• divide
    The Great Divide separates the drainage basins of North America between the Pacific Ocean (west) and the Arctic Ocean, Hudson Bay, Atlantic Ocean, and the Gulf of Mexico (east).

    Map courtesy National Geographic Society

    Fitzcarraldo
    The 1982 German movie Fitzcarraldo tells the story of a man who crosses a minor divide of the Amazon River by having a 340-ton steamship hauled across a mountain. Fitzcarraldo is based on a true story. However, the real Fitzcarraldo did not have the entire ship dragged up and down the mountain. He had the ship taken apart, carried across the mountain piece by piece, and re-assembled on the other side.

    A divide is the elevated boundary separating areas that are drained by different river systems. For this reason, the feature is often called a drainage divide. Water flowing on one side of a divide empties into one body of water, while water flowing on the other side empties into another. 
     
    Divides range in height from a slight rise in the land to the crest of a mountain range. A divide on the low-lying flood plains of northern Belgium, for example, may rise no higher than a few meters. At the other extreme, the Andes—one of the longest mountain ranges in the world—form a divide in South America. A mountain range that forms a divide is called a dividing range.
     
    There are three major types of divides: continental divides, major divides, and minor divides.
     
    Continental Divides
     
    A divide that separates different watersheds of a continent is called a continental divide. Because a continent may have more than two watersheds, a continent may have more than one continental divide. 
     
    North America, for instance, has about five continental divides. These continental divides separate the drainage systems leading to the Pacific Ocean, Arctic Ocean, Atlantic Ocean, Hudson Bay, and Gulf of Mexico. The most familiar continental divide in North America separates the watersheds of the Pacific Ocean in the west and the Arctic Ocean, Hudson Bay, Atlantic Ocean, and the Gulf of Mexico in the east. The so-called Great Divide roughly follows the crest of the Rocky Mountains.
     
    Major Divides
     
    A major divide forms when two rivers flow into the same body of water but do not meet. A major divide can be large or small. The watersheds of China’s Yellow and Yangtze Rivers form a major divide, for example. The Yellow River forms a watershed in China’s north. It empties into the Bohai Sea, part of the Pacific Ocean. The Yangtze River forms a watershed south of the divide, emptying into the East China Sea. Although the Yellow and Yangtze Rivers never meet, they both flow into the Pacific Ocean. 
     
    A major divide that separates smaller watersheds can be found in the West African country of Ghana. All rivers in Ghana ultimately flow into the Gulf of Guinea in the Atlantic Ocean. The Volta River system drains about two-thirds of the country’s waterways. However, there are a number of smaller rivers, such as the Ankobra and Tano Rivers, that are not tributaries of the Volta. They flow independently into the Gulf of Guinea. 
     
    Minor Divides
     
    A minor divide separates rivers that will later converge, or form a confluence. Most river systems have minor divides.
     
    North America's Missouri and Mississippi Rivers form a minor divide. The Missouri River's watershed extends as far north as the Canadian provinces of Alberta and Saskatchewan, and as far south as the U.S. state of Missouri. However, the Missouri is a tributary of the Mississippi River. The waters of the Missouri meet the Mississippi near Hartford, Illinois, and ultimately flow to the Gulf of Mexico. 
     
    Navigating Divides
     
    Minor divides are not huge obstacles to navigation. Engineers on ships can usually navigate across a minor divide—the watersheds ultimately flow together.
     
    Major divides and continental divides, however, can be very difficult to navigate. Natural features can sometimes help explorers navigate major divides. The Chicago Portage, for instance, is a natural water gap formed through glaciation—the same process that created the Great Lakes. The Chicago Portage links the watersheds of the Great Lakes and the Gulf of Mexico, and is the key reason the city of Chicago became such an important shipping and industrial hub.
     
    Water gaps such as the Chicago Portage are rare, however. In most cases, engineers and geographers must rely on both watercraft and terrestrial transportation to navigate divides.
     
    Before the Industrial Revolution, explorers had to portage between major divides. To portage is to carry boats or other vessels across dry land. For large ships, portaging can be a long, difficult, and expensive journey. Smaller watercraft, such as canoes, are easier to portage than large ships. For this reason, Native Americans were more skillful at portaging around the rivers of North America than European explorers, who brought large, heavy sailing vessels.
     
    The Industrial Revolution changed the way sailors navigated. Engineers constructed dams and canals between divides. River management techniques controlled the amount of water flowing through parts of a river, and portaging became less necessary. 
     
    The canals of the St. Lawrence Seaway are an example of industrial technology crossing a major divide. The canals make it possible for ships from the Atlantic Ocean to cross the divide separating the ocean from the watershed of the Great Lakes. Ships can efficiently transport both finished goods, such as shoes or cars, and raw materials, such as timber and iron, between the Great Lakes region and the rest of the world.
  • Term Part of Speech Definition Encyclopedic Entry
    boundary Noun

    line separating geographical areas.

    Encyclopedic Entry: boundary
    canal Noun

    artificial waterway.

    canoe noun, verb

    small, open boat with pointed ends.

    confluence Noun

    place where two rivers join and flow together.

    continent Noun

    one of the seven main land masses on Earth.

    Encyclopedic Entry: continent
    continental divide Noun

    point or area that separates which directions a continent's river systems flow.

    Encyclopedic Entry: continental divide
    converge Verb

    to meet or come together.

    crest Noun

    the top of a wave.

    dam Noun

    structure built across a river or other waterway to control the flow of water.

    divide Noun

    a ridge between two drainage systems.

    Encyclopedic Entry: divide
    efficient Adjective

    performing a task with skill and minimal waste.

    elevate Verb

    to raise higher than the surrounding area.

    engineer Noun

    person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

    finished good Noun

    item assembled and ready for sale.

    flood plain Noun

    flat area alongside a stream or river that is subject to flooding.

    Encyclopedic Entry: flood plain
    glaciation Noun

    process of a glacier carving out a landscape.

    Great Divide Noun

    continental divide in North America separating rivers that flow into the Pacific Ocean and rivers that flow into the Atlantic Ocean. Also called the Continental Divide of the Americas.

    Great Lakes Noun

    largest freshwater bodies in the world, located in the United States and Canada. Lake Huron, Lake Ontario, Lake Michigan, Lake Erie, and Lake Superior make up the Great Lakes.

    gulf Noun

    portion of an ocean or sea that penetrates land.

    Encyclopedic Entry: gulf
    hub Noun

    center.

    industrial Adjective

    having to do with factories or mechanical production.

    Industrial Revolution Noun

    change in economic and social activities, beginning in the 18th century, brought by the replacement of hand tools with machinery and mass production.

    iron Noun

    chemical element with the symbol Fe.

    major divide Noun

    line separating watersheds that never merge, but empty into the same body of water.

    minor divide Noun

    line separating watersheds that will later converge.

    mountain range Noun

    series or chain of mountains that are close together.

    navigate Verb

    to plan and direct the course of a journey.

    obstacle Noun

    something that slows or stops progress.

    portage Verb

    to carry boats or other watercraft across dry land, between bodies of water.

    province Noun

    division of a country larger than a town or county.

    Encyclopedic Entry: province
    raw material Noun

    matter that needs to be processed into a product to use or sell.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    river management Noun

    the art and science of controlling the flow, path, and power of rivers.

    river system Noun

    tributaries, mouth, source, delta, and flood plain of a river.

    sailor Noun

    person who works aboard a ship.

    shipping Noun

    transportation of goods, usually by large boat.

    St. Lawrence Seaway Noun

    series of canals, locks, and channels, including the St. Lawrence River, that allows ships to travel from the Atlantic Ocean to the Great Lakes.

    technology Noun

    the science of using tools and complex machines to make human life easier or more profitable.

    terrestrial Adjective

    having to do with the Earth or dry land.

    timber Noun

    wood in an unfinished form, either trees or logs.

    transportation Noun

    movement of people or goods from one place to another.

    tributary Noun

    stream that feeds, or flows, into a larger stream.

    Encyclopedic Entry: tributary
    vessel Noun

    craft for traveling on water, usually larger than a rowboat or skiff.

    watercraft Noun

    transportation vessel, such as a boat, for a body of water.

    water gap Noun

    small opening where flowing water has carved through a mountain range.

    watershed Noun

    entire river system or an area drained by a river and its tributaries.

    Encyclopedic Entry: watershed
    waterway Noun

    body of water that serves as a route for transportation.

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