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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: – – – – 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.