Landform
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Landforms are different shapes of the land on Earth.
Earth’s landforms are the result of internal and external forces. Some force cause
very fast changes while others take many, many years to change the surface of the
land.
Internal forces that shape Earth’s land include plate tectonics, volcanoes, and
earthquakes.
External forces that shape Earth’s land include weathering, erosion, deposition
and glaciers.
Some force are constructive (build land up) and others are destructive (tear land
down).
Examples of landforms include: mountains, valleys, canyons, plateaus, islands,
volcanoes, deltas, peninsulas, etc.
Questions:
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Give an example of a landform. Was this landform a result of constructive forces
or destructive forces?
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Name some landforms that might be made by constructive forces.
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Name some landforms that are made by destructive forces.
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What would our Earth look like if there were no forces acting on the land to
change it?
Glacier
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Glaciers are large sheets of ice that form on the sides of mountains.
Glaciers move slowly down the side of the mountain due to the pull of gravity.
As glaciers move, they scrape away pebbles, rocks and boulders. These rocks
move with the glacier and tear away even more land.
Glaciers also push rocks and soil ahead of it as it moves down the mountain.
The movement of glaciers causes the formation of valleys.
The rocks are deposited when the glacier stops moving or melts.
Questions:
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What is a glacier?
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Would glaciers be considered a constructive (building up) or destructive (tearing
down) force?
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How do glaciers cause weathering?
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How do glaciers cause erosion?
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How do glaciers aid in deposition?
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What force acts on glaciers?
Ocean Tides
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A tide is the rise and fall in the level of the ocean.
Tides are caused by the pull of gravity of the sun and the moon on Earth’s waters.
Since the moon is closer to Earth than the sun, it has a greater effect on tides.
There are 2 high tides and 2 low tides each day.
The highest tides occur about every 14 days when the moon, sun, and earth line
up.
Questions:
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What is a tide?
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What causes the tides on Earth?
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How many high and low tides occur in a 24 hour period?
Weathering
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Weathering is the breaking down of rocks into smaller pieces
Agents of weathering include water, wind, ice, growing plants, and man.
Water – As water runs over land, it carries rough pieces of sand which can chip
away rocks.
Wind – Wind that contains sand can wear away rocks.
Ice – When liquid water freezes in the cracks of rocks, it expands. This expansion
pushes apart the rock and breaks it.
Plants – The roots of plants and trees spread through cracks in rocks. As the roots
spread they push apart the rock and break it.
Questions:
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How does weathering change the way landforms look?
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Is weathering a constructive or destructive force? Why?
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How do glaciers weather rocks?
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How does water weather rocks?
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How can plants weather rocks?
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How does ice weather rocks?
Erosion and Deposition
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Erosion carries weathered materials away from a certain place (deconstructive).
Deposition drops the materials in a new location (constructive).
Moving water, wind, and glaciers are all agents of erosion and deposition.
As water moves, it carries away sediment. This sediment is eventually dropped in
a new location.
Wind also picks up sediment as it blows across the land. A good image of erosion
and deposition by wind is a sand dune. One side is eroded while the sand is
deposited on the other side.
Glaciers scrape away rocks and pebbles. They also push sediments out in front of
it. Once the glacier stops or once it melts, the sediments have been deposited into
a new location.
Questions:
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What is erosion?
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Name a situation that might cause erosion.
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What is deposition?
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What landforms could be formed by deposition?
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How are erosion and deposition similar? How are they different?
Layers of Earth
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The earth has three layers – crust, mantle and core
The crust is the thinnest layer of earth. It is the outermost layer and it is made up
of solid rocks.
The mantle is subdivided into two layers. The upper mantle is made of solid,
heavy rocks. The plates of earth are found in the layer. The lower mantle is made
is soft, melted rock. This is the magma that comes to the surface when a volcano
erupts.
The core is the hottest layer of earth. It is also subdivided into two layers. The
outer core is made up of liquid (molten) iron. The inner core is made of solid
iron. Even though there is tremendous heat, the inner core remains solid due to
the large amount of pressure from all sides of earth.
Questions:
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What are the three layers of earth?
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Which layers are solid? Which layers are liquid?
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Which layer contains melted rock that reaches earth during volcanic eruptions?
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What is the inner core made out of?
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Which layer is the thinnest?
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Why can we not dig to the center of the earth?
Volcano/Magma/Lava
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A volcano is a mountain built up from hardened lava, rocks, and ash that have
erupted out of Earth.
Some eruptions occur slowly, while others occur very quickly.
Magma is the melted rock below Earth’s surface. As it heats and expands, it
pushes in all directions causing the Earth’s surface to move where the crust is the
weakest.
Volcanoes usually form where two plates meet.
When magma reaches the surface, it is called lava.
Volcanic eruptions usually occur due to the built up pressure of the heat and
magma.
Questions:
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How do volcanic eruptions change the shape of the earth?
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What is magma?
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What is a volcano?
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Why do volcanoes occur more frequently at locations where two plates meet?
Continental Drift/Plate/Pangea
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Plates are the large pieces of Earth’s crust that float on the mantle. They move
very slowly.
Most earthquakes and volcanoes occur at or near the boundaries between plates.
Continental Drift is the theory of how plates have moved and continue to move
over time. This theory suggests that there was a time when all the continents were
connected together in one large land mass called Pangea.
Fossil evidence supports the continental drift theory – Scientists have found
matching rocks on the coast of South America and the coast of Africa, similar
fossils of animals that could not live in ocean water have been found in both
South America and Africa.
Pangea is the super-continent that existed 225million years ago.
Questions:
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Where do most earthquakes and volcanoes occur?
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What is continental drift?
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What is Pangea?
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Do Earth’s plates still move today?
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How does the movement of Earth’s plates affect the oceans?
Earthquake / Fault
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A fault is a crack in Earth’s crust.
An earthquake occurs when chunks of Earth’s crust move against each other
below Earth’s surface. This causes a release of energy which can be very
destructive to the surface. Strong earthquakes can cause buildings to fall and
highways to collapse. Earthquakes that occur under the ocean floor can cause
tsunamis.
The strength of an earthquake is measured on the Richter Scale (1 is the weakest,
9 is the strongest).
Questions:
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What is an earthquake?
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What is a fault?
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Why do earthquakes occur on fault lines?