GEL Week 2- Tectonic boundaries (3-4)

Plate tectonics

“How the earth works”:

Earth’s outer shell is broken into rigid plates that move

Rigid plates change the face of planet earth

Why is the idea of plate tectonics significant?

It is a powerful idea supported by evidence and allows geologists to predict geologic events and reconstruct the geologic past

What does the idea of plate tectonics describe?

Modern way of describing the result of seafloor spreading and continental drift

What are plate boundaries?

Crust is broken into ~20 tectonic plates, as it sits above the mantle

The plates move continuously at a rate of 1 to 15 cm/yr

How do plates interact?

Plates interact along their boundries

How can we locate plate boundaries?

They are identified by locations of earthquakes (they outline the edges of the plate)

Plate boundaries

locations on earth where tectonic plates meet

What are the 3 types of plate boundaries?

Divergent, Transform, and Convergent.

Divergent Plate Boundary

Tectonic plates move apart (plates spread away from each other)

Name an example of a divergent plate boundary

Iceland- MOR above sea level; has lots of volcanoes

East Africa- East African rift

Red Sea- divergent Boundary runs through middle, becomes wider

T/F - divergent plate boundaries create new crust and other geological structures

True

Transform Plate boundary

The tectonic plates slide sideways against each other

What take place during the transform boundary process?

Crust slides past; not created or destroyed. (some cut through continental crust, most offset spreading ridges)

Characteristics of transform boundaries:

Characterized by: Shallow earthquakes, no volcanoes

Name an example of a transform boundary

The San Andreas Fault= continental transform boundary (cuts through continental crust, moves laterally)

Convergent Plate Boundary

Tectonic plates move towards each other and collide

What happens at convergent boundaries?

Subduction

Subduction

Oceanic crust sinks back into the mantle because it’s denser. Subduction recycles oceanic crust.

Volcanic arc (product of subduction)

A curved line of volcanoes on an overriding plate, it is curved because Earth is

Volcanic island arc

Oceanic crust subducting beneath oceanic crust

Plate collision (convergent)

Continental crust will NOT subduct (not dense enough)

Mountains are smashed upward (makes mountains)

What does collison do?

Collision welds the continents together.

(also makes mountains)