Do Mantle Plumes Exist?

By Chad Weisenburger

ABSTRACT

            The existence of hot lower mantle upwellings rising to the surface has been debated since J. Morgan first propesed the idea in 1971. Morgan’s model has three parts: ocean volcanism is the result of plumes rising through the mantle, plumes originate at the core/mantle boundary, and plume flow drives plate tectonics. Today the first two parts are generally accepted, but plume flow driving plates is not. Since then, improvements in methods used to study mantle dynamics have given us a better idea of what may be happening beneath our feet. There are many ways to study the mantle, but I will focus on three: magma geochemistry, seismic tomography, and ocean floor topography.

Map of selected hotspots from http://pubs.usgs.gov/publications/text/world_map.html

OUTLINE

I. Plume Hypothesis

          A. Morgan 1971

                    1. Three main parts

II. Evidence for plumes

III. Structure of mantle plumes 

IV. Methods of plume study

          A. Geochemistry

                   1. Noble gasses

          B. Ocean-floor topography

                   1. Flood basalts

                   2. Swells     

                   3. Island chains

          C. Seismology

                   1. Basics of seismic imaging     

                   2. Finite-frequency tomography

III. Conclusions

          A. There are plume-like structures

          B. Future study

REFERENCES CITED

Anderson D. L., 1999, A theory of the Earth: Hutton and Humpty Dumpty and Holmes: Geological Society, London, Special Publications, v. 150, p. 13 – 35.

Anderson D. L., G. R. Foulger and Anders Meibom, Helium: Fundamental models: <www.mantleplumes.org/HeliumFundamentals.html>

Anderson Don L., Does the variation in ³He/⁴He prove that MORB and OIB come from different reservoirs?, www.mantleplumes.org/HowMany.html

Clouard, Valérie, Alain Bonneville, 2001, How many Pacific hotspots are fed by deep-mantle plumes?: Geology, v. 29, No. 8, p. 695-698.

Davies, Geoffrey F., Dynamic Earth, 458 pp., Cambridge University Press, Cambridge, 1999.

Foulger, G. R., The Emperor and Hawaiian Volcanic Chains: How well do they fit the plume hypothesis?, www.mantleplumes.org/Hawaii.html

Hamilton, Warren B., 2003, An Alternative Earth: GSA Today, v. 13 p.

Julian, Bruce R., Seismology: The hunt for plumes, <www.mantleplumes.org/Seismology.html>

Rafaella Montelli, Guust Nolet, F. A. Dahlen, Guy Masters, E. Robert Engdahl and Shu-Huei Hung, 2004, Finite-Frequency Tomography Reveals a Variety of Plumes in the Mantle: Science, v. 303, p. 338 – 343.