the Magellan Seamount Trail

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SEAMOUNTS 09WORKSHOP Seamounts as a Link
Between Geochemistry, Geophysics, Tectonics,
Geohazards and Bio-Evolution

• TOPICS IN THIS TALK
• Seamount Construction
• Mantle Plumes Hotspots
• Plate Motion Plume Motion
• Geochemistry Mantle Models
• Seamounts as Geohazards
• Physical State of Oceanic Crust
• Seamount Geology Biology

Anthony Koppers Tony Watts Dave Clague Hubert
Staudigel
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Sea Mountains Seamounts

• Harry Hess discovered the first seamounts during
  WOII using the first echo soundersThe
  flat-topped seamounts he mapped he named guyots
  while working for the Hydrographic Office of the
  US Navy

Hess (1942)
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Based on Wessel (2001), Koppers et al. (2003),
Hillier (2007), Hillier Watts (2007)
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• First Interpretation of the Volcanic Extrusive
  Series on La Palma, Canary Islands
• No Direct Sampling of Seamount Interior, Only
  Dredging and Drilling (with minimal penetration
  ranging 10-200 m only)
• La Palma Sections Only Include Submarine
  Volcanism (i.e. Shallow Deep Water Stages)

Staudigel Schmincke (1984)
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Staudigel Schmincke (1984)
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Puna Ridge Oahu Kilauea, Hawaii
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Garcia et al. (2007)
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Garcia et al. (2007)
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• Stage I The cycle of seamount volcanism
  typically starts with small erupted volumes of
  basaltic rocks with very diverse composition
  (e.g. Loihi Seamount).
• Stage II Main shield building phase producing
  majority (up to 98) of the entire volcano. Large
  melt fractions in the mantle typically yield
  tholeiitic mildly alkalic basalts.
• Stage III Termination of shield building by a
  cap of alkalic rocks, sometimes following a
  volcanic hiatus.
• Stage IV The cycle ends with a last phase of
  post-erosional (or rejuvenating) volcanism,
  following a volcanic hiatus from 1.5 to 10 Ma,
  but producing only very small volumes of highly
  undersaturated alkalic lavas.

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Clague Dalrymple (1987)
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Staudigel Schmincke (1984)
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Gravity Anomaly Map based on Satellite
Altimetry Version 15.2 by D. Sandwell W.M. Smith
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• Thermal Plumes Possible but Not Likely in
  Earth-Like Mantle
• Plume Heads Form With and Without Tails and Vice
  Versa
• Pulsing, Dying, Long-Lived, Super and Merging
  Plumes
• None have been Corroborated with Scientific
  Observations

Davies and Davies 2009
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Hawaii Samoa Hotspot Trails
Map by J. Konter
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Age data from Clague Dalrymple (1987), Duncan
Keller (2004), Sharp Clague (2006)
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Tarduno et al. (2003)
Koppers et al. (2004)

• Paleomagnetic data collected during ODP Leg 197
  shows a 15º hotspot shift southward
• First ever data proofing the mantle wind
  concept

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Steinberger Antretter (2006)
Stock (2003)

• Qualitatively, these systematics can be explained
  by the so-called mantle wind that blows in the
  opposite direction of plate motion and in the
  direction of the deep mantle return flow
• Interestingly, the predicted Louisville plume
  motions are all small in latitudinal direction
  (up to 2 only) compared to the 15 southern
  motion of Hawaii

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Koppers et al. (2008)
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Savaii Shield Volcanism 5 Ma
Koppers et al. (2008)
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Tearing of the Pacific Plate

• Natland (1980) suggested that lithospheric
  flexure at plate boundary results in shallow
  magma upwelling
• However, Abbott and Fisk (1986) claim stress
  related to the corner of the Tonga Trench would
  not cause deformation more than 200 km away

Natland (1980)
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Shield Isotope Signature for Savaii
Koppers et al. (2008)
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Hofmann (2007)
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Koppers et al. (1998)
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Seamount Landsliding Hazards (?)
Tuscaloosa Seamount
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Epicenter
Emperor Seamounts
Wave Front After 3.5 Hours
Hawaiian Ridge
1997 Kamchatka Tsunami, Epicenter at 54.66N,
161.78E NOAA Website and Mofjeld et al. (2004)
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Emperor Seamounts
Hawaiian Ridge
NOAA Website and Mofjeld et al. (2004)
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Loihi Vailulu'u Davidson Biology
Map by J. Konter
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Loihi Seamount and FeMO

• The Iron-Oxidizing Microbial Observatory (FeMO)
  uses the Loihi Seamount as a natural laboratory
  for studies of Earth's rust-forming microbes
• SBN is the crucial underpinning for seamount
  background info

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Mariprofundus Ferroxydans
Source Dave Emerson Clara Chan
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Dormant Davidson Seamount

• 10-14 Ma old seamount built on 20 Ma old
  seafloor
• Old deep-sea corals

• 2,400 m high seamount that still resides in 1,256
  m water depth
• 168 species of animals have been observed

Paduan et al. (2007)
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Dormant Davidson Seamount
MBARI
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• Seamount Exploration Only a handful of seamounts
  have been explored in some detail, much more
  exploration, mapping, sampling is required!
• Window for Deep Earth Geodynamics Seamounts
  provide a unique opportunity to study deep Earth
  and plate tectonic processes, such as mantle
  convection, mantle plumes, tectonic plate
  structures, plate motion and the chemical
  evolution of Earth.
• Geohazards Seamounts also play a role in
  subduction zone large-magnitude earthquakes and
  maybe tsunami generation. But their significance
  is yet undetermined. Also, because we have poor
  global bathymetry maps of the oceans (with
  limited vertical resolution), we dont know if
  and where tsunami waves might get scattered.

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• Small Seamounts and Abyssal Hills Maximum height
  of less than 1000 m and by far the most common
  type of seamount (i.e. hundreds of thousands of
  seamounts in this category). Because of their
  extreme abundance they play a key role in linking
  the lithosphere, biosphere and hydrosphere. They
  provide suitable hosts for microbial activity,
  they are likely to involve substantial
  geochemical fluxes from their hydrothermal
  systems.
• Mid-Size Seamounts Volcanic features that are
  tall enough to begin to develop a magma plumbing
  system that is above the crust they are built on.
  With their summits remaining below 700-1000 m
  water depth they have not yet entered their
  explosive stage!

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• Emerging Seamounts Their shallow-water summit
  regions allow for extensive explosive volcanism,
  forming hyaloclastite volcanic sediments.
  Seamounts reaching such shallow depths also begin
  to interact with the shallow ocean including
  interaction with the photic zone and (depending
  on the region) the oxygen minimum zone.
• Islands and Reefs Few very large seamounts grow
  to become islands (i.e. seamount/island ratio lt
  1)! Islands in tropical climates provide
  substrates for carbonate reefs, that may range
  from a relatively insignificant isolated reef to
  a massive coral reef that eventually almost
  entirely covers its volcanic foundation.

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• Ancient Deep Seamounts Once submerged below the
  photic zone and volcanically inactive, islands
  and coral reefs turn back into seamounts and they
  remain intact and uneroded for possibly over 100
  million years. Wave erosion might have flattened
  their tops, making them into so-called Guyots.
  The key biological role of ancient seamounts is
  likely to be the one of a stable substrate for
  colonization by deep sea corals.
• Seamount Destruction Seamounts are prone to
  large-scale slope failures and meet the end of
  their lifespan when they reach a subduction zone
  or when their host ocean basin closes during a
  continent-continent collision, typically far
  before they reach ages of 135 Ma.

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Tectonic History Since 5 Ma
Koppers et al. (2008)
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Hilton Porcelli (2003)
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Youngest Hawaiian Seamount
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Loihi Seamount and FeMO

• Basic questions about Fe-oxidizing microbes
• Who they are?
• How fast do they grow and form iron-oxide
  deposits?
• Where and why do they do it?
• What are their environmental impacts?
• Does this process affect ocean chemistry and
  ecosystem function?

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1977