HOW EARTH IS SHAPED Internal and external forces both shape the
Earths surface. The Earths internal and external structure,
including the tectonic plates, is responsible for the creation of
continents, mountain ranges, volcanoes, etc.
Slide 3
DEFINING INTERNAL & EXTERNAL FORCES Internal processes take
place within/inside the earths surface. For example: plate
tectonics, volcanic formations, earthquakes, etc. External
processes take place outside the earths surface. For example:
floods, avalanches, tornadoes, etc.
Slide 4
EARTHS STRUCTURE Many scientists believe that most of the
landmasses forming our present- day continents were once part of
one gigantic supercontinent called Pangaea. Due to continental
drift, they slowly separated. Due to plate tectonics, the physical
features of the planet are constantly changing.
Slide 5
WEGENERS THEORY OF CONTINENTAL DRIFT http://www.youtub
e.com/watch?v=QL 7LX5-ytOg http://www.youtub e.com/watch?v=QL
7LX5-ytOg
Slide 6
EARTHS LAYERS The Earth is composed of three main layers: The
core Inner and outer core The mantle The crust The crust and upper
mantle http://www.youtube.com/watch?v=bgnn096PfWQ
http://www.youtube.com/watch?v=bgnn096PfWQ
Slide 7
EXPLANATION OF EARTHS PLATES The earth's crust is not a solid
shell; it is broken up into huge, thick plates that drift atop the
soft, underlying mantle. The plates drift all over the globe; they
move both horizontally (sideways) and vertically (up and down).
Over long periods of time, the plates also change in size as their
margins are added to, are crushed together, or pushed back into the
earth's mantle.
Slide 8
THE EARTH AS A CRACKED EGG Think of the earths crust as a
cracked or fractured egg that is composed of many parts that form
the entire shell.
Slide 9
THE EARTHS PLATES
Slide 10
PLATE TECTONICS Plate tectonics is the movement of earths
plates. Plate tectonics is responsible for the folding, lifting,
bending, and breaking parts of the Earths surface. As the plates
converge or diverge they create landforms.
http://www.youtube.com/watch?v=1- HwPR_4mP4
http://www.youtube.com/watch?v=1- HwPR_4mP4
Slide 11
SUBDUCTION When two plates converge the heavier goes under the
lighter. The process of two plates converging is called subduction.
A trench is the deep valley that forms as a result of subduction
During subduction the submerged plate grinds against the plate
above it and heat is generated often causing a row of volcanoes.
When these volcanoes raise to the surface we call them island
chains.
Slide 12
FOLDS & FAULTS Moving plates that become compressed or
smashed are called folds. Moving plates that slide or move apart
from each other are called faults. A fault line is where two plates
meet. Also called a plate boundary. Earthquakes occur typically
along fault lines. Tension builds up along fault lines as the
plates grind against one another. This grinding causes sudden
vibrations that we call earthquakes.
Slide 13
HOW MOUNTAINS ARE FORMED
http://www.history.com/topics/himalayas/videos - mountain-building
http://www.youtube.com/watch?v=goszsQl0Bc0
Slide 14
Slide 15
REVIEW What is an internal force and provide three examples?
What is plate tectonics and what are three reasons that it is
important? What are the three layers of earth and which is made of
iron? In your own words define subduction and then draw an image to
represent what the process looks like.
Slide 16
EXTERNAL FORCES Weathering is when rocks break away or decay
over time. The Earth is changed by two basic kinds of weathering:
Physical weathering occurs when large masses of rock are physically
broken down into smaller pieces. Chemical weathering- changes the
chemical makeup of rocks. For example, rain water that contains
carbon dioxide from the air easily dissolves certain rocks, such as
limestone.
Slide 17
TYPES OF EROSION Erosion is the movement of surface material
from one location to another by water, wind and ice. Wind erosion
involves the movement of dust, sand, and soil from one place to
another. Plants help protect the land from wind erosion; however,
in dry places where people have cut down trees and plants, winds
pick up large amounts of soil and blow it away.
Slide 18
OTHER TYPES OF EROSION Glacial Erosion: as glaciers move, they
may destroy forests, carve out valleys, alter courses of rivers,
and wear down mountaintops, changing the landscape. Water erosion:
it begins when spring water and rainwater flow downhill in streams,
cutting into the land, and wearing away the soil and rock.
