Chapter 17Chapter 17Plate TectonicsPlate Tectonics

Section 17.3Section 17.3

The Theory of Plate TectonicsThe Theory of Plate Tectonics

VocabularyVocabulary

Divergent Boundary:Divergent Boundary: A plate boundary where two plates move A plate boundary where two plates move

away from each other.away from each other. Convergent Boundary:Convergent Boundary:

A plate boundary where two plates move A plate boundary where two plates move toward each other.toward each other.

Transform Boundary:Transform Boundary: A plate boundary where two plates move A plate boundary where two plates move

past each other in opposite directions.past each other in opposite directions.

VocabularyVocabulary

Plate:Plate: A section of the lithosphere that slowly A section of the lithosphere that slowly

moves over the asthenosphere, carrying moves over the asthenosphere, carrying pieces of continental and oceanic crust.pieces of continental and oceanic crust.

Plate Tectonics:Plate Tectonics: The theory that pieces of Earth’s lithosphere The theory that pieces of Earth’s lithosphere

are in constant motion, driven by convection are in constant motion, driven by convection currents in the mantle.currents in the mantle.

VocabularyVocabulary

Fault:Fault: A break in Earth’s crust where slabs of rock A break in Earth’s crust where slabs of rock

slip past each other.slip past each other.

Rift Valley:Rift Valley: A deep valley that forms where two plates A deep valley that forms where two plates

move apart.move apart.

IntroductionIntroduction

The lithosphere is broken into separate The lithosphere is broken into separate sections called __________.sections called __________.

True or False: Plates can carry True or False: Plates can carry continents or parts of the ocean floor but continents or parts of the ocean floor but not both.not both. FalseFalse

plates

A Theory of Plate MotionA Theory of Plate Motion

What is a scientific theory?What is a scientific theory? A scientific theory is a well-tested concept that A scientific theory is a well-tested concept that

explains a wide range of observations.explains a wide range of observations. State the theory of plate tectonics.State the theory of plate tectonics.

Pieces of Earth’s lithosphere are in constant, slow Pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the motion, driven by convection currents in the mantlemantle..

True or False: The theory of plate tectonics True or False: The theory of plate tectonics explains the formation, movement, and explains the formation, movement, and subduction of Earth’s plates.subduction of Earth’s plates. TrueTrue

Plate BoundariesPlate Boundaries

True or False: Crust is both created and True or False: Crust is both created and destroyed along a transform boundary.destroyed along a transform boundary. FalseFalse

Most divergent boundaries occur at the Most divergent boundaries occur at the ________________.________________.

When two plates collide, what determines When two plates collide, what determines which plate comes out on top?which plate comes out on top? The density of the plate determines which plate The density of the plate determines which plate

comes out on top.comes out on top.

mid-ocean ridge

Plate BoundariesPlate BoundariesConvergent BoundariesConvergent Boundaries

Types of Types of

Plates ConvergingPlates Converging

ResultResult

Oceanic/OceanicOceanic/Oceanic Subduction occurs.Subduction occurs.

Oceanic/ContinentalOceanic/Continental Ocean plateOcean plate

sinks.sinks.

Continental/ContinentalContinental/Continental Mountain RangesMountain Ranges

form.form.

The Continent’s Slow The Continent’s Slow DanceDance

About how fast do plates move?About how fast do plates move? Plates move from about one to ten Plates move from about one to ten

centimeters per year.centimeters per year.

True or False: The pieces of the super True or False: The pieces of the super continent Pangaea began to drift apart continent Pangaea began to drift apart about 225 million years ago.about 225 million years ago. True True