Guided Notes on the Guided Notes on the Theory of Plate TectonicsTheory of Plate Tectonics

Chapter 17, Section 3Chapter 17, Section 3

1. State the theory of plate 1. State the theory of plate tectonics in its entiretytectonics in its entirety

The earth’s crust and rigid upper mantle The earth’s crust and rigid upper mantle are broken into enormous slabs called are broken into enormous slabs called plates. These plates move in different plates. These plates move in different directions and at different speeds and this directions and at different speeds and this movement is caused by the Earth’s movement is caused by the Earth’s internal heat.internal heat.

2. What are the 3 types of movement 2. What are the 3 types of movement that can occur at plate boundaries?that can occur at plate boundaries?

Plates can come together, or convergePlates can come together, or converge

Plates can move away from each other, or Plates can move away from each other, or divergediverge

Plates can move horizontally past each Plates can move horizontally past each otherother

3. Divergent boundaries are 3. Divergent boundaries are places places where 2 tectonic plates are moving where 2 tectonic plates are moving apart.apart. Most divergent boundaries are Most divergent boundaries are found found on the seafloor,on the seafloor, where they where they form form ocean ridges.ocean ridges.

4. The process of seafloor spreading 4. The process of seafloor spreading along a along a divergentdivergent boundary may boundary may cause cause an ocean basin to grow wider.an ocean basin to grow wider.

5. A divergent boundary formed on a 5. A divergent boundary formed on a continent is called a continent is called a rift valleyrift valley, which , which is a is a long narrow depression in long narrow depression in continental crustcontinental crust..

6. Convergent boundaries are 6. Convergent boundaries are places places where 2 tectonics plates are moving where 2 tectonics plates are moving toward each othertoward each other..

3 Types of Convergent Boundaries3 Types of Convergent Boundaries

1.1. Continental-ContinentalContinental-Continental

One continental plate converges with One continental plate converges with another continental plate. Neither plate another continental plate. Neither plate is forced downward and a folded is forced downward and a folded mountain range is formed.mountain range is formed.

3 Types of Convergent Boundaries3 Types of Convergent Boundaries

2. 2. Oceanic-OceanicOceanic-Oceanic

Oceanic crust converges with oceanic crust. Oceanic crust converges with oceanic crust. One plate is forced downward, resulting in One plate is forced downward, resulting in a deep-sea trench and an island arc of a deep-sea trench and an island arc of volcanoes.volcanoes.

3 Types of Convergent Boundaries3 Types of Convergent Boundaries

3.3. Oceanic-ContinentalOceanic-Continental

An oceanic plate converges with a An oceanic plate converges with a continental plate and the oceanic plate is continental plate and the oceanic plate is forced downward. A trench forms along forced downward. A trench forms along with a volcanic mountain range on the with a volcanic mountain range on the edge of the continentedge of the continent

What is subduction?What is subduction?

Subduction is the process of one Subduction is the process of one crustal plate descending beneath crustal plate descending beneath another.another.

Where does it occur?Where does it occur?

Subduction occurs at a Subduction occurs at a subduction zone, where one plate subduction zone, where one plate descends beneath another.descends beneath another.

How does it happen?How does it happen?

If one oceanic plate becomes If one oceanic plate becomes denser than another plate denser than another plate (because it is cooler), then it will (because it is cooler), then it will descend below the other plate as descend below the other plate as they converge.they converge.

What forms as a result of it?What forms as a result of it?

A deep-sea trench and an island A deep-sea trench and an island arc of volcanoes form at arc of volcanoes form at subduction zones.subduction zones.

When subduction occurs between a When subduction occurs between a continental and oceanic plate…continental and oceanic plate…

When an oceanic and continental plate When an oceanic and continental plate converge, the oceanic plate is subducted converge, the oceanic plate is subducted because it is denser.because it is denser.

A trench is formed along the coast of the A trench is formed along the coast of the continent, along with a series of volcanoes continent, along with a series of volcanoes along the edge of the continental plate.along the edge of the continental plate.

10. When two continental plates 10. When two continental plates convergeconverge, the colliding edges of the , the colliding edges of the continents are continents are crumpled and uplifted crumpled and uplifted to form a mountain rangeto form a mountain range..

11. A transform boundary is 11. A transform boundary is a place a place where two plates slide horizontally where two plates slide horizontally past each otherpast each other..

12. What happens to crust at a 12. What happens to crust at a transform boundary?transform boundary?

Crust is only deformed or fractured. It is Crust is only deformed or fractured. It is neither subducted or uplifted. Transform neither subducted or uplifted. Transform boundaries are characterized by long boundaries are characterized by long faults and shallow earthquakes.faults and shallow earthquakes.