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Great Oxygenation Event
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O2 build-up in the Earth's atmosphere. Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga).
Stage 1 (3.85–2.45 Ga): Practically no O2 in the atmosphere. The oceans were also largely anoxic with the possible exception of O2 gases in the shallow oceans.
Stage 2 (2.45–1.85 Ga): O2 produced, and rose to values of 0.02 and 0.04 atm, but absorbed in oceans and seabed rock.
Stage 3 (1.85–0.85 Ga): O2 starts to gas out of the oceans, but is absorbed by land surfaces. There was no significant change in terms of oxygen level.
Stages 4 and 5 (0.85–present): O2 sinks filled and the gas accumulates.[1]
The Great Oxygenation Event, the beginning of which is commonly known in scientific media as the Great Oxidation Event (GOE, also called the Oxygen Catastrophe, Oxygen Crisis, Oxygen Holocaust,[2] Oxygen Revolution, or Great Oxidation) was the biologically induced appearance of dioxygen (O2) in Earth's atmosphere.[3] Geological, isotopic, and chemical evidence suggest that this major environmental change happened around 2.45 billion years ago (2.45 Ga),[4] during the Siderian period, at the beginning of the Proterozoic eon. The causes of the event are not clear.[5] The current geochemical and biomarker evidence for the development of oxygenic photosynthesis before the Great Oxidation Event has been mostly inconclusive.[6]
Oceanic cyanobacteria, which evolved into coordinated (but not multicellular or even colonial) macroscopic forms more than 2.3 billion years ago (approximately 200 million years before the GOE),[7] are believed to have become the first microbes to produce oxygen by photosynthesis.[8] Before the GOE, any free oxygen they produced was chemically captured by dissolved iron or organic matter. The GOE started when these oxygen sinks became saturated, at which point oxygen produced by the cyanobacteria was free to escape into the atmosphere.
Cyanobacteria: Responsible for the buildup of oxygen in the earth's atmosphere
The increased production of oxygen set Earth's original atmosphere off balance.[9] Free oxygen is toxic to obligate anaerobic organisms, and the rising concentrations may have destroyed most such organisms at the time. Cyanobacteria were therefore responsible for one of the most significant mass extinctions in Earth's history. Besides marine cyanobacteria, there is also evidence of cyanobacteria on land.[citation needed]
A spike in chromium contained in ancient rock deposits formed underwater shows the accumulation had been washed off from the continental shelves. Chromium is not easily dissolved and its release from rocks would have required the presence of a powerful acid. One such acid, sulfuric acid (H2SO4), might have been created through bacterial reactions with pyrite.[10] Mats of oxygen-producing cyanobacteria can produce a thin layer, one or two millimeters thick, of oxygenated water in an otherwise anoxic environment even under thick ice, and before oxygen started accumulating in the atmosphere, these organisms would already be adapted to oxygen.[11] Additionally, the free oxygen would have reacted with atmospheric methane, a greenhouse gas, greatly reducing its concentration and triggering the Huronian glaciation, possibly the longest episode of glaciation in Earth's history and called snowball Earth.[12]
Eventually, the evolution of aerobic organisms that consumed oxygen established an equilibrium in its availability. Free oxygen has been an important constituent of the atmosphere ever since.[12]
Contents
[hide]
1 Timing
2 Time lag theory
2.1 Tectonic trigger
2.2 Nickel famine
2.3 Bistability
2.4 Hydrogen gas
3 Late evolution of oxy-photosynthesis theory
4 Role in mineral diversification
5 See also
6 References
7 External links
Timing[edit]
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Orange labels: ice ages.
Also see: Human timeline and Nature timeline
See also: Oxygen cycle
The most widely accepted chronology of the Great Oxygenation Event suggests that free oxygen was first produced by prokaryotic and then later eukaryotic organisms that carried out oxygenic photosynthesis more efficiently. The excess of oxygen those organisms produce is a waste product. These organisms lived long before the GOE,[13] perhaps as early as 3,500 million years ago.
Initially, the oxygen they produced would have quickly been removed from the atmosphere by the chemical weathering of reducing minerals (those able to be oxidized), most notably iron. This 'mass rusting' led to the deposition of iron(III) oxide in the form of banded-iron formations such as the sediments in Minnesota and Pilbara, Western Australia. Oxygen only began to persist in the atmosphere in small quantities shortly (~50 million years) before the start of the GOE.[14] Without a mineral sink in the form of iron, oxygen could have accumulated very rapidly. For example, at today's rates of photosynthesis (which are much greater than those in Precambrian when there were no land plants), modern atmospheric O2 levels could be produced in around 2,000 years.[15]
Another hypothesis is that oxygen producers did not evolve until a few million years before the major rise in atmospheric oxygen concentration.[16] This is based on a particular interpretation of a supposed oxygen indicator, the mass-independent fractionation of sulfur isotopes, a marker used in previous studies. This hypothesis would eliminate the need to explain a lag in time between the evolution of oxyphotosynthetic microbes and the rise in free oxygen.
In either case, oxygen did eventually accumulate in the atmosphere, with two major consequences.
Firstly, it oxidized atmospheric methane (a strong greenhouse gas) to carbon dioxide (a weaker one) and water. This decreased the greenhouse effect of the Earth's atmosphere, causing planetary cooling, and triggered the Huronian glaciation. Starting around 2.4 billion years ago, this lasted 300-400 million years, and may have been the longest ever snowball Earth episode.[16][17]
Secondly, the increased oxygen concentrations provided a new opportunity for biological diversification, as well as tremendous changes in the nature of chemical interactions between rocks, sand, clay, and other geological substrates and the Earth's air, oceans, and other surface waters. Despite the natural recycling of organic matter, life had remained energetically-limited until the widespread availability of oxygen. This breakthrough in metabolic evolution greatly increased the free energy availability for living organisms, with truly global environmental impacts. For example, mitochondria evolved after the GOE, and with more energy available from oxygen, organisms had the means for new, more complex morphologies. These new morphologies in turn helped drive evolution through increasingly complex interactions between organisms.[18]
Timeline of glaciations, shown in blue.
Time lag theory[edit]
The gap between the start of oxygen production from photosynthetic organisms and the geologically rapid increase in atmospheric oxygen (about 2.5–2.4 billion years ago) may have been as long as 900 million years. Several hypotheses might explain the time lag:
Tectonic trigger[edit]
2.1 billion year old rock showing banded iron formation
The oxygen increase had to await tectonically driven changes in the Earth, including the appearance of shelf seas, where reduced organic carbon could reach the sediments and be buried.[19] The newly produced oxygen was first consumed in various chemical reactions in the oceans, primarily with iron. Evidence is found in older rocks that contain massive banded iron formations that were apparently laid down as this iron and oxygen first combined; most of the planet's commercial iron ore is in these deposits. Researchers found that the amount of oxygen in the air spiked each time smaller land masses collided to form a super-continent. These massive pile ups generated mountain chains and as these mountains eroded, they released nutrients into the ocean, feeding the cyanobacteria that carry out photosynthesis.[20]
Nickel famine[edit]
The early chemosynthetic organisms would have been a source of methane, which is an important trap for molecular oxygen, because oxygen readily oxidizes methane to carbon dioxide (CO2) and water in the presence of UV radiation. Modern methanogens require nickel as an enzyme cofactor. As the Earth's crust cooled, the supply of nickel from volcanoes was reduced and hence less methane was produced. This allowed the oxygen percentage of the atmosphere to rise as the decrease in production of methane allowed the oxygen producing algae and other such life forms to, in a sense, out-produce the methane producers.[21] From 2.7 to 2.4 billion years ago, the rate of deposition of nickel declined steadily; it was originally 400 times today's levels.[22]
Bistability[edit]
Another hypothesis posits a model of the atmosphere that exhibits bistability in oxygen concentrations. In this model, UV shielding decreases the rate of methane oxidation once oxygen levels are sufficient to support the formation of an ozone layer. This explanation proposes an atmospheric system experiencing two steady states, one with lower (0.02%) atmospheric oxygen content, and the other with higher (21% or more) oxygen content. The Great Oxygenation Event can then be understood as a switch between the lower to the upper stable steady states.[23]
Hydrogen gas[edit]
Another factor is the presence of hydrogen gas. The appearance of cyanobacteria might explain the decline of hydrogen gas and why Earth's air is so oxygen-rich.
Some bacteria living in the early oceans had the ability to separate water into hydrogen and oxygen molecules. By using the energy of the Sun, the separate hydrogen molecules were able to create organic compounds, and oxygen was a by-product. If the hydrogen-heavy compounds were buried, it would have allowed oxygen to accumulate in the atmosphere.
However, in 2001 scientists realized that the hydrogen would instead escape into space through a process called methane photolysis, in which hydrogen-containing methane reacts with oxygen releasing hydrogen. This hypothesis could explain why the early Earth stayed warm enough to sustain oxygen producing lifeforms.[24]
Late evolution of oxy-photosynthesis theory[edit]
There is a possibility that the oxygen indicator was misinterpreted. During the proposed time of the lag in the previous theory, there was a change from mass-independently fractionated (MIF) sulfur to mass-dependently fractionated (MDF) sulfur in sediments. This was assumed to be a result of the appearance of oxygen in the atmosphere (since oxygen would have prevented the photolysis of sulfur dioxide, which causes MIF). This change from MIF to MDF of sulfur isotopes also may have been caused by an increase in glacial weathering, or the homogenization of the marine sulfur pool as a result of an increased thermal gradient during the Huronian glaciation period.[16]
Role in mineral diversification[edit]
The Great Oxygenation Event triggered an explosive growth in the diversity of minerals on Earth. This now meant that many elements could occur in one or more oxidized forms in the near-surface environment.[25] It is estimated that the Great Oxygenation Event alone was directly responsible for more than 2,500 new minerals of the total of about 4,500 minerals found on Earth. Most of these new minerals were formed after the Great Oxygenation event as hydrated and oxidized forms due to dynamic mantle and crust processes.[26]
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See also[edit]
Geological history of oxygen
Iodide
Medea hypothesis
Pasteur point
Rare Earth hypothesis
Stromatolite
References[edit]
Jump up ^ Holland, Heinrich D. "The oxygenation of the atmosphere and oceans". Philosophical Transactions of the Royal Society: Biological Sciences. Vol. 361. 2006. pp. 903–915.
Jump up ^ Margulis, Lynn; Sagan, Dorion (1986). "Chapter 6, "The Oxygen Holocaust"". Microcosmos: Four Billion Years of Microbial Evolution. California: University of California Press. p. 99. ISBN 9780520210646.
Jump up ^ Sosa Torres, Martha E.; Saucedo-Vázquez, Juan P.; Kroneck, Peter M.H. (2015). "Chapter 1, Section 2 "The rise of dioxygen in the atmosphere"". In Peter M.H. Kroneck and Martha E. Sosa Torres. Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases. Metal Ions in Life Sciences. 15. Springer. pp. 1–12. doi:10.1007/978-3-319-12415-5_1.
Jump up ^ Zimmer, Carl (3 October 2013). "Earth's Oxygen: A Mystery Easy to Take for Granted". The New York Times. Retrieved 3 October 2013.
Jump up ^ "University of Zurich. "Great Oxidation Event: More oxygen through multicellularity." ScienceDaily. ScienceDaily, 17 January 2013".
Jump up ^ Planavsky, Noah J.; et al. (24 January 2014). "Evidence for oxygenic photosynthesis half a billion years before the Great Oxidation Event". Nature. 7: 283–286. doi:10.1038/ngeo2122. Retrieved 14 March 2016.
Jump up ^ Flannery, D. T.; R.M. Walter (2012). "Archean tufted microbial mats and the Great Oxidation Event: new insights into an ancient problem". Australian Journal of Earth Sciences. 59 (1): 1–11. Bibcode:2012AuJES..59....1F. doi:10.1080/08120099.2011.607849.
Jump up ^ "The Rise of Oxygen - Astrobiology Magazine". Astrobiology Magazine. Retrieved 2016-04-06.
Jump up ^ "University of Zurich. "Great Oxidation Event: More oxygen through multicellularity." ScienceDaily. ScienceDaily, 17 January 2013".
Jump up ^ "Evidence of Earliest Oxygen-Breathing Life on Land Discovered". LiveScience.com. Retrieved 2016-04-06.
Jump up ^ Oxygen oasis in Antarctic lake reflects Earth in distant past
^ Jump up to: a b Frei, R.; Gaucher, C.; Poulton, S. W.; Canfield, D. E. (2009). "Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes". Nature. 461 (7261): 250–253. Bibcode:2009Natur.461..250F. doi:10.1038/nature08266. PMID 19741707. Lay summary.
Jump up ^ Dutkiewicz, A.; Volk, H.; George, S. C.; Ridley, J.; Buick, R. (2006). "Biomarkers from Huronian oil-bearing fluid inclusions: an uncontaminated record of life before the Great Oxidation Event". Geology. 34 (6): 437. Bibcode:2006Geo....34..437D. doi:10.1130/G22360.1.
Jump up ^ Anbar, A.; Duan, Y.; Lyons, T.; Arnold, G.; Kendall, B.; Creaser, R.; Kaufman, A.; Gordon, G.; Scott, C.; Garvin, J.; Buick, R. (2007). "A whiff of oxygen before the great oxidation event?". Science. 317 (5846): 1903–1906. Bibcode:2007Sci...317.1903A. doi:10.1126/science.1140325. PMID 17901330.
Jump up ^ Dole, M. (1965). "The Natural History of Oxygen". The Journal of General Physiology. 49 (1): Suppl:Supp5–27. doi:10.1085/jgp.49.1.5. PMC 2195461  . PMID 5859927.
^ Jump up to: a b c Robert E. Kopp; Joseph L. Kirschvink; Isaac A. Hilburn; Cody Z. Nash (2005). "The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis". Proceedings of the National Academy of Sciences of the United States of America. 102 (32): 11131–6. Bibcode:2005PNAS..10211131K. doi:10.1073/pnas.0504878102. PMC 1183582  . PMID 16061801.
Jump up ^ First breath: Earth's billion-year struggle for oxygen New Scientist, #2746, 5 February 2010 by Nick Lane.
Jump up ^ Sperling, Erik; Frieder, Christina; Raman, Akkur; Girguis, Peter; Levin, Lisa; Knoll, Andrew (Aug 2013). "Oxygen, ecology, and the Cambrian radiation of animals". Proceedings of the National Academy of Sciences of the United States of America. 110: 13446–13451. doi:10.1073/pnas.1312778110. PMC 3746845  . PMID 23898193. Retrieved 1 October 2014.
Jump up ^ Lenton, T. M.; H. J. Schellnhuber; E. Szathmáry (2004). "Climbing the co-evolution ladder". Nature. 431 (7011): 913. Bibcode:2004Natur.431..913L. doi:10.1038/431913a. PMID 15496901.
Jump up ^ American, Scientific. "Abundant Oxygen Indirectly Due to Tectonics". Scientific American. Retrieved 2016-04-06.
Jump up ^ American, Scientific. "Breathing Easy Thanks to the Great Oxidation Event". Scientific American. Retrieved 2016-04-06.
Jump up ^ Kurt O. Konhauser; et al. (2009). "Oceanic nickel depletion and a methanogen famine before the Great Oxidation Event". Nature. 458 (7239): 750–753. Bibcode:2009Natur.458..750K. doi:10.1038/nature07858. PMID 19360085.
Jump up ^ Goldblatt, C.; T.M. Lenton; A.J. Watson (2006). "The Great Oxidation at 2.4 Ga as a bistability in atmospheric oxygen due to UV shielding by ozone" (PDF). Geophysical Research Abstracts. 8: 00770.
Jump up ^ Franzen, Harald. "New Theory Explains How Earth's Early Atmosphere Became Oxygen-Rich". Scientific American. Retrieved 2016-04-06.
Jump up ^ Sverjensky, Dimitri A.; Lee, Namhey (2010-02-01). "The Great Oxidation Event and Mineral Diversification". Elements. 6 (1): 31–36. doi:10.2113/gselements.6.1.31. ISSN 1811-5209.
Jump up ^ "Evolution of Minerals", Scientific American, March 2010
External links[edit]
First breath: Earth's billion-year struggle for oxygen New Scientist, #2746, 5 February 2010 by Nick Lane. [1]
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List of cities in Ontario
From Wikipedia, the free encyclopedia
Jump to: navigation, search
A city is a subtype of municipalities in the Canadian province of Ontario. A city can have the municipal status of either a single-tier or lower-tier municipality.
Ontario has 51 cities[1] that had a cumulative population of 9,293,031 and an average population of 182,216 in the 2011 Census.[2] Ontario's largest and smallest cities are Toronto and Dryden with populations of 2,615,060 and 7,617 respectively.[2]
Ontario's newest city is Markham, which changed from a town to a city on July 1, 2012.[3]
Contents
[hide]
1 History
2 Cities in Ontario
3 See also
4 References
History[edit]
Under the former Municipal Act, 1990, a city was both an urban and a local municipality.[4] Under this former legislation, the Municipal Board could change the status of a village or town to a city, upon review of an application from the village or town, if it had a population of 15,000 or more.[4] The Municipal Board could also incorporate a township as a city under the same conditions with the exception that the population requirements was 25,000 or more.[4] In the event an application was received from a village, town or township located within a county, the application could have only been approved by the Municipal Board if authorized by the Minister of Municipal Affairs.[4]
In the transition to the Municipal Act, 2001, these requirements were abandoned and, as at December 31, 2002, every city that:[5]
"existed and formed part of a county, a regional or district municipality or the County of Oxford for municipal purposes" became a lower-tier municipality yet retained its name as a city; and
"existed and did not form part of a county, a regional or district municipality or the County of Oxford for municipal purposes" became a single-tier municipality yet retained its name as a city.
The current legislation also provides lower and single-tier municipalities with the authority to name themselves as "cities", or other former municipal status types such as "towns", "villages" or "townships", or generically as "municipalities".[6]
Cities in Ontario[edit]
Toronto is Ontario's capital and Canada's largest city
Ottawa is Canada's capital and Ontario's second largest city
Downtown Brampton
Skyline of downtown Hamilton
Skyline of downtown London
Markham Civic Centre in Markham, Ontario's newest city
Vaughan as viewed from Canada's Wonderland
Downtown of Kitchener
Downtown of Windsor
Name[1][2]
Municipal
status[1]
Census division[1][7]
Population
(2011)[2]
Population
(2006)[2]
Change
(%)[2]
Area
(km²)[2]
Population
density[2]
Barrie[ON 1] Single-tier Simcoe 7005136063000000000♠136,063[8] 7005128430000000000♠128,430 7000590000000000000♠5.9 7001773900000000000♠77.39 7003175810000000000♠1,758.1
Belleville Single-tier Hastings 7004494540000000000♠49,454 7004488210000000000♠48,821 7000130000000000000♠1.3 7002247210000000000♠247.21 7002200000000000000♠200
Brampton[ON 2] Lower-tier Peel 7005523911000000000♠523,911 7005433806000000000♠433,806 7001208000000000000♠20.8 7002266339999999999♠266.34 7003196710000000000♠1,967.1
Brant Single-tier Brant 7004356380000000000♠35,638 7004344150000000000♠34,415 7000360000000000000♠3.6 7002843290000000000♠843.29 7001423009999900000♠42.3
Brantford[ON 3] Single-tier Brant 7004936500000000000♠93,650 7004901920000000000♠90,192 7000380000000000000♠3.8 7001724700000000000♠72.47 7003129230000000000♠1,292.3
Brockville Single-tier Leeds and Grenville 7004218700000000000♠21,870 7004219570000000000♠21,957 3000600000000000000♠−0.4 7001209009999900000♠20.9 7003104620000000000♠1,046.2
Burlington Lower-tier Halton 7005175779000000000♠175,779 7005164415000000000♠164,415 7000690000000000000♠6.9 7002185660000000000♠185.66 7002946800000000000♠946.8
Cambridge[ON 4] Lower-tier Waterloo 7005126748000000000♠126,748 7005120371000000000♠120,371 7000530000000000000♠5.3 7002113000000000000♠113 7003112170000000000♠1,121.7
Clarence-Rockland Lower-tier Prescott and Russell 7004231850000000000♠23,185 7004207900000000000♠20,790 7001115000000000000♠11.5 7002297860000000000♠297.86 7001778000000000000♠77.8
Cornwall Single-tier Stormont, Dundas and Glengarry 7004463400000000000♠46,340 7004459650000000000♠45,965 6999800000000000000♠0.8 7001615200000000000♠61.52 7002753200000000000♠753.2
Dryden[ON 5] Single-tier Kenora 7003761700000000000♠7,617 7003819500000000000♠8,195 2999290000000000000♠−7.1 7001658400000000000♠65.84 7002115700000000000♠115.7
Elliot Lake Single-tier Algoma 7004113480000000000♠11,348 7004115490000000000♠11,549 2999830000000000000♠−1.7 7002714569999900000♠714.56 7001159000000000000♠15.9
Greater Sudbury[ON 6] Single-tier Sudbury 7005160274000000000♠160,274 7005157857000000000♠157,857 7000150000000000000♠1.5 7003322738000000000♠3,227.38 7001497000000000000♠49.7
Guelph[ON 7] Single-tier Wellington 7005121688000000000♠121,688 7005114943000000000♠114,943 7000590000000000000♠5.9 7001872000000000000♠87.2 7003139540000000000♠1,395.4
Haldimand County Single-tier Haldimand 7004448760000000000♠44,876 7004452120000000000♠45,212 3000300000000000000♠−0.7 7003125157000000000♠1,251.57 7001359000000000000♠35.9
Hamilton[ON 8] Single-tier Hamilton 7005519949000000000♠519,949 7005504559000000000♠504,559 7000310000000000000♠3.1 7003111723000000000♠1,117.23 7002465400000000000♠465.4
Kawartha Lakes Single-tier Kawartha Lakes 7004732140000000000♠73,214 7004745610000000000♠74,561 2999820009999999999♠−1.8 7003308306000000000♠3,083.06 7001237000000000000♠23.7
Kenora Single-tier Kenora 7004153480000000000♠15,348 7004151770000000000♠15,177 7000110000000000000♠1.1 7002211750000000000♠211.75 7001725000000000000♠72.5
Kingston[ON 9] Single-tier Frontenac 7005123363000000000♠123,363 7005117207000000000♠117,207 7000530000000000000♠5.3 7002451170000000000♠451.17 7002273390000099999♠273.4
Kitchener[ON 10] Lower-tier Waterloo 7005219153000000000♠219,153 7005204668000000000♠204,668 7000710000000000000♠7.1 7002136790000099999♠136.79 7003160210000000000♠1,602.1
London[ON 11] Single-tier Middlesex 7005366151000000000♠366,151 7005352395000000000♠352,395 7000390000000000000♠3.9 7002420570000000000♠420.57 7002870600000000000♠870.6
Markham[ON 12] Lower-tier York 7005301709000000000♠301,709 7005261573000000000♠261,573 7001153000000000000♠15.3 7002212580000000000♠212.58 7003141930000000000♠1,419.3
Mississauga[ON 13] Lower-tier Peel 7005713443000000000♠713,443 7005668599000000000♠668,599 7000670000000000000♠6.7 7002292390000000000♠292.4 7003243990000000000♠2,439.9
Niagara Falls[ON 14] Lower-tier Niagara 7004829970000000000♠82,997 7004821840000000000♠82,184 7000100000000000000♠1 7002209710000000000♠209.71 7002395800000000000♠395.8
Norfolk County Single-tier Norfolk 7004631750000000000♠63,175 7004625630000000000♠62,563 7000100000000000000♠1 7003160760000000000♠1,607.6 7001393009999900000♠39.3
North Bay Single-tier Nipissing 7004536510000000000♠53,651 7004539660000000000♠53,966 3000400000000000000♠−0.6 7002319050000000000♠319.05 7002168200000000000♠168.2
Orillia Single-tier Simcoe 7004305860000000000♠30,586 7004302590000000000♠30,259 7000110000000000000♠1.1 7001286100000000000♠28.61 7003106920000000000♠1,069.2
Oshawa[ON 15] Lower-tier Durham 7005149607000000000♠149,607 7005141590000000000♠141,590 7000570000000000000♠5.7 7002145680000000000♠145.68 7003102700000000000♠1,027
Ottawa[ON 16] Single-tier Ottawa 7005883391000000000♠883,391 7005812129000000000♠812,129 7000880000000000000♠8.8 7003279022000099999♠2,790.22 7002316600000000000♠316.6
Owen Sound Lower-tier Grey 7004216880000000000♠21,688 7004217530000000000♠21,753 3000700000000000000♠−0.3 7001242200000000000♠24.22 7002895500000000000♠895.5
Pembroke[ON 17] Single-tier Renfrew 7004143600000000000♠14,360 7004139300000000000♠13,930 7000310000000000000♠3.1 7001143500000000000♠14.35 7003100070000000000♠1,000.7
Peterborough[ON 18] Single-tier Peterborough 7004786980000000000♠78,698 7004754060000000000♠75,406 7000440000000000000♠4.4 7001638000000000000♠63.8 7003123360000099999♠1,233.6
Pickering Lower-tier Durham 7004887210000000000♠88,721 7004878380000000000♠87,838 7000100000000000000♠1 7002231590000000000♠231.59 7002383100000000000♠383.1
Port Colborne Lower-tier Niagara 7004184240000000000♠18,424 7004185990000000000♠18,599 3000099999999999999♠−0.9 7002121970000000000♠121.97 7002151100000000000♠151.1
Prince Edward County Single-tier Prince Edward 7004252580000000000♠25,258 7004254960000000000♠25,496 3000099999999999999♠−0.9 7003105045000000000♠1,050.45 7001240000000000000♠24
Quinte West Single-tier Hastings 7004430860000000000♠43,086 7004426970000000000♠42,697 6999900000000000000♠0.9 7002494150000000000♠494.15 7001872000000000000♠87.2
Sarnia Lower-tier Lambton 7004723660000000000♠72,366 7004714190000000000♠71,419 7000130000000000000♠1.3 7002164710000000000♠164.71 7002439400000000000♠439.4
Sault Ste. Marie Single-tier Algoma 7004751410000000000♠75,141 7004749480000000000♠74,948 6999300000000000000♠0.3 7002223260000000000♠223.26 7002336600000000000♠336.6
St. Catharines[ON 19] Lower-tier Niagara 7005131400000000000♠131,400 7005131989000000000♠131,989 3000600000000000000♠−0.4 7001961100000000000♠96.11 7003136720000000000♠1,367.2
St. Thomas Single-tier Elgin 7004379050000000000♠37,905 7004361100000000000♠36,110 7000500000000000000♠5 7001355200000000000♠35.52 7003106730000000000♠1,067.3
Stratford Single-tier Perth 7004308860000000000♠30,886 7004305160000000000♠30,516 7000120000000000000♠1.2 7001269500000000000♠26.95 7003114600000000000♠1,146
Temiskaming Shores Single-tier Timiskaming 7004104000000000000♠10,400 7004104420000000000♠10,442 3000600000000000000♠−0.4 7002177910000000000♠177.91 7001585000000000000♠58.5
Thorold Lower-tier Niagara 7004179310000000000♠17,931 7004182240000000000♠18,224 2999840000000000000♠−1.6 7001830000000000000♠83 7002216000000000000♠216
Thunder Bay[ON 20] Single-tier Thunder Bay 7005108359000000000♠108,359 7005109160000000000♠109,160 3000300000000000000♠−0.7 7002328240000000000♠328.24 7002330100000000000♠330.1
Timmins Single-tier Cochrane 7004431650000000000♠43,165 7004429970000000000♠42,997 6999400000000000000♠0.4 7003297915000000000♠2,979.15 7001145000000000000♠14.5
Toronto[ON 21] Single-tier Toronto 7006261506000000000♠2,615,060 7006250328100000000♠2,503,281 7000450000000000000♠4.5 7002630210000000000♠630.21 7003414950000000000♠4,149.5
Vaughan Lower-tier York 7005288301000000000♠288,301 7005238866000000000♠238,866 7001207000000000000♠20.7 7002273520000099999♠273.52 7003105400000000000♠1,054
Waterloo[ON 22] Lower-tier Waterloo 7004987800000000000♠98,780 7004974750000000000♠97,475 7000130000000000000♠1.3 7001640190000000000♠64.02 7003154290000000000♠1,542.9
Welland Lower-tier Niagara 7004506310000000000♠50,631 7004503310000000000♠50,331 6999600000000000000♠0.6 7001810900000000000♠81.09 7002624400000000000♠624.4
Windsor[ON 23] Single-tier Essex 7005210891000000000♠210,891 7005216473000000000♠216,473 2999740000000000000♠−2.6 7002146320000000000♠146.32 7003144130000000000♠1,441.3
Woodstock Lower-tier Oxford 7004377540000000000♠37,754 7004358220000000000♠35,822 7000540000000000000♠5.4 7001490000000000000♠49 7002770500000000000♠770.5
Total cities — — 7006929338300000000♠9,293,383 7006878212000000000♠8,782,120 7000580000000000000♠5.8 7004259181500000000♠25,918.15 7002358600000000000♠358.6
Notes:
Jump up ^ The Barrie census metropolitan area (CMA) is formed around the City of Barrie.
Jump up ^ Brampton is Canada's ninth-largest city.
Jump up ^ The Brantford CMA includes the City of Brantford as well as the County of Brant, which is a single-tier city.
Jump up ^ The City of Cambridge, as well as the cities of Kitchener and Waterloo, form parts of the Kitchener - Cambridge - Waterloo CMA.
Jump up ^ Dryden is Ontario's smallest city by population.
Jump up ^ Greater Sudbury is Ontario's largest city by area. The Greater Sudbury CMA is formed around the City of Greater Sudbury.
Jump up ^ The Guelph CMA is formed around the City of Guelph.
Jump up ^ Hamilton is Canada's tenth-largest city. The Hamilton CMA includes the cities of Burlington and Hamilton.
Jump up ^ The Kingston CMA is formed around the City of Kingston.
Jump up ^ The City of Kitchener, as well as the cities of Cambridge and Waterloo, form parts of the Kitchener - Cambridge - Waterloo CMA.
Jump up ^ The London CMA includes the cities of London and St. Thomas.
Jump up ^ Markham is Ontario's newest city, incorporated July 1, 2012
Jump up ^ Mississauga is Canada's sixth-largest city.
Jump up ^ The City of Niagara Falls, as well as the cities of Port Colborne, St. Catharines, Thorold and Welland, form parts of the St. Catharines - Niagara CMA.
Jump up ^ The Oshawa CMA is formed around the City of Oshawa.
Jump up ^ Ottawa is Canada's capital and fourth-largest city. The Ontario portion of the Ottawa - Gatineau CMA includes the cities of Clarence-Rockland and Ottawa.
Jump up ^ Pembroke is Ontario's smallest city by area.
Jump up ^ The Peterborough CMA is formed around the City of Peterborough.
Jump up ^ The City of St. Catharines, as well as the cities of Niagara Falls, Port Colborne, Thorold and Welland, form parts of the St. Catharines - Niagara CMA.
Jump up ^ The Thunder Bay CMA is formed around the City of Thunder Bay.
Jump up ^ Toronto is Ontario's capital and Canada's and Ontario's largest city by population. The Toronto CMA includes the cities of Brampton, Mississauga, Pickering, Toronto and Vaughan.
Jump up ^ The City of Waterloo, as well as the cities of Cambridge and Kitchener, form parts of the Kitchener - Cambridge - Waterloo CMA.
Jump up ^ The Windsor CMA is formed around the City of Windsor.
See also[edit]
List of communities in Ontario
List of municipalities in Ontario
List of towns in Ontario
List of township municipalities in Ontario
List of villages in Ontario
References[edit]
^ Jump up to: a b c d "List of Ontario Municipalities". Ontario Municipal Affairs and Housing. September 21, 2012. Retrieved January 3, 2013.
^ Jump up to: a b c d e f g h "Population and dwelling counts, for Canada, provinces and territories, and census subdivisions (municipalities), 2011 and 2006 censuses (Ontario)". Statistics Canada. May 28, 2012. Retrieved January 3, 2013.
Jump up ^ "Markham to change from town to city". CBC News. May 30, 2012. Retrieved January 3, 2013.
^ Jump up to: a b c d "Municipal Act, R.S.O. 1990, Chapter M.45". Service Ontario. Retrieved June 29, 2013.
Jump up ^ "Municipal Act, S.O. 2001, Chapter 25". Service Ontario. Retrieved June 29, 2013.
Jump up ^ "The Municipal Councillor's Guide". Ontario Ministry of Municipal Affairs and Housing. Retrieved June 29, 2013.
Jump up ^ "Population and dwelling counts, for Canada, provinces and territories, and census divisions, 2011 and 2006 censuses (Ontario)". Statistics Canada. January 30, 2013. Retrieved June 27, 2013.
Jump up ^ "Corrections and updates: Population and dwelling count amendments, 2011 Census". Statistics Canada. February 14, 2013. Retrieved February 15, 2013.
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