These web pages contain a brief listing (with pictures) of multiple world locations where river systems cut through mountain ranges instead of taking easier routes around them. The processes that produce river systems that cut through mountain ranges require millions of years of geologic history. As such, they are evidence that the Earth we live on as been around for many millions (actually billions) of years.


   The picture above shows the Delaware Water Gap. There is more information about it in the “Ancestral Rivers of the Eastern United States” section. All pictures on this page (and the linked pages) were generated by either Delorme’s Topo USA computer program or by Google Earth.

   There are multiple areas throughout the world where river systems cut through mountain ranges instead of taking easier routes around them. These apparently “illogical” river paths are actually records of earlier ages when these rivers established their paths along expected downhill routes. Subsequent geologic forces changed the shape of the landscape, but these rivers had enough erosion power to maintain their original paths.



   There are two geological principles governing the processes involved. The most common is “antecedence”. In antecedence, the river involved was in place first. Subsequently the mountain range rose, but the river played the part of a stationary band saw. The river stayed put, but it cut a groove into the rising mountain range. The more familiar name for a “groove” is a “canyon”.

   When a land area is uplifted above sea level, river drainage systems will develop to carry excess rainfall back to the ocean. These rivers will occupy the lowest areas available. Subsequent tectonic forces may start building a mountain range across the path of the river. If the river can not erode down fast enough, the rising mountain range will act as a dam, and the river will seek out the next easiest alternative for a new course. On the other hand, if the river can erode down as fast as the new mountain range rises, it will dig a canyon through the rising mountain range.

   We look at this process and frequently (falsely) imagine that in the past the river was at the same elevation as the current high elevations of the mountain range. We then wonder how and why the surrounding lower terrain could have supported a river at this elevation. In fact an easier process is at work. Quite frequently the lower surrounding terrain is a reasonable approximation of the ancestral elevation of the river. After the river established its ancestral course, the mountain range rose. The river played the part of a stationary band saw. It cut a groove into the rising block of land.




   The other process that can cause rivers to cut through mountain ranges is superimposition. Here, the mountain range was in place first. Over many millions of years erosion will erode a mountain range down to mere stubs. Also, nearby rivers may drop some of their sediment to fill in adjacent lowlands. Eventually, you end up with a flat surface. If mountain building (or just subtle changes in the tilt of the land surface) causes rivers to relocate to new positions on this flat surface, it is quite possible one of these new river channels may end up directly over the ancient beveled mountain range.

   Subsequently, if there is a general uplift of all the surrounding terrain or if a lower exit elevation for the area should develop, erosion will set in. The newer, softer sediments that helped bury the stubs of the old mountain range will be easily eroded away. The remnants of the old mountains will have harder rock and will tend to resist erosion. Thus the old stubs will reemerge as surrounding areas erode away. However, the river may remain “stuck in its rut” and simply erode down into the old mountain range.


   Split Mountain, Utah is an example of superimposition. You can read about its history at “Canyon of Lodore, Colorado   and Split Mountain, Utah”. http://www.durangobill.com/Lodore.html




   The following pages link to specific areas of the world where examples of these processes can be seen. Some are low elevations that tend to be overlooked. Others are in areas where you would think it would be impossible for a river system to cut through a high mountain range. This includes the highest range of all - the Himalayas. Who would think that a current river could cut north to south across the Himalayas just 28 miles east of Mt. Everest. Thanks to Google Earth, there is a picture of exactly this phenomenon on the “Asia” page.

Ancestral Rivers in the Eastern United States

Ancestral Rivers in the Colorado River Basin

Ancestral Rivers in other areas of the Western United States

Ancestral Rivers in Mexico, Western Canada, and Alaska

Ancestral Rivers in South America

Ancestral Rivers in Europe

Ancestral Rivers in Asia

Ancestral Rivers in Africa

Ancestral Rivers in Australia and New Zealand




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