Transcript LA-geography-Awesome-power-of-rivers

Online Textbook
1. go to www.experiencestatehistory.com
2. Type in user name 9lastudent
3. Enter password student then click login
4. Go to programs then find Louisiana Journey click on it and choose
student edition
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