MICHAEL MANGA: Recent Refereed Publications
Abstracts
Gonnermann, H.M., M. Manga, and A.M. Jellinek (2002)
Dynamics and longevity of an initially stratified mantle,
Geophysical Research Letters, vol. 29, paper number
10.1029/2002GL01485 .
Abstract:
We performed laboratory experiments of thermochemical
convection in order to determine the rate at which an initially
density-stratified, and hence layered, mantle will be homogenized.
In the experiments, two layers of fluid with similar viscosities
are superposed and heated from below. Initially, in the "stratified"
regime, mechanical entrainment into both layers occurs by viscous
coupling and theoretical models for the entrainment rate agree well
with our experimental data. Over time entrainment and mixing reduce
the density difference between the layers until the "doming" regime
is reached. The density interface becomes unstable, thermal plumes
of the dense fluid penetrate into the overlying layer and the
entrainment rate reaches a constant. Applying our results to the
Earth's mantle, we confirm that it is possible for a compositionally
distinct layer to persist over the age of the Earth, even if the
initial density difference is less than 2%.
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