Plate BoundariesPlate BoundariesWhere Plates Meet

Plate BoundariesPlate Boundaries

Tectonic plates move and collide with each other.

A plate boundary is where the edges of two tectonic plates meet.

There are 3 different types:

1. Divergent

2. Convergent

3. Transform

Where two plates move apart.

1. Divergent

Where two plates push together.

Where two plates scrape by each other.

2. Convergent

3. Transform

1. Divergent Boundaries1. Divergent Boundaries

A divergent boundary is where 2 plates pull apart.

As the plates pull apart, a deep gap called a rift valley forms.

rift valley

1. Divergent Boundaries1. Divergent Boundaries

Divergent boundaries can occur underwater.

Below the oceans, mid-ocean ridges are the result of huge divergent boundaries.

The world’s longest mountain chain is the Mid-Atlantic Ridge, found below the Atlantic Ocean.

Here, the North and South American plates move away from the Eurasian and African plates…

MidMid--Atlantic RidgeAtlantic Ridge

North American

plate

South American

plate

Eurasian plate

African plate

IcelandIceland

Iceland is in the middle of a divergent boundary.

Iceland was formed when magma rose to the ocean surface to form an island.

Iceland is the only place on Earth where you can see an

ocean spreading center on land!

Mr. Enns went to Iceland 4 years ago to check it out…

IcelandIceland

North American

plate

Eurasian plate

Thingvellir

Eurasian Plate

North American

Plate

Thingvellir

1. Divergent Boundaries1. Divergent Boundaries

Divergent boundaries can also occur on land.

Continents split apart at divergent boundaries on land..

The Great Rift Valley in eastern Africa is a result of a continental divergent boundary.

Here, the Arabian plate is moving away from the African plate over millions of years…

African Rift ValleyAfrican Rift Valley

Arabian plate

Eurasian plate

African plate

Great African Rift Valley

Great African Rift Valley

2. Convergent Boundaries2. Convergent Boundaries

A convergent boundary is where 2 plates push together.

At these boundaries, crust material is either folded or destroyed.

When two plates collide, the density of the plates determines which plate comes out on top!

Oceanic crust is more densethan continental crust.

continental -continental

continental -oceanic

crust is folded: mountains

crust subducts: ocean trench

subduction

ContinentalContinental--ContinentalContinental

A continental-continental collision occurs when 2 continental plates push together.

Both plates have the same density, so their edges crumple and fold.

This forms mountain ranges, like the Himalayas.

Here, the Indian plate is colliding with the Eurasian plate.

ContinentalContinental--ContinentalContinental

Eurasian plate

Indian plate

The Himalayas

Eurasian plate

Indian plate

OceanicOceanic--ContinentalContinental

A oceanic-continental collision occurs when an oceanic plate collides with a continental plate.

Since the oceanic plate has a greater density, it sinks or subducts below.

This forms ocean trenches, coastal mountains & volcanoes.

The Cascade Mountains on the west coast are examples…

OceanicOceanic--ContinentalContinental

subduction zone

OceanicOceanic--ContinentalContinental

North American

plate

Juan de Fuca plate

Pacific plate

The Cascade Mountains

North American

plate

Juan de Fuca plate

Pacific plate

3. Transform Boundaries3. Transform Boundaries

A transform boundary is where 2 plates scrape past each other in opposite directions.

At these boundaries, crust material is neither created or destroyed.

They exist mainly at mid-ocean ridges, but also on land.

The San Andreas Fault in California is an example…

North American

plate

Juan de Fuca plate

Pacific plate

3. Transform Boundaries3. Transform Boundaries

The San Andreas Fault

North American

plate

Juan de Fuca plate

Pacific plate

Where two plates move apart.

1. Divergent

Where two plates push together.

Where two plates scrape by each other.

2. Convergent

3. Transform

Any Questions?Any Questions?