Plates on the Move

Three kinds of boundaries between plates “Divergent” – pulling part “Convergent – pushed together “Transform fault” – slide past each other

Divergent Boundaries

Plates pull apart & leave a gap Magma fills gap,

cools and hardens Examples:

Mid – Atlantic Ridge (beneath ocean)

Rift between North American plate and the Eurasian plate in Thingvellir Iceland

Convergent Boundaries

Plates ram into each other

Subduction process One plate cycles

under other Recycles earth’s

crust

Oceanic plate converging with Continental Plate Result: Oceanic

plate is “subducted” under the continental plate

Example: Juan de Fuca plate pushing under NA plate

Oceanic plate converging with another Oceanic plate Result: form a

“trench” where one oceanic plate slips under another

Example: Mariana trench Convergence

between Pacific plate and Phillipine plate

Continental Plate converging with Continental Plate When two

continental plates meet do not subduct

Instead crust buckles upwards forming Mountains (peak) Plateaus (flat)

Eg. Tibetan Plateau

Transform Fault Boundary

Two plates slide by each other

Most under ocean San Andreas Fault

Few land based TF Pacific Plate sliding

past North American plate

Complete the missing informationPlace on Earth

Type of Boundary

Description of Plate Movement

Thingvellir Rift NA plate pulling away from the Eurasian plate

Juan de Fuca Plate

(oceanic plate)

Convergent Boundary

(Oceanic + Continental)

Tibetan Plateau Indian plate pushing up Eurasian plate

San Andreas Fault Transform Fault Boundary

Answers

Place on Earth

Type of Boundary

Description of Plate Movement

Thingvellir Rift Divergent Boundary NA plate pulling away from the Eurasian plate

Juan de Fuca Plate

(oceanic plate)

Convergent Boundary

(Oceanic + Continental)

Oceanic plate subducting beneath NA Plate

Tibetan Plateau Convergent Boundary

(Continental + Continental)

Indian plate pushing up Eurasian plate

San Andreas Fault Transform Fault Boundary Pacific Plate sliding past NA Plate

At a Divergent boundary the plates are moving apart. The plates move apart due to convection currents inside the Earth.

As the plates move apart (very slowly), magma rises from the

mantle. The magma erupts to the surface of the earth. This is also accompanied by earthquakes.

When the magma reaches the surface, it cools and solidifies to form a new crust made up of igneous rock. This process is repeated many times, over a long period of time.

Eventually the new rock builds up to form a volcano. Divergent Boundaries tend to be found under the sea, e.g. the Mid-Atlantic Ridge. Here, chains of underwater volcanoes have formed along the plate boundary. One of these volcanoes may become so large that it erupts out of the sea to form a volcanic island, e.g. Surtsey and the Westman Islands near Iceland.

At a convergent boundary the plates are moving towards each other. This usually involves a continental plate and an oceanic plate.

The oceanic plate is denser than the continental plate so, as they move together, the oceanic plate is forced underneath the continental plate. The point at which this happens is called the subduction zone. As the oceanic plate is forced below the continental plate it melts to form magma and earthquakes are triggered. The magma collects to form a magma chamber. This magma then rises up through cracks in the continental crust. As pressure builds up, a volcanic eruption may occur.