Crosslink to another post with interesting information: http://www.cartographersguild.com/sh...?t=7052&page=3
Juggernaut1981 talks about river behavior, deltas, and Australian sand rivers. Also, Gamerprinter brings up the topic of underground rivers.
Bryan Ray, visual effects artist
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The Great Lakes are rising
I learned something on a National Geographic show a few weeks ago that the Great Lakes are rising. At first no one was sure why, and a small science post on Lake Ontario proves the truth of the matter, that the Great Lakes have been rising an inch per year for the last 10,000 years.
Apparently, during the last Ice Age, 4 miles (?) of ice sat above what is now the Great Lakes. The tremendous weight of this ice actually pushed the crust downward hundreds of feet lower than lands south of the Great Lakes. Now that the ice is gone, the crust is still gradually "healing" itself and rising to eventually attain the proper elevation. Thus the Great Lakes are rising. Actually some of the Lakes are getting deeper, while the majority of them are getting shallower.
There's evidence of submerged forestland in about 40 feet of water beneath Lake Huron. This is where its getting deeper. There's a tilting effect caused by the crust rising to the north of it.
I hadn't previously heard of this phenomenon. I found it extremely fascinating and since we seem to be talking River Police (and lakes in the above post) issues lately. I thought I'd add this to the conversation.
GP
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That is pretty cool. I watched that History Channel show "How the Earth was Made: The Great Lakes" and never knew about the giant salt basin underneath of the lakes and how it is protected by a giant granite dome.
If the radiance of a thousand suns was to burst at once into the sky, that would be like the splendor of the Mighty One...I am become Death, the Shatterer of worlds.
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Seems about right. It's worth noting that when rivers do split up high in their courses it's most commonly due to stream capture—which takes a very short amount of time, geologically speaking. Probably the most notable example is the Casiquiare which links the Orinoco and Amazon basins. It was originally a separate river, but has currently migrated far enough to capture the upper Orinoco, which will eventually (ie in a few thousand years or so) drain entirely into the Casiquiare. A bifurcating river is possible, just unlikely. A map with lots of bifurcating rivers needs further explanation (eg the area is full of karstic terrain, the bifurcations are artificial etc)
Otherwise yeah... and I must say it's a relief to see a forum where mapmakers actually keep this in mind instead of just filling their maps with circular rivers and rivers flowing from one sea to another etc
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