This has bugged me for a few years. North of Triple Divide Peak in Glacier National Park (Montana), the continental divide is supposed to divide the Arctic drainage area from the Pacific drainage area. (There is another continental divde that divides Arctic from Atlantic, but we don’t need to get into that). The information I have is that the Chukchi Sea is an arm of the Arctic and that the Seward Peninsula (the peninsula that Nome is on) is the southern boundary of the Chukchi Sea. Therefore, if the world made sense, the continental divide should pass through the length of the peninsula and end at Cape Prince of Wales. (Cape Prince of Wales is the closest point on the North American mainland to Asia, incidentally). But instead, all the maps I have show the continental divide about 200 miles north of there, meething the Arctic Sea at either Cape Lisburne or Point Hope (hard to tell which from the maps).
Does anyone know why it’s done that way? Did somebody decide that’s where the Arctic starts and the Pacific ends? Is there an official government ruling?
At last, a geomorphology question! My college years didn’t totally go to waste.
(Well, by the time I got to the end of your question, it became apparent that this is really a matter of geography.)
The Divide is what it is. On one side, rivers flow to the Arctic Ocean, on the other side they flow to the Pacific. That, my friend, is objectively defined by the geomorphology, the “situation on the ground,” to coin a phrase. Water has to flow toward either one side or the other, and that’s it.
The “boundaries” of oceans are, however, defined by geographers, and there some human subjectivity can enter into it. They can consider ocean currents, biota, prevailing winds, or whatever to decide where one ocean leaves off and another begins. But I suspect that their main criterion is to look at the coastlines of the continents to see a narrow pinch-off point like the Bering Strait. This is just visually intuitive for anybody looking at a map. It doesn’t necessarily match up with the lay of the land in the interior.
So the answer to your question is that geomorphologists defining continental divides and geographers defining oceanic boundaries are using different criteria for different things.
Are there just two Continental Divides in the US? The reason I ask is that I’ve driven along highways in two completely different parts of the country that had signs marking the Eastern Continental Divide (somewhere in western MD or West Virginia – along I-68) and the Western Continental Divide (somewhere in New Mexico or Arizona – along I-10).
I understand the principle, now, of the continental divide, but is there a third one (Central C.D.?) that determines if the water drains into the Mississippi, or is the river itself a divide?
And, while I have you here, ishmintingas, is it generally true that rivers flow toward the equator?
which tells you that there are three main divides:
–Atlantic/Pacific,
–Atlantic/Arctic,
–Arctic/Pacific.
[quote]
I understand the principle, now, of the continental divide, but is there a third one (Central C.D.?) that determines if the water drains into the Mississippi, or is the river itself a divide?
[quote]
That’s a secondary divide, not a first-order divide that separates the watersheds of oceans. Both the Mississippi and the Potomac drain to the Atlantic, ultimately–it’s just that the Mississippi basin drains to the Gulf of Mexico instead of the eastern seaboard.
Huh? Where’d you get that from? The way I understand it, rivers flow toward the ocean. What’s the equator got to do with it? Consider the Nile, the Mackenzie, the Ob, the Yenisei, the Lena, to name a few major rivers. They all flow away from the Equator. The Amazon, the Rhine, the Huang He, the Columbia, the Colorado, the Ganges flow approximately east or west. The Congo and the Niger curve around a lot.
Yeah, Ishmintingas is right. Just a little more detail, though. The Brooks Range forms the Contintal divide in Alaska. Most of the rivers south of it flow to the Yukon and into the Bering Sea, though there are some that come out north of the Seward peninsula. It would be pointless to try and draw a line between these little streams and call it the Continental Divide, just to keep the people who name bodies of water happy. BTW, the continental divide is anchored at Mt. Hamlet, el. 2034 ft., about 20 miles SE of Cape Lisburne.
The so-called Eastern Continetal divide is just the crest of the Appalachian Chain. It’s not a real divide because it starts in North Georgia and extends to either the Hudson river or the Gaspe peninsula, depending on how you define it.
Rivers don’t generally flow toward the equator. There is no physical mechanism that would cause this. It’s just that in North America and southern Asia, most of them flow south.
seperates the watersheds of the Atlantic and the Gulf of Mexico respectively. Generally, the Gulf of Mexico watershed in the eastern U.S. is fed mostly by the Mississippi via the Ohio. That is to say, most of the river sources you find near the Eastern Continental Divide (generally, the ridge of the Appalachians) empty into the Ohio, with a few emptying into the Mississippi or the Gulf itself through other routes.
The Western Continental Divide seperates water that flows into the Pacific from that which flows into the Gulf of Mexico. I think it is safe to say that all rivers with their sources near the Western Continental Divide empty into the Gulf, and not the Atlantic directly.
If you consider the 4 main bodies of water around N. America to be the Gulf of Mexico, The Atlantic, The Pacific, and The Arctic, then there in theory exists a “Continental divide” occuring at the boundaries of the of any two watersheds of these bodies of water.
Hmmm… I’d have said that it swung west through central New York (south of the Finger Lakes draining into the Hudson via the Mohawk) and around the Great Lakes. The Great Lakes and their tributaries feed the Atlantic via the St. Lawrence while rivers throughout Ohio, Indiana, Illinois, Wisconsin, and Minnesota feed the Gulf via the Mississippi. (In fact, Chicago takes drinking water from Lake Michigan and pumps (presumably treated) waste water into the Michigan-Illinois Canal that flows to the Mississippi, so that the minor divide actually approaches to within two miles of Lake Michigan.)
Tom, I’d have to say that’s the most tortuous piece of logic to define something that doesn’t really exist in the first place I’ve ever heard, no offense but have you forgotten Occam’s razor? The Finger Lakes drain to the Mohawk, to the Hudson, to the Atlantic. The watershed of the Great Lakes in the U.S. is practically nonexistant except for the state of Michigan. Anywhere you go from Watertown to Duluth, you are just a few miles from a stream leading to either the Atlantic or the Gulf of Mexico. The Great Lakes are basically a huge depression in the middle of the continent draining to the Atlantic.
And just a few miles away, all the water drains to the Gulf. Is that not the definition we’re working on? Starting from the Appalachians (dividing Gulf from Atlantic), where does the line continue that divides Gulf water from Atlantic water? In central New York, it makes a left turn to encompass the Great Lakes. The Great Lakes basin is, as you note, narrowly circumscribed about the actual lakes, but there is no line alongside the Hudson or extending up to the Gaspé where the water will wander back to the Gulf.
This map gives you an idea of what drains directly into the Great Lakes. Actually the Finger Lakes originally (prior to the canal system) drained into Lake Ontario via the Oswego but since it’s all heading to the Atlantic why argue the point. Only a small sliver of southern and western NY is draining towards the Miss. via the Allegheny.
Tom, All we’re doing is beating a dead horse here. As I said in my first post on this subject, “The so-called Eastern Continetal divide is just the crest of the Appalachian Chain. It’s not a real divide because it starts in North Georgia and extends to either the Hudson river or the Gaspe peninsula, depending on how you define it.” It does not exist a a true geological feature. It is left over from the early days of the Republic when the states ceded their western lands to the Federal government, although no state borders currently follow the crest of the mountains. If we’re going to argue about water flowing to the Gulf instead of the Atlantic we’d better start arguing about where the Atlantic stops and the Arctic begins too. And while we’re at it, does this eastern divide extend all the way down the spine of Florida? If so, it goes right thru the Okefenokee swamp. Both the St. Mary’s and the Suwanee flow from the swamp; one eastward and one westward. Some divide!
A continental divide is fairly easy to define. If you put a drop of water into a river, into which of the 4 large bodies of water surrounding the North American landmass does that water end up? Continental divides are easiest to picture if they coincide with a large mointain range, but there is no altitude requirement to define a watershed. Since a Continental Divide is merely a boundary between watersheds, most of this seems moot. I will admit that the Great Lakes kind of foul things up, since some water from the great lakes DOES drain into the Gulf via the Mississippi(via the canalized Chicago river). But the vast majority of it DOES empty into the Atlantic via the St. Lawrence, and if we ignore the tiny amount drained the wrong way by man-made waterways, then the eastern continental divide does indeed run due east-west through southern ohio, bend northwest in Indiana, and loop around lakes Michigan and Superior. But I am not concerned by this…
I’m up for a game of Where does the Arctic become the Atlantic? (I’m less sanguine about wrangling over the Atlantic/Gulf-and-Caribbean divide, as I suspect that we could find lots more passages to dispute.)
Sorry if my above post made me sound like an idiot. I just didn’t know much about exactly what a continental divide was, much less how rivers flow. Thanks to all above (except for me, of course) for educating this member of the Teeming Millions!
I will say this: In northern Ohio, there are, in fact, signs on the road telling you when you cross the divide from Erie dranage to Ohio/Missourissippi drainage… I believe it’s labelled the “Ohio divide”. Someone somewhere must figure that this line has some significance!
