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Plate Tectonics
• Lithosphere- 60 miles thick (crust and upper
part of the mantle.) It is the solid outer layer
of earth made up of tectonic plates.
• Plate tectonics is the theory that large pieces
of the lithosphere move and change shape.
Plate Tectonics
• Asthenosphere- hot, plastic portion of the
mantle
• Hypothesis 1- the plates of the lithosphere
float on top of the asthenosphere
• Hypothesis 2- the plates are driven by the
force of gravity acting on their own massive
weight.
Plate Boundaries
• Volcanoes and earthquakes are more likely to
occur where tectonic plates meet.
• Mountains and rift valleys also occur along
plate boundaries.
Mid Oceanic Ridges
• Mid oceanic ridges are mountain ranges in
ocean crust. In the center of the ridge is a rift
valley.
• Divergent Boundary- two plates move apart
and a gap is made. Hot rock then rises and
oceanic crust is made.
Subduction
• Convergent Boundary- where older
lithosphere is destroyed.
• Subduction- When one tectonic plate moves
beneath another.
• The Andes Mountains were made this way.
Miscellaneous
• Subduction of ocean crust makes volcanoes.
• Islands could form where two plates meet
• Colliding tectonic plates create mountains