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123-664: Busse Woods, the heart of the forest preserve, is a mature Great Lakes hardwood forest. A 440-acre (180 ha) segment of the woods, the Busse Forest Nature Preserve , is listed as a national natural landmark as a surviving fragment of flatwoods , a type of damp-ground forest formerly typical of extremely level patches of ground in the Great Lakes region. Parcels of land with slow rates of precipitation runoff into adjacent wetlands and streams were likely to develop into flatwoods. A flatwoods forest

246-511: A coastline is impossible to measure exactly . Canada borders approximately 5,200 miles (8,400 km) of coastline, while the remaining 5,300 miles (8,500 km) are bordered by the United States. Michigan has the longest shoreline of the United States, bordering roughly 3,288 miles (5,292 km) of lakes, followed by Wisconsin (820 miles (1,320 km)), New York (473 miles (761 km)), and Ohio (312 miles (502 km)). Traversing

369-685: A flood-control catchment for Salt Creek that flows in from Rolling Meadows and by the tall skyscrapers of eastern Schaumburg. The Friends of Busse Woods, a non-governmental organization, began operations in 2008. It cooperates with the Forest Preserve District of Cook County to oversee stewardship partnering operations at Busse Woods. Partnership operations include invasive species management , trash removal, and native plant reseeding and restocking. The operations are carried out by volunteer stewards. Great Lakes The Great Lakes ( French : Grands Lacs ), also called

492-533: A large watershed via many rivers and contain approximately 35,000 islands. There are also several thousand smaller lakes, often called "inland lakes", within the basin. The surface area of the five primary lakes combined is roughly equal to the size of the United Kingdom, while the surface area of the entire basin (the lakes and the land they drain) is about the size of the UK and France combined. Lake Michigan

615-405: A national basis. The total surface area of the lakes is approximately 94,250 square miles (244,100 km )—nearly the same size as the United Kingdom, and larger than the U.S. states of New York , New Jersey , Connecticut , Rhode Island , Massachusetts , Vermont , and New Hampshire combined. The Great Lakes coast measures approximately 10,500 miles (16,900 km), but the length of

738-456: A nuisance to industries by clogging pipes. The U.S. Fish and Wildlife Service estimated in 2007 that the economic impact of the zebra mussel could be about $ 5 billion over the next decade. The alewife first entered the system west of Lake Ontario via 19th-century canals. By the 1960s, the small silver fish had become a familiar nuisance to beach goers across Lakes Michigan, Huron, and Erie. Periodic mass die-offs result in vast numbers of

861-681: A possible reason for a decrease in population of various whitefish , important because of their culinary desirability and, hence, economic consequence. Moreover, between 1879 and 1899, reported whitefish harvests declined from some 24.3 million pounds (11 million kg) to just over 9 million pounds (4 million kg). By 1900, commercial fishermen on Lake Michigan were hauling in an average of 41 million pounds of fish annually. By 1938, Wisconsin's commercial fishing operations were motorized and mechanized, generating jobs for more than 2,000 workers, and hauling 14 million pounds per year. The population of giant freshwater mussels

984-560: A relatively small area of southeast Lake Michigan where savanna or prairie occasionally intruded). Logging, urbanization, and agriculture uses have changed that relationship. In the early 21st century, Lake Superior's shores are 91% forested, Lake Huron 68%, Lake Ontario 49%, Lake Michigan 41%, and Lake Erie, where logging and urbanization has been most extensive, 21%. Some of these forests are second or third growth (i.e. they have been logged before, changing their composition). At least 13 wildlife species are documented as becoming extinct since

1107-527: A result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland, where the land is rising at a rate of as much as 8–9 mm per year, or 1 m in 100 years. This is important for archaeologists, since a site that was coastal in the Nordic Stone Age now is inland and can be dated by its relative distance from the present shore. The term Würm

1230-489: A season, and can survive poor water quality conditions. The influx of parasitic lamprey populations after the development of the Erie Canal and the much later Welland Canal led to the two federal governments of the United States and Canada working on joint proposals to control it. By the mid-1950s, the lake trout populations of Lakes Michigan and Huron were reduced, with the lamprey deemed largely to blame. This led to

1353-746: A second fault line, the Saint Lawrence rift , formed approximately 570 million years ago, the basis for Lakes Ontario and Erie was created, along with what would become the Saint Lawrence River. The Great Lakes are estimated to have been formed at the end of the Last Glacial Period (the Wisconsin glaciation ended 10,000 to 12,000 years ago), when the Laurentide Ice Sheet receded. The retreat of

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1476-629: A small percid fish from Eurasia, became the most abundant fish species in Lake Superior's Saint Louis River within five years of its detection in 1986. Its range, which has expanded to Lake Huron, poses a significant threat to the lower lake fishery. Five years after first being observed in the St. Clair River, the round goby can now be found in all of the Great Lakes. The goby is considered undesirable for several reasons: it preys upon bottom-feeding fish, overruns optimal habitat, spawns multiple times

1599-797: A still lesser extent, glaciers existed in Africa, for example in the High Atlas , the mountains of Morocco , the Mount Atakor massif in southern Algeria , and several mountains in Ethiopia . Just south of the equator, an ice cap of several hundred square kilometers was present on the east African mountains in the Kilimanjaro massif , Mount Kenya , and the Rwenzori Mountains , which still bear relic glaciers today. Glaciation of

1722-414: Is "new" water, originating from rivers, precipitation, and groundwater springs. In the post-glacial period, evaporation , and drainage have generally been balanced, making the levels of the lakes relatively constant. Intensive human population growth began in the region in the 20th century and continues today. At least two human water use activities have been identified as having the potential to affect

1845-478: Is characterized by red maple , swamp white oak , and black ash trees. The black ash trees of Busse Woods are threatened by the emerald ash borer , which was reported in Illinois for the first time in 2006. Other parts of Busse Woods are better-drained and include species more typical of the forests of northern Illinois, such as the basswood , hickory , sugar maple , and white oak , the latter species being

1968-605: Is derived from a river in the Alpine foreland, roughly marking the maximum glacier advance of this particular glacial period. The Alps were where the first systematic scientific research on ice ages was conducted by Louis Agassiz at the beginning of the 19th century. Here, the Würm glaciation of the LGP was intensively studied. Pollen analysis , the statistical analyses of microfossilized plant pollens found in geological deposits, chronicled

2091-633: Is flat according to the International Joint Commission. Reports about this issue on the U.S. side highlight five large municipal systems (those of Detroit, Cleveland, Buffalo, Milwaukee and Gary ) as being the largest current periodic sources of untreated discharges into the Great Lakes. The fish of the Great Lakes have anti-depressant drugs meant for humans in their brains, which has caused concerns. The number of American adults who take anti-depressant drugs rose from 7.7% of all American adults in 1999–2002 to 12.7% in 2011–2014. As

2214-557: Is heavy. Pleasure boats can enter or exit the Great Lakes by way of the Erie Canal and Hudson River in New York. The Erie Canal connects to the Great Lakes at the east end of Lake Erie (at Buffalo, New York ) and at the south side of Lake Ontario (at Oswego, New York ). The lakes were originally fed by both precipitation and meltwater from glaciers which are no longer present. In modern times, only about 1% of volume per year

2337-424: Is measured, by surface area, either Lake Superior or Lake Michigan–Huron is the second-largest lake in the world and the largest freshwater lake. Lake Michigan is the largest lake, by surface area, that is entirely within one country, the United States. The Great Lakes began to form at the end of the Last Glacial Period around 14,000 years ago, as retreating ice sheets exposed the basins they had carved into

2460-515: Is the only one of the Great Lakes that is entirely within the United States; the others form a water boundary between the United States and Canada. The lakes are divided among the jurisdictions of the Canadian province of Ontario and the U.S. states of Michigan , Wisconsin , Minnesota , Illinois , Indiana , Ohio , Pennsylvania , and New York . Both the province of Ontario and the state of Michigan include in their boundaries portions of four of

2583-1024: The Central Rocky Mountains ), Wisconsinan or Wisconsin (in central North America), Devensian (in the British Isles), Midlandian (in Ireland), Würm (in the Alps ), Mérida (in Venezuela ), Weichselian or Vistulian (in Northern Europe and northern Central Europe), Valdai in Russia and Zyryanka in Siberia , Llanquihue in Chile , and Otira in New Zealand. The geochronological Late Pleistocene includes

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2706-995: The Chicago Sanitary and Ship Canal to the Gulf of Mexico via the Illinois River (from the Chicago River ) and the Mississippi River. An alternate track is via the Illinois River (from Chicago), to the Mississippi, up the Ohio, and then through the Tennessee–Tombigbee Waterway (a combination of a series of rivers and lakes and canals), to Mobile Bay and the Gulf of Mexico. Commercial tug -and- barge traffic on these waterways

2829-876: The Door Peninsula , the Peninsulas of Michigan , and the Ontario Peninsula . Some of these peninsulas even contain smaller peninsulas, such as the Bruce , Keweenaw , Leelanau , Niagara , and Thumb peninsulas. Population centers on the peninsulas include Grand Rapids , Flint , and Detroit in Michigan along with London , Hamilton , Brantford , and Toronto in Ontario. Although the Saint Lawrence Seaway and Great Lakes Waterway make

2952-529: The Environmental Protection Agency have shown that when the mercury comes in contact with many of the bacteria and compounds in the fresh water, it forms the compound methyl mercury , which has a much greater impact on human health than elemental mercury due to a higher propensity for absorption. This form of mercury is not detrimental to a majority of fish types, but is very detrimental to people and other wildlife animals who consume

3075-690: The Finger Lakes region of New York, as well as in Prince Edward County, Ontario , on Lake Ontario's northeast shore. The Great Lakes have been observed to help intensify storms, such as Hurricane Hazel in 1954, and the 2011 Goderich, Ontario tornado , which moved onshore as a tornadic waterspout . In 1996, a rare tropical or subtropical storm was observed forming in Lake Huron, dubbed the 1996 Lake Huron cyclone . Rather large severe thunderstorms covering wide areas are well known in

3198-522: The Great Lakes of North America , are a series of large interconnected freshwater lakes spanning the Canada–United States border . The five lakes are Superior , Michigan , Huron , Erie , and Ontario . (Hydrologically, Michigan and Huron are a single body of water, as they are joined by Straits of Mackinac .) The Great Lakes Waterway enables modern travel and shipping by water among

3321-670: The Himalayas , and other formerly glaciated regions around the world. The glaciations that occurred during this glacial period covered many areas, mainly in the Northern Hemisphere and to a lesser extent in the Southern Hemisphere. They have different names, historically developed and depending on their geographic distributions: Fraser (in the Pacific Cordillera of North America), Pinedale (in

3444-558: The Last Glacial Maximum occurring between 26,000 and 20,000 years ago. While the general pattern of cooling and glacier advance around the globe was similar, local differences make it difficult to compare the details from continent to continent (see picture of ice core data below for differences). The most recent cooling, the Younger Dryas , began around 12,800 years ago and ended around 11,700 years ago, also marking

3567-607: The Lesotho Highlands and parts of the Drakensberg . The development of glaciers was likely aided in part due to shade provided by adjacent cliffs. Various moraines and former glacial niches have been identified in the eastern Lesotho Highlands a few kilometres west of the Great Escarpment , at altitudes greater than 3,000 m on south-facing slopes. Studies suggest that the annual average temperature in

3690-521: The Niagara Escarpment precludes all natural navigation, the four upper lakes are commonly called the "upper great lakes". This designation is not universal. Those living on the shore of Lake Superior often refer to all the other lakes as "the lower lakes", because they are farther south. Sailors of bulk freighters transferring cargoes from Lake Superior and northern Lake Michigan and Lake Huron to ports on Lake Erie or Ontario commonly refer to

3813-727: The Owen Stanley Range , and the Saruwaged Range . Mount Giluwe in the Central Cordillera had a "more or less continuous ice cap covering about 188 km and extending down to 3200-3500 m". In Western New Guinea , remnants of these glaciers are still preserved atop Puncak Jaya and Ngga Pilimsit . Small glaciers developed in a few favorable places in Southern Africa during the last glacial period. These small glaciers would have been located in

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3936-720: The Sierra Nevada in northern California . In northern Eurasia, the Scandinavian ice sheet once again reached the northern parts of the British Isles , Germany , Poland , and Russia, extending as far east as the Taymyr Peninsula in western Siberia. The maximum extent of western Siberian glaciation was reached by about 18,000 to 17,000 BP, later than in Europe (22,000–18,000 BP). Northeastern Siberia

4059-732: The Upper Mississippi River , which in turn was formed during an earlier glacial period. In its retreat, the Wisconsin episode glaciation left terminal moraines that form Long Island , Block Island , Cape Cod , Nomans Land , Martha's Vineyard , Nantucket , Sable Island , and the Oak Ridges Moraine in south-central Ontario, Canada. In Wisconsin itself, it left the Kettle Moraine . The drumlins and eskers formed at its melting edge are landmarks of

4182-510: The biosphere . Since the 19th century, an estimated 160 new species have found their way into the Great Lakes ecosystem; many have become invasive; the overseas ship ballast and ship hull parasitism are causing severe economic and ecological impacts. According to the Inland Seas Education Association, on average a new species enters the Great Lakes every eight months. Introductions into the Great Lakes include

4305-584: The grooves left by these glaciers can be easily observed. In southwestern Saskatchewan and southeastern Alberta, a suture zone between the Laurentide and Cordilleran ice sheets formed the Cypress Hills , which is the northernmost point in North America that remained south of the continental ice sheets. The Great Lakes are the result of glacial scour and pooling of meltwater at the rim of

4428-586: The isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea . Then, as postglacial isostatic rebound lifted the region about 9500 BP, the deepest basin of the Baltic became a freshwater lake, in palaeological contexts referred to as Ancylus Lake , which is identifiable in the freshwater fauna found in sediment cores. The lake was filled by glacial runoff, but as worldwide sea level continued rising, saltwater again breached

4551-493: The state tree of Illinois. There are 10.4 miles (17 km) of paved bicycle trail, the Busse Woods Trail, through the forest preserve: a 7.3-mile (12 km) loop and two spurs providing pedestrian and bicycle access to the preserve. In contrast to the natural area, the northwest and southwest quadrants of the preserve are dominated by Busse Lake , a 590-acre (240 ha) artificial reservoir that serves as

4674-414: The zebra mussel , which was first discovered in 1988, and quagga mussel in 1989. Since 2000, the invasive quagga mussel has smothered the bottom of Lake Michigan almost from shore to shore, and their numbers are estimated at 900 trillion. The mollusks are efficient filter feeders, competing with native mussels and reducing available food and spawning grounds for fish. In addition, the mussels may be

4797-527: The " snowbelts " receive regular snow fall from this localized weather pattern, especially along the eastern shores of the lakes. Snowbelts are found in Wisconsin, Michigan, Ohio, Pennsylvania, New York, and Ontario. Related to the lake effect is the regular occurrence of fog, particularly along the shorelines of the lakes. This is most noticeable along Lake Superior's shores. The lakes tend to moderate seasonal temperatures to some degree but not with as large an influence as do large oceans; they absorb heat and cool

4920-778: The Alpine foreland . Local ice fields or small ice sheets could be found capping the highest massifs of the Pyrenees , the Carpathian Mountains , the Balkan Mountains , the Caucasus , and the mountains of Turkey and Iran . In the Himalayas and the Tibetan Plateau , there is evidence that glaciers advanced considerably, particularly between 47,000 and 27,000 BP, but the exact ages, as well as

5043-632: The Canadian side, Toronto , Hamilton and Mississauga . Though the five lakes lie in separate basins, they form a single, naturally interconnected body of fresh water, within the Great Lakes Basin . As a chain of lakes and rivers, they connect the east-central interior of North America to the Atlantic Ocean. From the interior to the outlet at the Saint Lawrence River, water flows from Superior to Huron and Michigan, southward to Erie, and finally northward to Lake Ontario. The lakes drain

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5166-524: The Center for Arctic Gas Hydrate, Environment and Climate at the University of Tromsø , published a study in June 2017 describing over a hundred ocean sediment craters, some 3,000 m wide and up to 300 m deep, formed by explosive eruptions of methane from destabilized methane hydrates , following ice-sheet retreat during the LGP, around 12,000 years ago. These areas around the Barents Sea still seep methane today. The study hypothesized that existing bulges containing methane reservoirs could eventually have

5289-430: The Chicago Sanitary and Ship Canal in order to keep several species of invasive Asian carp out of the lakes. These fast-growing planktivorous fish have heavily colonized the Mississippi and Illinois river systems. Invasive species, particularly zebra and quagga mussels, may be at least partially responsible for the collapse of the deepwater demersal fish community in Lake Huron, as well as drastic unprecedented changes in

5412-407: The Great Lakes accessible to ocean-going vessels, shifts in shipping to wider ocean-going container ships —which do not fit through the locks on these routes—have limited container shipping on the lakes. Most Great Lakes trade is of bulk material, and bulk freighters of Seawaymax -size or less can move throughout the entire lakes and out to the Atlantic. Larger ships are confined to working within

5535-459: The Great Lakes during mid-summer; these Mesoscale convective complexes or MCCs can cause damage to wide swaths of forest and shatter glass in city buildings. These storms mainly occur during the night, and the systems sometimes have small embedded tornadoes, but more often straight-line winds accompanied by intense lightning. Historically, the Great Lakes, in addition to their lake ecology , were surrounded by various forest ecoregions (except in

5658-441: The Great Lakes each year. Plastics in the water break up into very small particles known as microplastics . Microplastics can also come from synthetic clothing washed down our drains. Plastic waste found in the lakes include single-use plastics , plastics used in packaging, takeout containers as well as pre-production pellets produced by plastics industry . High concentrations of microplastics were discovered in 100 percent of

5781-438: The Great Lakes region include: Plant lists include: Logging of the extensive forests in the Great Lakes region removed riparian and adjacent tree cover over rivers and streams, which provide shade, moderating water temperatures in fish spawning grounds. Removal of trees also destabilized the soil, with greater volumes washed into stream beds causing siltation of gravel beds, and more frequent flooding. Running cut logs down

5904-480: The Great Lakes. A number of self-operating floating devices called Seabin, were put in the Great Lakes to capture plastic trash as part of the Great Lakes Plastic Cleanup project. The project captured 74,000 pieces of trash using this technology between 2020 and 2021; however, it does not claim to catch up with 22 million pounds (10.0 kt) of plastic that ends up in Great Lakes every year. The production, consumption, and throwing away of plastics seems to remain

6027-474: The Greenland climate was dry during the LGP, with precipitation reaching perhaps only 20% of today's value. The name Mérida glaciation is proposed to designate the alpine glaciation that affected the central Venezuelan Andes during the Late Pleistocene. Two main moraine levels have been recognized - one with an elevation of 2,600–2,700 m (8,500–8,900 ft), and another with an elevation of 3,000–3,500 m (9,800–11,500 ft). The snow line during

6150-570: The LGP as the Devensian . Irish geologists, geographers, and archaeologists refer to the Midlandian glaciation, as its effects in Ireland are largely visible in the Irish Midlands . The name Devensian is derived from the Latin Dēvenses , people living by the Dee ( Dēva in Latin), a river on the Welsh border near which deposits from the period are particularly well represented. The effects of this glaciation can be seen in many geological features of England, Wales, Scotland, and Northern Ireland . Its deposits have been found overlying material from

6273-505: The North American Laurentide ice sheet. At the height of glaciation, the Bering land bridge potentially permitted migration of mammals, including people, to North America from Siberia . It radically altered the geography of North America north of the Ohio River . At the height of the Wisconsin episode glaciation, ice covered most of Canada, the Upper Midwest , and New England , as well as parts of Montana and Washington . On Kelleys Island in Lake Erie or in New York's Central Park ,

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6396-410: The Polish River Vistula or its German name Weichsel). Evidence suggests that the ice sheets were at their maximum size for only a short period, between 25,000 and 13,000 BP. Eight interstadials have been recognized in the Weichselian, including the Oerel, Glinde, Moershoofd, Hengelo, and Denekamp. Correlation with isotope stages is still in process. During the glacial maximum in Scandinavia, only

6519-437: The Southern Hemisphere was less extensive. Ice sheets existed in the Andes ( Patagonian Ice Sheet ), where six glacier advances between 33,500 and 13,900 BP in the Chilean Andes have been reported. Antarctica was entirely glaciated, much like today, but unlike today the ice sheet left no uncovered area. In mainland Australia only a very small area in the vicinity of Mount Kosciuszko was glaciated, whereas in Tasmania glaciation

6642-401: The Straits of Mackinac. The straits are five miles (8 km) wide and 120 feet (37 m) deep; the water levels rise and fall together, and the flow between Michigan and Huron frequently reverses direction. Dispersed throughout the Great Lakes are approximately 35,000 islands . The largest among them is Manitoulin Island in Lake Huron, the largest island in any inland body of water in

6765-427: The U.S. A variety of steps taken to process industrial and municipal pollution discharges into the system greatly improved water quality by the 1980s, and Lake Erie in particular is significantly cleaner. Discharge of toxic substances has been sharply reduced. Federal and state regulations control substances like PCBs . The first of 43 " Great Lakes Areas of Concern " to be formally "de-listed" through successful cleanup

6888-452: The Wisconsin episode. It began about 30,000 years ago, reached its greatest advance 21,000 years ago, and ended about 10,000 years ago. In northwest Greenland, ice coverage attained a very early maximum in the LGP around 114,000. After this early maximum, ice coverage was similar to today until the end of the last glacial period. Towards the end, glaciers advanced once more before retreating to their present extent. According to ice core data,

7011-495: The air in summer, then slowly radiate that heat in autumn. They protect against frost during transitional weather and keep the summertime temperatures cooler than further inland. This effect can be very localized and overridden by offshore wind patterns. This temperature buffering produces areas known as " fruit belts ", where fruit can be produced that is typically grown much farther south. For instance, western Michigan has apple orchards, and cherry orchards are cultivated adjacent to

7134-459: The anti-depressant drugs pass out of human bodies and through sanitation systems into the Great Lakes, this has resulted in fish in the Great Lakes with twenty times the level of anti-depressants in their brains than what is in the water, leading to the fish being exceedingly happy and hence less risk-averse, to the extent of damaging the fish populations. Researchers have found that more than 22 million pounds (10.0 kt) of plastic end up in

7257-432: The arrival of Europeans, and many more are threatened or endangered. Meanwhile, exotic and invasive species have also been introduced. While the organisms living on the bottom of shallow waters are similar to those found in smaller lakes, the deep waters contain organisms found only in deep, cold lakes of the northern latitudes. These include the delicate opossum shrimp (order mysida ), the deepwater scud (a crustacean of

7380-427: The core of Great Lakes trash problem. Algae such as diatoms , along with other phytoplankton , are photosynthetic primary producers supporting the food web of the Great Lakes, and have been affected by global warming . The changes in the size or in the function of the primary producers may have a direct or an indirect impact on the food web. Photosynthesis carried out by diatoms constitutes about one fifth of

7503-555: The cyanobacteria ... will produce toxins", said Michael McKay, of the University of Windsor. Water quality testing was underway in August 2019. Until 1970, mercury was not listed as a harmful chemical, according to the United States Federal Water Quality Administration. In the 21st century, mercury has become more apparent in water tests. Mercury compounds have been used in paper mills to prevent slime from forming during their production, and chemical companies have used mercury to separate chlorine from brine solutions. Studies conducted by

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7626-400: The dramatic changes in the European environment during the Würm glaciation. During the height of Würm glaciation, c.  24,000  – c.  10,000  BP, most of western and central Europe and Eurasia was open steppe-tundra, while the Alps presented solid ice fields and montane glaciers. Scandinavia and much of Britain were under ice. During the Würm, the Rhône Glacier covered

7749-539: The end of the LGP and the Pleistocene epoch. It was followed by the Holocene , the current geological epoch . The LGP is often colloquially referred to as the "last ice age", though the term ice age is not strictly defined, and on a longer geological perspective, the last few million years could be termed a single ice age given the continual presence of ice sheets near both poles. Glacials are somewhat better defined, as colder phases during which glaciers advance, separated by relatively warm interglacials . The end of

7872-401: The fish that were studied by researchers from the Rochman Lab. About 50 million pounds (23 kt) of fish is harvested each year from Great Lakes which has raised concerns on how this might affect human health. Microscopic pieces of plastic have also been found in drinking water coming from Great Lakes. It is estimated that nearly 40 million people in the region rely on drinking water from

7995-443: The fish washing up on shore; estimates by various governments have placed the percentage of Lake Michigan's biomass which was made up of alewives in the early 1960s as high as 90%. In the late 1960s, the various state and federal governments began stocking several species of salmonids, including the native lake trout as well as non-native chinook and coho salmon; by the 1980s, alewife populations had dropped drastically. The ruffe ,

8118-443: The fish. Mercury has been known for health related problems such as birth defects in humans and animals, and the near extinction of eagles in the Great Lakes region. The amount of raw sewage dumped into the waters was the primary focus of both the first Great Lakes Water Quality Agreement and federal laws passed in both countries during the 1970s. Implementation of secondary treatment of municipal sewage by major cities greatly reduced

8241-423: The formation of a single contiguous ice sheet on the Tibetan Plateau, is controversial. Other areas of the Northern Hemisphere did not bear extensive ice sheets, but local glaciers were widespread at high altitudes. Parts of Taiwan , for example, were repeatedly glaciated between 44,250 and 10,680 BP as well as the Japanese Alps . In both areas, maximum glacier advance occurred between 60,000 and 30,000 BP. To

8364-417: The glaciers "rebounded" as it was uncovered. Since the glaciers covered some areas longer than others, this glacial rebound occurred at different rates. The Great Lakes have a humid continental climate, Köppen climate classification Dfa (in southern areas) and Dfb (in northern parts) with varying influences from air masses from other regions including dry, cold Arctic systems, mild Pacific air masses from

8487-410: The historical average level. Although "true tides—changes in water level caused by the gravitational forces of the sun and moon—do occur in a semi-diurnal (twice daily) pattern", such changes are quite small and generally obscured by other forces. The lake levels are affected primarily by changes in regional meteorology and climatology. The outflows from Lakes Superior and Ontario are regulated, while

8610-442: The ice sheet left behind a large amount of meltwater ( Lake Algonquin , Lake Chicago , Glacial Lake Iroquois , and Champlain Sea ) that filled up the basins that the glaciers had carved, thus creating the Great Lakes as they are today. Because of the uneven nature of glacier erosion , some higher hills became Great Lakes islands. The Niagara Escarpment follows the contour of the Great Lakes between New York and Wisconsin. Land below

8733-483: The key indicators even in the current era of sophisticated analyses and measuring instruments. According to the bi-national (U.S. and Canadian) resource book, The Great Lakes: An Environmental Atlas and Resource Book : "The largest Great Lakes fish harvests were recorded in 1889 and 1899 at some 67,000 tonnes (66,000 long tons; 74,000 short tons) [147 million pounds]." By 1801, the New York Legislature found it necessary to pass regulations curtailing obstructions to

8856-612: The lake and causing blooms," said Michael McKay, executive director of the Great Lakes Institute for Environmental Research (GLIER) at the University of Windsor . The largest Lake Erie bloom to date occurred in 2015, exceeding the severity index at 10.5 and in 2011 at a 10. In early August 2019, satellite images depicted a bloom stretching up to 1,300 square kilometres on Lake Erie, with the heaviest concentration near Toledo, Ohio . A large bloom does not necessarily mean

8979-650: The lake shore as far north as the Grand Traverse Bay . Near Collingwood, Ontario , commercial fruit orchards, including a few wineries, exist near the shoreline of southern Nottawasaga Bay . The eastern shore of Lake Michigan and the southern shore of Lake Erie have many successful wineries because of the lakes' moderating effects, as do the large commercial fruit and wine growing areas of the Niagara Peninsula located between Lake Erie and Lake Ontario. A similar phenomenon allows wineries to flourish in

9102-538: The lakes has been observed since records began in 1918. The water level of Lake Michigan–Huron had remained fairly constant over the 20th century. Recent lake levels include record low levels in 2013 in Lakes Superior, Erie, and Michigan-Huron, followed by record high levels in 2020 in the same lakes. The water level in Lake Ontario has remained relatively constant in the same time period, hovering around

9225-537: The lakes' levels: diversion (the transfer of water to other watersheds) and consumption (substantially done today by the use of lake water to power and cool electric generation plants, resulting in evaporation). Outflows through the Chicago Sanitary and Ship Canal is more than balanced by artificial inflows via the Ogoki River and Long Lake/ Kenogami River diversions. Fluctuation of the water levels in

9348-525: The lakes. Only barges can access the Illinois Waterway system providing access to the Gulf of Mexico via the Mississippi River. Despite their vast size, large sections of the Great Lakes freeze over in winter, interrupting most shipping from January to March. Some icebreakers ply the lakes, keeping the shipping lanes open through other periods of ice on the lakes. The Great Lakes are connected by

9471-609: The lakes. The lakes connect to the Atlantic Ocean via the Saint Lawrence River , and to the Mississippi River basin through the Illinois Waterway . The Great Lakes are the largest group of freshwater lakes on Earth by total area and the second-largest by total volume. They contain 21% of the world's surface fresh water by volume. The total surface is 94,250 square miles (244,106 km ), and

9594-415: The lakes. The province of Ontario does not border Lake Michigan, and the state of Michigan does not border Lake Ontario. New York and Wisconsin's jurisdictions extend into two lakes, and each of the remaining states into one of the lakes. As the surfaces of Lakes Superior, Huron, Michigan, and Erie are all approximately the same elevation above sea level, while Lake Ontario is significantly lower, and because

9717-603: The land, which then filled with meltwater. The lakes have been a major source for transportation, migration, trade, and fishing, serving as a habitat to many aquatic species in a region with much biodiversity . The surrounding region is called the Great Lakes region , which includes the Great Lakes Megalopolis . Major cities within the region include, on the American side, from east to west, Buffalo , Cleveland , Detroit , Chicago , and Milwaukee ; and, on

9840-505: The last glacial advance was lowered approximately 1,200 m (3,900 ft) below the present snow line, which is 3,700 m (12,100 ft). The glaciated area in the Cordillera de Mérida was about 600 km (230 sq mi); this included these high areas, from southwest to northeast: Páramo de Tamá, Páramo Batallón, Páramo Los Conejos, Páramo Piedras Blancas, and Teta de Niquitao. Around 200 km (77 sq mi) of

9963-555: The last glacial maximum, the Patagonian ice sheet extended over the Andes from about 35°S to Tierra del Fuego at 55°S. The western part appears to have been very active, with wet basal conditions, while the eastern part was cold-based. Cryogenic features such as ice wedges , patterned ground , pingos , rock glaciers , palsas , soil cryoturbation , and solifluction deposits developed in unglaciated extra-Andean Patagonia during

10086-512: The last glacial period, which was about 10,000 years ago, is often called the end of the ice age, although extensive year-round ice persists in Antarctica and Greenland . Over the past few million years, the glacial-interglacial cycles have been "paced" by periodic variations in the Earth's orbit via Milankovitch cycles . The LGP has been intensively studied in North America, northern Eurasia,

10209-627: The late glacial (Weichselian) and the immediately preceding penultimate interglacial ( Eemian ) period. Canada was almost completely covered by ice, as was the northern part of the United States , both blanketed by the huge Laurentide Ice Sheet . Alaska remained mostly ice free due to arid climate conditions. Local glaciations existed in the Rocky Mountains and the Cordilleran ice sheet and as ice fields and ice caps in

10332-468: The latter as the lower lakes and Lakes Michigan, Huron, and Superior as the upper lakes. This corresponds to thinking of lakes Erie and Ontario as "down south" and the others as "up north". Vessels sailing north on Lake Michigan are considered "upbound" even though they are sailing toward its effluent current. Lakes Huron and Michigan are sometimes considered a single lake, called Lake Michigan–Huron, because they are one hydrological body of water connected by

10455-494: The launch of the bi-national Great Lakes Fishery Commission . Several species of exotic water fleas have accidentally been introduced into the Great Lakes, such as the spiny waterflea, Bythotrephes longimanus , and the fishhook waterflea, Cercopagis pengoi , potentially having an effect on the zooplankton population. Several species of crayfish have also been introduced that may contend with native crayfish populations. More recently an electric fence has been set up across

10578-454: The lower Connecticut River Valley . In the Sierra Nevada , three stages of glacial maxima, sometimes incorrectly called ice ages , were separated by warmer periods. These glacial maxima are called, from oldest to youngest, Tahoe, Tenaya, and Tioga. The Tahoe reached its maximum extent perhaps about 70,000 years ago. Little is known about the Tenaya. The Tioga was the least severe and last of

10701-448: The main Wisconsin glacial advance. The upper level probably represents the last glacial advance (Late Wisconsin). The Llanquihue glaciation takes its name from Llanquihue Lake in southern Chile , which is a fan-shaped piedmont glacial lake. On the lake's western shores, large moraine systems occur, of which the innermost belong to the LGP. Llanquihue Lake's varves are a node point in southern Chile's varve geochronology . During

10824-484: The massive Missoula Floods . USGS geologists estimate that the cycle of flooding and reformation of the lake lasted an average of 55 years and that the floods occurred about 40 times over the 2,000-year period starting 15,000 years ago. Glacial lake outburst floods such as these are not uncommon today in Iceland and other places. The Wisconsin glacial episode was the last major advance of continental glaciers in

10947-502: The mountains of Southern Africa was about 6 °C colder than at present, in line with temperature drops estimated for Tasmania and southern Patagonia during the same time. This resulted in an environment of relatively arid periglaciation without permafrost , but with deep seasonal freezing on south-facing slopes. Periglaciation in the eastern Drakensberg and Lesotho Highlands produced solifluction deposits and blockfields ; including blockstreams and stone garlands. Scientists from

11070-476: The natural migrations of Atlantic salmon from Lake Erie into their spawning channels. In the early 19th century, the government of Upper Canada found it necessary to introduce similar legislation prohibiting the use of weirs and nets at the mouths of Lake Ontario's tributaries. Other protective legislation was passed, but enforcement remained difficult. On both sides of the Canada–United States border,

11193-467: The order amphipoda ), two types of copepods , and the deepwater sculpin (a spiny, large-headed fish). The Great Lakes are an important source of fishing . Early European settlers were astounded by both the variety and quantity of fish; there were 150 different species in the Great Lakes. Throughout history, fish populations were the early indicator of the condition of the Lakes and have remained one of

11316-516: The outflows of Michigan-Huron and Erie are not regulated at all. Ontario is the most tightly regulated, with its outflow controlled by the Moses-Saunders Power Dam , which explains its consistent historical levels. The Great Lakes contain 21% of the world's surface fresh water: 5,472 cubic miles (22,810 km ), or 6.0×10 U.S. gallons, that is 6 quadrillion U.S. gallons, (2.3×10 liters). The lakes contain about 84% of

11439-745: The preceding Ipswichian stage and lying beneath those from the following Holocene , which is the current stage. This is sometimes called the Flandrian interglacial in Britain. The latter part of the Devensian includes pollen zones I–IV, the Allerød oscillation and Bølling oscillation , and the Oldest Dryas , Older Dryas , and Younger Dryas cold periods. Alternative names include Weichsel glaciation or Vistulian glaciation (referring to

11562-430: The proglacial rivers' shifting and redepositing gravels. Beneath the surface, they had profound and lasting influence on geothermal heat and the patterns of deep groundwater flow. The Pinedale (central Rocky Mountains) or Fraser (Cordilleran ice sheet) glaciation was the last of the major glaciations to appear in the Rocky Mountains in the United States. The Pinedale lasted from around 30,000 to 10,000 years ago, and

11685-516: The proliferation of dams and impoundments have multiplied, necessitating more regulatory efforts. Concerns by the mid-19th century included obstructions in the rivers which prevented salmon and lake sturgeon from reaching their spawning grounds. The Wisconsin Fisheries Commission noted a reduction of roughly 25% in general fish harvests by 1875. The states have removed dams from rivers where necessary. Overfishing has been cited as

11808-469: The receding ice. When the enormous mass of the continental ice sheet retreated, the Great Lakes began gradually moving south due to isostatic rebound of the north shore. Niagara Falls is also a product of the glaciation, as is the course of the Ohio River, which largely supplanted the prior Teays River . With the assistance of several very broad glacial lakes, it released floods through the gorge of

11931-428: The routine discharge of untreated sewage during the 1970s and 1980s. The International Joint Commission in 2009 summarized the change: "Since the early 1970s, the level of treatment to reduce pollution from waste water discharges to the Great Lakes has improved considerably. This is a result of significant expenditures to date on both infrastructure and technology, and robust regulatory systems that have proven to be, on

12054-399: The same fate. During the last glacial period, Antarctica was blanketed by a massive ice sheet, much as it is today. The ice covered all land areas and extended into the ocean onto the middle and outer continental shelf. Counterintuitively though, according to ice modeling done in 2002, ice over central East Antarctica was generally thinner than it is today. British geologists refer to

12177-436: The shoreline of all the lakes would cover a distance roughly equivalent to travelling half-way around the world at the equator. A notable modern phenomenon is the formation of ice volcanoes over the lakes during wintertime. Storm-generated waves carve the lakes' ice sheet and create conical mounds through the eruption of water and slush. The process is only well-documented in the Great Lakes, and has been credited with sparing

12300-472: The sill about 8000 BP, forming a marine Littorina Sea , which was followed by another freshwater phase before the present brackish marine system was established. "At its present state of development, the marine life of the Baltic Sea is less than about 4000 years old", Drs. Thulin and Andrushaitis remarked when reviewing these sequences in 2003. Overlying ice had exerted pressure on the Earth's surface. As

12423-602: The southern shorelines from worse rocky erosion. It has been estimated that the foundational geology that created the conditions shaping the present day upper Great Lakes was laid from 1.1 to 1.2 billion years ago, when two previously fused tectonic plates split apart and created the Midcontinent Rift , which crossed the Great Lakes Tectonic Zone . A valley was formed providing a basin that eventually became modern day Lake Superior. When

12546-414: The surface freshwater of North America; if the water were evenly distributed over the entire continent's land area, it would reach a depth of 5 feet (1.5 meters). This is enough water to cover the 48 contiguous U.S. states to a uniform depth of 9.5 feet (2.9 m). Although the lakes contain a large percentage of the world's fresh water, the Great Lakes supply only a small portion of U.S. drinking water on

12669-480: The surrounding ice sheets. According to the sediment composition retrieved from deep-sea cores , even times of seasonally open waters must have occurred. Outside the main ice sheets, widespread glaciation occurred on the highest mountains of the Alpide belt . In contrast to the earlier glacial stages, the Würm glaciation was composed of smaller ice caps and mostly confined to valley glaciers, sending glacial lobes into

12792-614: The term Late Cenozoic Ice Age is used to include this early phase with the current glaciation. The previous ice age within the Quaternary is the Penultimate Glacial Period , which ended about 128,000 years ago, was more severe than the Last Glacial Period in some areas such as Britain, but less severe in others. The last glacial period saw alternating episodes of glacier advance and retreat with

12915-625: The timespan of the Late Pleistocene . The LGP is part of a larger sequence of glacial and interglacial periods known as the Quaternary glaciation which started around 2,588,000 years ago and is ongoing. The glaciation and the current Quaternary Period both began with the formation of the Arctic ice cap . The Antarctic ice sheet began to form earlier, at about 34 Mya, in the mid- Cenozoic ( Eocene–Oligocene extinction event ), and

13038-447: The total glaciated area was in the Sierra Nevada de Mérida , and of that amount, the largest concentration, 50 km (19 sq mi), was in the areas of Pico Bolívar , Pico Humboldt [4,942 m (16,214 ft)], and Pico Bonpland [4,983 m (16,348 ft)]. Radiocarbon dating indicates that the moraines are older than 10,000 BP, and probably older than 13,000 BP. The lower moraine level probably corresponds to

13161-650: The total photosynthesis. By taking CO 2 out of the water to photosynthesize, diatoms help to stabilize the pH of the water, as CO 2 would react with water to produce carbonic acid . Last Glacial Period The Last Glacial Period ( LGP ), also known as the Last glacial cycle , occurred from the end of the Last Interglacial to the beginning of the Holocene , c.  115,000  – c.  11,700 years ago, and thus corresponds to most of

13284-440: The total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km ), slightly less than the volume of Lake Baikal (5,666 cu mi or 23,615 km , 22–23% of the world's surface fresh water). Because of their sea-like characteristics, such as rolling waves, sustained winds, strong currents, great depths, and distant horizons, the five Great Lakes have long been called inland seas . Depending on how it

13407-562: The treatment plant, are temporarily overwhelmed by heavy rainstorms. Local sewage treatment authorities then must release untreated effluent, a mix of rainwater and sewage, into local water bodies. While enormous public investments such as the Deep Tunnel projects in Chicago and Milwaukee have greatly reduced the frequency and volume of these events, they have not been eliminated. The number of such overflow events in Ontario, for example,

13530-532: The tributary rivers into the Great Lakes also dislocated sediments. In 1884, the New York Fish Commission determined that the dumping of sawmill waste (chips and sawdust) had impacted fish populations. The first U.S. Clean Water Act , passed by a Congressional override after being vetoed by U.S. President Richard Nixon in 1972, was a key piece of legislation, along with the bi-national Great Lakes Water Quality Agreement signed by Canada and

13653-416: The warmer and shallower portions of the system such as Lake Erie, Saginaw Bay , Green Bay , and the southernmost portion of Lake Michigan. By the mid-1980s, most jurisdictions bordering the Great Lakes had controlled phosphate detergents . Blue-green algae, or cyanobacteria blooms, have been problematic on Lake Erie since 2011. "Not enough is being done to stop fertilizer and phosphorus from getting into

13776-430: The west pick up the air and moisture from the lake surface, which is slightly warmer in relation to the cold surface winds above. As the slightly warmer, moist air passes over the colder land surface, the moisture often produces concentrated, heavy snowfall that sets up in bands or "streamers". This is similar to the effect of warmer air dropping snow as it passes over mountain ranges. During freezing weather with high winds,

13899-427: The west, and warm, wet tropical systems from the south and the Gulf of Mexico. The lakes have a moderating effect on the climate; they can also increase precipitation totals and produce lake effect snowfall . The Great Lakes can have an effect on regional weather called lake-effect snow , which is sometimes very localized. Even late in winter, the lakes often have no icepack in the middle. The prevailing winds from

14022-604: The western parts of Jutland were ice-free, and a large part of what is today the North Sea was dry land connecting Jutland with Britain (see Doggerland ). The Baltic Sea , with its unique brackish water , is a result of meltwater from the Weichsel glaciation combining with saltwater from the North Sea when the straits between Sweden and Denmark opened. Initially, when the ice began melting about 10,300 BP, seawater filled

14145-728: The whole western Swiss plateau, reaching today's regions of Solothurn and Aargau. In the region of Bern, it merged with the Aar glacier. The Rhine Glacier is currently the subject of the most detailed studies. Glaciers of the Reuss and the Limmat advanced sometimes as far as the Jura. Montane and piedmont glaciers formed the land by grinding away virtually all traces of the older Günz and Mindel glaciation, by depositing base moraines and terminal moraines of different retraction phases and loess deposits, and by

14268-480: The whole, quite effective." The commission reported that all urban sewage treatment systems on the U.S. side of the lakes had implemented secondary treatment, as had all on the Canadian side except for five small systems. Though contrary to federal laws in both countries, those treatment system upgrades have not yet eliminated combined sewer overflow events. This describes when older sewerage systems, which combine storm water with sewage into single sewers heading to

14391-620: The world. The second-largest island is Isle Royale in Lake Superior. Both of these islands are large enough to contain multiple lakes themselves—for instance, Manitoulin Island's Lake Manitou is the world's largest lake on a freshwater island. Some of these lakes even have their own islands, like Treasure Island in Lake Mindemoya in Manitoulin Island. The Great Lakes also have several peninsulas between them, including

14514-523: The zooplankton community of the lake. Scientists understand that the micro-aquatic life of the lakes is abundant but know very little about some of the most plentiful microbes and their environmental effects in the Great Lakes. Although a drop of lake water may contain 1 million bacteria cells and 10 million viruses , only since 2012 has there been a long-term study of the lakes' micro-organisms. Between 2012 and 2019 more than 160 new species have been discovered. Native habitats and ecoregions in

14637-558: Was Ontario's Collingwood Harbour in 1994; Ontario's Severn Sound followed in 2003. Presque Isle Bay in Pennsylvania is formally listed as in recovery, as is Ontario's Spanish Harbour. Dozens of other Areas of Concern have received partial cleanups such as the Rouge River (Michigan) and Waukegan Harbor (Illinois). Phosphate detergents were historically a major source of nutrient to the Great Lakes algae blooms in particular in

14760-464: Was at its greatest extent between 23,500 and 21,000 years ago. This glaciation was somewhat distinct from the main Wisconsin glaciation, as it was only loosely related to the giant ice sheets and was instead composed of mountain glaciers, merging into the Cordilleran ice sheet. The Cordilleran ice sheet produced features such as glacial Lake Missoula , which broke free from its ice dam, causing

14883-517: Was eliminated as the mussels were harvested for use as buttons by early Great Lakes entrepreneurs. The Great Lakes: An Environmental Atlas and Resource Book (1972) notes: "Only pockets remain of the once large commercial fishery." Water quality improvements realized during the 1970s and 1980s, combined with successful salmonid stocking programs, have enabled the growth of a large recreational fishery. The last commercial fisherman left Milwaukee in 2011 because of overfishing and anthropogenic changes to

15006-468: Was more widespread. An ice sheet formed in New Zealand, covering all of the Southern Alps, where at least three glacial advances can be distinguished. Local ice caps existed in the highest mountains of the island of New Guinea , where temperatures were 5 to 6 °C colder than at present. The main areas of Papua New Guinea where glaciers developed during the LGP were the Central Cordillera ,

15129-512: Was not covered by a continental-scale ice sheet. Instead, large, but restricted, icefield complexes covered mountain ranges within northeast Siberia, including the Kamchatka-Koryak Mountains. The Arctic Ocean between the huge ice sheets of America and Eurasia was not frozen throughout, but like today, probably was covered only by relatively shallow ice, subject to seasonal changes and riddled with icebergs calving from

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