FORCES OF CHANGE

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FORCES OF CHANGE
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The Earths Three Layers
-Core -Mantle -Crust
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CORE
-super hot and solid -lies 4,000 miles below the
surface -made up of iron and nickel
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OUTER CORE

• Liquid
• 1,400 miles thick
• Band of melted iron and nickel
• Begins at about 1,800 miles below the surface
• Temps reach up to 8,500 F

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MANTLE
-Consist of silicon, aluminum, iron, magnesium,
oxygen, and other elements -The mixture
continually rises, cools, sinks, warms up, and
rises again, releasing 80 of the heart generated
from the earths interior
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CRUST
-Rocky shell -ranges from about 2 miles thick
under oceans -about 75 miles thick under
mountains -its broken into more than a dozen
great slabs called plates that rest- or actually
float- on a partially melted layer in the upper
mantle -plates carry the earths oceans and
continents
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Pangea
Continental drift- The theory that the continents
were once joined and then slowly drifted apart
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Moving of the Plates
-Plates move gradually about 4 inches a
year -They crash into each other, pull apart, or
grind and slide past each other -This action
constantly changes the planet, pushing up
mountains, creating volcanoes, and producing
earthquakes MAGMA-molten rock Plate Tectonics-
all activities which create many of the earths
physical features
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Subduction
- The process in which the heavier sea plate
dives beneath the lighter continental plate
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Accretion
-during this process pieces of the earths crust
come together slowly as the sea plate slides
under the continental plate
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Spreading
- A process by which new land is created when sea
plates pull apart and magma wells up between the
plates
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Faults

• Plates may grind of slide past each other,
  creating cracks in the earths crust
• Faulting occurs when the folded land cannot be
  bent any further, the blocks crack and breaks
  into huge blocks

San Andreas Fault
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Earthquakes
Occur where different plates meet one another and
tension builds up along fault lines as the plates
stick, the strain eventually becomes so intense
that the rocks snap and shift.
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Volcanic Eruptions
Rocky plates melt as they dive downward into the
hot mantle, if the molten rock is too thick, its
flow is blocked and pressure builds
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Weathering
- The process that breaks down rocks on the
earths surface into smaller pieces
PHYSICAL- occurs when large masses of rock are
physically, broken down into smaller
pieces CHEMICAL- changes the chemical makeup
of rocks, transforming their minerals or
combining them with new elements
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Wind Erosion
Involves the moving of dust, sand, and soil from
one place to another
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Glacial Erosion
Glaciers- large bodies of ice that slowly move
across the earths surface
Two Types Sheet and Mountain
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Water Erosion
Fast moving water-rain, rivers, streams, and
oceans