A reconstruction of Rodinia

[granpa]

A reconstruction of Rodinia.

Note how Alaska tucks into the Ross sea and Mexico curls up along Peru.

The light colored area surrounding the land is the continental shelf.

https://en.wikipedia.org/wiki/Ross_Sea

 

South America, Africa, Antarctica, India, and Australia together form Gondwana.

North America and Russia together form Laurasia.

Gondwana and Laurasia together form Rodinia.

 

One billion years ago Rodinia split into Laurasia and Gondwana which then moved so far apart that they actually collided on the other side of the world forming Pangea.

As they came together the Tethys ocean was trapped between them.

The Tethys Ocean continued to shrink until today all that is left is the Mediterranean ocean.

Only 130 million years ago Pangea began to split apart and the Atlantic Ocean began to form.

 

https://en.wikipedia.org/wiki/Triple_junction

In plate tectonics theory during the breakup of a continent, three divergent boundaries form, radiating out from a central point (the triple junction). One of these divergent plate boundaries fails (see aulacogen) and the other two continue spreading to form an ocean. The opening of the south Atlantic Ocean started at the south of the South American and African continents, reaching a triple junction in the present Gulf of Guinea, from where it continued to the west. The NE-trending Benue Trough is the failed arm of this junction.

In the years since, the term triple-junction has come to refer to any point where three tectonic plates meet.

https://en.wikipedia.org/wiki/Aulacogen

https://en.wikipedia.org/wiki/Supercontinent_cycle

 

https://en.wikipedia.org/wiki/Archean

There are two schools of thought concerning the amount of continental crust that was present in the Archean. One school maintains that no large continents existed until late in the Archean: small protocontinents were common, prevented from coalescing into larger units by the high rate of geologic activity. The other school follows the teaching of Richard Armstrong, who argued that the continents grew to their present volume in the first 500 million years of Earth history and have maintained a near-constant ever since.

 

https://en.wikipedia.org/wiki/Geography_of_Mars

Observers of Martian topography will notice a dichotomy between the northern and southern hemispheres.

Most of the northern hemisphere is flat, with few impact craters, and lies below the conventional zero elevation level (in other words one giant ocean) .

In contrast, the southern hemisphere is mountains and highlands, mostly well above zero elevation (in other words one giant continent) .

The two hemispheres differ in elevation by 1 to 3 km.

 

[studiot]

The point of a triple junction is that rotation becomes possible ie it introduces rotational dynamics into plate techtonics.

 

But what is the point of your post for discussion?

[granpa]

http://www.geosci.usyd.edu.au/users/prey/ACSGT/EReports/eR.2003/GroupB/Report1/styles.html

 

 

A: Doming by a mantle plume

B: A triple rift junction is initiated

C: Two of the rifts develop into an ocean and the third becomes a failed arm (aulacogen)

D: Less likely is that all three arms develop into oceans.

Edited January 5, 2015 by granpa