If we trace the stages of growth of the planet from Pangaean Earth, described in
the last chapter, to the present day - it describes a lop-sided development of new
crust. In other words, most of the new crustal surface required for a much larger
Earth has been formed on one side of the planet, namely in the Pacific Ocean bed
I liken this lop-sided development of the Earth’s new crust to that of the opening
of a clam-shell. The original super-continent Pangaea divided into two main parts,
the northern part named Laurasia (Euro-Asia and North America) and the southern part,
known as Gondwana (Africa, India, Australia, Antarctica and South America).
If we imagine Laurasia to comprise the top component of the clam-shell and Gondwana
the lower one, with its hinge in the Mediterranean area - a ‘closed’ clam-shell would
represent Pangaean Earth, 320 million years ago. As the clam-shell opens its ever
widening ‘gape’ represents the new-ocean bed being formed. When the clam-shell is
at maximum gape, the Pacific and Indian Ocean beds are fully developed.
The clam-shell started to open when Antarctica began to split away from the far eastern
coast of Asia. This occurred in the early Permian Period and coincided with the break
up of Pangaea into the two super-continents mentioned.
The progressive opening of the clam-shell is depicted in the left-hand series of
Euro-Asia (Laurasia) ...... ........... Silver blue
India (part of Gondwana)............ White
Australia (part of Gondwana) ...... Beige
Africa (part of Gondwana) ......... Red
New Guinea (part of Gondwana).. Green
Pacific Ocean Bed (new crust).... Blue
The following set of images gives more detail of the stages of the clam-shell opening,
the planetary diameter as a percentage of the present one, and the geological period
during the stage.