vanished beneath North America. Continental fragmentation continued episodically until about 2 billion years ago. North America is an ancient continent in several respects. Shopping. The buried crust underlying the southern part of the interior platform was accreted immediately after the continental fragments to the north had coalesced. The repeated melting and resolidification of this crust led to progressive vertical differentiation as lighter components separated from heavier ones and were distributed at the top. This event, called the Mazatzal orogeny, may be related to a collision between ancestral North America and an unknown continent to the south, and it concluded the main accretionary stage of North America. Precambrian Research, v. 53 ( 1991 ) p. 23-40. Whereas South America and Africa were not assembled until 0.7 Ga, and the assembly of Eurasia began at 0.3 Ga, most of the North American craton has been coherent since 1.7 Ga. In this regard, the shield is not representative of the craton as a whole, being strongly biased in favor of Archean crust (Fig. Radiogenic isotopic data from the Precambrian shield, and from inliers and subsurface samples on the platform indicate that about 55 percent of the area of the craton separated from the mantle in the Archean and about 45 percent in the Proterozoic (Fig. A thick sedimentary prism exposed in the northwestern corner of the Canadian Shield and the adjacent Cordilleras may mark a contemporaneous continental margin. Early Proterozoic rifting and subsequent collisional deformation govern the dimensions of the provinces. Paul F. Hoffman, 1989. (The shelf sediments, deposited about 2.4 billion years ago, are particularly significant in that they contain discrete layers strewn with boulders dropped from shelf ice, implying that seawater then had a temperature range similar to that of the present.) In the following 50 million years all but the southern part of the interior platform had coalesced into a craton that has changed little since. Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. "Precambrian geology and tectonic history of North America", The Geology of North America—An Overview, Albert W. Bally, Allison R. Palmer. To the south a series of localized basins developed in what is now the Rocky Mountains. The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. Tectonic evolution. Tectonic evolution of South America during the Late Proterozoic. Grassland, desert, and tundra communities, The European attitudes toward the environment, The role of Mexico, the West Indies, and Central America, The Mexican and the Central American segments. Geological Survey of Canada, Ottawa, Ontario K1A 0E4, Canada. The amalgamation began about 1.97 billion years ago, when the Slave province collided obliquely with the western Churchill province. Actively work with complex datasets (geochemical, chronological, structural) to unravel the tectonic history of mountain belts and cratons. 1): the familiar Superior, Wyoming, Slave, and Nain (North Atlantic) provinces, and the newly recognized Hearne, Rae, and Burwell provinces (formerly parts of the composite Churchill province). All three collisions were preceded by subduction of oceanic plates beneath the Churchill province. Abstract. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and also the northwestern part of Scotland, known as the Hebridean Terrane. As exposed in the Canadian Shield, the thickened crust consists of many varieties of granitic intrusions separated by belts of folded and faulted volcanic and sedimentary rocks. Similar deposits of like age are found on other continents, and they form the principle source of iron ore today. The core of the North American continent (Canadian shield) came together in the Paleoproterozoic (2.0–1.8 Ga) by plate collisions of Archean continents (Slave with Rae-Hearne, then Rae-Hearne with Superior) as well as smaller Archean continental fragments (Wyoming, Medicine Hat, … In the northeastern part of the shield, rocks as old as 3.8 billion years are found on the formerly contiguous coasts of western Greenland and Labrador. 2). Tanya Atwater, 1970. It was subducted beneath California leaving the San Andreas fault system behind as the contact between the North America and Pacific plates. Whereas South America and Africa were not assembled until 0.7 Ga, and the assembly of Eurasia began at 0.3 Ga, most of the North American craton has been coherent since 1.7 Ga. The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.. By analogy, North America may have been part of an earlier supercontinent between about 1.6 and 1.3 billion years ago.). The Geology of North America - An Overview. Precambrian bedrock of the Canadian Shield rising out of Reindeer Lake, on the border between northeastern Saskatchewan and northwestern Manitoba. Conversely, most of the Proterozoic crust underlies the Phanerozoic sedimentary veneer of the southern interior platform. The Archean protocraton of Laurentia is an aggregate of seven former microcontinents (Fig. The continental fragments constituting interior North America coalesced between about 2.0 and 1.8 billion years ago. Search for other works by this author on: You do not currently have access to this chapter. Plate tectonic history of the northeast Pacific and western North America. The Rocky Mountains took shape during a period of intense plate tectonic activity that formed much of the rugged landscape of the western United States, starting with the Cretaceous - Paleogene Laramide orogeny, about 70-40 million years ago is responsible for raising the Rocky Mountains. During other times in its past, … Info. Heat buildup beneath the stationary supercontinent induced a large-scale upwelling from the mantle that ultimately contributed to supercontinental breakup. Copy link. You could not be signed in. Shows the plate tectonic history of the northeast Pacific and western North America, 38 million years ago to Present (stable North America held fixed). This crust is much like that formed earlier in the shield: diverse granitic bodies intrude altered and deformed volcanic and derived sedimentary rocks. Includes the breakup and piecewise subduction of the Farallon plate and the consequent development of the San Andreas plate boundary. This chapter describes the constituents of Laurentia, their aggregation in the Early Proterozoic (Table 1), and subsequent adventures of the craton until the rifting events at the end of the Proterozoic, which gave the continent approximately its present shape. Consequently, the Churchill province experienced much more magmatism, metamorphism, and deformation in this interval than did the Slave, Superior, or Nain provinces. Western architecture: Colonial architecture in North America. © Geological Society of America, Inc. 1989, ISBN 978-0-8137-5445-1$9, This site uses cookies. By continuing to use our website, you are agreeing to our, American Association of Petroleum Geologists, Cushman Foundation for Foraminiferal Research, Mineralogical Society of Great Britain and Ireland. Please check your email address / username and password and try again. Although its known geologic history spans almost 4 billion years, two ages stand out as turning points. The formation of the Boston area started with the Greenville Mountains. About 1.85 billion years ago the Superior province collided with the southern Churchill province to form the bowlike Trans-Hudson orogenic belt, the crest of which underlies Hudson Bay. This younger crust in the interior platform has been sampled by oil drilling. Regional geologic mapping and isotope dating indicate that the processes of crustal thickening tended to occur incrementally in zones a few tens of miles wide and many hundreds of miles long. The collision produced the Thelon orogenic belt, which stretches from central Alberta to the northwestern corner of Greenland. Although its known geologic history spans almost 4 billion years, two ages stand out as turning points. It includes the Cascades, Sierra Nevada, and Basin and Range province; the Rocky Mountains are sometimes excluded from the cordillera proper, in spite of their tectonic history. (Dutch, 2009) The large plates with which it … Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Early history of the Earth ... Mountains and basins of western North America and Central Benjamin Bley de Brito Neves, Umberto G. Cordani 1991. This animation shows the plate tectonic and paleogeographic evolution of the South America from 160 million years ago to the present-day. In the present configuration of tectonic plates, the northeast Pacific region is dominated by the huge Pacific Plate. North America's continents, historical maps, North America spoken languages, physical map and satellite images. Over 1 billion years ago proto-North America, collided with another continent. Tap to unmute. The rocks are believed to have originated in oceanic volcanic island arcs between about 1.8 and 1.7 billion years ago. Learn about the North American Plate and how it is moving relative to other tectonic plates. The zonation of the Trans-Hudson belt is typical of collision zones: granitic rocks representing the eroded roots of a continental volcanic arc occur along the Churchill province margin, the medial zone comprises relics of oceanic island arcs, and the Superior province margin is characterized by shelf sediments overthrust by slivers of oceanic crust. It contains some of the oldest rocks on the Earth, its interior has been stable for the longest period of time, and it was the first continent to achieve approximately its present size and shape. Hundreds of granitic and subordinate basaltic magma bodies were emplaced in a broad zone from southeastern California to the coast of Labrador about 1.6 to 1.3 billion years ago. The largest of these fragments forms the Superior province, which is located in the south-central part of the Canadian Shield and is some 1,500 miles (2,400 km) wide. The oldest rocks in the world occur in the Canadian Shield. With an area of 76 million km (29 million sq mi), it is the Earth's second largest tectonic plate, behind the Pacific Plate (which borders the plate to the west). This animation shows the plate tectonic and paleogeographic evolution of North America from 200 million years ago to the present-day. It originated as an enclosed basin floored by highly stretched continental crust or trapped oceanic crust, which is analogous to the structure found in the present-day Black Sea. The history revealed by the mantle slabs helps explain some baffling geology, such as rocks carried 1,200 miles (2,000 km) from Mexico to Canada. Striking similarities between contemporaneous shelf sediments on the southern margins of the Wyoming and Superior provinces and between the crust of the Superior and Hearne provinces, however, suggest that they originally may have been juxtaposed. This magmatism seems not to have been induced by deformation of the continental plate but may have been a consequence of hot mantle upwelling beneath the plate. A. The Rae province includes northern, southwestern, and southeastern prongs. It contains some of the oldest rocks on the Earth, its interior has been stable for the longest period of time, and it was the first continent to achieve approximately its present size and shape. The Belt Basin, centred in Idaho and western Montana, contains large base-metal ore bodies embedded in sediments up to 12 miles (19 km) thick. Twenty chapters include concise reviews of current thinking about Precambrian basement, Phanerozoic orogens, cratonic basins, passive-margin geology of the Atlantic and Gulf Coast regions, marine and terrestrial geology of the Caribbean region, marine geology of the North Atlantic and northeast Pacific oceans, Quaternary geology, hydrogeology, and economic geology. 1-15. It extends westward beneath the Colorado Plateau of western Colorado and eastern Utah and the surrounding Cordilleras and eastward into parts of the younger Grenville and Appalachian orogenic belts. Volcanic island arcs were accreted to the western margin of the Slave province, forming the Wopmay Orogen; to the southern margin of the Superior province, forming the Penokean Orogen; and to the southeastern margin of the Nain province, forming the Ketilidian Orogen. Geologic and Tectonic Development of the North America-Caribbean Plate Boundary in Hispaniola (SPECIAL PAPER (GEOLOGICAL SOCIETY OF AMERICA)) Har/Map Edition by Paul Mann (Author), Grenville Draper (Author), John F. Lewis (Editor) & ISBN-13: 978-0813722627. The "Tectonic Map of North America," on a scale of 1: 5,000,000, has been compiled by the United States Geologi­ cal Survey in collaboration with other national geological sur­ veys, and with the assistance of various individuals. Indiana in its plate tectonic setting A short history of North America. The external margins of the composite protocontinent also were active between 1.9 and 1.8 billion years ago. She wrote two major research papers outlining the history of plate tectonic evolution of North America and tectonic problems of the San Andreas Fault , which assisted in documenting the history of the San Andreas Fault Line. Western North America is a patchwork is hundreds of terranes, which are crustal pieces or microplates (think of islands), that collided with and attached to North America across hundreds of millions of years -- adding piece-by-piece to the continent's width and building mountains as they produced volcanoes or pushed up sediments and rocks.This posts provides a very simplified timeline … The ratio of neodymium and samarium was used to estimate the age of the faux amphibolite volcanic deposits of the Nuvvuagittuq greenstone belt in Quebec, Canada. Tanya Atwater, 1989. The process of continental breakup began about 2.45 billion years ago along the southern margin of the Superior province, producing extensive sets of parallel dikes (vertical sheets of crystallized intrusive magma) and rift valleys containing lavas with chemical compositions characteristic of plates undergoing horizontal stretching. The magmas were generated by repeated partial melting in the crust and mantle over a period of about 250 million years. Watch later. The second occurred about 600 million years ago, when fragmentation of ancestral North America created the continental margins along which the peripheral orogenic belts developed. In any given region, relatively thin primeval oceanic crust evolved into thick continental crust over a period of about 50 million years. The east-side of the North American Plate straddles the Eurasian Plate and African Plate.This is the Mid-Atlantic Ridge where divergent tectonic plates pull apart from each other. The North American tectonic plate, shown above, encompasses the majority of the surface area of North America, as well as Greenland, the northern Caribbean, and parts of Siberia (Russia), Iceland, and the Azores (Portugal). Over time, collisions with the different subduction zones smeared exotic terranes along the continent's western margin, a rock record that has long hinted at North America's violent tectonic history. Following continental separation, sediments accumulated on subsiding continental shelves. Lastly, the San Andreas fault is between the North American Plate and Pacific Plate are transform plate boundaries. In turn, we find some of the youngest geologic rocks at these mid-oceanic ridges. Print. In Labrador, where the magmas are best exposed, they form large, subcircular intrusive bodies, called batholiths, that are up to 95 miles (150 km) in diameter and 6 miles (10 km) thick. Review the growth of the North American continent as a consequence of tectonic accretion. Includes tables of contents for the other volumes in this series. In addition, a similar uranium-lead technique revealed that the Acasta gneisses, which occur southeast of Great Bear Lake in the northwestern corner of the shield, were at least 3.8 billion (and possibly up to 3.96 billion) years old. Geologic and tectonic development of the North America-Caribbean plate boundary in Hispaniola / edited by Paul Mann, Grenville Draper, and John F. Lewis. Atwater is perhaps best known for her work on the plate tectonic history of western North America. This craton, known as Laurentia, included Greenland and northwest Scotland until their partial separation in the Late Cretaceous. Compare and contrast Precambrian and Phanerozoic tectonic processes as preserved in the rock record of North America. The rocks here are more than two billion years old in places, andwere assembled through time as smaller microcontinents and terranes, or fragments of crustal material, crashed together. North America is an old continent. The overall process of crustal transformation has much in common with activity associated with plate convergence, where oceanic volcanic arcs and derived sedimentary rocks are accreted onto the leading edge of the overriding plate and later are intruded by magmas generated in the mantle above the subducted plate. (A similar style of magmatism occurred from 300 to 150 million years ago in new crust near the active southern margin of the supercontinent Pangaea. Brushy Basin Member of the Morrison Formation on the Colorado Plateau, west of Green River, Utah, U.S. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. North American Plate Movement. North America is an ancient continent in several respects. As the thickened crust emerged above sea level, it was stripped by erosion and redeposited in adjacent depressions as detrital sediment. ... 83,000 lessons in math, English, science, history, and more. Each province is a Late Archean crustal aggregate and contains variable proportions of Early and/or Middle Archean crust. North America is an old continent. Summaries of the major features of the geology of North America and the adjacent oceanic regions are presented. Share. The Phanerozoic history of North America, when viewed from the perspective of Pangea, can be divided into three broad phases with gradational time boundaries, as described in the following paragraphs.. During the first phase, which lasted from the late Precambrian to the Pennsylvanian, Pangea was under construction and the North American craton was marked by various, persistent, … 1). This craton, known as Laurentia, included Greenland and northwest Scotland until their partial separation in the Late Cretaceous. The colonial architecture of the United States and Canada was as diverse as the peoples who settled there: English, Dutch, French, Swedish,... A rock formation called “faux amphibolite,” from the Nuvvuagittuq greenstone belt in northern Quebec, dated to 4.28 billion years ago. Between these three provinces is the sprawling Churchill province—which may be a composite of four or more individual fragments named the Wyoming, Hearne, Rae, and Burwell subprovinces. The first was about 1.8 billion years ago, when several continental fragments coalesced to form the stable crust underlying the Canadian Shield and northern interior platform. An excellent text for a graduate course or upper-level undergraduate course in regional geology. North America is only a recent representation of billions of years of continental evolution shaped by the forces of plate tectonics, sea level and climate change, and erosion. The continental crust that had been assembled by about 2.6 billion years ago soon began to break up into continental fragments. They were accreted piecemeal to the protocontinent to the north and then subjected to regional northwest-southeast compression between about 1.7 and 1.6 billion years ago. These rocks are estimated to be 4.28 billion years old. While parts of the craton peek out in Greenland and Canada, in the U.S., thick layers of sedimentary rocks keep most of these ancient assemblages under wraps in the center of the continent. Navigate parenthood with the help of the Raising Curious Learners podcast. Because it is difficult to track the drift of continental fragments of such antiquity, it is not known how many parent continents are represented by the fragments now located in North America. The magmatism was most profuse in the new crust of the southern interior platform, which was blanketed by up to 4 miles (6 km) of volcanic ash flows derived from the partial melting of the lower crust. This animation shows the plate tectonic and paleogeographic evolution of the North Atlantic region from 200 million years ago to the present-day. Tectonic History Greenville Mountain Formation. Rocks in the Minnesota River valley, near the southern limit of the shield southwest of Lake Superior, range in age up to 3.66 billion years. This is because tectonic plates collide and sink at these zones of subduction (convergent plate boundaries). The central core of present-day North America is its craton, the oldest, thickest part of the continent. During this period an unusual sedimentary deposit consisting mostly of alternating iron-rich minerals and chert—banded iron formations—accumulated in the area south of Lake Superior, in Wyoming, and in Labrador. The compositional range of the old rocks is essentially the same as that of much younger rocks, implying similar processes of formation. It was then that the present size and shape of the continent was determined. Their ages have been calculated from precisely measured ratios of the radioactive decay of trace amounts of certain isotopes in the rock sample. Thus, what is now the stable interior of the continent was, about 1.85 billion years ago, laced with great mountain ranges. The geology of Alaska is typical of that of the cordillera. 1989. These deformed rocks are known as “greenstone belts” and contain economically viable concentrations of gold, silver, copper, zinc, and lead. 1st.
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