Plate Movement and Plate Boundaries

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Plate Movement and Plate Boundaries

• Chapter 4, Section 3

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Plate Tectonics Theory

• Lithosphere is divided into plates
• Plates move around on the asthenosphere

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3 Causes of plate motion
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Slab Pull

• Oceanic plate sinks (more dense)
• Pulls rest of tectonic plate with it

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Ridge Push

• Oceanic crust is higher at ridge
• Pushes plate underneath continent

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Convection

• Happens in asthenosphere
• Hot magma rises, cool magma sinks
• Drags plates sideways

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3 Types of Plate Boundaries

• Convergent
• Divergent
• Transform Fault

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Convergent Boundaries
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Continent / Continent

• Plates thicken and buckle
• Push upwards
• Mountain formation

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Continent / Oceanic

• Oceanic plate sinks (more dense)
• Subduction zone
• Trenches form
• Volcanic mtns on coast

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Oceanic / Oceanic

• One slides under the other
• Subduction zones
• Volcanic Islands

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Divergent Boundary

• Plates spread apart
• Magma rises
• New lithosphere formed
• Mid Atlantic Ridge

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Transform Boundary

• Plates slide past each other
• Produce earthquakes

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Types of Plate Boundaries Divergent Convergen
t Transform
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Continent / Continent Examples

• Appalachian Mtns.
• Atlas Mtns.

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Continent / Oceanic Examples

• Andes
• Cascades
• Mt. St. Helens

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Oceanic / Oceanic Examples

• Aleutians
• Japan
• Philippines

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Plate Movement

• Approx. 3-6 cm per year
• Rate a fingernail grows!

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