Why the Victoria Plate in Africa rotates
Weaker and stronger lithospheric regions cause the rotation of the
Victoria microplate

Date:
June 8, 2020
Source:
GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
Summary:
The East African Rift System is a newly forming plate tectonic
boundary at which the African continent is being separated into
several plates.

According to GPS data, one of those, the Victoria microplate,
is moving in a counterclockwise rotation relative to Africa in
contrast to the other plates involved. Now, researchers have
found evidence that suggests that the configuration of weaker and
stronger lithospheric regions controls the rotation of continental
microplates and Victoria in particular.



FULL STORY ==========================================================================
The East African Rift System (EARS) is a newly forming plate tectonic
boundary at which the African continent is being separated into several
plates. This is not a clean break. The system includes several rift arms
and one or more smaller so-called microplates. According to GPS data,
the Victoria microplate is moving in a counterclockwise rotation relative
to Africa in contrast to the other plates involved.


========================================================================== Previous hypotheses suggested that this rotation is driven by the
interaction of a mantle plume -- an upward flow of hot rock within
the Earth's mantle - - with the microplate's thick craton and the
rift system. But now, researchers from the German Research Centre for Geosciences GFZ in Potsdam around Anne Glerum have found evidence that
suggests that the configuration of weaker and stronger lithospheric
regions predominantly controls the rotation of continental microplates
and Victoria in particular. Their findings were published in the journal
Nature Communications.

In the paper, the researchers argue that a particular configuration of mechanically weaker mobile belts and stronger lithospheric regions in the
EARS leads to curved, overlapping rift branches that under extensional
motion of the major tectonic plates induces a rotation. They used 3D
numerical models on the scale of the whole EARS to compute the lithosphere
and upper mantle dynamics of the last 10 million years.

"Such large models run on high performance computing clusters,"
says Anne Glerum, main author of the study. "We tested the predictive
strength of our models by comparing their predictions of velocity with GPS-derived data, and our stress predictions with the World Stress Map,
a global compilation of information on the present-day crustal stress
field maintained since 2009. This showed that the best fit was obtained
with a model that incorporates the first order strength distributions
of the EARS' lithosphere like the one we prepared." There are many more continental microplates and fragments on Earth that are thought to rotate
or have rotated. The lithosphere-driven mechanism of microplate rotation suggested in the new paper helps interpret these observed rotations and reconstruct plate tectonic motions throughout the history of the Earth.


========================================================================== Story Source: Materials provided by GFZ_GeoForschungsZentrum_Potsdam,_Helmholtz_Centre. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Anne Glerum, Sascha Brune, D. Sarah Stamps, Manfred
R. Strecker. Victoria
continental microplate dynamics controlled by the lithospheric
strength distribution of the East African Rift. Nature
Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-16176-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200608092937.htm

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