Nobody
knows what Rodinia actually looked like, but here is one
suggestion based on what geologists have written: North America (NA); Africa (A). Bear in mind that
eastern North America does not yet exist. That big range of
mountains, covering half the face of the planet, is
the
Grenvilles! These monsters were much more massive and high than the modest Himalayas of the present day.
The Grenvillian rocks are twisted sisters! We know
that the
Blair River rocks of Cape Breton belong to this very old group because
they include red- and black-banded gneiss. Gneissic riocks are igneous
rocks (fire-formed in volcanoes and in plutons). They were
created in island arcs millions of years before Rodinia became a fact.
In the final stages of collision, their gneiss was intruded
by
distinctive red and white plutonic rocks,which are found elsewhere in
the Grenville. About a billion years ago, all these rocks were the
subject of intense heat and pressure, and were converted into
metamorphic rocks.
The dark blue line indicates an oceanic trench, a place of
sea-floor spreading to both the east and the west; a volcanically
active place where new land was forming. Old land was being lost west
of Rodinia where that broad white line indicates a subduction zone.
This is a place where continental plates are in collision and being
drawn down or subducted into the mantle, where they are destroyed or at least reformed.
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