Convection & plate Convection & plate tectonicstectonics

Section 2 Section 2

Vocabulary for week 5Vocabulary for week 5

Convection currents Convection currents Continental driftContinental drift FossilFossil Alfred WegenerAlfred Wegener MesosaurusMesosaurus

Review Review

Types of heat transferTypes of heat transfer– RadiationRadiation– ConductionConduction– ConvectionConvection

define all of these.define all of these.

Convection Convection

The one the most important to us is The one the most important to us is convection.convection.– Convection currents: the movement of a Convection currents: the movement of a

fluid caused by the differences in fluid caused by the differences in temperature that transfers heat from temperature that transfers heat from one part of the fluid to another.one part of the fluid to another. Why is this important?Why is this important?

– these convection currents are part of what cause these convection currents are part of what cause the earths magnetic field and are a part of the the earths magnetic field and are a part of the driving force in plate tectonics.driving force in plate tectonics.

Continental driftContinental drift

The world hasn't always looked the The world hasn't always looked the same.same.– Once only Europe existedOnce only Europe existed– and the world was flat and the world was flat – The Americas were not connectedThe Americas were not connected– Only the east cost was discoverOnly the east cost was discover– Then in the 1700 geologist were sure Then in the 1700 geologist were sure

that the contents never movedthat the contents never moved

Continental drift continued Continental drift continued

In 1910 a young German scientist In 1910 a young German scientist suggested something amazing, he suggested something amazing, he figured out that the continents all fit figured out that the continents all fit together like a jigsaw puzzle.together like a jigsaw puzzle.– Alfred Wegener was the first to Alfred Wegener was the first to

hypothesize that earth continents moved.hypothesize that earth continents moved. He was also the first to suggest that all of the He was also the first to suggest that all of the

continents drifted together to form Pangaea.continents drifted together to form Pangaea.– Pangaea: single landmass that broke apart 200 Pangaea: single landmass that broke apart 200

million years ago, and gave rise to today's million years ago, and gave rise to today's continents continents

Evidence Evidence

Evidence from land featuresEvidence from land features– Mountains Mountains

Wegener found that when he pieced north Wegener found that when he pieced north and south America together that the and south America together that the mountain ranges lined up.mountain ranges lined up.

– Coal deposits Coal deposits He also noticed that the coal deposits in He also noticed that the coal deposits in

Europe matched up with the coal fields in Europe matched up with the coal fields in North AmericaNorth America

More evidence More evidence

Evidence from fossils Evidence from fossils – He found a fossilized fern (Glossopteris) He found a fossilized fern (Glossopteris)

that grew in a very specific time, on 5 that grew in a very specific time, on 5 different continents Africa, South different continents Africa, South America, Australia, India, and Antarctica. America, Australia, India, and Antarctica. This is very strong evidence that all of This is very strong evidence that all of the land where the ferns grew was at a the land where the ferns grew was at a different place than now. The ferns need different place than now. The ferns need a warm moist climate to grow and a warm moist climate to grow and Antarctica isn't either of those.Antarctica isn't either of those.

And even more EvidenceAnd even more Evidence

Evidence from climateEvidence from climate– in South Africa there are places where in South Africa there are places where

glaciers have been proven to have glaciers have been proven to have existed in the past. But the climate now existed in the past. But the climate now in South Africa the climate is much to in South Africa the climate is much to warm and mild. warm and mild.

And even more evidence than And even more evidence than beforebefore

The geological community believed that The geological community believed that mountains were formed because the mountains were formed because the earth was cooling, and the crust acted earth was cooling, and the crust acted like an apple skin and it would wrinkle. like an apple skin and it would wrinkle. Wegener said that if that’s the case we Wegener said that if that’s the case we should mountains all over the place, but should mountains all over the place, but they are only found at the edges of they are only found at the edges of continents.continents. He suggested that the He suggested that the continents collided causing a lifting or continents collided causing a lifting or crunchingcrunching

Rejected Rejected

Not so fastNot so fast– Even with all of his other evidence Even with all of his other evidence

Wegener couldn't prove HOW the Wegener couldn't prove HOW the continent moved he didn’t have the continent moved he didn’t have the technologies to prove it. So the technologies to prove it. So the geological community wouldn’t accept geological community wouldn’t accept his theory.his theory.

Today Today

With today's info we know how they With today's info we know how they move and that Wegener’s move and that Wegener’s explanation and hypotheses were explanation and hypotheses were correct.correct.

Convection Currents QuizConvection Currents Quiz

1. how do convection currents work?1. how do convection currents work?

2. refer to the drawing on the board 2. refer to the drawing on the board correctly name what it is asking for.correctly name what it is asking for.

3. who was the first person to come 3. who was the first person to come up with the idea that the continents up with the idea that the continents moved?moved?

Convection Current Quiz Convection Current Quiz cont.cont.

4.What year did he come up with the 4.What year did he come up with the idea?idea?

5. what was fossilized and how many 5. what was fossilized and how many different continents was it found on,different continents was it found on,

Bonus:Bonus: 6.list all of the continents the fossil 6.list all of the continents the fossil

was found on.was found on.

Sea floor spreading Sea floor spreading

What is sea floor spreading?What is sea floor spreading?– The process by which molten material The process by which molten material

adds new oceanic crust to the sea floor. adds new oceanic crust to the sea floor. – What effect does it have on us?What effect does it have on us?

It moves the plates and spreads out the It moves the plates and spreads out the continents. continents.

Where does this happen?Where does this happen?– At the mid-oceanic ridgesAt the mid-oceanic ridges

Mid-oceanic ridge: an undersea mountain Mid-oceanic ridge: an undersea mountain chain where new ocean floor is produced; a chain where new ocean floor is produced; a divergent plate boundary divergent plate boundary

Sea floor spreadingSea floor spreading

In sea floor spreading the sea floor In sea floor spreading the sea floor spreads apart along both sides of the spreads apart along both sides of the mid-oceanic ridge as new crust is mid-oceanic ridge as new crust is added. As a result, the ocean floor added. As a result, the ocean floor moves like conveyor belts, carrying moves like conveyor belts, carrying the continents along with them. the continents along with them. – Who came up with the idea of sea floor Who came up with the idea of sea floor

spreading?spreading? Harry Hess. In 1960Harry Hess. In 1960

Evidence for seafloor Evidence for seafloor spreadingspreading

There are three main types of There are three main types of evidence for Hess theory.evidence for Hess theory.– Molten materialMolten material– Magnetic stripesMagnetic stripes– Drilling samplesDrilling samples

Evidence from molten Evidence from molten materialmaterial

In the 1960’s scientist were able to dive to In the 1960’s scientist were able to dive to the ocean floor in Alvin a small submarine the ocean floor in Alvin a small submarine designed to take the enormous amount of designed to take the enormous amount of pressures at the bottom of the ocean.pressures at the bottom of the ocean.– When they got down there they saw pillow When they got down there they saw pillow

shaped or they look like they just got shaped or they look like they just got squeezed from a tube of tooth past shaped squeezed from a tube of tooth past shaped rock formations.rock formations. These can only be formed when molten material These can only be formed when molten material

come in contact with seawater immediately after come in contact with seawater immediately after reaching the surface. reaching the surface.

Evidence from magnetic Evidence from magnetic stripesstripes

Magnetic stripes are when patterns in Magnetic stripes are when patterns in the seafloor made when the Earth the seafloor made when the Earth Magnetic poles switch.Magnetic poles switch.– When the poles switch the magnetic metals When the poles switch the magnetic metals

in the molten material will line up to the in the molten material will line up to the north, then when it switches they line up to north, then when it switches they line up to the new north or current south. the new north or current south. This leaves a time line for two things 1This leaves a time line for two things 1stst we know we know

how old the sea floor is at different places 2how old the sea floor is at different places 2ndnd we we know when the last time the poles switched wasknow when the last time the poles switched was

– 780,000 years ago. 780,000 years ago.

Evidence from drilling. Evidence from drilling.

Drilling Drilling A ship called the Glomar Challenger was A ship called the Glomar Challenger was

designed to drill into the ocean floor, designed to drill into the ocean floor, through 6 km of water. These samples through 6 km of water. These samples were examined by scientist and dated were examined by scientist and dated every time the youngest rocks came every time the youngest rocks came from the ridges and the oldest rocks from the ridges and the oldest rocks were the farthest away. Proving that were the farthest away. Proving that seafloor spreading was taking place. seafloor spreading was taking place.

Subduction Subduction

What is subduction?What is subduction?– Subduction: is the process by which the Subduction: is the process by which the

ocean floor sinks beneath a deep-ocean ocean floor sinks beneath a deep-ocean trench and back into the mantle .trench and back into the mantle . Think of a conveyer belt, new crust is made Think of a conveyer belt, new crust is made

at the mid-oceanic crust and as it gets at the mid-oceanic crust and as it gets farther away from the ridge it gets cooler farther away from the ridge it gets cooler and denser. This causes it to sink at the and denser. This causes it to sink at the trench where is goes down into the mantle. trench where is goes down into the mantle.

How it works. How it works.

What effect does this have?What effect does this have?

When old crust is taken faster then When old crust is taken faster then new crust can be made the ocean new crust can be made the ocean start to get smaller and when new start to get smaller and when new crust is made faster then the old crust is made faster then the old crust is taken the ocean is getting crust is taken the ocean is getting bigger. bigger. – Is this happening today?Is this happening today?

Yes the Pacific ocean is getting smaller and Yes the Pacific ocean is getting smaller and the Atlantic ocean is getting bigger.the Atlantic ocean is getting bigger.

The end The end