[Rockhounds] A Seismic Shift – Earth’s Plate Tectonics Recently Underwent a Fundamental Change

[Kreigh Tomaszewski]

Earth is truly unique among our Solar System’s planets. It has vast water
oceans and abundant life. However, Earth’s distinctiveness extends beyond
its biodiversity and oceans—it is the sole planet within our solar system
that experiences the phenomenon of plate tectonics, a process intrinsic to
the shaping of its geological structure, climate, and, potentially, the
progression of life itself.

The term ‘plate tectonics’ signifies the dynamic movement and intricate
interaction of tectonic plates across Earth’s crust. These tectonic plates
are set in motion by the painstakingly slow yet persistent flow of Earth’s
mantle, referred to as convection. This process transports heat from the
inner core to the surface of our planet.

Researchers believe that convection in the mantle, which started shortly
after Earth’s formation 4.5 billion years ago, occurs at the scale of the
whole mantle. So, when plates collide at Earth’s surface, one gives way and
sinks into the hot mantle and ends up in a sort of plate graveyard on top
of Earth’s metallic core.

However, a new study from the University of Copenhagen
<https://scitechdaily.com/tag/university-of-copenhagen/> published in the
journal *Nature* suggests that this style of plate tectonics may be a more
recent feature of Earth’s geologic history.

“Our new results suggest that for most of Earth’s history, convection in
the mantle was stratified into two distinct layers, namely upper and lower
mantle regions that were isolated from each other,” says Zhengbin Deng,
former assistant professor at the University of Copenhagen and first author
of the new study.

The transition between the upper and lower mantle occurs at about 660 km
below Earth’s surface. At this depth, certain minerals undergo a phase
transition. Deng and colleagues believe that this phase transition may be
the reason why the upper and lower mantle regions remained mostly isolated.

“Our findings indicate that in the past, recycling and mixing of subducted
plates into the mantle was restricted to the upper mantle, where there is
strong convection. This is very different from how we think plate tectonics
operates today, where subducting plates sink to lower mantle,” says
associate professor Martin Schiller who is also behind the new study.

https://scitechdaily.com/a-seismic-shift-earths-plate-tectonics-recently-underwent-a-fundamental-change/