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The Mississippi River is the longest river in the United States, with a length of 2,320 miles (3,730 km) from its source in Lake Itasca in Minnesota to its mouth in the Gulf of Mexico.
The Mississippi River is part of the Missouri-Mississippi river system, which is the largest river system in North America and among the largest in the world: by length (3,900 miles (6,300 km)), it is the fourth longest, and by its average discharge of 572,000 cu ft/s (16,200 m³/s), it is the tenth largest.
The widest point of the Mississippi River is Lake Winnibigoshish, near Grand Rapids, Minnesota at over 7 miles (11 km) across.The Mississippi River runs through 10 states and was used to define portions of these states' borders.
The Mississippi River drains most of the area between the Rocky Mountains and the Appalachian Mountains, except for the areas drained to the Hudson Bay via the Red River of the North, by the St. Lawrence River and the Great Lakes, the Rio Grande (and numerous other rivers in Texas), the Alabama River-Tombigbee River, and the Chattahoochee River-Appalachicola River.
The Mississippi River empties into the Gulf of Mexico about 100 miles (160 km) downstream from New Orleans. Measurements of the length of the Mississippi from Lake Itasca to the Gulf of Mexico vary somewhat, but the United States Geological Survey's number is 2,340 miles (3,770 km). The retention time from Lake Itasca to the Gulf is about 90 days.
The Mississippi river discharges at an annual average rate of between 200 and 700 thousand cubic feet per second (7,000–20,000 m3/s).[10] Although it is the 5th largest river in the world by volume, this flow is a mere fraction of the output of the Amazon, which moves nearly 7 million cubic feet per second (200,000 m3/s) during wet seasons. On average the Mississippi has only 9% the flow of the Amazon River but is nearly twice that of the Columbia River and almost 6 times the volume of the Colorado River.
The Mississippi River downcut through the limestone bedrock forming the great bluffs that we now see. Across the floodplain, which is shared with the Missouri River, is another line of bluffs, also composed of limestone. The great breadth of the floodplain relative to the size of the Mississippi and Missouri Rivers is due to the large volume of glacial meltwater that flowed through this river valley in the waning stages of the Ice Age.
Draped across the top of the limestone bluffs is a blanket of wind-blown silt, called loess (pronounced "luss"), that is over 50 feet thick in places. In the waning days of the Ice Age, the meltwaters carried huge volumes of sediment from the melting glaciers. This sediment was deposited in the floodplain and became exposed in the winter when the meltwaters receded. Winter winds whipped up the exposed clay and silt from the floodplain and deposited them on the bluffs.
The Mississippi River, like all rivers, is in a constant state of change. Various forms of the Mississippi River have flowed through our area for more than a million years, but the Upper Mississippi River Valley as we know it was primarily shaped during the most recent glacial stage of the Great Ice Age, The Wisconsin period.
The Wisconsin glaciation period started about 75, 000 years ago and ended about 12,000 years ago when the North American climate began to warm. It was a world hardly recognizable today. Minnesota and Wisconsin were populated by a variety of very large animals called megafauna which lived in the cold climate on the margins of the glacial ice. Because larger animals lost body heat more slowly, bigger was indeed better.
Giant-sized animals including mastodons, mammoths and caribou roamed this area. Because of the north-south orientation of the river, many of our ancient fishes had merely moved south as the waters grew too cold, and then expanded back into the northern portion of the river as the glaciers retreated. Ancient fish that predate the glaciers and still live in the waters of the Upper Mississippi River include long-nosed and short-nosed gar, sturgeon and paddlefish.
Hickman County, in the Mississippi Embayment region, is a gently rolling area adjacent to the Mississippi River. Upland ridges and hills rarely attain elevations of 500 feet. The highest point, 510 feet, is on the divide between Obion and Sand Creeks about 2 1/2 miles south-southeast of Fulgham.
Local reliefs are moderate, generally about 50 feet. The bluffs along the Mississippi are 100 to 200 feet in height and are the sites of the greatest local relief in the county. The bluff at Columbus-Belmont State Park rises approximately 170 feet above the river, and Chalk Bluff is almost 200 feet high.
The lowest elevation is approximately 276 feet, the point where the Mississippi River leaves the county.
In Hickman County, water is obtained from unconsolidated sediments of the Tertiary and Quaternary ages. The oldest geologic formation exposed on the surface in Hickman County is the Tertiary Claiborne Formation. The Tertiary began 70 million years ago, and deposits consisted of marine and fresh to brackish-water sediments. The distribution of deposits indicates that the area was near the northern limit of the Gulf embayment (also called Mississippi Embayment). Portions of the embayment must have been swampy because thin beds of lignite (brown coal) and carbonaceous clays occur in the western half of the eight-county Jackson Purchase area. These geological deposits are a marked contrast to the underlying older hard rocks, because most of the Cretaceous and younger sediments remain unconsolidated and soft.Over the last one million years unconsolidated Quaternary sediments have been deposited along the larger streams and rivers.
To log Earthcache answer the following questions and do the following:
1. Standing at the coordinates facing the river, what historical area is to your right and up on top of the bluff?
2. How many states are visible from where you are standing?
3. Guess how far it is to the other side of the river, directly west.
E-mail me the answers to these prior questions.
4. Take a picture of yourself in front of the guage at the posted coordinates with the guage in the background. Post picture on the log.
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