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E HOT SPOTS
« on: March 08, 2017, 01:58:31 pm »
New Concepts in Global Tectonics Newsletter, no. 38 3 ARTICLES
GULF OF CALIFORNIA ELECTRICAL HOT-SPOT HYPOTHESIS:
CLIMATE AND WILDFIRE TELECONNECTIONS
Bruce A. LEYBOURNE - leybourneb@hotmail.com
(Geostream Consulting LLC, www.geostreamconsulting.com)
Bay St. Louis, MS, USA
Giovanni P. GREGORI - giovanni.gregori@idac.rm.cnr.it
(Professor -Istituto di Acustica O. M. Corbino - Retired) Roma, Italy.
Cornelis F. de HOOP - cdehoop@lsu.edu
(School of Renewable Natural Resources, Louisiana State University Agricultural Center)
Baton Rouge, LA, USA

Introduction:

The prevailing view that radioactive decay is the major thermal source for the interior of the planet may create limitations in geophysical modeling efforts. New theoretical insights (Gregori 2002) provide for an electrical source from the core-mantle-boundary (CMB) by a tide-driven (TD) geodynamo which is enhanced by various solar induction processes. Joule heating at density boundaries within the upper mantle and base of the lithosphere from CMB electrical emanations may provide some of the hotspot energy for upper mantle melts and associated magmatism driving seafloor spreading and lithospheric rupture. Estimates of the total budget of the endogenous energy of the Earth supporting the electrical hot-spot hypothesis are as follows (Gregori, 2002):
1) The general scenario is that the TD geodynamo has a very low performance in terms of magnetic energy output (<<1%), while almost its entire energy output supplies (via Joule’s heating) the endogenous energy budget. Indeed it can be sufficient for justifying the entire observed energy budget of the Earth, while other sources, such as radioactivity, are just optional.
2) A different consideration is due to chemical and phase transformation processes, occurring within deep Earth. Observations are evident that the Earth operates like a car battery, being recharged and discharged at different times. This occurs by storing energy within the deep Earth interior. Within a car battery, such storage occurs via a reversible chemical reaction. In the case of the Earth, such storage occurs via a conspicuous change of liquid vs. solid phase. It should be stressed that such inference is a matter of observational evidence, and of strict implications. It is NOT a result of any kind of speculation.
3) The timing of such recharging and discharging is manifested, as the most evident effect, in terms of the Earth’s electrocardiogram, displaying one heartbeat every ∼27.4 Ma (with an error bar of, say, < ±0.05 Ma). Every heartbeat elapses a few Ma, and during it some large igneous province (LIP) is generated. At present, we are close to the peak of one such heartbeat, and a present LIP is Iceland.
4) The manifestation of such huge endogenous energy budget, at least according to the observational evidence referring to the last few million years, occurs in terms of a ∼ 60% release as a gentle geothermal heat flow, while the entire remaining 40% includes all other forms of energy, such as volcanism, seismicity, continental drift or sea floor spreading, geodynamics, and tidal phenomena. Therefore, the planetary-integrated role of heat flow cannot be neglected (such as it is being generally assumed when dealing with climate models). Tectonic theorist might consider electrical stimulation from the interior of the planet as a plausible driving mechanism of surge channel activity and plate motions. This driver has remained elusive in modern theoretical constructs.
Two recent lines of observational evidence linked to electrical stimulation within a geologic hotspot exemplify the importance of understanding this tectonic driving mechanism and testing the validity of our hypothesis. The Guaymas Basin Rift, (Fig. 1, and Fig. 2 – Area 2) a geologic hotspot within the Gulf of California is considered a geothermal power source for the region. In the first scenario gentle geothermal heat flow from TD joule heating within the hotspot is invigorated during bursts of regional seismic activity. Solar induced and electrically stimulated seismic activity provides additional thermal energy at the base of the lithosphere. This heat may take up to 6 - 7 months for transmigration and escape at the surface. This timing is consistent with the observational data and rationally explains the local sea surface thermal signatures over the Guaymas Rift coincident with El Nino climate teleconnections (Fig. 2 – Area 3 and 4). In the second scenario Coronal Mass Ejections (CME) induce powerful surges of electrical activity from the deep interior of the planet. These powerful surges overcome resistance in the lithosphere by traveling along more conductive zones generally associated with basaltic fault intrusions and their signature geomagnetic anomaly trends. Ionized gases may be forced through the fracture systems and wildfires may be sparked by electrical arcing (lightning) or direct combustion from intense joule heating near the surface. The unprecedented wildfire storm in October 2003 occurred simultaneously with a powerful CME. Geospatial wildfire patterns suggests these wildfires followed fault and geomagnetic anomaly trends associated with the extension of the East Pacific Rise into the North American continent and Pacific fracture zones traversing the west coast of California. Details of each scenario are discussed below.
I. El Nino Climate Teleconnection
Sea Surface Temperature (SST) anomalies over the Gulf of California/Baja (Fig. 2 - Area 2) are teleconnected to the peak El Nino SST anomaly patterns also seen in Fig. 2. Note the spurious SST anomaly over the Cocos Ridge associated with El Nino (Fig. 2 – Area 3). Earthquakes beginning in November 1996 at the beginning of a solar sunspot cycle (Hale Cycle) signal the beginning of an increased period of seismic activity associated with heat inputs driving the 1997/98 El Nino (Fig. 3). Blot (1976) and Blot et al. (2003) indicate thermal transmigration rates of approximately 0.15 km/day accounting for the approximately 7 month delay of sea surface thermal signatures after high impact earthquake bursts which even triggered a small tsunami in Hawaii (Walker, per. com). Seismic precursors to El Nino by 6-7 months have also been documented (Walker, 1988, 1995 and 1999) over the last 7 recent El Nino events. The resulting clustered seismic activity is hypothesized to be electrical in nature and is associated with joule heating at density boundaries near the base of the lithosphere (Gregori, 2000 and 2002). Electrical stimulus of these earthquakes is highly suspect, especially below the lithosphere. This scenario provides a geophysical mechanism for explaining the SST anomaly teleconnections. These SST anomaly patterns overlying earthquake events are hypothesized to be the result of increased heat emission from seafloor volcanic extrusions and/or associated hydrothermal venting. The volcanism is triggered by electrical bursts from the core-mantle-boundary induced by solar coupling to the internal geodynamo. The larger implication is that El Nino may be solar-tectonically modulated (Leybourne, 1997; Leybourne and Adams, 2001).

Cedros Trench Cedros Trench Guaymas Basin Rift Salton Trough
Fig. 1. SST drape over bathymetry in the Gulf of California Salton Trough region exhibits thermal anomalies coincident with the adjacent Cedros Trench. Thermal signatures in this area are often teleconnected to El Nino SST anomalies off the coast of South America. The Guaymas Basin Rift is the likely energy source for this local thermal signature and is a known geologic hot-spot supplying Southern California with geothermal power (Image by Haas 2002, NAVOCEANO-MSRC). New Concepts in Global Tectonics Newsletter, no. 38 5
1- US. West Coast2 – San Andreas/Guaymas3 – Central America4- South America

Fig. 2. Eastern Pacific SST anomalies peak in January of 1998 during 97/98 El Nino event in area 2 - San Andreas/Guaymas. This corresponds to the viewing angle in Fig. 1 exhibiting teleconnection SST anomalies over Guaymas Rift and Cedros Trench. Area 3 Central American exhibits the main intertropical convergence SST anomaly coincident with spurious teleconnection pattern over the Cocos Ridge trend (NAVOCEANO-MSRC).

Fig. 3. (a) Two distinct clusters of earthquakes off the Coast of South America in Nov. 96 are apparent. (b) SST’s seem to emanate in a similar pattern to the earthquake paired clusters. The northern SST anomaly is on the continental shelf as is the northern earthquake cluster, while the southern SST anomaly is further offshore over the continental slope as is the southern earthquake cluster. These SST anomalies appeared (June 1997) just north of earthquake positions possibly due to prevailing long shore currents, about 7 months after the paired earthquake clusters. (c) Chart indicates earthquakes/day (frequency), magnitudes are added for simple power indicator (magnitude add), along with an average (magnitude avg). A spike in earthquake activity begins Nov. 12th and tapers off Nov. 14th revealing the intense episodic nature of these events. (d) SST Max. Anomaly/month indicating anomalies > 7° C by June 97 followed by a year of elevated SST anomalies associated with the 97/98 El Nino. (e) Joule energy released during (f). Earthquake events Nov. 96.

II. Wildfire Teleconnection
Wildfire outbreaks during a period of geomagnetic storms in October 2003 may be linked to electrical emanations from within the earth (Leybourne et. al., 2004). In late October 2003, a powerful Coronal Mass Ejection (CME) directed straight at Earth erupted on the Sun’s surface, when wildfires simultaneously broke out along an arc shaped pattern of geomagnetic anomaly trends extending from Mexico to north of Los Angeles (Fig. 4). The wildfire ignitions slowed dramatically when the CME period ended. The geomagnetic anomalies are inter-splayed by fault systems connected to the Gulf of California hotspot through the San Andreas Fault complex and to the Hawaii hotspot through the Murray Fracture Zone. These orthogonal fault systems intersect in the San Gabriel Mountains where a huge wildfire out break occurred near strong geomagnetic signatures (Fig. 5). Strong electrical impulses emitted from the CMB during CME may not only joule heat local geologic hotspots, but unconverted superfluous electrical energy and ionic plasmas could be transmitted further along conductive igneous complexes (generally associated with geomagnetic signatures) and fault systems through the lithospheric fractions of the earth, arcing to power lines and igniting tree lighter or underbrush. In 1859 during the strongest CME on record, telegraph wires in western United States and Europe caught fire and were destroyed. Potential voltage differences between hotspot locations may create electrical ground shorts at geomagnetic intersection areas (Fig. 6), starting fires near power line circuits or from discharges directly to the ionosphere. An electrical hot-spot hypothesis based on Gregori’s theoretical construct is understood in terms of deep earth electromagnetic induction coupled to solar perturbations. The induction process creates anomalous electric currents from the internal-geodynamo.

Fig. 4. Arc-shaped fire pattern appears linked to geomagnetic anomaly trends (insert). http://activefiremaps.fs.fed.us/fire_imagery.php?firePick=southern_california; http://pubs.usgs.gov/sm/mag_map/ mag_s.pdfNew Concepts in Global Tectonics Newsletter, no. 38 7
Fig. 5. Geomagnetic anomalies in San Gabriel Mountains along intersecting faults and mylonite units. http://wrgis.wr.usgs.gov/docs/gump/anderson/rialto/rialto.html

Fig. 6. Geophysical composite map: a) Basalt flow remnant magnetization signatures indicating global hotspot locations and indicated Pacific links (Quinn, 1997). b) Southern California geomagnetic crustal anomalies have coincident links to the San Andreas orthogonal fault complex associated with an intersection in the San Gabriel Mountains where a huge wildfire outbreak occurred near the strong geomagnetic signatures during the October, 2003 CME (USGS 2002). c) Pacific Ocean Basin GEOSAT structural trends indicating possible electrical conduits (red lines) between Murray (North) and Molokai (South) Fracture Zones which intersects at Hawaiian, Guaymas, and Juan de Fuca hotspots (orange circles), geographical links (green lines) (Smoot and Leybourne, 2001). d) Southern view in Fig. 1 with geographical links (Haas, 2002).

Conclusions:
Thus, Earth’s endogenous energy may stimulate ocean basin heating associated with El Nino from episodes of increased seismic stimulation and electrical wildfire propagation during CME via geologic hotspot controls. Atmospheric pressure teleconnections are also suspected (Namias, 1989) in some cases. A distinction is made between the control on the TD geodynamo exerted by the e.m. induction within very deep Earth (i.e. within the mantle, which occurs only for e.m. signals of some very low frequency, say with a period T > 22 years), and the e.m. solar induction within some much shallower structures characterized by much higher frequencies and much shorter periods. Such kinds of phenomena also include the e.m. induction effects within manmade systems, such as power lines (causing blackouts), pipelines, and communication cables (Meloni et al., 1983; Lanzerotti and Gregori, 1986). Should we address these as distinct phenomena? The relationships between the different e.m. signals within such different frequency bands is not clearly defined but these various affects at different time scales may to some degree be physically driven by electrical stimulation from the interior of the planet.

References:
Blot, C., 1976. Volcanisme et sismicite dans les arcs insulaires. Prevision de ces phenomenes. Geophysique 13, ORSTOM, Paris, 206p.
Blot, C., Choi, D.R. and Grover, J.C., 2003. Energy transmigration from deep to shallow earthquakes: A phenomenon applied to Japan –Toward scientific earthquake prediction-. New Concepts in Global Tectonic Newsletter, Eds. J.M. Dickens and D.R. Choi, no. 29, p. 3-16.
Gregori, G., 2002. Galaxy-Sun-Earth Relations: The origins of the magnetic field and of the endogenous energy of the Earth. Arbeitskreis Geschichte Geophysik, ISSN: 1615-2824, Science Edition, Schroder, W., Germany.
Gregori, G., 2000. Galaxy-Sun-Earth Relations: The dynamo of the Earth, and the origin of the magnetic field of stars, planets, satellites, and other planetary objects. In Wilson A., (ed.), 2000. The first solar and space weather conference. The solar cycle and terrestrial climate. ESA SP-463, 680p., European Space Agency, ESTEC, Noordwijck, The Netherlands, p. 329-332.
Gregori, G., 1993. Geo-electromagnetism and geodynamics: “corona discharge” from volcanic and geothermal areas. Phys. Earth Planet. Interiors, v. 77, p. 39-63.
Haas, A., 2002. Figs. 1, 2, and 3d. Produced by: Major Shared Resource Center (MSRC) at Naval Oceanographic Office (NAVOCEANO), Stennis Space Center, MS, 2002.
Leybourne, B.A., 1996. A tectonic forcing function for climate modelling. Proceedings of 1996 Western Pacific Geophysics Meeting, Brisbane, Australia. EOS Trans. AGU, Paper # A42A-10. 77 (22): W8.
Leybourne, B.A., 1997. Earth-Ocean-Atmosphere coupled model based on gravitational teleconnection. Proc. Ann. Meet. NOAA Climate Monitoring Diag. Lab. Boulder, CO., p. 23, March 5-6, 1997. Also: Proc. Joint Assemb. IAMAS-IAPSO. Melbourne, Australia, JPM9-1, July 1-9.
Leybourne, B.A. and Adams, M.B., 2001. El Nino tectonic modulation in the Pacific Basin. Marine Technology Society Oceans ’01 Conference Proceedings, Honolulu, Hawaii.
Leybourne, B.A., Haas, A., Orr, B, Smoot, N.S., Bhat, I., Lewis, D., Gregori, G., and Reed, T., 2004. Electrical wildfire propagation along geomagnetic anomalies. The 8th World Multi-Conference on Systemics, Cybernetics and Informatics, Orlando, FL., p. 298-299 (July 18-24).
Meloni, A., Lanzerotti, L.J., and Gregori, G., 1983. Induction of currents in long submarine cables by natural phenomena. Rev. Geophys. Space Phys., v. 21, no. 4, p. 795-803.
Namias, J., 1989. Summer earthquakes in southern California related to pressure patterns at sea level and aloft. Scripps Institution of Oceanography, University of California, San Diego. Journal of Geophysical Research, v. 94, # B12, p. 17,671-17,679.
Quinn, J.M., 1997. Use of satellite geomagnetic data to remotely sense the lithosphere, to detect shock-remnant-magnetization (SRM) due to meteorite impacts and to detect magnetic induction related to hotspot upwelling. International Association of Geomagnetism and Aeronomy, Upsala, Sweden.
Smoot, N.C. and Leybourne, B.A., 2001. The Central Pacific Megatrend. International Geology Review, v. 43, no. 4, p. 341, 2001.
USGS –United States Geological Survey, 2002. Magnetic anomaly map of North America. Dept. of the Interior.
http://pubs.usgs.gov/sm/mag_map/ mag_s.pdf; http://wrgis.wr.usgs.gov/docs/gump/anderson/rialto/rialto. html
Walker, D.A., 1988. Seismicity of the East Pacific: correlations with the Southern Oscillation Index? EOS Trans. AGU. v. 69, p. 857.
Walker, D.A., 1995. More evidence indicates link between El Ninos and seismicity. EOS Trans. AGU, v. 76, no. 33.
Walker, D.A., 1999. Seismic predictors of El Nino revisted. EOS Trans. AGU, v. 80, no. 25.
« Last Edit: March 08, 2017, 10:06:26 pm by Admin »

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PREVENT ERUPTIONS
« Reply #1 on: March 13, 2017, 07:29:02 pm »
3/16/17, 11:34AM
Charles Chandler - Hi Charles. On Tuesday I told Dong Choi, editor of NCGT, that the Electrical Hot Spots article he published around 2004, which described Earth as an electrical battery, is similar to your model and that, if your model is right, you have an idea how to stop eruptions and possibly quakes. He replied that he agrees that Earth acts like a leaky battery and explains many things well, including John Casey's finding that earthquakes correlate with sunspot minima. He said he looks forward to receiving your manuscript. I mentioned your model, because I thought he might be interested in your idea for stopping eruptions. But he said he doesn't think nature's acts are stoppable, although he said it's an interesting idea and who knows, maybe it would work.

I noticed that Jeff Wolinsky had a brief mention of his model and links to his videos in NCGT's 3rd quarter issue last year. So it looks like NCGT will be hopefully a good place to publicize much of your model. I think they may even like to publish your tornado model, because they seem to be very interested in learning to prevent natural disasters, at least via prediction and preparation. G'Day

-----

Tuesday, March 14, 2017 3:33 AM
From: "Dong Choi (NCGT)" <editor@ncgt.org>
I look forward to receiving Charles Chandler's manuscript. I agree that the Earth acts like a battery. This explains many phenomena very well. The earthquake - solar cycle anticorrelation is also well explained by the leaky battery theory, as proposed by Giovanni Gregori. Electric Earth is the way to see the real Earth.
I don't think nature's acts - volcanic eruptions and earthquakes - are stoppable. But the idea is very interesting. Something to keep thinking for us. One day, it may become a reality. Who knows?
I am watching Indonesian volcanoes. They will be a sentinel of the coming mini-ice age. Don't forget California and New Madrid. We will detect when a huge energy is released from the Earth's outer core. There must be some signs.

---

Hi Dr. Dong Choi. Tuesday, 14 March 2017 11:24 AM
Thank you for the book suggestion. I'm waiting to see if it's available via the library first.
I just read Dark Winter and got a lot of good info from that. I'll try to get the new book soon.
Last week I read from NCGT Newsletter no. 38 the article, GULF OF CALIFORNIA ELECTRICAL HOT-SPOT HYPOTHESIS, which is interesting and is similar to my friend Charles Chandler's model. Both agree that the Earth acts like a battery that generates electric currents. Charles developed his model about 4 years ago. I told Charles about the article and suggested that he inquire about possibly submitting some of his material to NCGT. Charles' model is much more thorough than the NCGT article, but the latter was written around 2004, so they may have developed their model more by now.

If Charles' model is close to correct, he has determined how volcanic eruptions and earthquakes could possibly be stopped. Quakes would be more difficult, because a final quake would be triggered, so people would have to be evacuated. But for volcanoes he says a 5 km deep borehole some distance from the volcano should stop eruptions, like lightning rods prevent lightning damage. The borehole would act like a lightning rod for electric currents from the Moho, causing the nearby volcano channel to freeze up gradually. He says a borehole near an earthquake fault could heal the fault, which is an idea that I think your co-editor Louis Hissinck is familiar with. But a nuclear explosive would need to be dropped into the borehole in order to produce a shock wave that would seal it. He thinks a good test site would be Istanbul where a fault is near the surface, requiring little drilling. As for the volcano nearby boreholes, he estimated they'd cost about $20 million to drill 5 km deep.
So, in light of John's and your findings about quakes and eruptions being triggered by solar minima in conjunction with planetary tidal influences, it seems that humanity might be able to prepare for catastrophic events by preventing them, at least in part. I suppose the Indonesian volcanoes would be the most important ones to prevent from erupting.
Do you have any comments?

--------------------------------------------

On Thu, 3/9/17, Dong Choi (NCGT) <editor@ncgt.org> wrote:
Subject: RE: Surge Tectonics
Date: Thursday, March 9, 2017, 4:20 AM
 
Hi, Lloyd, The book you need to read is; "Surge tectonics: a new hypothesis of global geodynamics", authored by Arthur Meyerhoff and others. Kluwer Academic Publishers in 1996. The book has been cited numerous times in our papers. I am one of the co-authors of this book. Art Meyerhoff was the greatest geologist our history ever had. I am glad I am one of his students; he raised me to occupy the present position - editor of NCGT Journal. The book presents scientific grounds of the surge tectonics. The book appeared two years after his death. 
 
The surge channel is identified by the presence of low velocity lenses or layers under inactive or active tectonic belts in the upper mantle. In the New Madrid paper I showed the presence of a low velocity lens under the Mississippi Valley. The low velocity lens is where liquid or gas is contained and energy or magma flow occurs. Although I did not specifically refer to the surge channels in many of my papers, their presence is confirmed in many seismic tomographic images.
 
As you may have noticed already, the current geology is facing serious challenges; same as politics - fake news, fake science. Political correctness and financial correctness distort factual evidence. Plate tectonics have been dominating the geological scene for over 50 years, but no evidence has ever been presented. All hard data show otherwise - vertical tectonics is the primary movement. We have documented numerous evidence that shows the sunken continents in the present oceans.
 
I am glad there is a serious person who reads our papers objectively. Please ask me anything, I'll try to answer as much as I can. Dong Choi
 
 -----Original Message-----
From: lloyd kinder Sent: Thursday, 9 March 2017 4:06 PM
To: Dong Choi (NCGT) <editor@ncgt.org>
Subject: Surge Tectonics
 
Hi Mr. Choi. From what I've read so far in NCGT, it seems that there have been considerable successes using Surge Tectonics to predict major earthquakes. Do you recall if there are any writings in NCGT that specify what exact evidence there is for surge channels and migration of surge energy from the mantle to the surface? I enjoy many of the illustrations, tables and maps in NCGT, but haven't yet come across the kinds of evidence for surge channels that I hope to read soon. I hope you may be able to refer me to one or more NCGT journal or newsletter issues that have such evidences. Otherwise, can you refer me to any books or papers outside of NCGT, esp. something fairly recent? Thanks for any help or just a reply.
« Last Edit: March 16, 2017, 11:36:11 am by Admin »

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Re: E HOT SPOTS
« Reply #2 on: March 15, 2017, 10:51:27 am »
522 New Concepts in Global Tectonics Journal, V. 4, No. 3, September 2016. www.ncgt.org
Caveats on tomographic images
Gillian R. Foulger (g.r.foulger@durham.ac.uk), Giuliano F. Panza, Irina M. Artemieva, Ian D. Baslow, Fabio Cammarano, John R. Evans, Warren B. Hamilton, Bruce R. Julian, Mechele Lustrino, hand Thybo and Tatiana B. Yanovskaya.
Terra Nova, v. 25, no. 4, p. 259–281, 2013. doi: 10.1111/ter.12041.
(The following is an exerpt from Summary of this paper. Permission granted by the senior author)
Summary
Problems with travel-time tomography include inadequate correction for structure outside the study volume, inability to retrieve three-dimensional structure, corruption of the mantle image by inadequate correction of the crust and boundary layer beneath, inability to retrieve true anomaly amplitudes and inhomogeneous ray coverage. Some regions simply cannot be imaged using current techniques, particularly in remote oceanic regions. Perhaps the most vexed problem is assessing realistically the true errors in results. Because of the fundamental experimental set-up, errors in structures calculated using teleseismic tomography are largest in the vertical direction. This results in a propensity to downward-smear structures, producing artificially vertically elongated anomalies. For surface-wave tomography, lateral resolution of anomalies is poorest and therefore lateral smearing can be strong.
The information in three-dimensional models is difficult to impart in a few maps and cross-sections. The wide array of choices, such as which particular result to favour, and which colour palette, line of section, and zero-contour wave speed to select, means that there is broad scope for producing figures that support preferred models. The widespread use of relative wave speeds commonly leads to misinterpretations. Translation of seismic anomalies to geology is not straightforward. More physical parameters vary in the mantle than seismic parameters mapped. Simplifying assumptions, such as seismic wave speed being everywhere a direct proxy for temperature, are not supported, and neither are geochemical models that rely on such work.
The wave speeds of both compressional and shear-waves are anisotropic in the mantle, and if this is neglected, which is usually thecase, erroneous results and interpretations may result. The upper 200 km of the mantle is the most heterogeneous and anisotropic region of the mantle and beneath this, heterogeneity drops dramatically (Gung et al., 2003). Many weak anomalies imaged by seismic tomography may result simply from uncorrected anisotropy. Anisotropy at ~200 km beneath cratons and at ~80 - 200 km beneath ocean basins may be related to shear in the boundary layer, the difference in depth simply reflecting a variable depth to the maximum shear (Anderson, 2011).
In recent years, much progress has been made in improving computational techniques and incorporating these advances into tomographic practice. This includes using local structure in global parameterizations, and three-dimensional ray-tracing instead of assuming straight or piecewise- straight rays (Hung et al., 2001, 2004). Similarly, Christoffersson and Husebye (2011) have revisited the basics of the inversion methods used, showing that at least some of the often-noted smearing and weakening of velocity anomalies by traditional damped inverses can be mitigated by using better tuned methods. Progress is also being made on describing better the uncertainties in the results, including calculating probability density functions (Mosegaard and Tarantola, 2002; Sambridge, 1999a,b). However, these advances cannot eliminate the fundamental difficulties we have highlighted above, which are inherent in the experimental setup. There is, nevertheless, a good case for re-processing many older data sets that have only been analysed using earlier, more primitive methods, the results of which continue to influence dynamic models of the mantle.
Other seismic results that do not depend on tomography should be included in interpretations, and interpretive work should emphasize only the deductions that are required by the data. Published, coloured tomography images and simplistic, cartoon- like interpretations should be treated with scepticism. Blue colours in tomographic cross-sections cannot be assumed to indicate cold, sinking material and red cannot be assumed to indicate hot, rising material. Likewise, increased awareness is needed that petrology/geochemistry cannot, in general, determine the depth of origin of magma sources. As a consequence, joint interpretation is more difficult than commonly realized. A more cautious approach will enable the current, unprecedented experimental tools available in both seismology and petrology/geochemistry to contribute reliably to answering the fundamental questions about the structure and dynamics of the Earth’s interior that have been disputed ever since plate tectonics was accepted and still remain controversial.