Back in high school, I read a lot of Isaac Asimov essays. In one of them, he mentions that the Mississippi is considered to flow from Minnesota to New Orleans simply as a historical accident. When explorers traveled west, they found the mouth of the Mississippi first, and thought the Missouri river was just a tributary.
However, as it turns out, the Missouri is huge. Most rivers are defined by their longest route, and if one were to assign labels from scratch based on the maps we have today, the river would be defined to flow from Montana to New Orleans, with the part of the Mississippi north of St. Louis being considered a tributary. Under that definition, Asimov said, the Missouri-Mississippi river would be considered the longest in the world, beating out the Nile by several hundred miles. (I think the name of the essay was something like “The longest river in the world has no name”, but it’s been over a decade, so I’m not too sure of that.)
Is this true? Is the Nile considered the longest river in the world based simply on the arbitrary technicality of labels?
Since I was just looking at rivers while being corrected in another thread …
Most lists will still show the Nile longer. Of course, if you play the same game with tributaries of other rivers, you can make the Amazon and its tributaries the longest, as in the list wiki provides:
Note that that list has the Mississippi-Missouri-Jefferson in 4th place. Following the rule of a river’s source being it’s furthest tributary, they are adding the Kagera to the Nile (fair is fair), giving it about another 250 miles.
BTW, if you follow the “main stem by volume”, the source of the Mississippi is in Potter County, PA. At Cairo, Ill, the Ohio is far larger than the upper Mississippi, and it’s hard to look at a map or an aerial photograph, and argue that it isn’t the main river, with the upper Mississippi being the tributary. The main stem by volume is “Mississippi - Ohio - Allegheny”. The Allegheny arises from a spring in some farmer’s field up in northern PA.
Are there formal rules? Or is it pretty much a matter of tradition?
A “main stem by volume” rule makes pretty good sense. One might also argue by the angle of interception: if one river clearly bumps into the side of another, the “straight through” river is the main branch, and the one that “comes to an end” is the tributary. This doesn’t help much when rivers meet in a “Y” confluence.
If you want a good laugh, come and see the San Diego River. I stepped over it just yesterday.
Awesome, thanks. So, he was right to an extent, the Missouri-Mississippi system IS longer than the Nile, but you can play the same game with the Nile itself and it beats the M-M system. And the Amazon is longer still.
Do schools still teach that the Nile, Amazon and Mississippi are numbers 1, 2, and 3? Because that seems to leave out the actual geologically relevant information.
The “T junction rule” would be another reason to consider the Ohio the main branch at Cairo. A sensible way to handle the “Y” branches is to give them each a new name, letting them join to form a new river, like the Allegheny and Monongahela joining to form the Ohio at Pittsburgh. In that case, the two rivers appear about equal sized, though the Allegheny turns out to have the greater volume when you measure them.
But, yeah, traditional river names make these lists hard to agree on.
Well, looking at that list, I see that subtracting 250 miles from the Nile-Kagera still leaves you longer than the Mississippi-Missouri-Jefferson. What WOULD be shorter would be the Nile using the Blue Nile as the source, rather than the White Nile. The Blue Nile is the larger volume branch, but much shorter.
FWIW I recall either being taught, or reading, when I was a kid in 1960s or 70s England that the Mississippi-Missouri was indeed the longest river in the world (with the Nile as runner up). I am pretty sure I saw this in more than one place, and, as it was in Britain, it does not seem likely to have been the product (directly, anyway) of U.S. jingoism. I did always feel that it was a bit of a cheat, however. Clearly, where they join, the Missouri is a tributary, having much less volume and flowing in from the side, almost at a right angle. (The lion’s share of the suspended mud comes from the Missouri though, I believe.)
They are close enough that more careful measurement in later years could have changed the ranking, too. Then again, we can tack on the Red Rock, and stretch things for a few more miles.
I think the modern definition is the main branch is the one that drains the most area. I remember asking this quaetion after watch a “find the source of the Nile” movie.
Of course, the drainage basin definition would also make the Missouri the main branch. But that seems kind of an odd criterion, since that means that other, completely unconnected, rivers springing up or drying out could change which of two branches is main.
It’s well established that the world’s longest river is either Nile or Amazon. Similarly, the world’s third longest river is either Yangtze or Mississippi. These are all measurements of maximum length between the source of the farthest tributary and the river’s mouth, meaning that even the Mississippi-Missouri system only places fourth or possibly third longest.
I have the feeling you’re mixing up two Asimov essays. In one, he complains that the longest river in North America has no real name, but the made-up combination “Missouri-Mississippi”.
In another, he’s talking about the Amazon river, and shows that it can be considered the longest in the world if you consider all its tributaries.
At least, that’s what I recall. I’d have to do a lot of digging through my old Asimov books to be sure.
BTW, if you really want to follow out the furthest tributary source of the Mississippi, the system becomes “Mississippi - Missouri - Jefferson - Beaverhead - Red Rock - Hell Roaring”. Hell Roaring Creek begins up by the Continental Divide near the ID / MT border. The ultimate source of the Missouri is held to be Brower’s Spring: