Re: geology

Dan Clemmensen (
Thu, 24 Jul 1997 22:58:03 -0400 wrote:
> I was trying to say that you dont need scientists to explain it, you can tell
> from looking at how the continents fit. I got the info from a book called
> science frontiers, and it is a composium of articles, they refer to
> "geologists" in that article. Why do need a specific name? If you want more
> info it's the "expanding earth hypothesis" and goes way back, 1933.
> danny

Geology has come a very long way since then. The contenental drift
(Plate tectonics) hsa been around even longer, and indeed started from
just the same observatin you mention: the contenents do fit together
like a jigsaw puzzle in many places. The theory was initially
since it didn't fit the conventional wisdom of the time and since there
wasn't much else going for it. Then, in the 1960's, came the Deep Sea
Drilling Project (DSDP), in which the drill ship Glomar Challenger took
a lot of drill samples from the ocean floor. The samples showed that
the midocan ridges are very young, that the magnetic reversals are
symmetric about the ridges, and that the crust gets progressively older
as you move away from the ridges. Sure enough, it really did look like
whole thing is expanding! However, the alternative explanation was that
the conental plates are being pushed away from the ridges and are
other plates or are banging into each other. Sure enough when geologists
looked at the other side of the plates, they found subduction zones.
are places where one plate is overriding another. Siesmic studies have
looked at these zones extensively. Siesmic data can be used to create a
picture of the insides of the earth using a mathematical procedure
known as tomography (the same math that is used with X-ray data to
to a CAT scan). Data shows the subducted plates (which are still cold
and dense compared to the upper mantle material) driving far down
into the mantle. A lot of related phenomena (such as oceanic trenches
and volcanic arcs) are highly correlates and with and easily explained
this theory. Counter-evidence is hard to come by, and a competing
theory (such as expansion) will have to explain all of these phenomena
before it can compete.

Now I have a neat speculative theory for you: why does all the major
seem to be toward the center of the Pacific, causing the "ring of fire?"
Maybe something (antimatter meteor?) took a chunk out there and the
is now adjusting? (Estimated silliness factor on this is 90%, but what
the heck.)

Comment from our geologist friends?