UM, LM correlations

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The probability that 18out of 24 randomly
chosen points lie within the belts (23.5 of the
CMB area) is about 1 in 7 million ( p 1.47
10-7 ) considered by authors to be
remarkable
CMB backtracked LIPs
you ought to have done a better job! -Ernest
Rutherford
69
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About 32 of the worlds active non-arc volcanoes
or volcano clusters in the oceans occur in region
O1 (19 of area) which roughly corresponds to the
20 Ma age contour. Only about 7 occur well away
from the LVAs associated with spreading ridges
and most of these are in oceanic region O2 (27
of area).
(Lekic et al., 2010).
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Distance of hotspots from Plume Generation Zones
at CMB (-1 contour)
Most hotpots formed on or near ridges
50 of hotspots 25 of LIPs formed gt1000 km
away from CMB plume generation zone
Evidence that most (1/2) hotspots are from
plumes from the CMB
2000 km
1000 km
Most of these are over ridge-related or
ridge-like LVAs, are on active or abandoned
ridges, or are underlain by slabs or are on
tectonic shears or rifts
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Although the correlations of hotspots with the
edges of LLSVPs (i.e. the no-anomaly contour
and with the edges of LVAs associated with ridges
can both be considered remarkable, a
straightforward hypothesis test shows that the
upper mantle correlation is far superior (p of
chance occurrence is an an order of magnitude
lower). The so-called Plume Generation Zone in
D actually corresponds almost exactly with the
median value of D wavespeeds (The second
quartile). The above does not imply that the
upper mantle LVZ correlates with the lower mantle
LLSVP in fact, they are uncorrelated (Ray etc.).
They have completely different shapes (see
previous 2 slides).
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About 32 of the worlds active non-arc volcanoes
or volcano clusters in the oceans occur in region
O1 (19 of area) which roughly corresponds to the
20 Ma age contour. Only about 7 occur well away
from the LVAs associated with spreading ridges
and most of these are in oceanic region O2 (27
of area).
(Lekic et al., 2010)
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Hotspots are where supercontinents and ridges were
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Hotspot locations show almost perfect correlation
with the lithospheric stress field associated
with upper mantle downwellings but have much
poorer correlations with stresses inferred from
upwellings and from lower mantle effects. For a
search radius of 100 km, only 3 minor volcanic
provinces are in regions of substantial inferred
convergence rather than extensionthe chances
that the correlation between positive divergence
and hotspot locations could be randomly obtained
is almost null (1). On the other hand, half of
all hotspot locations are more than 1000 km away
from the vertical projections of so-called Plume
Generation Zones at the CMB (Torsvik, Burke) and
this was considered to be a remarkably good
correlation.
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Near base of thermal boundary layer (Region B)
Schaeffer 2013
LVZ
All hotspots, ridges backtracked LIPs occur in
red yellow regions
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Upper (B) Lower (D) Boundary Layers of the
Mantle Hypothesis test Null Hypothesis
Region D (the Core-Mantle Boundary) correlates
better with hotspots backtracked LIPs than any
other region of the mantle. D therefore contains
Plume Generation Zones, e.g. fixed points above
the core (Burke, Torsvik). Result the
hypothesis fails
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EXAM QUESTION If A B both correlate with C,
does A correlate with B?
ANSWER if A and B are positively correlated and
B and C are positively correlated then are A and
C also positively correlated? Is the positive
correlation transitive? For example, if the
price of stock B increases along with the price
of stock A, and the price of stock C increases
with the price of the stock B. Then is it the
case that the price of the stock C increases with
the price of the stock A always? Yes, one may
jump into conclusion that they do so. Not because
of he/she may be thinking about Pearsons
correlation coefficient, but it may due to
thinking in line with causation. In fact, if one
knows about Pearsons correlation coefficient
he/she may not conclude so. An article by
Langford, Schwertman and Owens in The American
Statistician gives rather deep look at the
problem.
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LVZ
Excellent correlations with hotspots LIPs
CMB
D boundary layer (poor correlations)
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Region D exhibits little correlation with upper
mantle, surface tectonics, hotspots or the
transition zone
CMB (D)
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slabs
Slabs
Pacific plateaux formed at boundaries triple
junctions of new plates
Over-ridden oceanic plates, mantle fluxed by
slab volatiles
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The low velocity zones (LVAs) associated with
present day ridges are in the same places as they
were when Pangea broke up the antipodal Pacific
plates reorganized oceanic plateaus erupted.
The surface expressions of ridges migrate but
only within the confines of the 2000-km wide
LVAs associated with ridges at 150-200 km
depth. Hotspots LIPs backtrack to these same
ridge-related regions. Plates D are highly
mobile since they are next to inviscid
boundaries. Why is there apparently a fixed
reference frame in the convecting mantle?
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Plate reconstructions show that subduction
repeatedly occurs along the same bands. Regions
that are warmed from above by the insulating
effects of large plates and not cooled from below
by stagnant slabs tend the control the locations
of divergence of plates the colder regions
control the locations of convergence and
subduction. These effects also control the
boundary conditions at the top of the lower
mantle, topography and temperature. much of the
long-wavelength geoid originates in the deep
mantle, the dynamic topography appears to
originate from density variations in the upper
mantle More than 1600 spherical harmonic
coefficients are used in modern global tomography
but only one has any degree of correlation
between the top and the bottom of the mantle
(Adams Anchor)most of the power is in degree 2
3.
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Surface hotspots correlate with ridges
ridge-like mantle structure with extensionanal
stress
EXTENSIONAL STRESS
EXTENSIONAL STRESS
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STATISTICS 100 of hotspots fall in LVAs of
the upper mantle, mostly those associated with
ridges, in regions of extension
Only 3 hotspots are not near yellow/red. All
LIPs backtrack to red.
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If the upper and lower mantles correlate, this is
why
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European, African, Asian (Changbai), Yellowstone
most continental hotspots are underlain by
slabs
Cold slab
Cooled mantle
CAN BOTH UPPER MANTLE LOWER MANTLE BE COOLED BY
LONG-LIVED FLAT (STAGNANT) SLABS?
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start
Free-slip
Slip-free
Free-slip
60 Myr later
Non-fixed non-vertical upwellings
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Houser, Masters, Flanagan, Shearer (20008)
410
650
Cool 650, warm 410
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