Plates vs Plumes: A Geological Controversy

Since the advent of the mantle plume hypothesis in 1971, scientists have been faced with the problem that its predictions are not confirmed by observation. For thirty years, the usual reaction has been to adapt the hypothesis in numerous ways. As a result, the multitude of current plume variants now amounts to an unfalsifiable hypothesis.
In the early 21st century demand became relentless for a theory that can explain melting anomalies in a way that fits the observations naturally and is forward–predictive. From this the Plate hypothesis emerged–the exact inverse of the Plume hypothesis. The Plate hypothesis attributes melting anomalies to shallow effects directly related to plate tectonics. It rejects the hypothesis that surface volcanism is driven by convection in the deep mantle.
Earth Science is currently in the midst of the kind of paradigm–challenging debate that occurs only rarely in any field. This volume comprises its first handbook. It reviews the Plate and Plume hypotheses, including a clear statement of the former. Thereafter it follows an observational approach, drawing widely from many volcanic regions in chapters on vertical motions of Earth’s crust, magma volumes, time–progressions of volcanism, seismic imaging, mantle temperature and geochemistry.
This book will be indispensable to Earth scientists from all specialties who are interested in this new subject. It will be suitable as a reference work for those teaching relevant classes, and an ideal text for advanced undergraduates and graduate students studying plate tectonics and related topics.

Spis treści:
Proposed contents list.
Proposed title: Plates or Plumes?.
Part A: Backdrop.
1. Introduction, Background & History: History of emergence of the plume hypothesis, including early skepticism, widespread, largely uncritical adoption of plume hypothesis, resurgence of skepticism from year 2000 on. Philosophical schools. Di stinction of classical and contemporary plume models. The latter is, in practice, unfalsifiable.
2. Alternative Models: a) Plate–tectonic processes model – the new, primary competing model. Introduction to, and explanation of the model, including how it involves extensional lithospheric stress and variable mantle fertility. Stress in the lithosphere – Discussion of extensional tectonics, including super–continent breakup (and the possibility that it might be self–organised), examples e.g., Afar, Bouvet triple junction, Azores. Mantle fertility – origins from recycled material, evidence for this. b) Meteorite impacts (subsidiary section as probably only rarely triggers large igenous province (LIP) eruptions), example: Bushveld complex, S Africa,. c) Planetary (even more subsidiary section as included for completeness only) Mars & Venus..
Part B: Observations.
3. Vertical Motions: Key to the classical plume hypothesis (according to plume advocates) as impinging plume head predicted to cause domal uplift. However, a) not observed before emplacement of many LIPs (examples: Siberian Traps, Ontong Java Plateau, Deccan Traps), b) where it is observed it may be complicated (example North Atlantic Volcanic Province). Use of vertical motions to estimate mantle temperature. Delamination model & vertical motions predicted, examples of Siberia, Columbia River Basalts.
4. Volcanism: Volume & Rate: Large igneous provinces – Summary of phenomenon, plume hypothesis predicts emplacement in ∼ 1 Myr, largest examples, volcanic margins e.g., north Atlantic, Central Atlantic Magmatic Province (CAMP), Paraná basalts. Chronology of volcanism. Island chains – plume hypothesis predicts volcanic time–progressive volcanic chains. Comparison of this model with observations, hotspot reference frames.
5. Structure of the mantle: Seismology – Teleseismic tomography, whole–mantle tom ography, the transition–zone discontinuities, the African and Pacific “superplumes”, the core–mantle boundary.
6. Temperature & heat: Mantle not isothermal, fusible material produces large melt volume at lower temperature, possibility of reheating of subducted slabs and delaminated blobs by mantle heat bath, rifting decompression melting. Surface heat flow.
7. Geochemistry: Origin of ocean–island basalt (OIB), core–mantle boundary tracers (e.g. Re–Os, Pt–Os and Hf–W isotopes), evidence that OIB geochemistry is recycled near–surface materials. How such materials get recycled: a) oceanic crust and metasomatised oceanic lithospheric mantle at subduction zones, b) continental lower crust and metasomatised continental lithosphere via delamination, c) the role of eclogite. Noble gases – especially helium isotope ratios..
Part C: Some case histories.
8. Atlantic volcanism: Discussion of Iceland (in detail, as primary example) plus Azores, Canary Islands, Cape Verde islands, St. Helena, Tristan & Bouvet “hot spots” as additional case histories.
9. Pacific volcanism: diffuse volcanism (e.g., western Pacific), time–progressive chains (e.g., Louisville) and non–time–progressive chains (e.g., Cook–Austral chain). Linear volcanic/gravity swells and troughs emanating from East Pacific Rise, e.g. Pukapuka ridge. Hawaii–Emperor system (in detail, as primary example) plus Easter, Louisville, Galapagos, Samoa & Bowie “hot spots”.
10. Continental volcanism: Slab–related processes including a) slab break–off (e.g. Turkey), b) slab tearing (e.g., Mexico), c) flat–slab subduction (e.g., Basin & Range, Yellowstone & the High Lava Plains, E China), and d) back–slab volcanism (e.g., Italy, Japan, Kamchatka). Continental rifting (e.g., E Africa, Karoo, Antarctica, Europe e.g. Rhine Graben, No rway). Possible mention of lesser more diffuse continental volcanism e.g. Hoggar (north Africa) and Mongolia..
Part D: Wider issues.
11. Discussion: “Top–down” vs. “bottom–up” – The role of convection in the mantle, including issues such as importance of core cooling, cooling from the surface of the Earth, internal radiogenic heating, and variation of physical parameters within the Earth including radiative transfer, thermal expansivity & viscosity. The problem that convection modelling is apparently able to predict almost anything.
12. Future challenges: Reinterpretation of observations at “hot spots” that have traditionally been assumed to be due to plumes; tackling the “great unknowns” – a) explanation of vertical motions (or lack of them) associated with e.g. Ontong Java Plateau, b) origin of the melt volumes erupted, c) imaging of the mantle in “the controversial region”, i.e., ∼ 400 – 1000 km depth where the vertical continuity of structures is unclear, and d) mapping temperature variations in the mantle, and e) the origin of OIB.

Nota biograficzna:
Gillian Foulger is Professor of Geophysics at the University of Durham where she has worked since 1985 on earthquake seismology and plate tectonics. She lived and researched in Iceland for seven years, where she acquired a mistrust of theories that do not fit practical observations without contortion. She manages the world–famous website www.mantleplumes.org and is widely acclaimed for leading the global debate regarding the existence of mantle plumes. For this she was awarded the prestigious Price Medal by the Royal Astronomical Society in 2005.

Okładka tylna:
Since the advent of the mantle plume hypothesis in 1971, scientists have been faced with the problem that its predictions are not confirmed by observation. For thirty years, the usual react ion has been to adapt the hypothesis in numerous ways. As a result, the multitude of current plume variants now amounts to an unfalsifiable hypothesis.
In the early 21st century demand became relentless for a theory that can explain melting anomalies in a way that fits the observations naturally and is forward–predictive. From this the Plate hypothesis emerged–the exact inverse of the Plume hypothesis. The Plate hypothesis attributes melting anomalies to shallow effects directly related to plate tectonics. It rejects the hypothesis that surface volcanism is driven by convection in the deep mantle.
Earth Science is currently in the midst of the kind of paradigm–challenging debate that occurs only rarely in any field. This volume comprises its first handbook. It reviews the Plate and Plume hypotheses, including a clear statement of the former. Thereafter it follows an observational approach, drawing widely from many volcanic regions in chapters on vertical motions of Earth’s crust, magma volumes, time–progressions of volcanism, seismic imaging, mantle temperature and geochemistry.
This book will be indispensable to Earth scientists from all specialties who are interested in this new subject. It will be suitable as a reference work for those teaching relevant classes, and an ideal text for advanced undergraduates and graduate students studying plate tectonics and related topics.