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Landforms
Investigation 3 – Go With The Flow
Part 1: Slope
• Vocabulary
– Slope - the angle or slant of a stream channel or
land surface
• Main Ideas
– Canyons are deeper and deltas are longer in a
stream table model with a steep slope.
– Water flowing through channels with steep slopes
causes more erosion.
Part 2: Flood
• Vocabulary
– Flood – a very heavy flow of water, which is
greater than the normal flow of water and goes
over the stream’s normal channel.
– Flash Flood – rises and falls rapidly with little or
no advanced warning. Can be caused by heavy
rainfall, dam failure, or the thaw of an ice jam.
• Main Ideas
– Floods erode an unusual amount of material.
– Floods erode materials more quickly than normal
water flow.
Science Stories
Rivers and Controlling the Flow
River Features
• Many factors influence the shape of the land
around river channels:
– Earth materials underneath
– Force of the water
– Amount of sand and rock carried along by the river
Science Stories
Rivers and Controlling the Flow
• As a river continues downstream, it often flows
over wide areas of sediment called flood plains
– Sediment is deposited by the river when it
overflows its banks and floods nearby land
• A large river may speed up as it nears its
mouth, however it actually slows when it
reaches the mouth.
Science Stories
Rivers and Controlling the Flow
Mississippi River
• Begins at a small lake in Minnesota.
• Divided into 2 regions – 1) fast, clear flowing section and 2) a
more sluggish, sediment-filled section.
• Drains the central portion of the country (40% of the US).
• Important for commerce and transportation.
Hudson River
• Begins in Adirondack Mountains and extends to NY Harbor.
• Discovered by Henry Hudson in 1609 (thought it connected
the Atlantic and Pacific oceans).
• Important drainage basin in the Northeast.
• Important for commerce and transportation.
Science Stories
Rivers and Controlling the Flow
History of Flow Control
• A levee is an embankment or mound along a
river’s edge. Miles of levees line the Mississippi
River.
– Natural levees formed when rivers deposit large
quantities of sediment after a flood
– Artificial levees are higher and wider
• Erie Canal was built to connect the Hudson
River to the Great Lakes.
Part 3
• Vocabulary
– Levee – an embankment along a stream that protects
land from flooding. Levees can be natural or
constructed.
– Dam – a construction or wall across a river that holds
back water flowing through the river, creating a
reservoir or lake.
– Floodplain – area around a river that is covered by
water flowing over the riverbank during a flood.
• Main Ideas
– People control the flow of water in a river with dams,
levees, and new channels.
Science Stories
Shapes of the Earth
• Landforms result from a combination of
constructive and destructive forces:
– Constructive include crust deformations (i.e.,
mountains), volcanic eruptions (i.e., islands), and
deposition of sediment (i.e., deltas, islands)
– Destructive include weathering and erosion (i.e.,
canyons, caverns)
Science Stories
Shapes of the Earth
• The Earth’s surface is constantly in motion
– Crust is broken into 30 tectonic plates
• Beneath the crust is the mantle, which is
made out of molten rock, or magma.
– The crust floats on the molten rock
• When plates collide, they push upward against
each other, creating mountains (uplift).
– Mountains also form when magma pushes up a
portion of the crust.
Science Stories
Shapes of the Earth
• Earthquakes happen when two plates move
past each other along a fault, or break in the
Earth’s surface.
• Volcanoes form where plates collide and
where they pull apart (rift). They also form
over hot spots in the middle of plates.
• Waves can deposit sand and soil and create
beaches and sand dunes. They can also erode
the shoreline.
Science Stories
Shapes of the Earth
• Glaciers are large, moving pieces of ice. They are
unpredictable and ever-changing, and change the
shape of the land.
– They move slow, but pick up boulders, sand, and other
sediment as they move, and deposit them in a new place.
• Caverns are formed from either:
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–
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1) acid rain dissolving limestone
2) action of waves against sea cliffs
3) sand carried by strong wind
4) cooling lava
• Sinkholes are caused by caverns forming too close to
the surface and the ceiling collapsing.