3.3 Plates Move Apart 3.3 Plates Move Apart

Learn about: Learn about: Different plate boundaries Different plate boundaries What happens when plates What happens when plates move apart. move apart. How the direction and speed of How the direction and speed of plates can be measured.plates can be measured.

Plate BoundariesPlate Boundaries There are three kinds of plate There are three kinds of plate

boundariesboundaries DivergentDivergent ConvergentConvergent TransformTransform

Both the kind of boundary and the Both the kind of boundary and the kind of plate affects how plates kind of plate affects how plates interactinteract

Divergent BoundaryDivergent Boundary

Most divergent Boundaries occur on Most divergent Boundaries occur on the ocean sea floor. the ocean sea floor.

Types of Divergent BoundariesTypes of Divergent Boundaries

((What happens there?)What happens there?) 1.1. Oceanic – Oceanic Oceanic – Oceanic

Divergence Divergence Mid-Ocean RidgesMid-Ocean Ridges Rift Valleys Rift Valleys

2.2. Continental – Continental – Continental Continental DivergenceDivergence

Rift Valleys Rift Valleys

Mid Ocean Ridges

Rift Valleys

Oceanic-Oceanic Oceanic-Oceanic DivergenceDivergence

This is where two oceanic plates This is where two oceanic plates were diverging forming new crustwere diverging forming new crust

Oceanic-Oceanic Divergence Oceanic-Oceanic Divergence (Continued)(Continued)

This is where oceanic plates are This is where oceanic plates are being ripped apart magma comes up being ripped apart magma comes up from deep within the earth’s crust from deep within the earth’s crust and forms pillow basalts and under and forms pillow basalts and under water ventswater vents

The Mid Atlantic RidgeThe Mid Atlantic Ridge The Mid Atlantic Ridge is an example of The Mid Atlantic Ridge is an example of

oceanic-oceanic divergenceoceanic-oceanic divergence Over millions of years the continents have Over millions of years the continents have

moved enough to create an oceanmoved enough to create an ocean The ridge also contains the longest The ridge also contains the longest

mountain chain in the world mountain chain in the world

(6214 miles long) (6214 miles long)

(15 miles wide) (15 miles wide)

(6 miles deep)(6 miles deep)

http://www.wwnorton.com/college/geo/egeo/flash/2_5.swf

Mid- Atlantic Ridge Mid- Atlantic Ridge (continued)(continued)

Review Oceanic-Oceanic Review Oceanic-Oceanic Divergent BoundariesDivergent Boundaries

With your neighbor, review what With your neighbor, review what happens at Divergent Oceanic-happens at Divergent Oceanic-Oceanic Boundaries Oceanic Boundaries

Remember to put these concepts into Remember to put these concepts into your own words. your own words.

How can you best remember the How can you best remember the information? information?

(You have 2 minutes)(You have 2 minutes)

Continent-Continent Continent-Continent Divergence BoundaryDivergence Boundary

Continental plates diverge in the Continental plates diverge in the same way as Oceanic platessame way as Oceanic plates

Cliffs and ridges are more easily Cliffs and ridges are more easily visible in continental divergencevisible in continental divergence

Continental- Continental Continental- Continental divergent Boundary divergent Boundary

Same as Oceanic – Oceanic Boundaries rift Same as Oceanic – Oceanic Boundaries rift vallies will occur. vallies will occur.

What is different?What is different? In this case, rift valley’s happen on land. In this case, rift valley’s happen on land. Two piece of land are pulled apart, Two piece of land are pulled apart,

revealing magma. (it will cool and harden)revealing magma. (it will cool and harden) Creating what is called a Creating what is called a continental rift continental rift

valleyvalley (it could fill with water, making a (it could fill with water, making a lake.) lake.)

Rift Valleys Rift Valleys

East African Rift ValleyEast African Rift Valley

The East African Rift Valley formed The East African Rift Valley formed when a three way split almost tore when a three way split almost tore Africa apartAfrica apart

Example of a Continental rift valley.Example of a Continental rift valley.

East African Valley (On land Rift Valley)East African Valley (On land Rift Valley)

Review the difference!Review the difference!

What is the difference between?What is the difference between? Oceanic – Oceanic divergence andOceanic – Oceanic divergence and Continental – Contiental diverganceContinental – Contiental divergance (you have 1 minute)(you have 1 minute)

3.4 Convergent Boundaries3.4 Convergent Boundaries

Learn: Learn:

What happens when:What happens when: two continental plates converge two continental plates converge An oceanic plate converges with An oceanic plate converges with

another plateanother plate One plate scrapes past another.One plate scrapes past another.

Types of Convergent Types of Convergent BoundariesBoundaries Continental – Continental Collision Continental – Continental Collision

Contiental – Oceanic SubductionContiental – Oceanic Subduction Oceanic – Oceanic Convergent Oceanic – Oceanic Convergent

Continental-ContinentalContinental-ContinentalConvergenceConvergence

When two continental crusts collide the When two continental crusts collide the pressure builds up and they form pressure builds up and they form MountainsMountains Since both plates are approximately equal Since both plates are approximately equal

density neither subducts and no volcanoes density neither subducts and no volcanoes are formedare formed

Oceanic-Oceanic Oceanic-Oceanic ConvergenceConvergence

When oceanic plates collide a subduction When oceanic plates collide a subduction zone occurszone occurs One plate goes under the other deep beneath One plate goes under the other deep beneath

the ocean floor the ocean floor (creating a deep ocean trench.)(creating a deep ocean trench.)

Island Arcs- can form when oceanic Island Arcs- can form when oceanic plates convergeplates converge

JapanJapan Japan is part of an Island Arc formed Japan is part of an Island Arc formed

by oceanic-oceanic convergenceby oceanic-oceanic convergence

Continental – Oceanic Convergent Continental – Oceanic Convergent

BoundaryBoundary Occurs when ocean crust and continental Occurs when ocean crust and continental

crust are pushed together crust are pushed together What happens there? (Subduction Zone)What happens there? (Subduction Zone)

Subduction – one plate is pushed under Subduction – one plate is pushed under another.another.

Which Plate always goes under? And why? Which Plate always goes under? And why?

Subduction Zone? Subduction Zone? What kinds of landforms are created at a Subduction Zone?

•Deep Ocean Trenches

•Volcanoes (after a long period of time.)

•Coastal Mountain Ranges (Parallel to the Coast.)

(see next slide for an illustration)

Transform FaultsTransform Faults Transform faults occur along Transform faults occur along

divergent oceanic and continental divergent oceanic and continental plate boundariesplate boundaries

Plates slide past each other building Plates slide past each other building up tension until the tension is up tension until the tension is released during an earthquakereleased during an earthquake

San Andreas FaultSan Andreas Fault

The San Andreas fault is a surface The San Andreas fault is a surface fault line going through San fault line going through San FranciscoFrancisco In 1906 an Earthquake hit San Francisco In 1906 an Earthquake hit San Francisco

setting breaking gas and water lines and setting breaking gas and water lines and causing fires that could not be stoppedcausing fires that could not be stopped

Hot SpotsHot Spots

Another type of Another type of tectonic activity are tectonic activity are areas called hot spotsareas called hot spots

A hot spot is where A hot spot is where magma rises to the magma rises to the earths crust melting earths crust melting the land and forming the land and forming a line of volcanoes as a line of volcanoes as the earth’s crust the earth’s crust moves past itmoves past it

Hot SpotsHot Spots

HawaiiHawaii In oceans hot spots form Island In oceans hot spots form Island

chains chains Since the hot spot is under mafic Since the hot spot is under mafic

rocks the lava flows smoothly down rocks the lava flows smoothly down the mountain creating shield the mountain creating shield volcanoes like Hawaiivolcanoes like Hawaii

Yellowstone National ParkYellowstone National Park Hotspots below continents are highly Hotspots below continents are highly

explosive and form craters called explosive and form craters called calderascalderas

The force required for Felsic rock is The force required for Felsic rock is so great the eruption vaporizes the so great the eruption vaporizes the land and sends ash over large parts land and sends ash over large parts of continentsof continents