Traverse Gap
Encyclopedia
The Traverse Gap is an ancient river channel occupied by Lake Traverse
and Big Stone Lake
and the valley connecting them at Browns Valley, Minnesota
. It is located on the border of the U.S. state
s of Minnesota
and South Dakota
. Traverse Gap has an unusual distinction for a valley
: it is crossed by a continental divide
, and in some floods water has flowed across that divide from one drainage basin
to the other. Before the Anglo-American Convention of 1818 it marked the border between British territory in the north and U.S. – or earlier, French – territory in the south.
. The Laurentide Ice Sheet
decayed and receded as the Wisconsonian glaciation drew to a close, and Glacial Lake Agassiz formed from its meltwaters. Outlets to the north were blocked by the glacier, and the outlet to the south was dammed by the Big Stone Moraine
which had been left by the retreat of the ice sheet. Lake Agassiz filled until it overtopped the moraine about 11,700 years ago. The resulting enormous outflow of the lake carved a natural spillway
through the moraine, through which cascaded Glacial River Warren
. This great river not only created the gap, it also cut the valleys of the present-day Minnesota
and Upper Mississippi River
s. River Warren drained Agassiz in two or more intervals over the next 2300 years, separated by times when the ice sheet receded sufficiently to uncover other outlets for Lake Agassiz. About 9400 years ago, Agassiz found a permanent outlet to the north. With its former source
now draining elsewhere, the River Warren ceased to flow, and the spillway gorge became the Traverse Gap.
Despite the low elevation and flat topography of its floor, the Traverse Gap marks southernmost point of the Northern Divide between the watershed
s of the Arctic
and the Atlantic Ocean
s. On the north, Lake Traverse is the source of the Bois des Sioux River, a source stream of the Red River of the North
, which drains via Lake Winnipeg
and the Nelson River
to Hudson Bay
in the Arctic Ocean. To the south, Big Stone Lake is the source of River Warren's remnant, the Minnesota River, tributary to the Mississippi
, which drains to the Gulf of Mexico
and the Atlantic
. Big Stone Lake is now fed by the Little Minnesota River
, the headwaters of which are in South Dakota. The Little Minnesota enters the gap from the west and meanders south through the old channel to Big Stone Lake. The Little Minnesota, part of the Mississippi watershed, is less than one mile (1.6 km) from Lake Traverse in the drainage basin of Hudson Bay.
The floor of Browns Valley is flat, which allows the waters of one basin to flood across the continental divide into the other basin in times of high water. The maximum elevation on the floor of the valley is 987 feet (300.8 m) above sea level. The Browns Valley Dike at the south end of Lake Traverse is at the same elevation; this structure was built to reduce the likelihood of flooding south across the continental divide. At 983.9 feet (299.9 m), that divide is lower than the level of the dike, and flooding at Lake Traverse has the potential to drain over the Big Stone Dike into the Minnesota River watershed. At the south end of the gap, the Big Stone Lake reservoir pool is maintained at 967 feet (294.7 m), and it has recently flooded to over 975 feet (297.2 m). The Little Minnesota River upstream and at a higher elevation near the divide has flooded to a level where it drained across that divide into Lake Traverse. While the natural state of the area has been altered by the dike and control structures on the two lakes, interbasin flooding did occur prior to construction of those improvements. The Traverse Gap therefore allows waters which would naturally flow to the Atlantic Ocean to flow to the Arctic instead, and in the past has allowed water from Lake Traverse to flow in the other direction to Big Stone Lake in the Atlantic basin.
The continental divide crosses the gap transversely at its northern end. The Minnesota-South Dakota border longitudinally bisects the old channel. Roberts County
is on the South Dakota side. To the east is Traverse County, Minnesota
and the community of Browns Valley near the continental divide. The southeast part of the gap is in Big Stone County, Minnesota
.
and Folsom
types, the human remains have been dated approximately 9,000 years b.p.
The Traverse Gap was used by Native Americans
, who recognized its geographic significance. Two buffalo
skulls were placed on the continental divide, where travelers would stop to smoke a pipe to mark the place where the waters divided. The native trails were later used by fur trade
rs who had posts at Lake Traverse and Big Stone Lake, and then by Red River ox cart
s on the earliest of the Red River Trails
.
The rural part of the valley floor contains pastures, cropland, and marshes along the Little Minnesota River. The vale was named "Browns Valley" after one of its pioneer residents, which in turn gave its name to the incorporated community near its northern end. The valley floor is crossed by Minnesota State Highway 28
, which becomes South Dakota Highway 10 at the south end of Lake Traverse.
under the Historic Sites Act
. It received this designation in April 1966 from the United States Secretary of the Interior
, giving it recognition as an outstanding example of a geological feature of the United States' natural history. The designation describes it as "a channel cut by the Ancient River Warren during the Ice Age, containing the Hudson Bay-Gulf of Mexico divide, with a lake on each side as evidence of the irregularities in Ice Age sedimentation".
Lake Traverse
Lake Traverse is the southernmost body of water in the Hudson Bay watershed of North America. It lies along the border between the U.S. states of Minnesota and South Dakota...
and Big Stone Lake
Big Stone Lake
Big Stone Lake is a long, narrow freshwater lake and reservoir forming the border between western Minnesota and northeastern South Dakota in the USA. The lake covers 12,610 acres of surface area, stretching 26 miles from end to end and averaging around 1 mile wide, and at an elevation of 965...
and the valley connecting them at Browns Valley, Minnesota
Browns Valley, Minnesota
As of the census of 2000, there were 690 people, 285 households, and 171 families residing in the city. The population density was 878.5 people per square mile . There were 317 housing units at an average density of 403.6 per square mile...
. It is located on the border of the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
s of Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
and South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
. Traverse Gap has an unusual distinction for a valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
: it is crossed by a continental divide
Continental divide
A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not connected to the open sea...
, and in some floods water has flowed across that divide from one drainage basin
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
to the other. Before the Anglo-American Convention of 1818 it marked the border between British territory in the north and U.S. – or earlier, French – territory in the south.
Geological history
The Traverse Gap was cut at the end of the last ice ageIce age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
. The Laurentide Ice Sheet
Laurentide ice sheet
The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and...
decayed and receded as the Wisconsonian glaciation drew to a close, and Glacial Lake Agassiz formed from its meltwaters. Outlets to the north were blocked by the glacier, and the outlet to the south was dammed by the Big Stone Moraine
Moraine
A moraine is any glacially formed accumulation of unconsolidated glacial debris which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past glacial maximum. This debris may have been plucked off a valley floor as a glacier advanced or it may have...
which had been left by the retreat of the ice sheet. Lake Agassiz filled until it overtopped the moraine about 11,700 years ago. The resulting enormous outflow of the lake carved a natural spillway
Spillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...
through the moraine, through which cascaded Glacial River Warren
Glacial River Warren
right|thumb|210px|The course of the Minnesota River follows the valley carved by Glacial River WarrenGlacial River Warren or River Warren was a prehistoric river that drained Lake Agassiz in central North America between 11,700 and 9,400 years ago...
. This great river not only created the gap, it also cut the valleys of the present-day Minnesota
Minnesota River
The Minnesota River is a tributary of the Mississippi River, approximately 332 miles long, in the U.S. state of Minnesota. It drains a watershed of nearly , in Minnesota and about in South Dakota and Iowa....
and Upper Mississippi River
Upper Mississippi River
The Upper Mississippi River is the portion of the Mississippi River upstream of Cairo, Illinois, United States. From the headwaters at Lake Itasca, Minnesota, the river flows approximately 2000 kilometers to Cairo, where it is joined by the Ohio River to form the Lower Mississippi...
s. River Warren drained Agassiz in two or more intervals over the next 2300 years, separated by times when the ice sheet receded sufficiently to uncover other outlets for Lake Agassiz. About 9400 years ago, Agassiz found a permanent outlet to the north. With its former source
Source (river or stream)
The source or headwaters of a river or stream is the place from which the water in the river or stream originates.-Definition:There is no universally agreed upon definition for determining a stream's source...
now draining elsewhere, the River Warren ceased to flow, and the spillway gorge became the Traverse Gap.
Topography and hydrology
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
s of the Arctic
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...
and the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
s. On the north, Lake Traverse is the source of the Bois des Sioux River, a source stream of the Red River of the North
Red River of the North
The Red River is a North American river. Originating at the confluence of the Bois de Sioux and Otter Tail rivers in the United States, it flows northward through the Red River Valley and forms the border between the U.S. states of Minnesota and North Dakota before continuing into Manitoba, Canada...
, which drains via Lake Winnipeg
Lake Winnipeg
Lake Winnipeg is a large, lake in central North America, in the province of Manitoba, Canada, with its southern tip about north of the city of Winnipeg...
and the Nelson River
Nelson River
The Nelson River is a river of north-central North America, in the Canadian province of Manitoba. Its full length is , it has mean discharge of , and has a drainage basin of , of which is in the United States...
to Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
in the Arctic Ocean. To the south, Big Stone Lake is the source of River Warren's remnant, the Minnesota River, tributary to the Mississippi
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
, which drains to the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
and the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Big Stone Lake is now fed by the Little Minnesota River
Little Minnesota River
The Little Minnesota River is a headwaters tributary of the Minnesota River in northeastern South Dakota and west-central Minnesota in the United States...
, the headwaters of which are in South Dakota. The Little Minnesota enters the gap from the west and meanders south through the old channel to Big Stone Lake. The Little Minnesota, part of the Mississippi watershed, is less than one mile (1.6 km) from Lake Traverse in the drainage basin of Hudson Bay.
The floor of Browns Valley is flat, which allows the waters of one basin to flood across the continental divide into the other basin in times of high water. The maximum elevation on the floor of the valley is 987 feet (300.8 m) above sea level. The Browns Valley Dike at the south end of Lake Traverse is at the same elevation; this structure was built to reduce the likelihood of flooding south across the continental divide. At 983.9 feet (299.9 m), that divide is lower than the level of the dike, and flooding at Lake Traverse has the potential to drain over the Big Stone Dike into the Minnesota River watershed. At the south end of the gap, the Big Stone Lake reservoir pool is maintained at 967 feet (294.7 m), and it has recently flooded to over 975 feet (297.2 m). The Little Minnesota River upstream and at a higher elevation near the divide has flooded to a level where it drained across that divide into Lake Traverse. While the natural state of the area has been altered by the dike and control structures on the two lakes, interbasin flooding did occur prior to construction of those improvements. The Traverse Gap therefore allows waters which would naturally flow to the Atlantic Ocean to flow to the Arctic instead, and in the past has allowed water from Lake Traverse to flow in the other direction to Big Stone Lake in the Atlantic basin.
Geography
The ancient channel at Browns Valley is a mile (1.6 km) wide and some 130 feet (40 m) deeper than the surrounding terrain through which it was carved. The distance from Lake Traverse to Big Stone Lake is about five miles (8 km).The continental divide crosses the gap transversely at its northern end. The Minnesota-South Dakota border longitudinally bisects the old channel. Roberts County
Roberts County, South Dakota
As of the census of 2000, there were 10,016 people, 3,683 households, and 2,618 families residing in the county. The population density was 9 people per square mile . There were 4,734 housing units at an average density of 4 per square mile...
is on the South Dakota side. To the east is Traverse County, Minnesota
Traverse County, Minnesota
As of the census of 2000, there were 4,134 people, 1,717 households, and 1,129 families residing in the county. The population density was 7 people per square mile . There were 2,199 housing units at an average density of 4 per square mile...
and the community of Browns Valley near the continental divide. The southeast part of the gap is in Big Stone County, Minnesota
Big Stone County, Minnesota
As of the census of 2000, there were 5,820 people, 2,377 households, and 1,611 families residing in the county. The population density was 12 people per square mile . There were 3,171 housing units at an average density of 6 per square mile...
.
Human settlement
The area has seen human presence for thousands of years. A Paleo-Indian skeleton now known as "Browns Valley Man" was unearthed in 1933, under circumstances which suggested death or internment after deposition of the gravel but before creation of significant topsoil. Found with tools of the ClovisClovis point
Clovis points are the characteristically-fluted projectile points associated with the North American Clovis culture. They date to the Paleoindian period around 13,500 years ago. Clovis fluted points are named after the city of Clovis, New Mexico, where examples were first found in 1929.At the right...
and Folsom
Folsom point
Folsom points are a distinct form of chipped stone projectile points associated with the Folsom Tradition of North America. The style of toolmaking was named after Folsom, New Mexico where the first sample was found within the bone structure of a bison in 1927....
types, the human remains have been dated approximately 9,000 years b.p.
The Traverse Gap was used by Native Americans
Native Americans in the United States
Native Americans in the United States are the indigenous peoples in North America within the boundaries of the present-day continental United States, parts of Alaska, and the island state of Hawaii. They are composed of numerous, distinct tribes, states, and ethnic groups, many of which survive as...
, who recognized its geographic significance. Two buffalo
American Bison
The American bison , also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds...
skulls were placed on the continental divide, where travelers would stop to smoke a pipe to mark the place where the waters divided. The native trails were later used by fur trade
Fur trade
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of world market for in the early modern period furs of boreal, polar and cold temperate mammalian animals have been the most valued...
rs who had posts at Lake Traverse and Big Stone Lake, and then by Red River ox cart
Red River ox cart
The Red River cart was a large two-wheeled cart made entirely of non-metallic materials. Often drawn by oxen, though also by horses or mules, these carts were used throughout most of the 19th century in the fur trade and in westward expansion in Canada and the United States, in the area of the Red...
s on the earliest of the Red River Trails
Red River Trails
The Red River Trails were a network of ox cart routes connecting the Red River Colony and Fort Garry in British North America with the head of navigation on the Mississippi River in the United States...
.
The rural part of the valley floor contains pastures, cropland, and marshes along the Little Minnesota River. The vale was named "Browns Valley" after one of its pioneer residents, which in turn gave its name to the incorporated community near its northern end. The valley floor is crossed by Minnesota State Highway 28
Minnesota State Highway 28
Minnesota State Highway 28 is a highway in west-central and central Minnesota, which runs from South Dakota Highway 10 at the South Dakota state line near Browns Valley and continues east to its eastern terminus at its intersection with the former route of U.S...
, which becomes South Dakota Highway 10 at the south end of Lake Traverse.
Natural Landmark designation
Under the name of Ancient River Warren Channel, the Traverse Gap has been designated as a National Natural LandmarkNational Natural Landmark
The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...
under the Historic Sites Act
Historic Sites Act
The Historic Sites Act of 1935 was enacted by the United States Congress largely to organize the myriad federally-own parks, monuments, and historic sites under the National Park Service and the United States Secretary of the Interior...
. It received this designation in April 1966 from the United States Secretary of the Interior
United States Secretary of the Interior
The United States Secretary of the Interior is the head of the United States Department of the Interior.The US Department of the Interior should not be confused with the concept of Ministries of the Interior as used in other countries...
, giving it recognition as an outstanding example of a geological feature of the United States' natural history. The designation describes it as "a channel cut by the Ancient River Warren during the Ice Age, containing the Hudson Bay-Gulf of Mexico divide, with a lake on each side as evidence of the irregularities in Ice Age sedimentation".
See also
- Geology of Minnesota
- Glacial history of MinnesotaGlacial history of MinnesotaThe glacial history of Minnesota is most defined since the onset of the last glacial period, which ended some 10,000 years ago. Within the last million years, most of the Midwestern United States and much of Canada were covered at one time or another with an ice sheet. This continental glacier had...
- Laurentide ice sheetLaurentide ice sheetThe Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and...
- Proglacial lakes of MinnesotaProglacial lakes of MinnesotaThe proglacial lakes of Minnesota were lakes created in what is now the U.S. state of Minnesota in central North America in the waning years of the last glacial period. As the Laurentide ice sheet decayed at the end of the Wisconsin glaciation, lakes were created in depressions or behind moraines...
- Wisconsin glaciationWisconsin glaciationThe last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....