What casues the Hawaii hot-spot, and why does it not make a
divergent plate boundry?
Peter Sims
Hi Peter,
You've asked a question that lots of people would like to know the answer
to. I don't think anyone has an idea of even what a hotspot IS, let
alone what causes it. I should probably back up and say that lots of
people have ideas, it's just that none of these ideas are good enough to
have convinced any of the other folks who have ideas of their own. One
of the latest thoughts is that there are perturbations at the core-mantle
boundary which somehow provide upwelling plumes of heat, these being the
hotspots.
As for why the hotspot doesn't cause a divergent boundary, I guess it
just isn't powerful enough. It only manages to burn a few "little" holes
through the plate at any one time. For example the three "holes"
presently being fed by the Hawaiian hotspot correspond to Kilauea, Mauna
Loa, and Lo'ihi.
There is a relatively new idea that there are occasionally huge plumes of
magma that rise through the mantle. These things are sort of
mushroom-shaped, or perhaps upside-down teardrop-shaped. Anyway they
consist of a huge blob of magma followed by a much skinnier tail, and are
called "diapirs". The idea goes that when the head on one of these
diapirs arrives at the surface, huge volumes of magma erupt to form what
are called flood basalts. As the theory states, these events ARE
sufficient to rift tectonic plates. Then, once the main blob of magma
has erupted the tail continues to rise to the surface and erupt, only it
is a much smaller volume of lava erupting. This is what constitutes a
hotspot. There are numerous hotspots around the world that can be tied
to specific flood basalts, and in cases 2 specific flood basalts (because
the splitting plate also divided the basalt). This theory is becoming
quite popular, one might even say it is starting to reach bandwagon
status. One of the main problems though: Where is the flood basalt
province that corresponds to the Hawaiian hotspot??
Keep asking good questions.
Sincerely,
Scott Rowland
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