Plate Tectonics

The Earth’s Crust in Motion…

Essential Question:

• What is the theory of

continental drift?

Continental Drift…

Most scientists believe that millions of years ago, Earth was very different from the way it is today. There was only one super continent. Over time, the continent broke apart, becoming today’s seven continents.

The Continental Drift Theory

In 1910 Alfred Wegener begins to wonder…

What’s the relationship Between the continents? Perhaps all these pieces used to be connected. Continental drift=slow movement over Earth’s surface 300 million years ago…

What is the theory of Continental Drift?

Alfred Wegener first proposed the theory

of continental drift.

Continental Drift is a

theory that states that the continents

were once a single landmass that broke

apart and moved into the positions

they are today.

Wegener named this

supercontinent Pangaea.

Supercontinent

Pangaea – all lands

•Reptiles and insects

•Tropical forests

-coal deposits

Tens of Millions of years!

Pangaea Puzzle…

• Can you and your team mate

create the super-continent

Pangaea?

This is how the continents fit together! Pangaea means all lands.

Evidence to Support the Theory

• Fossils of tropical plants found on an

island in the Arctic Ocean are evidence for

the theory of continental drift.

• Pieces of the continents fit together like

pieces of a puzzle.

Evidence to Support the Theory

• Wegner studied fossils of the Lystrosaurus an

animal that lived in fresh water.

• He found fossils of this animal on both the

continents of South America and Africa.

• Mountain Ranges of different continents

seem to match. A mountain range on the

Eastern United States and Canada match

mountain ranges in Greenland and

Europe.

Evidence to Support the Theory

• Diamonds found in African &

South American coal mines

Are the same size and

clarity.

Theory Rejected!!

Wegener’s theory was rejected by scientists during his day, because he could not explain what force pushes or pulls continents apart.

• 1. The idea that continents move slowly on Earth’s surface is known as ____________ _____________.

• 2. _______ _______ was the scientist who put forth the idea of continental drift.

• 3. Wegener’s evidence for continental drift included all of the following EXCEPT:

• a. matching fossils.

• b. matching mountain ranges.

• c. matching river beds.

• d. matching coal beds.

QOTD 1-19-12 Fossils of Lystrosaurus, an early land-

dwelling reptile, have been found in

Antarctica, India, and South Africa.

The distribution of these fossils

suggests that these areas were once

• a. made of the same chemical elements.

• b. covered by oceanic crust.

• c. home to a wide variety of organisms.

• d. connected to one another.

WAC ATTACK…

• Explain how Pangaea

supports the theory of

continental drift.

Question of the Day 3-25-14 • 1. The crust and solid upper mantle is called

the _____________.

• 2. It moves on top of a thick syrupy layer called

the ______________.

• 3. Why did the lithospheric plates break apart

and move?

• 4. If a fossil of a tropical plant was found on an

island in the Arctic, what would this reveal

about its past?

Essential Question:

• What is plate tectonic

theory?

Structure of the Earth’s Interior

Now, scientists believe

that…

The upper mantle and crust make

up the lithosphere.

The asthenosphere is a soft layer that can bend like plastic.

The lithospheric

Plates float and move

On top of the

asthenosphere.

How does it work?

Plates – pieces of the lithosphere

Plates fit closely together along cracks called Plate Boundaries

Convection Currents movement

How does it work? How is heat is

transferred in the mantle? Is it by radiation, conduction, or convection.

Convection is heat transfer by the movement of heated liquid.

Lithospheric Plates The lithosphere is broken into separate

sections called plates.

The geological theory that states that

pieces of Earth’s lithosphere are in

constant, slow motion, driven by

convection currents in the mantle is plate

tectonics.

Earth’s Puzzle

• What plate do we live on?

• What plates do we border?

• USGS Earth’s Plates

• How far do we move every year?

Review Time!!

1. Earth’s crust is divided into

sections called ____________.

Review Time!!

2. How many major sections is Earth’s

crust divided into?

Review Time!!

3. The place where plates meet is called

a …

Review Time!!

4. Most volcanoes and

earthquakes are located

at the ………..…between

two tectonic plates

Essential Question:

• How do lithospheric plates

move?

• How do the different types

of movement create

different landforms?

Types of Boundaries

• Divergent

• Convergent

• Transform

Divergent Boundaries The place where two plates move apart or

diverge is called a divergent boundary.

When a divergent boundary develops on land,

two of Earth’s plates slide apart.

A deep valley called a rift valley forms along the

divergent boundary.

Convergent Boundaries

A convergent boundary is where two

plates come together, or converge. The

result of the plates hitting together is called

a collision.

Transform Boundaries

A transform boundary is a place

where two plates slip past each other,

moving in opposite directions.

These transform boundaries cause

EARTHQUAKES!

Plate Movements-Icing on the

Cake Activity

A

Divergent

B

Convergent

C

Transform

•plates are moving apart

•new crust is created

•Magma is coming to the surface

•plates are coming together •crust is returning to the mantle

•plates are slipping past each other

•crust is not created or destroyed

A

Divergent

B

Convergent

C

Transform

Continental crust

rift valley

Oceanic crust mid-

ocean ridge

2 continental plates

mountain range

Plates move

against each

other

Stress builds up

Stress is released

earthquake

2 oceanic plates or oceanic + continental subduction

The Big Picture

Let’s Play

Mountains

Plates move apart

Volcanoes

Changes the shape of the ocean

floor

Causes Earthquakes

Plates collide

Two plates slide past one

another

One plate slides under another

When two plates

converge

________ may

work its way

through the

crust.

magma

A ____________ is

formed when magma

breaks through to the

surface.

volcano

New _______ is

formed when the

lava cools and

hardens.

land

An _______________

occurs when plates move

and the crust slips or

breaks

past one

another.

earthquake

Essential Question:

• What is sea floor

spreading?

Sea-Floor Spreading The mid-ocean ridge is the

longest chain of mountains on the

ocean floor.

Most of the mountains in the mid-

ocean ridge lie hidden under

hundreds of meters of water.

Hess proposed that the ocean floors move, carrying the continents along with them. The movement begins at the mid-ocean ridge.

At the mid-ocean ridge, molten material rises from the mantle and erupts. This is called Sea Floor Spreading.

Sea Floor Spreading

The process that continually adds new material to the ocean floor is called sea-floor spreading.

The ocean floor plunges into deep

underwater canyons called deep-

ocean trenches.

Subduction is the process by which

the ocean floor sinks beneath a deep-

ocean trench and back into the

mantle.

Ticket Out:

• 1. Most volcanoes and earthquakes are located where two ___________ ________ meet.

• 2. The upper mantle and crust make up the _______________.

3. The ____________is a soft layer that allows the lithosphere to float on top of it.

Key Terms for Map

convergent boundary

divergent boundary

transform boundary

subduction

rift valley

mid-ocean ridge

continental crust

oceanic crust

mountain range

earthquake