Thread: The birth and death of plate boundaries

"The Birth and Death of Plate Boundaries:
The following processes can form new plate boundaries:
a. continental rifting
b. continental collisions "
(quoting from notes)

I truly understand how "continental rifting" can form new plate boundaries, but how can "continental collisions" form new plate boundaries?

Furthermore, the above only explains the "birth" part........how can continental rifting and continetal collisions give "death" to plate boundaries?

Awaiting for your favorable reply!

Good question!

Continental rifting is indeed the most logical way of creating plate boundaries (such as the new north-south rift which is emerging in Africa, crossing for example through Ethiopia).
But it isn't hard to understand the collision part either. There are many ways to experience for yourself that collision doesnt give a clean 'snap', but creates a complicated pattern of cracks and fault lines. In the case of colliding continents this could mean smaller cracks running at a straight angle to the original boundary line (a horizontal collision line with smaller vertical cracks)

Take this boundary line for example:

http://www.u.arizona.edu/~mstrauss/e...nic%20rift.jpg

If you look carefully you'll find dozens of small cracks along the mid-oceanic rift (->continental rifting). This may not be real plate boundaries (I don't know how far they go on under the surface), but it's the same thing.

Here's an example of faults created by collision:
http://www.nicholas.duke.edu/eos/fie...ctures/map.jpg

As you see this is the San Andreas fault area at the US west coast. All the lines on the map are bigger and smaller cracks in the plates, and this picture is not even complete (not all faultlines in the area have been discovered yet).

The death of plate boundaries also occures in area's such as these, when two continents that have collided into eachother are melting together. Plate material becomes very hot because of the friction of the collision, so it can be melted together.

Anyway, I'm not a real expert on this field so correct me if I'm wrong

Thank you very much!