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Environmental Science

Canada: A young nation, but an old country Canada has been in existence since 1867 as a nation where the act of confederation brought together Ontario, new brun, nova scotia, quebec to create a political entity Driving of the last spike in 1885 finished the transcontinental railway Last to join the political and economic group was Newfoundland in 1949 The process of continental building has taken more than 4bill yrs to accomplish Construction on NA began at least 4000 million yrs ago with the formation of acasta gneiss of the northwest territories (part of slave province of Canadian shield) The building of north America was complete by 65 mya, but modern landscape is the result of geologically recent glaciations that have occurred in the last 2.5 million yrs The last ice sheet left the southern portions of the country 12,000 yrs ago and Labrador melted 6000 yrs ago What are the main geological building blocks of NA? Canadian shield: the exposed part of a craton that consists of very old (4billion to 1 billion yrs old) Archean and Proterozoic rocks that are devoid of fossils (no fossils) consists of gently undulating surface that rises unnoticeably, almost like an arch, in its center o Craton: composed of complex assemblages of geologic provinces and was created by separate landmasses being fused together by plate tectonics o Geologic provinces: broad regions of similar rocks, usually covering many thousand square kilometre, with characteristics that differ significantly from rock types present in adjacent areas (subdivided into smaller units called subprovinces) o Subprovinces: fault-bounded units containing distinct rock types, structures and mineral deposits that record particular geologic events o Provinces and subprovinces were identified by broad-scale field mapping and from the basis of the earliest geologic maps in Canada o Terrance: discrete fragments of oceanic or continental materal that have been added to a craton at an active margin by accretion (provinces and subprovinces) The north American craton is the largest in the world and extends from the atlantic seaboard, west beneath the rocky mountains and south as far as texas North American craton: a large, continent size block of distinct geology making up the basement of much of NA and Greenland Peneplain: a surface of low relief and great areal extent and age (Canadian shield) o The outer, gently sloping margins of the shield are buried below younger sedimentary rocks and the ancient peneplain surface now forms an unconformity btw the craton below and younger cover rocks above (separates metamorphic rocks from the craton and overlying Paleozoic cover rocks) o During mountain-building episodes (collision of land masses with the craton), fossiliferous sedimentary rocks were deposited when the outer margins of the craton were depressed and flooded by shallow seaso Rocks get younger as you travel from geographic interior of NA to its coats o Rocks that were uniform in character over enormous distances changed abruptly across very sharp boundaries o The working of plate tectonics by geologists studying the sea floor provided the key to the origin of the Canadian shield How did the North American Continent Evolve? Within the oldest part of the continent, several geological provinces (remains of individual continents that collided) are rimmed by intensely deformed rocks that form ancient orogens Orogens: consist of crushed and deformed rocks that represent the remains of mountain belts or volcanic arc formed during collision Wilson cycle: process of repeated continental aggradation (deposition of material by a river or stream) and breakup resulted in the development of supercontinents o It is possible to work on the geology of Australia or south America and recognize the same tectonic events as those that affected parts of NA Stage 1-Arctica: North America in the Archean o Some of the oldest rocks (Acasta Gneiss) dated on earth are found in the Slave Province (center of the North American continent) and is around 4 billion yrs old o Arctica: an ancient continent that are partly formed by the oldest rocks (Acasta Gneiss) and was formed around 2.5 billion yrs ago, completed 2 billion yrs ago o Slave province: the focus of mineral exploration activity like diamonds o Superi
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