Lake Monongahela

Last updated
Lake Monongahela
Lake Monogahela.jpg
Lake Monongahela during its most expansive period. Based on the map of John A. Harper; 1997.
USA Pennsylvania relief location map.svg
Red pog.svg
Lake Monongahela
Location Pennsylvania, Ohio & West Virginia
Coordinates 39°58′N80°00′W / 39.97°N 80°W / 39.97; -80 Coordinates: 39°58′N80°00′W / 39.97°N 80°W / 39.97; -80
Lake type former lake
Etymology Monongahela River
Primary inflows Laurentide Ice Sheet
Primary outflows Ohio River
Basin  countriesUnited States
First flooded900,000 years before present
Max. length122 mi (196 km)
Max. width365 mi (587 km)
212 mi (341 km)
Residence time 170,000 years in existence
Surface elevationc. 1,160 ft (354 m)
ReferencesLake Monongahela: Anatomy of an Immense Ice Age Pond; John A. Harper; Bureau of Topographic and Geologic Survey; 1997.

Lake Monongahela was a proglacial lake in western Pennsylvania, West Virginia, and Ohio. It formed during the Pre-Illinoian ice epoch when the retreat of the ice sheet northwards blocked the drainage of these valleys to the north. The lake formed south of the ice front continued to rise until it was able to breach a low divide near New Martinsville, West Virginia. The overflow was the beginning of the process which created the modern Ohio River valley.

Contents

Preglacial drainage

The Monongahela flowed north from Lewis County to Pittsburgh. Here, the Lower Allegheny joined and they continued westward in the Ohio River valley to Beaver, Pennsylvania. At Beaver, the predecessor of the upper Ohio River joined and together the water flowed northwest, up the Beaver River into Ohio. Using a combination of waterways it crossed the divide into the Lake Erie basin to join the ancestral St. Lawrence River through Canada. [1]

The preglacial Monongahela River drained three fourths of combined drainage of the modern Ohio, Monongahela, and Allegheny Rivers. [1]

Lake Monongahela

Around 900,000 years before present (YBP) the Laurentide Ice Sheet reached southward into western Pennsylvania, blocking the preexisting drainage that flowed northward. [2] The ice dammed these rivers, creating large lakes, forcing the water to find a new drainage pattern, which exists to the present. On the upper Ohio, Monongahela and the Allegheny Rivers this impounded water has become known as Lake Monongahela. The ancestral Monongahela River, referred to as the Pittsburgh River, had flowed northwards from West Virginia, past Pittsburgh, into the Lake Erie basin and out the St. Lawrence River to the ocean. The lake began when the ice dammed the valley near Pittsburgh. [2] The lake changed sizes as the ice front moved and as the volume of water changed. At its largest, it rose to 1,100 feet (340 m) above sea level. Eventually the water found a low divide near New Martinsville, West Virginia, creating an outlet to the south and west into the Teays River. Thus, the upper Ohio network of river valleys came into form. [2]

Once Lake Monongahela formed, the water drowned the existing landforms. The lake did not erode the topography—it simply covered the land with water and lacustrine sediment. The sediment settled on both topographic highs and lows beneath the surface of the lake. Drowned terraces and abandoned meander channels, as well as low hills, slopes, and valley bottoms, received this covering of sediment. As such, sediments found on different terraces can actually be the same age. [1] Marine (1997) found five terrace levels along the rivers, but he had to conclude that the lake deposits found on them resulted from only two episodes of glacial damming. Deposits on the fifth and fourth terrace levels represent damming during a pre-Illinoian glaciation, whereas the third- and second-terrace-level deposits represent damming during Illinoian glaciation. The first terrace (the modern floodplain) consists simply of Wisconsinan outwash and Holocene alluvial deposits, which fill river valleys that had been cut to bedrock by the end of Illinoian time. [1]

I. C. White, the first director of the West Virginia Geological Survey, named this body of water Lake Monongahela (White, 1896). It resembled a man-made lake more than a natural lake. The river system was blocked and the water backed into all the side valleys. This happened at least twice. Each lake left evidence at a different elevation (White, 1896; Leverett, 1934) throughout the valley. [1] As the water rose, it reached the divides of the side valley, until it finally escaped over the divide of the ancestral Ohio River, carving the notch lower. Once flowing over the divide, the water followed the front of the ice sheet, creating the Ohio River. The three Allegheny Rivers shown above merged into one, which joined the Monongahela at Pittsburgh. The newly combined waters moved down the Ohio and then up the ancestral tributary of the Ohio until it flowed over the divide at New Martinsville. The Ohio replaced the Monongahela as the dominant stream. [1]

Terraces

The lake's age has been determined by the lake sediments and terrace deposits. The sediments reveal a change in the magnetic polarity during the life of the lake, with the oldest deposits being between 730,000 and 900,000 years ago. Other terrace deposits show later periods of ponding. [2] Pollen from a pine-spruce forest dominate the oldest sediments. This reflects a climate which would have been created by the proximity of the ice sheet. Younger sediments contain pollen and plant fossils of a hemlock-hardwoods association, reflecting the moderating climate as the ice sheets retreated northward. [2]

White (1896) and Marine (1997) described five terraces that occur along or near the valley walls of the Ohio, Monongahela, and Allegheny Rivers and their major tributaries in Pennsylvania and West Virginia. These relatively flat landforms contain soils composed of highly weathered deposits of clay, silt, sand, and gravel distributed at elevations as high as 300 feet (91 m) above present stream levels. These sediments are lacustrine, or lake-derived, deposition. [1] Campbell (1902) named the Carmichaels Formation are lacustrine sediments exposed at Carmichaels in Greene County, Pa. These deposits are found throughout southwestern Pennsylvania and northern West Virginia. They typically contain reddish-orange to tan clays, silts, and sands. They can contain cobbles and boulders from the local bedrock (Donahue and Kirchner, 1998). The clays are of high quality and were the source for the early pottery industry in the Pittsburgh area. Carmichaels Formation deposits occur on the upper two terrace levels in all the river valleys or on the lower terraces in the Monongahela Valley and in the valleys of the eastern tributaries of the Allegheny River. [1] The other outwash deposits on the Allegheny, Ohio, and Beaver River terraces have no names. These deposits are typically red rust-colored, deeply weathered gravels composed of small, rounded pebbles generally less than 1 inch (2.5 cm) in diameter. Up to 10% of the pebbles are granites and other crystalline rocks. Some are cemented to form sandstones and other conglomerates. Others are loose assortments of silt, sand, and gravel. These outwash deposits occur on several terrace levels. [1]

See also

Related Research Articles

Ohio River Major river in the midwestern United States

The Ohio River is a 981-mile (1,579 km) long river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing southwesterly from far-western Pennsylvania south of Lake Erie to its mouth on the Mississippi River at the southern tip of Illinois. It is the third largest river by discharge volume in the United States and the largest tributary by volume of the north-south flowing Mississippi River that divides the eastern from western United States. The river flows through or along the border of six states, and its drainage basin includes parts of 14 states. Through its largest tributary, the Tennessee River, the basin includes several states of the southeastern U.S. It is the source of drinking water for three million people.

Allegheny River River in Pennsylvania and New York, United States

The Allegheny River is a 325-mile (523 km) long headwater stream of the Ohio River in western Pennsylvania and New York, United States. The Allegheny River runs from its headwaters just below the middle of Pennsylvania's northern border northwesterly into New York then in a zigzag southwesterly across the border and through Western Pennsylvania to join the Monongahela River at the Forks of the Ohio on the "Point" of Point State Park in Downtown Pittsburgh, Pennsylvania. The Allegheny River is, by volume, the main headstream of both the Ohio and Mississippi Rivers. Historically, the Allegheny was considered to be the upper Ohio River by both Native Americans and European settlers.

Monongahela River River in Pennsylvania and West Virginia, United States

The Monongahela River —often referred to locally as the Mon —is a 130-mile-long (210 km) river on the Allegheny Plateau in north-central West Virginia and southwestern Pennsylvania. The river flows from the confluence of its west and east forks in north-central West Virginia northeasterly into southwestern Pennsylvania, then northerly to Pittsburgh and its confluence with the Allegheny River to form the Ohio River. The river's entire length is navigable via a series of locks and dams.

Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.

Teays River

The Teays River (pronounced taze) was a major preglacial river that drained much of the present Ohio River watershed, but took a more northerly downstream course. Traces of the Teays across northern Ohio and Indiana are represented by a network of river valleys. The largest still existing contributor to the former Teays River is the Kanawha River in West Virginia, which is itself an extension of the New River. The name Teays from the Teays Valley is associated with this buried valley since 1910. The more appropriate name would be ancestral Kanawha Valley. The term Teays is used when discussing the buried portion of the ancestral Kanawha River. The Teays was comparable in size to the Ohio River. The River's headwaters were near Blowing Rock, North Carolina; it then flowed through Virginia, West Virginia, Ohio, Indiana and Illinois.. The largest tributary to the Teays River was the Old Kentucky River, which extended from southern Kentucky through Frankfort and subsequently flowed northeast, meeting other tributaries and eventually joining the Teays.

Western Pennsylvania Place in Pennsylvania, United States

Western Pennsylvania is a region in the U.S. state of Pennsylvania, covering the western third of the state. Pittsburgh is the region's principal city, with a metropolitan area population of about 2.4 million people, and serves as its economic and cultural center. Erie, Altoona, and Johnstown are its other metropolitan centers. As of the 2010 census, Western Pennsylvania's total population is nearly 4 million.

The Maumee Torrent, also known as the Maumee Megaflood, was a catastrophic draining of Lake Maumee, the ancestor of present-day Lake Erie, that occurred approximately 14,000 to 17,000 years ago during the late Wisconsin glaciation. It happened when the waters of Lake Maumee, possibly in response to an advance of the ice front at the eastern end of the lake, overtopped a "sag" or low spot in the Fort Wayne Moraine, which was a deposit of glacial debris that acted as a natural dam at the site of present-day Fort Wayne, Indiana. This unleashed a massive flow of water that scoured a one- to two-mile-wide outlet running southwest to the Wabash River known as the "Wabash-Erie Channel", which probably followed the course of earlier, less massive drainage. The channel, now a small stream called the Little River, is the largest topographical feature in Allen County, Indiana. As much as 30 feet of fine sand, silt and organic sediments were deposited in the channel before drainage reversed and was captured by the present-day Maumee River. U.S. Route 24 between Fort Wayne and Huntington follows the channel.

Transportation in Pittsburgh Overview of transportation in Pittsburgh, Penssylvania, United States

Pittsburgh, surrounded by rivers and hills, has a unique transportation infrastructure that includes roads, tunnels, bridges, railroads, inclines, bike paths, and stairways.

Lacustrine plain Lakes filled by sediment

A lacustrine plain or lake plain is a plain formed due to the past existence of a lake and its accompanying sediment accumulation. Lacustrine plains can be formed through one of three major mechanisms: glacial drainage, differential uplift, and inland lake creation and drainage. Lake plains can have various uses depending on where and how they form.

Geography of Pennsylvania

The geography of Pennsylvania varies from sea level marine estuary to mountainous plateau. It's significant for its natural resources and ports, and is notable for its role in the history of the United States.

Lake Tight

Lake Tight, named for geologist William G. Tight, was a glacial lake in what is present-day Ohio, Kentucky, and West Virginia, during the Ice Age the early Pleistocene before 700 ka.

Glacial history of Minnesota

The 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 a profound effect on the surface features of the area over which it moved. Vast quantities of rock and soil were scraped from the glacial centers to its margins by slowly moving ice and redeposited as drift or till. Much of this drift was dumped into old preglacial river valleys, while some of it was heaped into belts of hills at the margin of the glacier. The chief result of glaciation has been the modification of the preglacial topography by the deposition of drift over the countryside. However, continental glaciers possess great power of erosion and may actually modify the preglacial land surface by scouring and abrading rather than by the deposition of the drift.

Geology of Pennsylvania Overview of the geology of the U.S. state of Pennsylvania

The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and plays an important role in shaping everyday life in the state. They are: the Atlantic Coastal Plain Province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachian Plateau Province, and the Central Lowlands Province.

Kankakee Outwash Plain

The Kankakee Outwash Plain is a flat plain interspersed with sand dunes in the Kankakee River valley in northwestern Indiana and northeastern Illinois of the United States. It is just south of the Valparaiso Moraine and was formed during the Wisconsin Glaciation. As the glacier, stopped at the Valparaiso Moraine, melted, the meltwater was carried away to the outwash plain. On the south side of the moraine, where the elevation drops, the meltwaters eroded away valleys, carrying sand and mud with them. As the muddy meltwater reached the valley where the slope lessened, the water slowed, depositing the sand on the outwash plain. This created a smooth, flat, and sandy plain. Before its draining, the Kankakee Marsh, located on the outwash plain, was one of the largest freshwater marshes in the United States.

The Prehistory of West Virginia spans ancient times until the arrival of Europeans in the early 17th century. Hunters ventured into West Virginia's mountain valleys and made temporary camp villages since the Archaic period in the Americas. Many ancient human-made earthen mounds from various mound builder cultures survive, especially in the areas of Moundsville, South Charleston, and Romney. The artifacts uncovered in these areas give evidence of a village society with a tribal trade system culture that included limited cold worked copper. As of 2009, over 12,500 archaeological sites have been documented in West Virginia.

Lake Kankakee

Lake Kankakee formed 14,000 years before present (YBP) in the valley of the Kankakee River. It developed from the outwash of the Michigan Lobe, Saginaw Lobe, and the Huron-Erie Lobe of the Wisconsin glaciation. These three ice sheets formed a basin across Northwestern Indiana. It was a time when the glaciers were receding, but had stopped for a thousand years in these locations. The lake drained about 13,000 YBP, until reaching the level of the Momence Ledge. The outcropping of limestone created an artificial base level, holding water throughout the upper basin, creating the Grand Kankakee Marsh.

Erie Plain

The Erie Plain is a lacustrine plain that borders Lake Erie in North America. From Buffalo, New York, to Cleveland, Ohio, it is quite narrow, but broadens considerably from Cleveland around Lake Erie to Southern Ontario, where it forms most of the Ontario peninsula. The Erie Plain was used in the United States as a natural gateway to the North American interior, and in both the United States and Canada the plain is heavily populated and provides very fertile agricultural land.

Blair Gap

Blair Gap, one of the gaps of the Allegheny is a water gap along the eastern face atop the Allegheny Ridge or Allegheny Front escarpment. Like other 'gaps of the Allegheny' the slopes of Blair Gap were amenable to foot travel, pack mules, and possibly wagons allowing Amerindians, and then, after about 1778-1780 settlers, to travel west into the relatively depopulated Ohio Country decades before the railroads were born and tied the country together with steel. Historically, the gap was used for the upper sections of the Allegheny Portage Railroad, which as was authorized by the enabling acts in 1824 of Pennsylvania's Main Line of Public Works as part of the Pennsylvania Canal System which originally envisioned linking Pittsburgh to Philadelphia by canals. In the early 1900s, US Route 22 followed alongside the watercourse through the gap.

Gaps of the Allegheny

The gaps of the Allegheny, meaning gaps in the Allegheny Ridge in west-central Pennsylvania, is a series of escarpment eroding water gaps along the saddle between two higher barrier ridge-lines in the eastern face atop the Allegheny Ridge or Allegheny Front escarpment. The front extends south through Western Maryland and forms much of the border between Virginia and West Virginia, in part explaining the difference in cultures between those two post-Civil War states. While not totally impenetrable to daring and energetic travelers on foot, passing the front outside of the water gaps with even sure footed mules was nearly impossible without navigating terrain where climbing was necessary on slopes even burros would find extremely difficult.

Portage Escarpment

The Portage Escarpment is a major landform in the U.S. states of Ohio, Pennsylvania, and New York which marks the boundary between the Till Plains to the north and west and the Appalachian Plateau to the east and south. The escarpment is the defining geological feature of New York's Finger Lakes region. Its proximity to Lake Erie creates a narrow but easily traveled route between upstate New York and the Midwest. Extensive industrial and residential development occurred along this route.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 Lake Monongahela: Anatomy of an Immense Ice Age Pond; John A. Harper; Bureau of Topographic and Geologic Survey; 1997
  2. 1 2 3 4 5 Blake Jr., Bascombe M. "Lake Monongahela." e-WV: The West Virginia Encyclopedia. 07 October 2010. Web. 07 July 2014