Thursday, March 13, 2008

Some Mississippi Geography

[Updated 3/14, 3/17]
Not sure how to organize these blogs. I was going to just blog once a day but there are a few topics that cover the whole river. So, today I'll start the river geography post.

It has been fascinating watching the landscape change as I've driven down river.

From the source to St. Anthony Falls in Minneapolis, the river has what I'd call a very shallow valley. For example, if flows through a very flat sand plain between St. Cloud, MN and Minneapolis.After St. Anthony Falls, the river flows through what can best be described as a ravine to the junction with the Minnesota River right at the Minneapolis St. Paul Airport. It is between 50 and 100 feet deep and in places, at the base it is no wider than the river itself.

During the end of the last Ice age, the Minnesota River (call Glacial River Warren) carried a huge amount of water and carved a much wider valley.

For some reason (I may decide to research this some time in the future, starting at the downriver end of St. Paul there are some very tall, very steep bluffs along the river. South of Red Wing, Mn it is not uncommon to see vertical cliff faces of limestone.

It also looks like the rivers entering the Mississippi from the east (Wisconsin, Illinois)are significantly larger than the rivers entering from Minnesota and Iowa. From the east the St. Croix, Wisconsin, Chippewa, Illinois and Ohio rivers join the Mississippi. On the west side, the only big rivers seem to be the Minnesota and Des Moines.The river valley slowly widens as you drive into Iowa. At Clinton Iowa, the bluffs disappear abruptly. From there South [I'll fill in where it ends when I get there], The river runs in a rather wide valley. Bot the valley ends at some rather steep hills. On top of the hills it's rolling plains.

South of Hannibal the limestone bluffs returned. As I was driving down the Illinois side, the river was right next to the road on the right and the bluffs were next to the road on the left. It turns out that the valley was still just as wide. The river was just on the far east side of the valley (St. Louis on the other side of the river is in the river valley.

The river's current is much more noticeable after St. Louis. Above St. Louis, the Lock and Dam system creates 29 "pools." South of St. Louis there are no more dams and the river is free flowing. I would not want to be in that current in a small boat (e.g. smaller than a barge).

South of the Ohio River the valley flattens out. It is the aluvial plain of the Mississippi--thousands of years of flood have deposited all the mud it was carrying down from the north. Also south of the Ohio, the river seems much bigger and faster. (I couldn't get to Fort Defiance at the confluence of the Mississippi and Ohio--it was flooded.

Surprise--at about Vicksburg, hills--it is not flat. Took the last 40 miles of the Natchez trace to Natchez--a National Park Service Parkway from Nashville to Natchez that follows the historic trail.

[More to come as I see more]

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