Topic 12 continued:Tectonic Plates

There are three (3) types of plate boundaries:

1) divergent plate boundary – where two plates separate or diverge.

2) convergent plate boundary – where two plates collide or converge.

3) transform plate boundary – where two plates slide past each other.

Divergent Plate Boundaries

When the plates move APART, magma rises from below to fill in the separation, resulting in lava flows and volcanoes.

The divergence also results in earthquakes.Divergence within oceanic crust produces

volcanic activity creating mid-ocean ridges (mountain ranges at the bottom of the ocean floor).

Divergence within the continental crust, results in a continental rift valley.

Convergent Plate Boundaries When two plates converge, the denser plate will sink under

the other. This is called subduction. The bending down of the subducting plate warps the crust

and an oceanic trench is formed.

*If the two plates that collide are oceanic plates, then that can result in a volcanic island arc

*If the two plates that collide are different (one oceanic and one continental), then that can result in a series of volcanoes & young mountains.

Transform Plate Boundaries

When two plates are sliding past one another, earthquakes occur.

The San Andreas fault system in California is an example.

Hot spots are volcanic activities that occur in the interior parts of plates away from plate boundaries.

The spot or location is fixed.Hawaii is an example

of a Hot Spot Over time, the plates

move over the hot spotand a chain of volcanoesare formed

Continents fit together like a jigsaw puzzle There are similar minerals, fossils, rocks and

surface features where the continents may have fit together.

The rocks created at the mid-ocean ridges get older as you move further away from the ridge.

Environmental hazards; volcanic activity, earthquakes, and tsunamis

Changes in Earth’s climate (from mountain ranges, volcanic particles and ash)

EFFECTS OF PLATE TECTONICS