Erosion
• The process by which water, ice, wind or gravity
moves fragments of rock and soil.
Water Erosion
• Rivers, streams, and runoff
Ice Erosion
• Glaciers
Wind Erosion
Mass Movements (Gravity)
• Landslides, mudslides, slump and creep
landslide clip.mpeg
Erosion Lab
• Station 1. Demonstrates beach erosion. Using a pan, make a sand
pile at one end and pour water at the other end. Slide the pan
back and forth to create wave movement. Record observations.
• Rebuild the beach. Design a “jetty” or dam to prevent erosion;
repeat and record results.
• Station 2: Place sand in a small bowl and blow gently to move
the sand. Record observations.
• Station 3: Place a pile of ice cubes (glacier) on a mound of dirt.
Observe and record what happens as it melts.
• Discussion Questions:
• How does erosion occur?
• What is the result of each type of erosion?
Deposition
• When soil and rocks are
eroded, they are placed
(deposited) in a new
location.
• When this happens, it is
called “deposition”.
• Deposition is a constructive
force. It builds or creates
new landforms and features,
such as a shoreline, beach,
and river deltas.
Deposition
• Beach/Shoreline
Depostion
• Formation of delta:
Deposition
• Formation of winding
(meandering) streams and
oxbow lakes.
The Mighty Mississippi
• Welcome to the Mississippi River. It is the longest river in the world -- four
thousand three hundred miles. It starts in Minnesota and continues south
past New Orleans before flowing into the Gulf of Mexico. A common
nickname for the Mississippi River is "Old Man River". Rivers are longer than
they are wide.
Formation
• The Mississippi River basin was formed by glaciers, moving and
melting millions of years ago, which left in their wake sometimes
miles-wide floodplains, that still fill up occasionally, covering
towns, roads, farms, and everything else that might stand in the
way of its mighty waters.
Glaciers
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Newly fallen snow is about 80 percent air. Through some melting, evaporation, and
refreezing, the light, fluffy snow turns into small, round granules called firn. If the
firn remains on the ground for about one year, it will reduce to 50 percent air.
When additional snow, along with dust, volcanic ash, and other air-deposited
substances layer on top, the firn is compressed and changes into solid ice. This
glacial ice is denser—composed of less than 20 percent air.
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As the ice sheet thickens, the force of gravity causes it to move. Ice moves by
changing shape or by slipping and shifting along cracks in the ice sheets. Like
water, ice seeks the lowest levels and flows downhill. The ground beneath the
glacier weakens due to the downward pressure of the ice and constant water
saturation. This ground breaks off and moves with the flow of ice, EROSION, lifting
through periods of re-freezing and melting.
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Scientists believe that glaciers have had a big role in shaping much of North
America, including the Mississippi River valley. They theorize that as the glaciers
developed, they picked up and carried gravel and even huge boulders (erosion). These
varying sizes of debris carved out U-shaped valleys.
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As the glaciers melted, rivers flooded and eroded, and more rocks and soil were carried
away. The sediments soon are dropped (deposited), forming channels, riverbeds, and banks.
Erosion & Deposition
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During seasonal floods in northern states, large amounts of silt and other soil
sediments were extracted and sent flowing down the river. During its journey
downstream, the rushing water took even more silt and soil from the river’s
banks. All of these materials traveled all the way down until they reached the edge
of the continental shelf at the end of Louisiana’s coast.
Delta
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Over time, the sediments spread over large areas in a continuous flow. The
continuous stream of silt and other land-making materials began to overlap each
other. In due time, the materials started to get higher and higher until the land began
to peak out of the water.
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After this land emerged, it kept growing in size until it built up too high for the river
to continue flowing in that particular direction. The Mississippi River then started to
revert its flow in a different direction, doing all it could to spill into the Gulf of
Mexico. This process of blocking and changing direction of the Mississippi kept
occurring until it reached its present location. Today, there is a huge delta that was
created by the changing course of the Mississippi River.
Where is the Mississippi River?
• It is in the central part of the United States.
• It starts in Minnesota, and flows south to the Gulf of Mexico.
Mississippi River
Map and river basin
A little Big River history
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The Mississippi has a unique history. The North American Indians called
it “Messipi” which means “Big River”. The first non American Indian
man to reach the river was Hernando de Soto in 1541. He called the river
“Rio de Espiritu Santo” or “River of the Holy Spirit”. In the 1600s, the
French discovered the river and claimed the entire river for France. The
French called the river “Louisiana” named after their king Louis XIV.
• In the two hundred years that followed, the United States became a nation
and claimed the area for itself. The Mississippi and its connecting rivers
became major transportation routes. People, goods, livestock, and timber were
transported to towns that were springing up all along the river. The land
surrounding the river was very fertile and was used to grow crops and raise
livestock.
Did You Know
• Today, the Mississippi is still an important part of life in the United States.
Over 12 million people rely on the river for their daily drinking water and the
river is still used for transportation and commerce. The flow of water in the
river is regulated by a series of 27 locks and dams on the upper Mississippi.
Built in the 1930s, they were designed to maintain a channel for ships and
barges to travel. The dams make the river deeper and wider but do not stop
the flow of water.
• Ocean going ships can move upstream as far as Baton Rouge, Louisiana and
smaller ships and barges can go up stream as far as Minneapolis, Minnesota.
• Coal, petroleum products (gas and oil), sand, gravel, salt, chemicals, grain and
livestock are transported along the river. Shipping at the lower end of the
Mississippi includes iron, steel, rubber, paper, wood, and coffee. The
headwaters segment is not used for shipping. The lakes that are formed by
dams are used for recreational boating and fishing.
Fun Facts
• The Mississippi River is home to:
• 241 fish species 37 mussel species 45 amphibians 50 mammals
40% of the nation's migratory birds
• In 2002 Martin Strel swam the entire length of the river.
• A raindrop falling in Lake Itasca would arrive at the Gulf of
Mexico in about 90 days
• At the headwaters of the Mississippi, the average speed of the
water is near 1.2 miles per hour. At New Orleans, the speed of
the river is about 3 miles per hour.
• At its headwaters, the Mississippi is less than 3 feet deep. In New
Orleans, it is over 200 feet deep.
River Ecosystems
• The Mississippi River, along with its lakes,
tributaries and wetlands provide a habitat for
hundreds of species of animals, fish and birds.
The River is the largest continuous system of
wetlands in North America. It has wetland, open
water, and floodplain habitats. A large percent
of North America's duck, goose, swan, and
wading bird populations use the river every year
as they migrate south for the winter
Danger on the River
Mississippi River, the river also has a dangerous side. Flooding is the
number one natural disaster in the United States. Most flooding on the
Mississippi is caused by too much rain falling in too short an amount
of time. The water rises about the banks and flows into the land
around it. Sometimes, dams and levies can break causing flooding.
The quick rising muddy water destroys homes, businesses, crops,
livestock and sometimes even human life.
The River in Danger
• Hundreds of years of human use have changed
the Mississippi River. The locks and dams have
changed the natural course of the river and have
affected the natural ecosystem. Much of the
floodplains and wetlands areas have been
destroyed by farming and housing
developments.
More Problems
• Water, full of pesticides, chemicals and waste,
runs into the river from cities and farms. These
changes have added to flooding problems and
cause hypoxia. Hypoxia occurs when there is
not enough oxygen available in the water for
marine life to live. This is a problem in the Gulf
of Mexico where the water from the Mississippi
ends up.
An Important Resource
• The Mississippi River is a very important part of
North America. It is responsible for a more
prosperous economy and for a large percentage
of the ecology of the United States. The Mighty
Mississippi deserves our respect and our
attention as we search for ways to preserve the
river and river basin for the future
Mighty Mississippi Review Sheet
• http://www.instructorweb.com/lesson/mississi
ppi.asp