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 POST CLAM-SHELL

 EXPANSION

Multiple strike/slip faults in the lower western side of North America will have caused the characteristic ‘staircases’ to develop. The western passive margin became fragmented into rectangular slabs which then moved at different rates to each other, and some were rotated in the process. These slabs were jostled about by the opposing tectonic forces indicated in the previous diagrams.

 

Once a fault line is established, a crust segment can move at a different rate to another or in an opposite direction to another. These direction flows can even reverse and the San Andreas fault, for instance, has movements which are contrary to movements which took place many millions of years ago.

 

The Alaskan peninsula was pushed round in an anti-clockwise direction as the Atlantic Ocean-bed pushed north-westwards. This rotation movement has been confirmed by researchers (Embry, 1998) using magnetic anomaly data and geographical positioning.

 

Simple Stretching of the Crust

 

Before the crust ruptured in the western hemisphere and the Atlantic Ocean bed had started to form, much of the crust of western Europe had been stretched to thinner depths. There is now a gradient of crust thinning which runs westwards.

 

By then the British Isles had been transported in a south-west direction away from its former neighbour Denmark. At the same time, the Scandinavian peninsula skewed westwards as the Baltic Sea bed formed by the stretching of its crust.

 

We can trace these movements by sedimentary geology. Chalks and limestones which had formed in water filled basins, being brittle by nature, fragmented as the more ductile platform rock beneath them stretched under tension. Some of these fragments were carried considerable distances away from their original positions, riding piggy-back on the stretching crust.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Formation of the Mediterranean Basin

 

Just before the clam-shell started to ‘open’ - the Mediterranean area probably looked like the image below. The clam-shell hinge line is indicated in red.

 

 

 

 

 

 

 

 

 

 

 

Notice that the northern part of the African continent was much more eastward with respect to the European land mass.

 

The peninsula of Morocco fitted snugly into the area near Corsica.

The Canary Islands were near the southern tip of Spain.

Sicily was much further east and attached to Crete.

The Black Sea was much narrower, there was no Aegean Sea between Greece and Turkey, and the land space for Libya and western Egypt was not in existence.

 

It can be seen from the following sequence of images that crustal stretching in the eastern Mediterranean created these new areas of land mass and at the same time allowed the African plate to move westward, taking with it the Canary Islands and the Island of Sicily.

 

A strike/slip relationship existed between the north African plate and the Iberian peninsula and is probably still active today.