Unit1 : Louisiana’s Physical and Cultural Geography
Louisiana’s Geologic History
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Geology is the study of____________________________________.
• Geologists look at______, __________ and land f______________ to
determine how each region of the earth was formed.
______________(Greek for all land) is the name of the supercontinent that geologists
believe connected all of the world’s landmass about ______ million years ago.
At the end of the_______________, Pangaea began to break apart in a process
known as continental drift.
An ancient Gulf of Mexico formed between North and South America, covering the
area that is now Louisiana.
During this time the mouth of the Mississippi River was located in modern
day_________________.
Gulf Coastal Plain
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Over millions of years, the Mississippi River deposited ______________into the Gulf
of Mexico and began to slowly fill part of it up.
When the river current__________, sediments settled to the bottom and created a
coastal plain, a relatively_____, _______ region built up by ___________________.
Louisiana is the only __________made up entirely by the______________________.
Louisiana and the Ice Age
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Most of the gulf coastal plain was made up during a time when Earth’s climate when
through long periods of ____________and_______________.
During Ice Ages, much of the world’s water was trapped in___________ ,
and_____________ were about________feet lower than they are today.
Louisiana’s coastline extended all the way out to the _____________________(the
edge of landmass where the Gulf ’s floor drops into very deep water.)
The Power of Rivers
Floodplains
• When rainfall brings more water than a river can__________, excess water spills over
the_______________ and covers the flat valley floor.
• This area is a ________________and serves as a __________until the river can move
the water into the Gulf
Unit1 : Louisiana’s Physical and Cultural Geography
Mississippi River Floodplain
Meandering Streams
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Because water always seeks the path of_________________, Louisiana’s rivers
meander or wind in ________and ___________.
When water flow encounters an obstacle the current will bounce to the opposite
riverbank and begin to __________it. This forms a curve that allows water flow to
return to the other bank.
Point Bars
• When the current slows along the inside of a_________, the sediment falls to
the ___________of the river creating a_____________.
• The meander gets ________until it creates nearly a________________.
• Because water seeks the path of least resistance, the river eventually
_______________ itself out by cutting across the point bar.
Point Bars and Oxbow Lakes
Natural Levees
• Natural Levees are created when a river overflows its banks and spills onto the
floodplain.
• Most of the sediment settles along the riverbank, and as the bank builds up
higher and higher, it angles away from the river toward the floodplain.
• This process raises the riverbed, and it eventually become higher than the
floodplain around it.
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Unit1 : Louisiana’s Physical and Cultural Geography
Terraces
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Over time, the floodplains surrounding the Mississippi River eroded leaving old
river beds as elevated ridges known as terraces.
Most terraces are 50-100 ft. higher than the surrounding floodplain.
Macon Ridge and Highland Road are examples of terraces.
Deltas
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Deltas occur when a river flows into an ocean.
Sediment settles on the ocean floor in a fan-shaped pattern. When water is
shallow, new land is built up.
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A bar is a barrier of mud (also made of river sediment) that interferes with a
river’s current.
Following the path of least resistance, the river splits to flow around the bar.
Bars
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Coastal Marshes
• Coastal marshes are wet grasslands formed by river sediment deposited along
the coast.
• Depending on their nearness to the ocean, coastal marshes can be freshwater,
saltwater, or brackish.
Mud Lumps
• Mud lumps are strange formations caused by pressure.
• As heavy sediment piles up on the river bottom, lighter sediment is squeezed to
the surface in an almost geyser-like way.
• Mud lumps can be up to 12 ft. high and cover 20 acres.
Barrier Islands
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Barrier islands are created when a river abandons its delta.
Without fresh sediment, the delta begins to erode and marsh is washed away
leaving a lagoon between the mainland and the bar.
Grand Isle is moving at a rate of 16 feet per year due to erosion on the western
end and sediment build-up on the eastern end.
Barrier Islands are extremely important :
• They help absorb the impact of storms
• They protect the mainland from erosion
• They block saltwater from entering the marsh during storms
• They serve as habitat for birds, turtles, fish and shellfish
Rivers and Bayous
Mississippi River
Unit1 : Louisiana’s Physical and Cultural Geography
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Red River
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The Mississippi is the largest river in the United States and the 4 largest in the
world.
It starts in Minnesota and flows over 2000 miles to the Gulf of Mexico.
It drains 32 states and 2 Canadian provinces.
375 billion gallons of water flow through Louisiana each day
“Mississippi” is an Algonquian Indian word meaning large river.
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The Red River is the 2 largest river in Louisiana.
Begins in New Mexico and enters the Mississippi River near Simmesport.
Named for the reddish sediment it carries.
Has high salt content due to the fact that it flows over an underground salt
dome near the Texas-Oklahoma border.
The only major river in Louisiana that has white water rapids.
Atchafalaya River
• The largest distributary of the Mississippi River.
• Distributary is a branch of a river that flows away from the main stream.
• Flows 125 miles from the Mississippi at Simmesport to the Gulf of Mexico at
Morgan City.
• The Atchafalaya Basin is the largest swamp wilderness in the United States.
• Half of all the nations migratory birds winter here
• Home to 200 bird species
• Largest refuge of the Louisiana Black Bear
• Supplies the world with 23 million lbs. of crawfish each year.
Ouachita River
Ouachita begins in the Arkansas mountains and runs through northeast
Louisiana.
• Merges with Tensas and Little River to form Black River
• Tamed by a series of locks that allow commercial barge traffic to travel to
Arkansas.
Sabine, Pearl and Calcasieu Rivers
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Sabine River begins in north-central Texas and makes up the Louisiana-Texas
border.
Unit1 : Louisiana’s Physical and Cultural Geography
• Toledo Bend reservoir built in 1960s.
• The Pearl River begins in central Mississippi and forms our boundary with Ms.
At the toe of the Louisiana boot.
• Named because mouth of the river was a popular place for the
French to look for pearls.
• Calcasieu lies entirely within the state beginning in west-central La. and flowing
past Lake Charles to the Gulf.
Bayou Teche
• Begins near Opelousas and joins the Atchafalaya near the Gulf of Mexico.
• Settled by Acadians (Cajuns)
• Important tourist region
Bayou Lafourche
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Now a distributary, used to be a channel of the Mississippi River
Exits the river at Donaldsonville
Settled by many French, Spanish, African and Native Americans.
HWY 1 runs the length of the bayou and is known as the “longest street in America
because of the many communities along it.
Intracoastal Waterway
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3000 mile waterway allows ships to go from Texas to Florida
Provides ships a safe inland route along the Gulf Coast
Gulf of Mexico
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5 largest sea in the world
Covers almost 600,000 square miles and has and average depth of 5300 ft.
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Louisiana has over 1000 miles of coastline along the Gulf (6 longest coastline
of any state)
Gulf affects climate and economy
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Lakes
Oxbow Lakes
• Formed when two ends of a meander fill in with sediment
• Very common in Louisiana
• False River and Lake Bruin created by Mississippi River
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Unit1 : Louisiana’s Physical and Cultural Geography
Depression Lakes
• Created when land sinks along a fault
• Examples: Catahoula Lake, Calcasieu Lake, Lake Maurepas, and Lake
Pontchartrain
Raft Lakes
• Only found along the Red River
• Created when bayous flooded as a result of the Great River Raft (log
jam)
• Examples: Lake Bistineau, Black Lake, Saline Lake, and Iatt Lake
• Lakes dried up when jam was cleared in the 1830s
• Man-made dams have allowed lakes to fill up again
Coastal Lakes
• Formed when cheniers (ridges of high ground in the coastal marsh) slowed the
flow of water into the Gulf
Reservoirs
• Man-made lakes found mainly in North Louisiana.
• Used to control floods, supply water to cities and provide a place for recreation.
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Toledo Bend Reservoir is the 3 largest man-made lake in the U.S.
• 1200 mile shoreline
• Covers 186,000 acres
Home to hydroelectric dam that provides electricity to the region
Coastal Erosion
• Louisiana loses approximately 35 square miles of land per year to coastal
erosion.
• Lost an area the size of Rhode Island in the last 50 years.
• On average, the size of two football fields (2.5 acres) disappear every hour.
• Hurricane Katrina destroyed approximately 64,000 acres in one day.
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Louisiana’s Climate
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Climate is the long-term weather pattern of a region.
• Affected by latitude, altitude, nearness to large landmasses or bodies
of water
Louisiana’s climate is mostly affected by its southern latitude and its nearness
to the Gulf of Mexico.
We are located in a temperate zone.
• Close enough to the equator to have a relatively warm climate
• Only Hawaii, Texas and Florida are closer to the equator.
Louisiana has a humid subtropical climate.
A humid subtropical climate has hot summers, mild winters, and abundant
precipitation throughout the year.
About 58 inches of rain fall each year in our state
Winter and spring are the wettest seasons.
Hurricanes
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Hurricanes are enormous violent storms that start in moist air over warm
waters over the Gulf of Mexico and Atlantic Ocean.
Unit1 : Louisiana’s Physical and Cultural Geography
Large complexes of thunderstorms drift together to form giant
storms
• Hurricane season runs from June 1 through November 30.
• Louisiana typically suffers the most violent storms in September.
Storm Surge
• Storm surge is the most dangerous part of a hurricane.
• Due to low atmospheric pressure, water bulges several feet higher than normal.
• High winds push water on shore.
• Storm surge may be up to 20 feet high and travel many miles inland.
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Naming Hurricanes
• For many years, hurricanes were only given female names in alphabetical order.
• Male names (alternating alphabetically with female names) have been used
since 1979.
• Names rotate on a 6 year cycle
• If a hurricane is particularly noteworthy, the name is retired and never used
again.
Noteworthy Hurricanes
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Tornadoes
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Hurricane Audrey struck Cameron parish on June 28, 1957 killing 400 people.
Andrew struck Florida in 1992, passed over the Gulf and struck the
Atchafalaya Basin costing $2.4 billion in damage.
Hurricane Katrina took the lives of nearly 1,000 people, caused a million
people to lose their homes and cost over $100 billion dollars in damage.
Violent wind storms created by thunderstorms
Usually less than 1 mile in diameter but may travel up to 50 miles across land
Most common during spring when cold fronts mix with warm moist air.
Circulate in counter-clockwise motion
Earthquakes
• Weak areas in the earth’s crust called faults cause land to break off and slide
downward to the bottom of the gulf.
• This is an example of tectonic forces.
• Most faults are in south Louisiana and run in an east-west direction parallel to
the Gulf.
• Ground movement is usually so slow that we don’t notice it.
Unit1 : Louisiana’s Physical and Cultural Geography
The Land Takes Shape
How Land Formed
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Since the Gulf Coastal Plain is made up of layers and layers of sediment, ALL
native rock in Louisiana is sedimentary rock.
Geologists believe rock was formed between 2 and 66 million years ago.
Oldest land is in Northern Louisiana
Oldest exposed rock is 60 million year old shale near Caddo Lake.
Geographic Location
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Louisiana ranks 31 of the 50 states in size covering 48,523 square miles.
One of the wettest states with 3,600 square miles of water.
¼ of the state is wet in some way (rivers, lakes, bayous, and reservoirs)
Over 1/3 of nation’s wetlands are found in Louisiana.
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Natural Land Regions
Overview
• Natural land regions are determined by climate, soil, vegetation and relief.
• Louisiana has low relief because more than half the state is less that 100 ft.
above sea level.
• Louisiana has 3 natural land regions: coastal marshes, floodplains, and uplands
Coastal Marshes
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Louisiana Gulf Coast is made almost entirely of coastal marshes.
Low wet grassland created when sediment collected at mouth of rivers as they
enter the Gulf.
Marsh vegetation includes grasses and other plants but few trees.
• Live oak trees thrive on cheniers in the coastal marsh.
Floodplains
• Low, flat valleys through which a river flows.
• Floodplains include swamps, sloughs, bayous, and lakes.
• Deciduous trees (cypress, oak, hickory, pecan, etc.) dominate the area.
• Some of Louisiana’s richest agricultural land.
Uplands
• Areas of Louisiana with the highest elevation.
• Formed when magma pressure and tectonic forces pushed land upward.
• Largest upland area is the Piney Hills in northern Louisiana.
• Driskill Mtn. is highest point in Louisiana at 535 ft.
• Kisatchie Hills and Dolet Hills in Western Louisiana and much of Florida Parishes
are also uplands.
• Dominated by coniferous trees, but deciduous trees are also found.
Unit1 : Louisiana’s Physical and Cultural Geography
Population
2010 Census
• With 4,533,372 people, Louisiana is the 25th most populated state.
• With 233,740 people, St. Tammany Parish is the 5th most populated county in
the state of Louisiana out of 64 counties.