What are the four stages of the evolution of an ocean basin from first to last?

Question

What are the four stages of the evolution of an ocean basin from first to last?

a) (1) The upper crust is deformed by ductile stretching while the lower crust is broken along normal faults; (2) tension pulls apart the crusts and crust slab sink in the middle, forming a rift valley; (3) continued spreading creates a narrow sea; (4) after continued spreading, an ocean and ridge system are created. b) (1) The upper crust is broken along reverse faults while the lower crust is deformed by ductile stretching; (2) tension pulls apart the crusts and crust slab sink in the middle, forming a rift valley; (3) continued spreading creates a narrow sea; (4) after continued spreading, an ocean and ridge system are created. c) (1) The upper crust is broken along normal faults while the lower crust is deformed by ductile stretching; (2) tension pulls apart the crusts and exposes the mantle between them; (3) continued spreading creates a narrow sea; (4) after continued spreading, an ocean and ridge system are created. d) (1) The upper crust is broken along normal faults while the lower crust is deformed by ductile stretching; (2) tension pulls apart the crusts and crust slab sink in the middle, forming a rift valley; (3) continued spreading creates a narrow sea; (4) after continued spreading, an ocean and ridge system are created. e) (1) The upper crust is broken along normal faults while the lower crust is deformed by ductile stretching; (2) tension pulls apart the crusts and exposes the mantle between them; (3) the exposed mantle cools into oceanic crust; (4) continued spreading creates an ocean and ridge system.

Explanation / Answer

First stage is Embryonic – Here rift valley forms as continent begins to split. For example formation of   Great Rift Valley, Eastern Africa

Second stage is the Juvenile stage-Here the sea-floor basalts starts forming as continental sections diverge. For eample formation of   Red Sea

Third stage is the Mature phase in which broad ocean basin widens and trenches expand and subduction starts. Example is the formation of Atlantic Ocean

Fourth stage is the Declining stage – Here subduction eliminates much of sea floor and oceanic ridge. Example is the formation of Pacific Ocean

Fifth stage is the Terminal stage- In this stage narrow ocean basin, possibly shallowing because of sediment input young mountain ranges along edge. For example the formation of Mediterranean Sea, Persian Gulf

Last is the Continental Collision stage –Here last of the sea floor is eliminated and continents collide forming a continental mountain chain.

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