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Natural Land Regions

Coastal Marshes Created when sediment collected at the mouths of rivers as they entered the Gulf Low wet grassland; usually no trees Exception: Cheniers: ridges of high ground in the marsh that run parallel to the coastline; live oak trees grow here Saltwater, freshwater, or brackish

Floodplains Low, flat valleys through which rivers flow Include: Swamps, sloughs, bayous, and lakes Vegetation: Deciduous trees (Cypress, Oak, Hickory, Pecan, Magnolia, Tupelo Gum, and Cottonwood) sugarcane

Uplands Areas with the highest elevation Formed when magma pressure and tectonic forces pushed the land upward Erosion then washed away soft material, leaving the hills Vegetation: Some deciduous trees; Dominated by coniferous trees Coniferous: evergreen, cone-bearing trees or shrubs Contain ancient terraces (often called hills)created by rivers

Sketch Louisiana landforms

Examples of Uplands Largest upland area – Piney Hills Piney Hills is the V-shaped region in the northern part of the state that includes Driskill Mountain (rises 535 feet above sea level) Uplands: Kisatchie National Forest, Dolet Hills, Florida Parishes

Uplands

Did you know Louisiana once had Prairies? Prairies: wide flat areas where short grasses flourish, but few trees appear Common in southwest Louisiana Large herds of Buffalo used to roam Agriculture and urban development destroyed most of the natural prairies and animal life that once existed

Awesome Power of Rivers Rivers’ sediment creates the land, and their movement shapes it Louisiana Landforms: Floodplains, Meandering Streams, Point Bars, Natural Levees, Terraces, Deltas, Coastal Marshes, Barrier Islands, Cheniers

1. Floodplains Floodplain: flat valley floor covered by excess water caused by heavy rains that spills over the riverbanks Reservoir: holds excess water

2. Meandering Streams Meandering Streams: winds its way back and forth across the floodplain in loops and curves; Water always seeks the path of least resistance and goes around obstacles

3. Point Bars Point Bar: formed from sediment falling to the bottom of the river after the current slows along the inside of the meander Oxbow lake: The meander gets larger until it creates nearly a full circle around a narrow neck of land; the river eventually straightens itself out by cutting across the point bar. The ends of the old meander close up to form an oxbow lake.

Oxbow lake

4. Natural levees sediment builds along the riverbank forming strips of elevated land.

5. Terraces Terraces: elevated ridges that formed from the old riverbeds; 50-100 feet higher than the surrounding floodplain. Ex. Terrace: Macon Ridge: 100 miles long and 20 miles wide; Highland Road in Baton Rouge Loess: loamy wind-blown deposits rest on terraces; behaves like clay when wet; when the thick layer of loess eroded it left the region scarred with deep gullies and high bluffs; ex. Vicksburg, Mississippi

6. Deltas Deltas: a landform shaped like a fan or a bird’s foot where a river flows into the ocean; most famous delta is the Miss. River Delta Bar: underwater barrier of mud that interferes with the river’s current; process continues forming bird’s-foot shape.

7. Coastal Marshes Coastal Marshes: wet grasslands formed by river sediment deposited along the coast during floods Brackish: fresh and saltwater mixed together Louisiana has the largest marshland area in the U.S.

8. Barrier Islands Barrier Islands: created after a river abandons its delta; without fresh sediment to maintain it, the delta erodes away; sturdy bar that formed at the river’s mouth remains. Waves and tides deposit sand leaving a crescent shape island.

Barrier Islands Importance: 1) absorb storms; 2) protect the mainland from erosion; 3) block saltwater from entering the marsh during storms; 4) home to thousands of birds, turtles, fish, and shellfish

Before and After Katrina

9. Cheniers Cheniers: ridges of high ground in the coastal marsh that run paralles to the coastline; composed of shell and sand; remnants of Gulf of Mexico beaches; 4 to 5 feet high and several yards wide Example: Pecan Island and Holly Beach Chenier is French for “place of oaks”; live oaks thrive on them Significance of a chenier: people live on them because they do not flood; protect coastal marshes from hurricanes

Other Land Forms Rocks: All native rock in Louisiana is sedimentary rock; sediment compressed into rock Louisiana rock formed between 2 and 66 million years ago

Hills After Gulf Coastal Plain formed, geologic forces caused the land to push upward forming mountains which eroded away the forming hills

Salt Domes Reminders of the ancient sea that once covered Louisiana   Parts of the sea dried up leaving a layer of salt and other minerals exposed   Salt was covered by sediment and now lies about 10 miles below the ground The weight exerted so much downward pressure that in some places the salt squeezed upward like toothpaste in tall vertical columns called salt domes Louisiana has hundreds of salt domes

They appear as wooded hills about 2 miles in diameter   Example: Five Islands: Jefferson Island, Avery Island, Weeks Island, Cote Blanche, and Belle Isle     North Louisiana, salt domes do not protrude above the earth’s surface; salt appears as a white sandy crust    Salt mining is an important industry   Mine shafts are dug into salt domes and the hard rock-like salt is mined and brought to the surface for crushing   2nd largest salt mine in world is Belle Isle   Salt Domes were once used as storage for oil

Salt Dome Locations

Salt Dome

Salt Dome

Aquifers Aquifer: underground water reservoir As sediment deposits slowly build up the land, freshwater sometimes becomes trapped between two layers of sediment. Water Table: depth in the ground at which water is located We are now drawing out more water that is being replaced by nature. North Louisiana is facing a problem of the falling water table of the Sparta Aquifer

Sparta Aquifer

Avery Island Salt Dome