Plate TectonicsPlate TectonicsChapter 17Chapter 17

The Earth’s Drifting Continents

The Earth’s Drifting Continents

German scientist Alfred Wegener, 1900’s proposed the Theory of Continental Drift

It was widely disputed, 30 years after his death, enough evidence was collected to support his theory

German scientist Alfred Wegener, 1900’s proposed the Theory of Continental Drift

It was widely disputed, 30 years after his death, enough evidence was collected to support his theory

Evidence Evidence

Glossopteris, located in 250 myo rocks, were found in South Africa, Australia, India, and Antarctica

Antarctica once had a warmer climate

Rock formations and deposits lined up on several continents

Evidence of glaciers in now warm climates

Glossopteris, located in 250 myo rocks, were found in South Africa, Australia, India, and Antarctica

Antarctica once had a warmer climate

Rock formations and deposits lined up on several continents

Evidence of glaciers in now warm climates

The EvidenceThe Evidence

The Real Issue………..The Real Issue………..

How could the continents move through the solid rock bottoms of the oceans?

In the 1950’s, scientists using better instruments found underwater mountain chains with rift valleys in their centers

How could the continents move through the solid rock bottoms of the oceans?

In the 1950’s, scientists using better instruments found underwater mountain chains with rift valleys in their centers

Midocean ridgeMidocean ridge

Earth’s Spreading Ocean Floor

Earth’s Spreading Ocean Floor

Midocean ridges form the single largest mountain range in the world

80,000 km long and 3 km highLava erupts to form new sea floor

and spreadAs it spreads it takes continents

with itThis explained the mechanism for

continental drift!

Midocean ridges form the single largest mountain range in the world

80,000 km long and 3 km highLava erupts to form new sea floor

and spreadAs it spreads it takes continents

with itThis explained the mechanism for

continental drift!

Magnetic stripes on the ocean floor were further evidence that the sea floor was spreading

The patterns are identical on each side of the ridge

Closer examination shows that the magnetic poles have reversed themselves nine times in the past 3.5 million years

Magnetic stripes on the ocean floor were further evidence that the sea floor was spreading

The patterns are identical on each side of the ridge

Closer examination shows that the magnetic poles have reversed themselves nine times in the past 3.5 million years

Iceland, "the land of fire and ice", is being split by an oceanic ridge that surfaces to create an oceanic island in the North Atlantic Ocean. Red triangles show Iceland's active volcanoes, including Krafla. Reykjavik is Iceland's capital.

Iceland, "the land of fire and ice", is being split by an oceanic ridge that surfaces to create an oceanic island in the North Atlantic Ocean. Red triangles show Iceland's active volcanoes, including Krafla. Reykjavik is Iceland's capital.

If the ocean floor is being created, is the Earth getting

bigger?

If the ocean floor is being created, is the Earth getting

bigger? Rock in the ocean is relatively young Ocean floor is being destroyed in trenches in

a process called subduction The denser ocean crust is pushed downward

into the mantle and melts

Rock in the ocean is relatively young Ocean floor is being destroyed in trenches in

a process called subduction The denser ocean crust is pushed downward

into the mantle and melts

The Earth’s Moving PlatesThe Earth’s Moving Plates

The Theory of Plate Tectonics, which links continental drift and seafloor spreading, explains how the Earth has evolved over time. It helps to explain the formation, movement, collisions, and destruction of the Earth’s crust

The Theory of Plate Tectonics, which links continental drift and seafloor spreading, explains how the Earth has evolved over time. It helps to explain the formation, movement, collisions, and destruction of the Earth’s crust

Lithospheric PlatesLithospheric PlatesThere are seven major plates,

Pacific, North American, South American, Eurasian, African, Indo-Australian, and Antarctic

There are many small plates, Caribbean, Arabian are examples

Each plate moves at a different speed and direction

Some are oceanic and some are continental

There are seven major plates, Pacific, North American, South American, Eurasian, African, Indo-Australian, and Antarctic

There are many small plates, Caribbean, Arabian are examples

Each plate moves at a different speed and direction

Some are oceanic and some are continental

Plate BoundariesPlate Boundaries Divergent boundary-

plates moving apart

Divergent boundary- plates moving apart

Convergent boundary- plates that are moving together

Convergent boundary- plates that are moving together

Transform boundary, slip-strike, lateral faults- plates slide past one another

Transform boundary, slip-strike, lateral faults- plates slide past one another

Tectonic HumorTectonic Humor

More About Our Moving Earth

More About Our Moving Earth

Plate MotionPlate Motion The power of the convection currents

in the mantle is thought to be the force that moves the plates

The power of the convection currents in the mantle is thought to be the force that moves the plates

Collision of Continental and Oceanic Plates

Collision of Continental and Oceanic Plates

Collision of Continental Collision of Continental PlatesPlates

Collision of Continental Collision of Continental PlatesPlates

Collision of Oceanic Collision of Oceanic PlatesPlates

Collision of Oceanic Collision of Oceanic PlatesPlates

Will the Earth Continue to Change?

Will the Earth Continue to Change?

The Earth’s Changing Surface

The Earth’s Changing Surface

Stress is what causes the surface of the Earth to change

As the rocks undergo stress, they slowly change shape and volume

They also move up and down or sideways

Stress is what causes the surface of the Earth to change

As the rocks undergo stress, they slowly change shape and volume

They also move up and down or sideways

Types of StressesTypes of Stresses Compression

squeezes the rock Tension causes the

rocks to stretch out over a larger area

Shearing of the rock causes it to twist or tear

Compression squeezes the rock

Tension causes the rocks to stretch out over a larger area

Shearing of the rock causes it to twist or tear

FaultingFaulting A break or a crack

along which rocks move

Earthquakes are sometimes along these faults

A break or a crack along which rocks move

Earthquakes are sometimes along these faults

Faulted Mountains and Valleys

Faulted Mountains and Valleys

Mountains formed when there are many normal faults in one area

Blocks of rock are uplifted

Valleys may form when the block of land between 2 normal faults slides downward

Mountains formed when there are many normal faults in one area

Blocks of rock are uplifted

Valleys may form when the block of land between 2 normal faults slides downward

Folded Mountains

Folded Mountains

When stress is applied to the rock formation and it bends but doesn’t break

Forms an anticline which is an upward fold and a syncline which is a downward fold

When stress is applied to the rock formation and it bends but doesn’t break

Forms an anticline which is an upward fold and a syncline which is a downward fold

Volcanic MountainsVolcanic

Mountains Single peak

mountains formed from volcanoes

Single peak mountains formed from volcanoes

The Floating CrustThe Floating Crust

Isostasy is the balance between the downward force of the crust and the upward force of the mantle

Isostasy is the balance between the downward force of the crust and the upward force of the mantle

Peaceful changes!!!!!!Peaceful changes!!!!!!