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Louisiana - At a Glance
Louisiana, shaped like a boot with the toe pointed eastward, is bounded on the north by Arkansas, on the east by Mississippi, on the west by Texas, and on the south by the Gulf of Mexico. Somewhat larger than New York State, Louisiana has an area of 48,114 square miles, of which 3,593 square miles are covered by water. Geology Geologically, Louisiana is "new." Much of it consists of marine and alluvial sediments deposited after the principal structural features of surrounding regions had assumed their final form. There are 11 interior salt domes in north Louisiana and not less than 100 salt domes in the coastal area. Salt domes, or plugs, are an important element in the origin of the south Louisiana oil fields. Features of the state include pine hills, bluffs, prairies, coastal marshes and alluvial plains. Rolling hill country, planted with longleaf and shortleaf pine commercial forests, is found in each of the upland regions. Ranging in elevation from 100 to 300 feet in the southernmost uplands, the hills rise to a maximum of a little more than 400 feet near the Arkansas boundary. Two high points west of the Mississippi rise above 440 feet in the north central area of the state. The uplands slope gently toward the coast, the average incline being about two feet to the mile. Except in the delta, the shoreline of southern Louisiana is generally sandy; there are numerous sand and shell ridges extending for miles parallel to the shore either in close proximity to the Gulf or some distance inland. Mississippi River The Mississippi River snakes south through the continental United States from its source at Lake Itasca in northern Minnesota, entering the Gulf of Mexico through a vast, fan-shaped delta in Louisiana. The river travels for approximately 2,350 miles through a great basin, draining 41 percent of the United States - all or part of 31 states - and three Canadian provinces for a total of 1,245 million square miles. Waters from as far east as the state of New York and as far west as Montana contribute to flows in the lower river. The Mississippi River has the fourth largest drainage basin in the world, exceeded in size only by the watershed of the Amazon, Congo and Nile rivers. The average flow on the Mississippi downstream is approximately 4.3 million gallons per second. This great river, the third longest in the world, has enormous geologic impact upon the land through which it flows. The existing Louisiana shoreline is the result of the deposition of Mississippi River sediments over a period of approximately 6,000 years, and of the action on those soil deposits by the waters of the Gulf of Mexico. Behind chenieres and islands on the Louisiana gulf coast and extending from 10 to 60 miles inland are 6.5 million acres of wetlands, or 40 percent of the nation's marsh ecosystem. Some delta building continues in Louisiana today. The Atchafalaya River is the Mississippi's major tributary and carries a tremendous load of silt. Much of this silt is being deposited at the mouth of the river and a new land mass is gradually taking form in northern Atchafalaya Bay. Eventually, as natural levees and interior marsh develops, the delta will take on the physical appearance of the active delta at the mouth of the Mississippi River. Scientists have estimated that the new delta will contain approximately 192,000 acres and will extend out beyond Point au Fer Island by the year 2020. "Mud lumps" are small mud islands unique to the mouths of the Mississippi River passes. They range up to 12 feet in height and vary in diameter from a few square feet to 20 acres. They are produced by geological processes occurring at river mouths and consist of mostly sediments of sandy silts and clay.
Fifth largest sea in the world, with a surface area of 582,100 square miles and an average depth of 5,297 feet, the Gulf supplies Louisiana with seafood and recreational opportunities. The Gulf collects about two-thirds of all waste material discharged into U.S. rivers. Rivers and Bayous The most important rivers in the state are the Mississippi, Red, Atchafalaya, Ouachita, Sabine and Pearl. A peculiar feature of the many streams is that they run upon a higher elevation than their floodplains. This is especially true of the Mississippi, which meanders through Louisiana between ridges build up by successive depositions of silt. The river is of little value, therefore, as a drainage channel for the state. Were it not for a continuous line of levees, one-third of the state would be flooded by the Mississippi during high water periods. The largest bayous are the Teche, Lafourche and Bouef. Lakes Louisiana has more than 150 natural lakes as well as the nation's fourth-largest man-made lake, Toledo Bend Reservoir, which sprawls 70 miles along the Louisiana-Texas border northwest of Leesville. The reservoir covers 186,000 acres and has 1,200 miles of shoreline.
Climate The weather in the coastal region is diverse. The moody Gulf of Mexico is the state's weather-maker and gives Louisiana its semi-humid subtropical climate. Most of Louisiana is humid and subtropical. Snow rarely falls in the southern sections, with only small snowfalls usually recorded in the northern areas. The statewide annual rainfall is about 56 inches a year, with the northern regions averaging 46 inches and some of the southern coastal parishes averaging as high as 66 inches of rainfall a year. The average annual temperature for the northern regions of Louisiana is 66 degrees, while 60 degrees is the annual temperature in the southern region. The highest July average temperature in the northern regions is 83 degrees, while in east central Louisiana - the "Florida parishes" - the highest July average is 81 degrees. The lowest January average temperature in the north is 49 degrees, while in the southeast region, the lowest January average temperature is 57 degrees. The average number of days each year with temperatures 90 degrees and above is 102 days in the northern regions, 86 days in the southwestern area and 57 days in New Orleans. Colleges/Universities
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Location
Gulf of Mexico
Three classes of natural lakes occur in Louisiana. Coastal lagoons are arms of the sea isolated behind barrier beaches or surrounded by delta ridges. They are found in the delta region of the state. Barataria Bay and lakes Pontchartrain, Maurepas and Salvador are typical.
Oxbow lakes result from cut-off segments of the Mississippi River mainly above Baton Rouge to the Arkansas border, usually in the shape of a crescent and as wide as the river from which they were cut off.
