Plate Plate TectonicsTectonics

Moving Continents?Moving Continents?

The idea that the Earth's crust is not The idea that the Earth's crust is not completely stable is not new.completely stable is not new.

Understanding the WHY and HOW of Understanding the WHY and HOW of this has been a problem since the this has been a problem since the beginning of geological studies.beginning of geological studies.

11stst Step Step

Have to have evidence.Have to have evidence.

Way back in 1620 Francis Bacon noted the similarity Way back in 1620 Francis Bacon noted the similarity of the coastlines of Africa and South America. of the coastlines of Africa and South America.

In the 1800’s Antonio Snider-Pelligrini noticed In the 1800’s Antonio Snider-Pelligrini noticed similar fossil plants in coal beds of Europe and North similar fossil plants in coal beds of Europe and North America America

In 1908 Taylor and Baker noticed a correlation of In 1908 Taylor and Baker noticed a correlation of global mountain chains. global mountain chains.

What is the problem?What is the problem?

The discoveries these scientists made The discoveries these scientists made were going against the belief that the were going against the belief that the continents were stable and fixed. continents were stable and fixed.

To even think that the continents could To even think that the continents could be moving was ridiculous to people in be moving was ridiculous to people in the past and if a scientist were to the past and if a scientist were to propose it they would be ridiculed. propose it they would be ridiculed.

The Start of Something NewThe Start of Something New

Alfred Wegener shocked Alfred Wegener shocked the world when he went the world when he went against common belief and against common belief and proposed his theory of proposed his theory of Continental DriftContinental Drift

He claimed that the He claimed that the continents can move and continents can move and that all the continents had that all the continents had once been joined to form once been joined to form one large super-continent one large super-continent called Pangaea (all land), called Pangaea (all land), and the ocean was called and the ocean was called Panthalassia (all ocean)Panthalassia (all ocean)

Continental Drift Continental Drift

Wegener was in his school library one Wegener was in his school library one night when he found some scientific night when he found some scientific articles describing the discovery of articles describing the discovery of similar fossil plants in coal beds of similar fossil plants in coal beds of Europe and North America.Europe and North America.

Intrigued by the article Wegener began Intrigued by the article Wegener began to look for more occurrences like this. to look for more occurrences like this.

Wegener’s EvidenceWegener’s Evidence

His curiosity lead His curiosity lead him to discover him to discover multiple lines of multiple lines of evidence that he evidence that he could use to could use to develop his theory. develop his theory.

What was his What was his evidence?evidence?

Puzzle-like FitPuzzle-like Fit

Matching FossilsMatching Fossils

Matching Mountain ChainsMatching Mountain Chains

Matching Glacial EvidenceMatching Glacial Evidence

This Guy!This Guy!

Continental DriftContinental Drift

In 1915 Wegener published his theory of In 1915 Wegener published his theory of Continental Drift with his supporting evidence, Continental Drift with his supporting evidence, but it didn’t go over so well. but it didn’t go over so well.

"Can we call geology a science when there exists "Can we call geology a science when there exists such differences of opinion on fundamental such differences of opinion on fundamental matters as to make it possible for such a theory matters as to make it possible for such a theory as this to run wild.“as this to run wild.“

Wegener's theory is a fairly tale and should be Wegener's theory is a fairly tale and should be ignored due to its deleterious effect on students ignored due to its deleterious effect on students

What’s wrong with it?What’s wrong with it?

Wegener developed a theory with Wegener developed a theory with plenty of supporting evidence, so plenty of supporting evidence, so what is the problem with it?what is the problem with it?

Why wasn’t his theory excepted?Why wasn’t his theory excepted?

ObjectionsObjections

HE HAD NO MECHANISM!!!!!!HE HAD NO MECHANISM!!!!!!

Wegener developed his entire Wegener developed his entire theory, but forgot to think about how theory, but forgot to think about how the continents move. the continents move.

He said that the continents “plowed” He said that the continents “plowed” through the ocean crustthrough the ocean crust

ObjectionsObjections

Wegener worked so hard to develop this Wegener worked so hard to develop this theory and because of his mechanism he theory and because of his mechanism he was laughed at and ridiculedwas laughed at and ridiculed

He was not respected in the science He was not respected in the science community and his ideas were thought to community and his ideas were thought to be fairy tale be fairy tale

But Wegener did not give upBut Wegener did not give up

A Life of Finding the TruthA Life of Finding the Truth

Despite all of the criticism Wegener was Despite all of the criticism Wegener was receiving he still went ahead and receiving he still went ahead and continued his search for a mechanismcontinued his search for a mechanism

He knew that his theory was valid, but He knew that his theory was valid, but could not find the mechanismcould not find the mechanism

He devoted the rest of his life towards He devoted the rest of his life towards research and discovery of the true reason research and discovery of the true reason how continents movehow continents move

Alfred’s Last StandAlfred’s Last Stand

In 1930 Wegener went In 1930 Wegener went on an expedition to on an expedition to Greenland but never Greenland but never came back.came back.

All of his work went for All of his work went for nothing and he nothing and he received no received no recognition for the recognition for the contributions that he contributions that he made towards sciencemade towards science

Yes, it is a real squirrel and yes it is truly waterskiing!

Heading in the Right Heading in the Right DirectionDirection

Despite all of Wegner’s hard work he did not gain Despite all of Wegner’s hard work he did not gain any respect until well after his death any respect until well after his death

In the 1950’s and 1960’s discoveries about In the 1950’s and 1960’s discoveries about earthquakes, magnetism, and the age of rocks on earthquakes, magnetism, and the age of rocks on the ocean floor added support to some of the ocean floor added support to some of Wegener’s ideas. Wegener’s ideas.

Harry HessHarry Hess WWII Naval Submarine WWII Naval Submarine

Officer (1939-1945)Officer (1939-1945)

Developed this idea of Sea Developed this idea of Sea Floor Spreading.Floor Spreading.

He says that new ocean crust He says that new ocean crust is created at Mid Ocean is created at Mid Ocean Ridges and old crust is Ridges and old crust is destroyed in deep trenches.destroyed in deep trenches.

How did he come up with How did he come up with this?this?

While mapping the ocean floor Harry Hess While mapping the ocean floor Harry Hess discovered a gigantic volcanic ridge system discovered a gigantic volcanic ridge system that nearly stretched around the world. that nearly stretched around the world. a ridge system 65,000 km longa ridge system 65,000 km long the most extensive mountain range in the worldthe most extensive mountain range in the world

The Mid-Atlantic RidgeThe Mid-Atlantic Ridge is the best knownis the best known divides Atlantic Ocean basin in two nearly equal divides Atlantic Ocean basin in two nearly equal

partsparts

Atlantic Ocean BasinAtlantic Ocean Basin

One More Key ComponentOne More Key Component

In the 1960’s Drummond Matthews In the 1960’s Drummond Matthews and Frederick Vine (known as and Frederick Vine (known as Matthews and Vine) took a closer Matthews and Vine) took a closer look at the ocean floor and provided look at the ocean floor and provided even more evidence to support the even more evidence to support the idea of sea floor spreading. idea of sea floor spreading.

Magnetic ReversalsMagnetic Reversals

Earth has a magnetic Earth has a magnetic fieldfield

Similar to a giant dipole Similar to a giant dipole magnetmagnet There is a magnetic north There is a magnetic north

and a magnetic southand a magnetic south

Magnetic poles usually Magnetic poles usually match up with geographic match up with geographic north and south. north and south.

Rocks and MagnetismRocks and Magnetism Ocean crust is composed of a rock known as Ocean crust is composed of a rock known as

basalt.basalt. Basalt is very rich in magnesium and iron.Basalt is very rich in magnesium and iron. Formed when lava cools at the surfaceFormed when lava cools at the surface

When the lava cools, the magnetic particles When the lava cools, the magnetic particles line up with the magnetic poles of the Earth.line up with the magnetic poles of the Earth.

But Earth’s magnetic field isn’t always pointing But Earth’s magnetic field isn’t always pointing in the same direction. in the same direction.

Magnetic ReversalsMagnetic Reversals

Earth’s present magnetic Earth’s present magnetic field is called field is called normalnormal Magnetic north matches Magnetic north matches

with geographic northwith geographic north magnetic south matches magnetic south matches

with geographic southwith geographic south

At various times in the At various times in the past, Earth’s magnetic field past, Earth’s magnetic field has completely has completely reversedreversed magnetic north matches magnetic north matches

with geographic southwith geographic south magnetic south matches magnetic south matches

with geographic northwith geographic north

Matthews and Vine also noticed that the age of Matthews and Vine also noticed that the age of the seafloor increased as you move from the the seafloor increased as you move from the mid-ocean ridge towards the continents. mid-ocean ridge towards the continents.

Matthews and VineMatthews and Vine

How do Matthews and Vine’s How do Matthews and Vine’s discoveries relate to Seafloor discoveries relate to Seafloor

Spreading?Spreading?

Tying it TogetherTying it Together Seafloor spreading theory indicates that Seafloor spreading theory indicates that

Oceanic crust is created at mid-ocean ridges (young)Oceanic crust is created at mid-ocean ridges (young) Destroyed at trenches near continents (old)Destroyed at trenches near continents (old)

This means that ocean crust is created in the middle This means that ocean crust is created in the middle of the ocean, being pushed to the side until it is of the ocean, being pushed to the side until it is destroyed in a trench. destroyed in a trench. Magnetic reversals show that the ocean is spreading from Magnetic reversals show that the ocean is spreading from

the middle with its symmetrical patterns of magnetic the middle with its symmetrical patterns of magnetic reversals.reversals.

The seafloor gets older as you move from the mid-ocean The seafloor gets older as you move from the mid-ocean ridge outward which shows that new crust forms in the ridge outward which shows that new crust forms in the middle and is destroyed on the outside. middle and is destroyed on the outside.

SHHHHHHHHHHH!

Plate TectonicsPlate Tectonics The outer portion of the Earth, the The outer portion of the Earth, the

lithosphere, is composed of large irregular lithosphere, is composed of large irregular sections or plates that “float” on the sections or plates that “float” on the asthenosphere.asthenosphere.

TerminologyTerminology Lithosphere – “rock layer” – made up Lithosphere – “rock layer” – made up

of the crust and the uppermost part of of the crust and the uppermost part of the mantle.the mantle. This puts the “plate” in plate tectonics!This puts the “plate” in plate tectonics!

Asthenosphere – “weak layer” – Asthenosphere – “weak layer” – made up of the upper part of the made up of the upper part of the mantle that the lithosphere moves mantle that the lithosphere moves over top. over top.

Plate TectonicsPlate Tectonics

The continents are embedded in lithospheric The continents are embedded in lithospheric plates. As these plates move, they carry the plates. As these plates move, they carry the continents with them. The ocean basins are continents with them. The ocean basins are part of lithospheric plates as well.part of lithospheric plates as well.

Plate TectonicsPlate Tectonics

So, let me get this straight…..So, let me get this straight….. The outer portion of the Earth, the The outer portion of the Earth, the

lithosphere (crust and uppermost mantle), lithosphere (crust and uppermost mantle), is broken up into large irregular platesis broken up into large irregular plates

These plates contain oceanic and These plates contain oceanic and continental crustcontinental crust

The plates “float” on the asthenosphere The plates “float” on the asthenosphere (upper part of mantle directly under the (upper part of mantle directly under the lithosphere) carrying the continents on lithosphere) carrying the continents on themthem

Hold UpHold Up

Why do we care about plate Why do we care about plate tectonics?tectonics?

Because it explains the distribution Because it explains the distribution and formation of volcanoes, and formation of volcanoes, earthquakes, and mountains. earthquakes, and mountains.

AssignmentAssignment

In front of you is a map of the world and In front of you is a map of the world and a chart with earthquakes, volcanoes, a chart with earthquakes, volcanoes, and their longitude and latitude. You and their longitude and latitude. You need to plot each of these on your map need to plot each of these on your map putting an “E” for earthquake in one putting an “E” for earthquake in one color, and a “V” for volcano in a color, and a “V” for volcano in a different color. Once you finish that you different color. Once you finish that you will need to answer some guiding will need to answer some guiding questions on the back.questions on the back.

QuestionsQuestions

Do you notice any trends associated with Do you notice any trends associated with the location of the earthquakes and the location of the earthquakes and volcanoes?volcanoes?

Why do you think the volcanoes and Why do you think the volcanoes and earthquakes are occurring where they do?earthquakes are occurring where they do?

In a different color find three possible In a different color find three possible locations for both volcanoes and locations for both volcanoes and earthquakes, then circle them. earthquakes, then circle them.

Look FamiliarLook Familiar

Plate TectonicsPlate Tectonics

As the plates move and interact at As the plates move and interact at their boundary they create things their boundary they create things like earthquakes, volcanoes, and like earthquakes, volcanoes, and mountains. mountains.

Moving PlatesMoving Plates Remember that the Lithospheric plates are Remember that the Lithospheric plates are

floating on top of the asthenosphere.floating on top of the asthenosphere.

The asthenosphere is the upper portion of The asthenosphere is the upper portion of the mantle.the mantle.

What two layers is the mantle between?What two layers is the mantle between?

What do we know about these layers?What do we know about these layers?

Mantle ConvectionMantle Convection

The mantle is The mantle is undergoing undergoing Convection.Convection.

Convection is the Convection is the transfer of heat transfer of heat through movement through movement of a material.of a material.

Plate BoundariesPlate Boundaries

Three TypesThree Types

Convergent Convergent

Divergent Divergent

Transform Transform

ConvergentConvergent

DivergentDivergent

TransformTransform

How fast are they moving?How fast are they moving?