dynamics of mantle plumes

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…Dynamics of the mantle…

(from Harpp and White,2001, G-cubed)

Fine-scale variations

in the Galapagos G

alap

agos

Isl

ands

Global scale: mantle contains both well-mixed regions and heterogeneity

Fine scale heterogeneity

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, 2002Detail 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

InternationalSeptember 2003)

Courtesy of Shijie Zhong, U. Colorado

B=1 Ra = 107

Color indicates Temperature

Earth’s surface

Core-mantle boundary

Double Diffusive Convection Model of D”

N. Montague and L. Kellogg, JGR, 2000

time

time

horizontal distanceN. Montague and L. Kellogg, JGR, 2000

A dense layer stabilizes the flow

With a dense layer in D”

No dense layer

time

N. Montague and L. Kellogg, JGR, 2000

B= 1M

ore

tem

pera

ture

-dep

en

den

t vis

cosi

ty

Kellogg and Montague, in preparation

Hansen & YuenVarying 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

Mixing in 2-D with particles •Added at subduction zones •Removed at mid-ocean ridges

2900 km

670 km

Normalized viscosity

Dep

th

0 km

1 10 100

Hunt and Kellogg, 2000

Constant viscosity

Pressure-dependent viscosity: smooth increase

Transition zone viscosity: Jump at 670 km

Hunt & Kellogg, 2000 - effect of viscosity on mixing

viscosity

1 10 100

1 10 100

1 10 100

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

Continental crust produces: 4.6 to 10 TW

A uniform, depleted mantle could produce: 5 – 7 TW

Total BSE Heat production: 20 TW + (from cosmochemistry)

Requires (AT LEAST) 3 to 10.4 TWproduced elsewhere (mantle or core)

Lithospheric Conduction

HotspotVolcanism

Plate recycling

Mars?

MercuryMoon

Venus?

IoEarth

Comparisons of mantle cooling regimes

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.