Prairies are
ecosystems considered part of the
temperate grasslands, savannas, and shrublands biome
A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...
by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the dominant
vegetation type. Temperate grassland regions include the
Pampas of
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
,
Brazil and
Uruguay, and the
steppe of
Ukraine,
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eight ...
and
Kazakhstan. Lands typically referred to as "prairie" tend to be in
North America. The term encompasses the area referred to as the
Interior Lowlands of
Canada, the
United States, and
Mexico, which includes all of the
Great Plains as well as the wetter, hillier land to the east.
In the U.S., the area is constituted by most or all of the states of
North Dakota,
South Dakota,
Nebraska,
Kansas, and
Oklahoma, and sizable parts of the states of
Montana,
Wyoming,
Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...
,
New Mexico,
Texas,
Missouri,
Iowa,
Illinois,
Indiana,
Wisconsin, and western and southern
Minnesota. The
Palouse
The Palouse ( ) is a distinct geographic region of the northwestern United States, encompassing parts of north central Idaho, southeastern Washington, and, by some definitions, parts of northeast Oregon. It is a major agricultural area, primar ...
of
Washington
Washington commonly refers to:
* Washington (state), United States
* Washington, D.C., the capital of the United States
** A metonym for the federal government of the United States
** Washington metropolitan area, the metropolitan area centered o ...
and the
Central Valley of
California are also prairies. The
Canadian Prairies
The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie Provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...
occupy vast areas of
Manitoba,
Saskatchewan, and
Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Terri ...
. Prairies contain various lush
flora
Flora is all the plant life present in a particular region or time, generally the naturally occurring ( indigenous) native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms '' gut flora'' or ''skin flora''.
...
and
fauna, often contain rich soil maintained by
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') le ...
, with a
temperate climate and a varied view.
Etymology
According to
Theodore Roosevelt: ''Prairie'' () is the
French word for "meadow" formed ultimately from the
Latin root word ''pratum'' (same meaning).
Formation
The formation of the
North American Prairies started with the uplift of the
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
near
Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Terri ...
. The mountains created a
rain shadow that resulted in lower precipitation rates downwind.
The
parent material
Parent material is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are ...
of most prairie soil was distributed during the
last glacial advance that began about 110,000 years ago. The glaciers expanding southward scraped the landscape, picking up geologic material and leveling the terrain. As the glaciers retreated about 10,000 years ago, they deposited this material in the form of
till. Wind based
loess deposits also form an important parent material for prairie soils.
Tallgrass prairie evolved over tens of thousands of years with the disturbances of grazing and fire. Native
ungulate
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, c ...
s such as
bison
Bison are large bovines in the genus ''Bison'' (Greek: "wild ox" (bison)) within the tribe Bovini. Two extant taxon, extant and numerous extinction, extinct species are recognised.
Of the two surviving species, the American bison, ''B. bison'' ...
,
elk
The elk (''Cervus canadensis''), also known as the wapiti, is one of the largest species within the deer family, Cervidae, and one of the largest terrestrial mammals in its native range of North America and Central and East Asia. The commo ...
, and
white-tailed deer
The white-tailed deer (''Odocoileus virginianus''), also known as the whitetail or Virginia deer, is a medium-sized deer native to North America, Central America, and South America as far south as Peru and Bolivia. It has also been introduced t ...
roamed the expansive, diverse grasslands before
European colonization of the Americas
During the Age of Discovery, a large scale European colonization of the Americas took place between about 1492 and 1800. Although Norse colonization of North America, the Norse had explored and colonized areas of the North Atlantic, colonizin ...
. For 10,000-20,000 years, native people used fire annually as a tool to assist in hunting, transportation, and safety. Evidence of ignition sources of fire in the tall grass prairie are overwhelmingly human as opposed to lightning. Humans, and grazing animals, were active participants in the process of prairie formation and the establishment of the diversity of
graminoid and
forbs species. Fire has the effect on prairies of removing
trees, clearing dead plant matter, and changing the availability of certain nutrients in the soil from the ash produced. Fire kills the
vascular tissue
Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There ...
of trees, but not prairie species, as up to 75% (depending on the species) of the total plant
biomass is below the soil surface and will re-grow from its deep (upwards of 20 feet
)
roots. Without
disturbance, trees will encroach on a grassland and cast shade, which suppresses the
understory. Prairie and widely spaced
oak trees evolved to coexist in the
oak savanna ecosystem.
Fertility
In spite of long recurrent
droughts and occasional
torrential rains, the grasslands of the
Great Plains were not subject to great soil
erosion. The root systems of native prairie grasses firmly held the soil in place to prevent run-off of soil. When the plant died, the
fungi and
bacteria returned its nutrients to the soil. These deep roots also helped native prairie plants reach water in even the driest conditions. Native grasses suffer much less damage from dry conditions than many farm crops currently grown.
Geographical regions
Prairie
Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...
in North America is usually split into three groups: wet, mesic, and dry. They are generally characterized by
tallgrass prairie, mixed, or
shortgrass prairie, depending on the quality of soil and rainfall.
Wet
In wet prairies the soil is usually very moist, including during most of the growing season, because of poor
water drainage. The resulting
stagnant water
Water stagnation occurs when water stops flowing. Stagnant water can be a major environmental hazard.
Dangers
Malaria and dengue are among the main dangers of stagnant water, which can become a breeding ground for the mosquitoes that tran ...
is conducive to the formation of
bogs and
fens. Wet prairies have excellent farming soil. The average precipitation is a year.
Mesic
Mesic prairie has good drainage, but good soil during the growing season. This type of prairie is the most often converted for agricultural usage; consequently, it is one of the most endangered types of prairie.
Dry
Dry prairie has somewhat wet to very dry soil during the growing season because of good drainage in the soil. Often, this type of prairie can be found on uplands or slopes. Dry soil usually doesn't get much vegetation due to lack of rain.
[
] This is the dominant biome in the Southern Canadian agricultural and climatic region known as
Palliser's Triangle
Palliser's Triangle, or the Palliser Triangle, is a semi-arid steppe occupying a substantial portion of the Western Canadian Prairie Provinces, Saskatchewan, Alberta and Manitoba, within the Great Plains region. While initially determined to be uns ...
. Once thought to be completely unarable, the Triangle is now one of the most important agricultural regions in Canada thanks to advances in irrigation technology. In addition to its very high local importance to Canada, Palliser's Triangle is now also one of the most important sources of wheat in the world as a result of these improved methods of watering wheat fields (along with the rest of the Southern prairie provinces which also grow wheat, canola and many other grains). Despite these advances in farming technology, the area is still very prone to extended periods of drought, which can be disastrous for the industry if it is significantly prolonged.
An infamous example of this is the
Dust Bowl
The Dust Bowl was a period of severe dust storms that greatly damaged the ecology and agriculture of the American and Canadian prairies during the 1930s. The phenomenon was caused by a combination of both natural factors (severe drought) an ...
of the 1930s, which also hit much of the United States
Great Plains ecoregion, contributing greatly to the
Great Depression.
Environmental history
Bison hunting
Nomadic hunting has been the main human activity on the prairies for the majority of the archaeological record. This once included many now-extinct species of
megafauna
In terrestrial zoology, the megafauna (from Greek μέγας ''megas'' "large" and New Latin ''fauna'' "animal life") comprises the large or giant animals of an area, habitat, or geological period, extinct and/or extant. The most common threshold ...
.
After the other extinctions, the main hunted animal on the prairies was the
plains bison
The Plains bison (''Bison bison bison'') is one of two subspecies/ecotypes of the American bison, the other being the wood bison (''B. b. athabascae''). A natural population of Plains bison survives in Yellowstone National Park (the Yellowstone ...
. Using loud noises and waving large signals, Native peoples would drive bison into fenced pens called
buffalo pounds to be killed with bows and arrows or spears, or drive them off a cliff (called a
buffalo jump
A buffalo jump, or sometimes bison jump, is a cliff formation which Indigenous peoples of North America historically used to hunt and kill plains bison in mass quantities. The broader term game jump refers to a man-made jump or cliff used for hun ...
), to kill or injure the bison ''en masse''. The introduction of the horse and the gun greatly expanded the killing power of the plains Natives. This was followed by the policy of indiscriminate killing by European Americans and Canadians for both commercial reasons and to weaken the independence of plains Natives, and caused a dramatic drop in bison numbers from millions to a few hundred in a century's time, and almost caused their extinction.
Farming and ranching
The very dense soil plagued the first European settlers who were using wooden
plows, which were more suitable for loose forest soil. On the prairie, the plows bounced around, and the soil stuck to them. This problem was solved in 1837 by an
Illinois blacksmith named
John Deere who developed a
steel moldboard plow that was stronger and cut the roots, making the fertile soils ready for farming. Former grasslands are now among the most productive
agricultural land
Agricultural land is typically land ''devoted to'' agriculture, the systematic and controlled use of other forms of lifeparticularly the rearing of livestock and production of cropsto produce food for humans. It is generally synonymous with bot ...
s on Earth.
The tallgrass prairie has been converted into one of the most intensive crop producing areas in North America. Less than one tenth of one percent (<0.09%) of the original landcover of the tallgrass prairie biome remains. States formerly with landcover in native tallgrass prairie such as Iowa, Illinois, Minnesota, Wisconsin, Nebraska, and Missouri have become valued for their highly productive soils and are included in the
Corn Belt
The Corn Belt is a region of the Midwestern United States that, since the 1850s, has dominated corn production in the United States. In the United States, ''corn'' is the common word for maize. More generally, the concept of the Corn Belt conn ...
. As an example of this land use intensity, Illinois and Iowa rank 49th and 50th, out of 50 US states, in total uncultivated land remaining.
Drier shortgrass prairies were once used mostly for open-range ranching. With the development of
barbed wire
A close-up view of a barbed wire
Roll of modern agricultural barbed wire
Barbed wire, also known as barb wire, is a type of steel fencing wire constructed with sharp edges or points arranged at intervals along the strands. Its primary use is ...
in the 1870s and improved
irrigation techniques, this region has mostly been converted to cropland and small fenced pastures.
Biofuels
Research by
David Tilman, ecologist at the
University of Minnesota, suggests that "
Biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (EIA ...
s made from high-diversity mixtures of prairie plants can reduce global warming by removing carbon dioxide from the atmosphere. Even when grown on infertile soils, they can provide a substantial portion of global energy needs, and leave fertile land for food production."
Unlike corn and soybeans, which are both directly and indirectly major food crops, including livestock feed, prairie grasses are not used for human consumption. Prairie grasses can be grown in infertile soil, eliminating the cost of adding nutrients to the soil. Tilman and his colleagues estimate that prairie grass biofuels would yield 51 percent more energy per acre than ethanol from corn grown on fertile land.
Some plants commonly used are lupine,
big bluestem
''Andropogon gerardi'', commonly known as big bluestem, is a species of tall grass native to much of the Great Plains and grassland regions of central and eastern North America. It is also known as tall bluestem, bluejoint, and turkeyfoot.
Taxon ...
(turkey foot), blazing star,
switchgrass
''Panicum virgatum'', commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico. Switchgrass is one of the ...
, and
prairie clover.
Preservation
Because rich and thick
topsoil made the land well suited for agricultural use, only 1% of tallgrass prairie remains in the U.S. today. Shortgrass prairie is more abundant.
Significant preserved areas of prairie include:
* Alderville Black Oak Savanna;
Rice Lake,
Ontario
*
American Prairie
American Prairie is a prairie-based nature reserve in Central Montana being developed as a private project of the American Prairie Foundation (APF). This independent non-profit organization is creating a wildlife conservation area that aims to c ...
,
Phillips and
Blaine counties,
Montana
*
Clymer Meadow Preserve,
Hunt County,
Texas
*
Cypress Hills Interprovincial Park
Cypress Hills Interprovincial Park is a natural park in Canada straddling the Alberta / Saskatchewan boundary and jointly administered by the two provinces. Located south-east of Medicine Hat, it became Canada's first interprovincial park i ...
,
Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Terri ...
and
Saskatchewan
*
Goose Lake Prairie State Natural Area,
Grundy County, Illinois
Grundy County is a county in the U.S. state of Illinois. According to the 2010 census, it has a population of 50,063. Its county seat is Morris.
Grundy County is part of the Chicago-Naperville- Elgin, IL- IN- WI Metropolitan Statistical Ar ...
*
Grasslands National Park
Grasslands National Park (French: ') is a Canadian national park located near the village of Val Marie, Saskatchewan, and one of 44 national parks and park reserves in Canada's national park system (though one of only two in Saskatchewan it ...
,
Saskatchewan
*
Hoosier Prairie,
Lake County, Indiana
*
James Woodworth Prairie Preserve, a ''virgin prairie'' owned by
University of Illinois
The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Universi ...
,
Glenview, Illinois
Glenview is an incorporated village located in Cook County, Illinois, United States, approximately 15 miles northwest of the Chicago Loop. Per the 2020 census, the population was 48,705. The current Village President is Michael Jenny.
Geograph ...
*
Jennings Environmental Education Center
Jennings Environmental Education Center is a Pennsylvania state park in Brady Township, Butler County, Pennsylvania in the United States. It is north of Butler at the intersection of Pennsylvania Route 8 and Pennsylvania Route 528. The cente ...
,
Pennsylvania
*
Kissimmee Prairie Preserve State Park
Kissimmee Prairie Preserve State Park is a Florida state park, located approximately 25 miles north of Okeechobee, off US 441
U.S. Route 441 (US 441) is a auxiliary route of U.S. Route 41. It extends from US 41 in Miami, Flor ...
,
Okeechobee County,
Florida
*
Konza Prairie,
Manhattan, Kansas
*
Midewin National Tallgrass Prairie
The Midewin National Tallgrass Prairie (MNTP) is a tallgrass prairie reserve and similarly preserved as United States National Grassland operated by the United States Forest Service. The first national tallgrass prairie ever designated in the U.S ...
, in
Will County, Illinois
*
Mnoké Prairie,
Indiana Dunes National Park,
Porter, Indiana
Porter is a town in Westchester Township, Porter County, Indiana, Westchester Township, Porter County, Indiana, Porter County, in the U.S. state of Indiana. The population was 4,858 at the 2010 United States Census, 2010 census. Porter is in the I ...
*
Nachusa Grasslands, a
Nature Conservancy preserve near
Franklin Grove,
Illinois
*
Wichita Mountains Wildlife Refuge
Wichita Mountains Wildlife Refuge, located in southwestern Oklahoma near Lawton, has protected unique wildlife habitats since 1901 and is the oldest managed wildlife facility in the United States Fish and Wildlife Service system. The refuge's ...
, in
Comanche County, Oklahoma
Comanche County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 124,098, making it the fourth-most populous county in Oklahoma. Its county seat is Lawton. The county was created in 1901 as part o ...
*
Neal Smith National Wildlife Refuge
The Neal Smith National Wildlife Refuge is a federal national wildlife refuge located in Jasper County, Iowa, United States. The refuge, formerly known as Walnut Creek, is named after Congressman Neal Edward Smith, who championed its creation. I ...
,
Iowa
*
Nine-Mile Prairie,
Nebraska
* Ojibway prairie in
Windsor, Ontario.
*
Paynes Prairie Preserve State Park
Paynes Prairie Preserve State Park is a Florida State Park, encompassing a savanna in Alachua County, Florida lying between Micanopy and Gainesville. It is also a U.S. National Natural Landmark. It is crossed by both I-75 and U.S. 441 (which h ...
,
Alachua County
Alachua County ( ) is a county in the north central portion of the U.S. state of Florida. As of the 2020 census, the population was 278,468. The county seat is Gainesville, the home of the University of Florida since 1906, when the campus o ...
,
Florida
*
Richard Bong State Recreation Area
Richard Bong State Recreation Area is a unit of the state park system of the U.S. state of Wisconsin. It is located in the town of Brighton, in Kenosha County. This managed prairie contains of mountain bike trails. Other recreational activiti ...
, in
Kenosha County, Wisconsin
*
Russell R. Kirt Prairie,
College of DuPage
College of DuPage is a public community college with its main campus in Glen Ellyn, Illinois. The college also owns and operates facilities in the Illinois communities of Addison, Carol Stream, Naperville and Westmont. With more than 20,000 ...
,
Illinois
*
Tallgrass Aspen Parkland
The Tallgrass Aspen Parkland is an ecoregion located in southeastern Manitoba and northwestern Minnesota. The area is characterized by a mosaic of habitat types, including tallgrass prairie, aspen woodland, sedge meadow wetlands, riparian woodland, ...
,
Manitoba &
Minnesota
*
Tallgrass Prairie National Preserve
Tallgrass Prairie National Preserve is a United States National Preserve located in the Flint Hills region of Kansas, north of Strong City. The preserve protects a nationally significant example of the once vast tallgrass prairie ecosystem. O ...
,
Kansas
*
Tallgrass Prairie Preserve
The Joseph H. Williams Tallgrass Prairie Preserve, in Osage County, Oklahoma near Foraker, Oklahoma, is the largest protected tract of tallgrass prairie in the world. Managed by The Nature Conservancy, the preserve contains owned by the Conserv ...
,
Oklahoma
*
University of Wisconsin–Madison Arboretum,
University of Wisconsin–Madison
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, the ...
,
Wisconsin
*
Zumwalt Prairie,
Wallowa County, Oregon
Wallowa County () is the northeastern most county in the U.S. state of Oregon. As of the 2020 census, the population was 7,391, making it Oregon's fifth-least populous county. Its county seat is Enterprise. According to ''Oregon Geographic Name ...
Virgin prairies
''Virgin prairie'' refers to prairie land that has never been plowed. Small virgin prairies exist in the American Midwestern states and in Canada.
Restored prairie refers to a prairie that has been reseeded after plowing or other disturbance.
Prairie garden
A ''prairie garden'' is a
garden primarily consisting of plants from a prairie.
Physiography
The originally treeless prairies of the upper Mississippi basin began in
Indiana, and extended westward and north-westward, until they merged with the drier region known as the
Great Plains. An eastward extension of the same region, originally tree-covered, extended to central
Ohio. Thus, the prairies generally lie between the
Ohio and
Missouri rivers on the south and the Great Lakes on the north. The prairies are a contribution of the glacial period. They consist for the most part of glacial drift, deposited unconformably on an underlying rock surface of moderate or small relief. Here, the rocks are an extension of the same stratified
Palaeozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ''z ...
formations already described as occurring in the Appalachian region and around the
Great Lakes. They are usually fine-textured limestones and shales, lying horizontal. The moderate or small relief that they were given by mature preglacial erosion is now buried under the drift.
The greatest area of the prairies, from
Indiana to
North Dakota, consists of till plains, that is, sheets of unstratified drift. These plains are 30, 50 or even 100 ft (up to 30 m) thick covering the underlying rock surface for thousands of square miles except where postglacial stream erosion has locally laid it bare. The plains have an extraordinarily even surface. The till is presumably made in part of preglacial soils, but it is more largely composed of rock waste mechanically transported by the creeping ice sheets. Although the crystalline rocks from
Canada and some of the more resistant stratified rocks south of the Great Lakes occur as boulders and stones, a great part of the
till has been crushed and ground to a clayey texture. The till plains, although sweeping in broad swells of slowly changing altitude, often appear level to the eye with a view stretching to the horizon. Here and there, faint depressions occur, occupied by marshy sloughs, or floored with a rich black soil of postglacial origin. It is thus by sub-glacial aggradation that the prairies have been levelled up to a smooth surface, in contrast to the higher and non-glaciated hilly country just to the south.
The great ice sheets formed terminal
moraine
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice she ...
s around their border at various end stages. However, the morainic belts are of small relief in comparison to the great area of the ice. They rise gently from the till plains to a height of 50, 100 or more feet. They may be one, two or three miles (5 km) wide and their hilly surface, dotted over with boulders, contains many small lakes in basins or hollows, instead of streams in valleys. The morainic belts are arranged in groups of concentric loops, convex southward, because the ice sheets advanced in lobes along the lowlands of the Great Lakes. Neighboring morainic loops join each other in re-entrants (north-pointing cusps), where two adjacent glacial lobes came together and formed their moraines in largest volume. The moraines are of too small relief to be shown on any maps except of the largest scale. Small as they are, they are the chief relief of the prairie states, and, in association with the nearly imperceptible slopes of the till plains, they determine the course of many streams and rivers, which as a whole are consequent upon the surface form of the glacial deposits.
The complexity of the glacial period and its subdivision into several glacial epochs, separated by interglacial epochs of considerable length (certainly longer than the postglacial epoch) has a structural consequence in the superposition of successive till sheets, alternating with non-glacial deposits. It also has a physiographic consequence in the very different amount of normal postglacial erosion suffered by the different parts of the glacial deposits. The southernmost drift sheets, as in southern
Iowa and northern
Missouri, have lost their initially plain surface and are now maturely dissected into gracefully rolling forms. Here, the valleys of even the small streams are well opened and graded, and marshes and lakes are rare. These sheets are of early
Pleistocene origin. Nearer the Great Lakes, the till sheets are trenched only by the narrow valleys of the large streams. Marshy sloughs still occupy the faint depressions in the till plains and the associated moraines have abundant small lakes in their undrained hollows. These drift sheets are of late Pleistocene origin.
When the ice sheets extended to the land sloping southward to the Ohio River,
Mississippi River and Missouri River, the drift-laden streams flowed freely away from the ice border. As the streams escaped from their subglacial channels, they spread into broader channels and deposited some of their load, and thus aggraded their courses. Local sheets or aprons of gravel and sand are spread more or less abundantly along the outer side of the morainic belts. Long trains of gravel and sands clog the valleys that lead southward from the glaciated to the non-glaciated area. Later, when the ice retreated farther and the unloaded streams returned to their earlier degrading habit, they more or less completely scoured out the valley deposits, the remains of which are now seen in terraces on either side of the present flood plains.
When the ice of the last glacial epoch had retreated so far that its front border lay on a northward slope, belonging to the drainage area of the Great Lakes, bodies of water accumulated in front of the ice margin, forming glacio-marginal lakes. The lakes were small at first, and each had its own outlet at the lowest depression of land to the south. As the ice melted further back, neighboring lakes became confluent at the level of the lowest outlet of the group. The outflowing streams grew in the same proportion and eroded a broad channel across the height of land and far down stream, while the lake waters built sand reefs or carved shore cliffs along their margin, and laid down sheets of clay on their floors. All of these features are easily recognized in the prairie region. The present site of
Chicago was determined by an Indian portage or carry across the low divide between
Lake Michigan and the headwaters of the
Illinois River. This divide lies on the floor of the former outlet channel of the glacial Lake Michigan. Corresponding outlets are known for
Lake Erie,
Lake Huron, and
Lake Superior
Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...
. A very large sheet of water, named
Lake Agassiz, once overspread a broad till plain in northern
Minnesota and North Dakota. The outlet of this glacial lake, called river Warren, eroded a large channel in which the
Minnesota River evident today. The
Red River of the North
The Red River (french: rivière Rouge or ) is a river in the north-central United States and central Canada. Originating at the confluence of the Bois de Sioux and Otter Tail rivers between the U.S. states of Minnesota and North Dakota, it fl ...
flows northward through a plain formerly covered by Lake Agassiz.
Certain extraordinary features were produced when the retreat of the ice sheet had progressed so far as to open an eastward outlet for the marginal lakes. This outlet occurred along the depression between the northward slope of the Appalachian plateau in west-central New York and the southward slope of the melting ice sheet. When this eastward outlet came to be lower than the south-westward outlet across the height of land to the Ohio or Mississippi river, the discharge of the marginal lakes was changed from the Mississippi system to the
Hudson system. Many well-defined channels, cutting across the north-sloping spurs of the plateau in the neighborhood of
Syracuse, New York
Syracuse ( ) is a city in and the county seat of Onondaga County, New York, United States. It is the fifth-most populous city in the state of New York following New York City, Buffalo, Yonkers, and Rochester.
At the 2020 census, the city's ...
, mark the temporary paths of the ice-bordered outlet river. Successive channels are found at lower and lower levels on the plateau slope, indicating the successive courses taken by the lake outlet as the ice melted farther and farther back. On some of these channels, deep gorges were eroded heading in temporary cataracts which exceeded Niagara in height but not in breadth. The pools excavated by the plunging waters at the head of the gorges are now occupied by little lakes. The most significant stage in this series of changes occurred when the glacio-marginal lake waters were lowered so that the long escarpment of Niagara limestone was laid bare in western New York. The previously confluent waters were then divided into two lakes. The higher one,
Lake Erie, supplied the outflowing
Niagara River, which poured its waters down the escarpment to the lower,
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border span ...
. This gave rise to
Niagara Falls. Lake Ontario's outlet for a time ran down the
Mohawk Valley to the
Hudson River
The Hudson River is a river that flows from north to south primarily through eastern New York. It originates in the Adirondack Mountains of Upstate New York and flows southward through the Hudson Valley to the New York Harbor between New ...
. At this higher elevation, it was known as
Lake Iroquois Lake Iroquois can refer to:
* Lake Iroquois (South Dakota)
* Lake Iroquois (Vermont) in Vermont in the United States
* Lake Iroquois, Illinois in Iroquois County in Illinois in the United States
*Glacial Lake Iroquois
Glacial Lake Iroquois was a ...
. When the ice melted from the northeastern end of the lake, it dropped to a lower level, and drained through the St. Lawrence area. This created a lower
base level
In geology and geomorphology a base level is the lower limit for an erosion process. The modern term was introduced by John Wesley Powell in 1875. The term was subsequently appropriated by William Morris Davis who used it in his cycle of erosion ...
for the Niagara River, increasing its erosive capacity.
In certain districts, the subglacial till was not spread out in a smooth plain, but accumulated in elliptical mounds, 100–200 feet. high and long with axes parallel to the direction of the ice motion as indicated by striae on the underlying rock floor. These hills are known by the Irish name,
drumlin
A drumlin, from the Irish word ''droimnín'' ("littlest ridge"), first recorded in 1833, in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated ...
s, used for similar hills in north-western
Ireland. The most remarkable groups of drumlins occur in western
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* ...
, where their number is estimated at over 6,000, and in southern Wisconsin, where it is placed at 5,000. They completely dominate the topography of their districts.
A curious deposit of an impalpably fine and unstratified silt, known by the
German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
name bess (or
loess), lies on the
older drift
Old and Young Drift are geographic names given to the morainic landscapes that were formed in Central Europe; the Old Drift during the older ice ages and the Young Drift during the latest glaciations – the Weichselian in North Germany and th ...
sheets near the larger river courses of the upper Mississippi basin. It attains a thickness of or more near the rivers and gradually fades away at a distance of ten or more miles (16 or more km) on either side. It contains land shells, and hence cannot be attributed to marine or lacustrine submergence. The best explanation is that, during certain phases of the glacial period, it was carried as dust by the winds from the flood plains of aggrading rivers, and slowly deposited on the neighboring grass-covered plains. The glacial and
eolian origin of this sediment is evidenced by the angularity of its grains (a bank of it will stand without slumping for years), whereas, if it had been transported significantly by water, the grains would have been rounded and polished. Loess is parent material for an extremely fertile, but droughty soil.
Southwestern
Wisconsin and parts of the adjacent states of
Illinois,
Iowa, and
Minnesota are known as the
driftless zone
The Driftless Area, a topographical and cultural region in the American Midwest, comprises southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and the extreme northwestern corner of Illinois.
Never covered by ice during the last ...
, because, although bordered by drift sheets and moraines, it is free from glacial deposits. It must therefore have been a sort of oasis, when the ice sheets from the north advanced past it on the east and west, and joined around its southern border. The reason for this exemption from glaciation is the converse of that for the southward convexity of the morainic loops. For while they mark the paths of greatest glacial advance along lowland troughs (lake basins), the driftless zone is a district protected from ice invasion by reason of the obstruction which the highlands of northern Wisconsin and Michigan (part of the Superior upland) offered to glacial advance.
The course of the upper
Mississippi River is largely consequent upon glacial deposits. Its sources are in the morainic lakes in northern
Minnesota. The drift deposits thereabouts are so heavy that the present divides between the drainage basins of
Hudson Bay,
Lake Superior
Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...
, and the
Gulf of Mexico evidently stand in no very definite relation to the preglacial divides. The course of the Mississippi through Minnesota is largely guided by the form of the drift cover. Several rapids and the
Saint Anthony Falls (determining the site of
Minneapolis) are signs of immaturity, resulting from superposition through the drift on the under rock. Farther south, as far as the entrance of the
Ohio River, the Mississippi follows a rock-walled valley deep, with a flood-plain wide. This valley seems to represent the path of an enlarged early-glacial Mississippi, when much precipitation that is today discharged to Hudson Bay and the Gulf of St Lawrence was delivered to the Gulf of Mexico, for the curves of the present river are of distinctly smaller
radii
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
than the curves of the valley.
Lake Pepin
Lake Pepin is a naturally occurring lake on the Mississippi River on the border between the U.S. states of Minnesota and Wisconsin. It is located in a valley carved by the outflow of an enormous glacial lake at the end of the last Ice Age. The ...
( below
St. Paul
Paul; grc, Παῦλος, translit=Paulos; cop, ⲡⲁⲩⲗⲟⲥ; hbo, פאולוס השליח (previously called Saul of Tarsus;; ar, بولس الطرسوسي; grc, Σαῦλος Ταρσεύς, Saũlos Tarseús; tr, Tarsuslu Pavlus; ...
), a picturesque expansion of the river across its flood-plain, is due to the aggradation of the valley floor where the
Chippewa River, coming from the northeast, brought an overload of fluvio-glacial drift. Hence, even the father of waters, like so many other rivers in the Northern states, owes many of its features more or less directly to glacial action.
The fertility of the prairies is a natural consequence of their origin. During the mechanical transportation of the till, no vegetation was present to remove the minerals essential to plant growth, as is the case in the soils of normally weathered and dissected peneplains. The soil is similar to the Appalachian piedmont which though not exhausted by the primeval forest cover, are by no means so rich as the till sheets of the prairies. Moreover, whatever the rocky understructure, the till soil has been averaged by a thorough mechanical mixture of rock grindings. Hence, the prairies are continuously fertile for scores of miles together. The true prairies were once covered with a rich growth of natural grass and annual flowering plants, but today, they are covered with farms.
See also
*
Great Plains
:*
Shortgrass prairie
:*
Mixed grass prairie
A mixed-grass prairie is an ecotone located between the tallgrass prairies and shortgrass prairies. The mixed-grass prairie is richer in ecological diversity than either the tall- or shortgrass prairie. The mixed-grass prairie occurs in the ...
:*
Tallgrass prairie
*
Prairies Ecozone
The Prairies Ecozone is a Canadian terrestrial ecozone which spans the southern areas of the Prairie provinces of Alberta, Saskatchewan, and Manitoba. It is a productive agricultural area, and is commonly referred to as "Canada's breadbasket". Far ...
*
Interior Plains
The Interior Plains is a vast physiographic region that spreads across the Laurentian craton of central North America, extending along the east flank of the Rocky Mountains from the Gulf Coast region to the Arctic Beaufort Sea. In Canada, it e ...
*
Canadian Prairies
The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie Provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...
*
Geography of North America
*
North American Prairies Province The North America Prairies is a large grassland floristic province within the North American Atlantic Region, a floristic region within the Holarctic Kingdom. It lies between the Appalachian Province and the Rocky Mountains and includes the prair ...
*
Aspen parkland
Aspen parkland refers to a very large area of transitional biome between prairie and boreal forest in two sections, namely the Peace River Country of northwestern Alberta crossing the border into British Columbia, and a much larger area stretch ...
*
Buffalo Commons
The Buffalo Commons is a conceptual proposal to create a vast nature preserve by returning of the drier portion of the Great Plains to native prairie, and by reintroducing the American bison ("buffalo"), that once grazed the shortgrass prairie. ...
*
Coastal plain
A coastal plain is flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area. Some of the largest coastal plains are in Alaska and the southeastern United States. The Gulf Co ...
*
Coastal prairie
*
Dust Bowl
The Dust Bowl was a period of severe dust storms that greatly damaged the ecology and agriculture of the American and Canadian prairies during the 1930s. The phenomenon was caused by a combination of both natural factors (severe drought) an ...
*
Field
Field may refer to:
Expanses of open ground
* Field (agriculture), an area of land used for agricultural purposes
* Airfield, an aerodrome that lacks the infrastructure of an airport
* Battlefield
* Lawn, an area of mowed grass
* Meadow, a grass ...
*
Flooded grasslands and savannas
*
Flood-meadow
*
Grassland
A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge ( Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natu ...
*
Heath
*
Meadow
A meadow ( ) is an open habitat, or field, vegetated by grasses, herbs, and other non-woody plants. Trees or shrubs may sparsely populate meadows, as long as these areas maintain an open character. Meadows may be naturally occurring or artifici ...
*
Outback
*
Pampas
*
Pasture
Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or swin ...
*
Plain
*
Prairie dog
*
Prairie madness
Prairie madness or prairie fever was an affliction that affected settlers in the Great Plains during the migration to, and settlement of, the Canadian Prairies and the Western United States in the nineteenth century. Settlers moving from urban ...
*
Prairie restoration
Prairie restoration is a conservation effort to restore prairie lands that were destroyed due to industrial, agricultural, commercial, or residential development. For example, the U.S. state of Illinois alone once held over of prairie land an ...
*
Puszta
*
Rangeland
*
Savanna
A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...
*
Steppe
*
Switchgrass
''Panicum virgatum'', commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico. Switchgrass is one of the ...
*
Temperate grasslands, savannas, and shrublands
*
Veld
*
Water-meadow
*
Wet meadow
References
External links
The Prairie Enthusiasts– grassland protection and restoration in the upper
Midwest
Prairie Plains Resource InstituteThe Native Prairies Association of TexasMissouri Prairie FoundationAmerica’s GrasslandsDocumentary produced by
Prairie Public Television
Prairie Public Television is a state network of public television stations operated primarily by Prairie Public Broadcasting. It comprises all of the PBS member stations in the U.S. state of North Dakota.
The state network is available via flags ...
{{Authority control
*