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Re: Iceland & the Rift Valley
>> Iceland appears to be a spreading center 'filtered'
>> through continental crust.
>What does this mean? How can continental crust maintain itself at a
>spreading center? It ought to be rafted away within a few million years. It
>sounds like you are describing East Africa (the Rift Valley), not Iceland.
>Would you care to elaborate?
A spreading center is by definition a place where new crust is being formed. As
it is created, it IS rafted away over millions of years. The "hole" this creates
is filled by even more upwelling crust. Therefore Iceland is growing larger all
the time, and may eventually form a new continent.
The Rift Valley is a different situation. It is a fault line where land east of
the fault is moving north relative to the mainland. Thus the continent is
being broken apart, in the same way that California will someday join Vancouver
Island, but no more crust is formed in the process.