Continental Drift & Plate Tectonics Theory

Continental Drift & Plate Tectonics Theory

By Mom

Take your time to read the slides.

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There's no rush.

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Learnig is a process​

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Continental Drift Theory

In the early 1900's (about 70 years before your dad was born),

a scientist called Alfred Wegener proposed the Continental Drift Theory.

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He said that one time the continents were all together and then broke and drifted apart over millions of years.​

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Wegener said that after observing that the boundaries of the continents appear to look like pieces of a large puzzle.

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Studies of fossils and plants and similar glacial ridges in rocks on different continents also support the continental theory.

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The Continental Theory says that all the continents once formed a large, single landmass called PANGEA.

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It existed 245 million years ago when dinosaurs were roaming Earth.​

About 180 million years ago, PANGEA began to split into two (2) smaller continents:

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LAURASIA

&

GONDWANA​

About 65 million years ago, then LAURASIA & GONDWANA broke apart to form the 7 modern continents we now know.​

This theory was accepted until it was replaced 50 years ago with the Tectonic Plates Theory​

Multiple Choice

Which of the following information WAS NOT used to support the Theory of Continental Drift proposed in the early 1900's?

• the continents appear to look like puzzle piece

• similar fossils records from different continents

• similar glacial ridges in rocks from different continents

• the existence of volcanic islands.

Multiple Choice

About 180 millions ago, a large continental landmass split into two parts, called

• Pangaea and Laurasia

• Gondwana and Pangaea

• Gondwana and Eurasia

• Laurasia and Gondwana

Multiple Choice

According to the theory of continental drift, all of the continent were together as a single large landmass called

• Laurasia

• Gondwana

• Pangaea

• Panthalassa

Multiple Choice

Approximately __________ years ago. two landmasses broke apart and began forming the modern continents.

• 300 million

• 180 million

• 65 million

• 5 million

Sea-Floor Spreading

In the middle of the ATLANTIC OCEAN you can find a submerge mountain range called MID-OCEAN RIDGE.

Mid-Ocean Ridge

They are part of a worldwide system of mid-ocean ridges formed by Sea-Floor Spreading

Mid-Ocean Ridge

When two tectonic plates pull away from each other, and a crack forms in the ocean floor.

How Sea-Floor Spreading Occurs?

​THEN...

Magma from the Mantle pours onto the ocean floor through the crack and creates a new oceanic crust.

How Sea-Floor Spreading Occurs?

​THEN...

A MID-OCEAN RIDGE is formed along the crack. As the sea-spread floor spread, new ocean crust pushes the old crust away

New & Old Oceanic Crust

Sea-floor spreading is part of the Plate Tectonics Theory.

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In the Atlantic, the plates move away from the mid-ocean ridge at the rate of about 1cm per year.

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As the sea-floor spreads, the Earth's crust is changing and moving the continents as well.​

Supports Plate Tectonic Theory

Multiple Choice

Sea-floor spreading is part of the Plate Tectonics Theory.

• True

• False

Multiple Choice

Mid-Ocean Ridges are formed by Sea-Floor Spreading.

• True

• False

Multiple Choice

A crack is formed in the floor when two tectonic plates ________________

• push away

• pull away

• don't move

• sink

Multiple Choice

________ from the ________ pours onto the ocean floor though the crack and creates a new ____________ crust.

• Water; Mantle; Oceanic

• Magma; Crust; Oceanic

• Magma; Mantle; Oceanic

• Magma; Mantle; Continental

Multiple Choice

Each year, the continents of Europe and North America, move apart ____________ cm due to the sea-floor spreading in the Atlantic Ocean.

• 1 - 2 cm

• 10 - 20 cm

• 100 - 200 cm

• more than 200 cm

Theory of Plate Tectonics

The theory of plate tectonics was proposed on 1960.

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It says the lithosphere is broken into pieces called Tectonic Plates​

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The tectonic plates are moving on top of the upper mantle.

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They carry both the continents and the ocean floors.​

Tectonic plates are in motion due to the movement of convection currents in the mantle.

The plates move against each other at their boundaries causing volcanoes, earthquakes and mountain formations.

There are three types of plate boundaries:

1. Divergent

2. Convergent

3. Transform​

Multiple Choice

The theory that said that pieces of the lithosphere move around the part of the upper mantle is called the theory of

• continental drift

• sea-floor spreading

• plate tectonics

Multiple Choice

What causes the tectonic plates to move?

• slow continental drift

• convection currents in the mantle

• magnetic forces from the inner core

• radiation from within the crust

Multiple Select

What are the three types of plate boundaries? (Select all)

• transform

• convection

• divergent

• convergent

DIVERGENT

​1. two plates are moving apart

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2. creates mid-ocean ridges in the oceanic crust.

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3. creates rift valleys on land​

CONVERGENT

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​1. two plates are moving together

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2. Eventually one plate slides beneath the other (SUBDUCTION)

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3. can occur between one oceanic and one continental plate; or two oceanic plates or two continental plates. ​

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Forms: Folded Mountain Ranges​, Volcanic Mountains

SUBDUCTION ZONE

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​Occurs when an oceanic plate is pushed down into the mantle below another plate.

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This creates volcanic islands in the ocean and volcanic arcs in lands​

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TRENCH = Oceanic Plate moves under a continental plate​ through subduction.

TRANSFORM

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1. two plates slides past each other,

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2. Like San Andreas Fault in California.

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3. The plate material It is neither created nor destroyed​

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Multiple Choice

Divergent Boundaries occur when

• an oceanic plate is subducted below a continental plate

• two tectonic plates move away from each other

• two continental plates slide past each other

• two tectonic plates move toward each other.

Multiple Choice

When an oceanic plate moves under a continental plate through subduction, what is formed on the sea floor?

• A mountain

• A trench

• a mid-ocean ridge

• a transform fault.

Multiple Choice

The San Andreas Fault in California ia a famous example of the boundary where two tectonic plates slide and grind past one another. THIS FAULT IS CALLED A...

• Convergent Boundary

• Transform Boundary

• Divergent Boundary

• Earthquake Boundary

Multiple Choice

A folded mountain range will formed at what type of tectonic boundary?

• Convergent Boundary

• Transform Boundary

• Divergent Boundary

• Earthquake Boundary

Multiple Choice

The majority of volcanic mountains are formed on the

• Convergent Boundary

• Transform Boundary

• Divergent Boundary

• Earthquake Boundary

Poll

How do you feel about the Plate tectonics Lesson?

Poll

Do you feel ready for your test Next WEEK?