Two microplates - two pieces of the puzzle.
sure I am not the first to point out the next fundamental controversy
about Hawaii Hotspot. Let's consider the border between the two
first: the microplate between Mendocino and Murray Fracture Zones. Let's
assume Kure Atoll, Midway Atoll belong to this microplate.
second: the microplate between Murray and Molokai Fracture Zones. Let's
assume Pearl and Hermes Atoll, Laysan Island belong to this microplate.
Rolling events back.
Murray Fracture Zone points roughly to Pearl and Hermes Atoll that is
approx 2,300 from Kilauea, current location of the hotspot. Rolling
events back, we may suggest that at proposed 8-9 sm/year speed, the
hotspot was at Pearl and Hermes Atoll location some 25-30 million years
see how the microplates were positioned one relative to another back 25
MY ago, let's just cut the oceanic crust that was spread for the past 25
MY (including the crust that has been overridden by the NA continent).
There is huge difference between the amount of crust that was spread by
the microplates. Roughly, the second plate added approx more than 400km
of it's length than the first microplate did.
Back 25 MY:
- the oceanic floor of Pearl and Hermes Atoll was approx 400km east relative to Midway Atoll .
- then in no time the hot spot must had jumped from Midway Atoll over that 400km east to build Pearl and Hermes Atoll.
the hotspot slowly returns to its normal position; the Pearl and Hermes
Atoll, that was left behind the hotspot, returns back on the faster
moving microplate to get in line with Kure and Midway Atolls. This
concept of "smart" oscillating hotspot looks unrealistic to me.
break in the path around Pearl and Hermes Atoll seems to exist, but as
the break distance is considerably less than expected 400km, we may
conclude that the microplates did spread at different rates, but the
spot is the feature of geometry of global tectonic forces around the
Suggesting another mechanism for Hawaii - moving convergent "coldspot".
microplates are spreading out at different rates and are bumping into
the wall of oldest crust. There must be convergent/divergent zones to
accommodate the different rates of the crust spreading. Why not to
suggest Hawaii to be a part in the convergent process?
Comparing magma beneath the divergent boundary to the stuff beneath a convergent "coldspot".
material of the accommodated crust is not exactly the same as the
material of the fresh magma coming from bottom into the divergent
boundary. Accommodated sediments change chemical composition and melting
point of the stuff beneath the convergent "spot". In fact as the
melting point gets lower, the spot along the path better be called
"coldspot", not "hotspot". Many other parameters should be different
between the fresh magma and the stuff beneath the spot, but, I, Sergey
D. Sukhotinsky, the author of this post, think that this probably should
be the theme for another post.
Conditions to maintain the process of pumping magma/lava up.
- sufficient temperature gradient along the magma/lava path;
- deformations within the spot of the amplitude and speed to cause sufficient local displacements of magma/lava;
Conditions the process of pumping magma/lava stops at:- too much oceanic crust is brought up and down by the convergent coldspot:
a)the cold layer gets too thick, the temperature gradients gets too low;
b)the spot "diffuses"; the greater region gets the deformations, local displacements of magma/lava diminishes;
- the spot moves off the focus of global tectonic forces, the amplitude of crust deformations drops.
regions cools down as magma stops pumping up; the region gets resistant
to deformations due to the increased thickness of crust.
The focus of global tectonic forces probably is the intersection of the two lines:
- North to South fracture line through the Pacific plate.
to East probable fracture line connecting south borders of Asia and
North America. Thick and rigid continents prevent Pacific plate from
bending between continents along West-East line when Moon's plane of
orbit gets North. Thus the max bending stress of Pacific plate would be
along the probable WE fracture line connecting south borders of Asia and
The "coldspot" process resumes:
- the focus of global tectonic forces moves south-east on the plate as the plate itself moves north-west;
- magma under the new location is not spoiled with sediments;
amplitude of crust deformations is good at the location because the
crust here is pre-bent by the load of the chain of volcanoes and the
chain itself ceased to bend due to the increased thickness.
fracture segment develops south-east to the old sub-chain of volcanoes.
The fracture pumps magma up developing new segment of the volcano
How to tell if the concept is correct.
I need more time to figure it out; right now I got a couple of ideas on where to look for the evidences:
relief of the chain of volcanoes should show that the region is under
west-east compression, that contradicts slab-pull concept but is in line
with ridge-push concept;
should be a gap in the age of the sediments (and crust) on the both
west and east sides of the chain because some crust was consumed to
build the volcanoes and to recycle the bottom of the spot into
underlying magma. The time-width of the time-gap should roughly be equal
to the time span a volcano was active within. That is somewhat greater
time than it is now usually thought of. That's because the evidence of
early activity of a segment of volcano chain is hidden deep within the
volcano or even got molten and got recycled into the underlying magma.
I'd like to estimate the time gap could be as great as up to 10MY.