Download Geodynamics

Dynamics of Mantle Plumes
• Methods for modeling basic thermal plumes
(with and without tracers)
• Plumes interacting with plates (and ridges)
• Plumes in thermo-chemical convection
• More elaborate proposals for plumes
Dynamics of the mantle…
Global scale: mantle
contains both well-mixed
regions and heterogeneity
Fine scale heterogeneity
Fine-scale
variations in
the
(from
Harpp and White,
Galapagos
2001, G-cubed)
Galapagos Islands
Harpp and White, G-cubed 2001
Hawaiian emperor track (Steinberger et al. Nature 04)
From Garnero,
Annual Reviews of Earth
& Planetary Sciences, 2000
Figure courtesy of
E. Garnero, ASU
Farnetani et al.
2002: Model 1:
uniform mantle, low
viscosity plume
Farnetani et al.
2002: Model 3:
viscosity jump
in transition
zone
Thin dense layer
at base
Low viscosity in
plume
Farnetani et al: EPSL, 2002
Detail of mixing in plume:
black tracers are from basal b.l.
grey are from transition zone
Courtesy of Shijie Zhong,
U. Colorado (see:
Entrainment of a dense layer
by thermal plumes
Zhong and Hager,
Geophysical Journal
International
September 2003)
Courtesy of Shijie
Zhong, U. Colorado
Double Diffusive Convection Model of D”
B=1
Ra = 107
Earth’s surface
Core-mantle boundary
Color indicates Temperature
N. Montague and L.
Kellogg, JGR, 2000
time
N. Montague and L. Kellogg, JGR, 2000
time
horizontal distance
N. Montague
and L. Kellogg,
JGR, 2000
A dense layer stabilizes the flow
With a dense layer in D”
No dense layer
time
More temperature-dependent viscosity
B= 1
Kellogg and Montague, in preparation
Hansen & Yuen
Varying properties with depth allows layering
Layered
convection
experiments
by Anne
Davaille,
(Nature 402,
756,
Dec. 1999)
Davaille experiments + several numerical models (redrawn from
Davaille, 1999; color points are numerical models from various sources)
Courtillot, V., Davaille, A., Besse, J., Stock, J.,
Earth and Planetary Science Letters, 2003.
Courtillot, V., Davaille, A., Besse, J., Stock, J.,
Earth and Planetary Science Letters, 2003.
Olympus Mons (Mars)-Hawaii Comparison
0 km
Hunt and Kellogg, 2000
Depth
670 km
Mixing in 2-D with particles
•Added at subduction zones
•Removed at mid-ocean ridges
2900 km
1
10
100
Normalized viscosity
Hunt & Kellogg, 2000 - effect of viscosity on mixing
Constant viscosity
viscosity
1
10
100
1
10
100
1
10
100
Pressure-dependent viscosity: smooth increase
Transition zone viscosity: Jump at 670 km
D. L. Hunt & L. H. Kellogg, 2000
Distribution of heterogeneities
Heat budget of the Earth
(all values given in terawatts)
various sources
Total global heat flow: 44 TW
Total BSE Heat production:
20 TW + (from cosmochemistry)
Continental crust produces: 4.6 to 10 TW
A uniform, depleted mantle could produce:
5 – 7 TW
Requires (AT LEAST) 3 to 10.4 TW
produced elsewhere (mantle or core)
Comparisons of mantle cooling regimes
Lithospheric Conduction
Moon
Mercury
Mars?
Venus?
Earth
Plate recycling
Io
Hotspot
Volcanism
Kellogg et al., 1999
After a figure in E. M.
Moores, L. H. Kellogg, and
Y. Dilek, Ophiolites,
Tectonics, and Mantle
Convection: a contribution to
the "Ophiolite Conundrum",
in Optiolites and the
Oceanic Crust, GSA Special
Paper 349, 3-12, 2000.
After a figure in E. M.
Moores, L. H. Kellogg, and
Y. Dilek, Ophiolites,
Tectonics, and Mantle
Convection: a contribution
to the "Ophiolite
Conundrum", in Optiolites
and the Oceanic Crust,
GSA Special Paper 349,
3-12, 2000.
http://www.nsf.gov/pubs/2004/nsf04593/nsf04593.htm
or link to this from: http://www.csedi.org
National Science Foundation
Cooperative Studies Of The Earth's Deep Interior (CSEDI)
NSF 04-593
Full Proposal Deadline(s) (due by 5 p.m. proposer's local time):
September 20, 2004
August 25, 2005 and annually thereafter
Synopsis of Program:
The Division of Earth Sciences (EAR) invites the submission of proposals for collaborative, interdisciplinary
studies of the Earth's interior within the framework of the community-based initiative known as Cooperative
Studies of the Earth's Deep Interior (CSEDI). Funding will support basic research on the character and dynamics
of the Earth's mantle and core, their influence on the evolution of the Earth as a whole, and on processes
operating within the deep interior that affect or are expressed on the Earth's surface.
Projects may employ any combination of field, laboratory, and computational studies with observational,
theoretical, or experimental approaches. Support is available for research and research infrastructure through
grants and cooperative agreements awarded in response to investigator-initiated proposals from U.S. universities
and other eligible institutions. Multidisciplinary work is required. EAR will consider co-funding of projects with
other agencies and supports international work and collaborations.