- The East Pacific Rise: Tectonic plates are driven by an additional force of heat drawn from Earth’s core.
Plate tectonics is the widely accepted theory that the Earth's
crust is divided into several sections that float around on the
mantle - the mostly solid layer between the core and the crust.
But how they move around has been a subject of much debate among
scientists since the theory was first accepted in the 1950s.
The sections, known as plates, move at a rate of about 2 to 5
centimeters per year, which is a similar speed to how fast your
fingernails grow. When they grind past each other, it's called a
transform plate boundary, which can cause earthquakes. When they
move away from each other, it's known as a divergent boundary,
where lava spews out, and volcanoes can form. Sometimes, when
they meet each other head on, one plate starts moving upwards to
form mountains, while the other is pushed downwards where it
melts. This is a convergent boundary.
Scientists have wondered for many decades whether the plates are
being passively moved around by the mantle, or are the active
drivers of movement themselves, dragging the mantle along with
A new study, published in the journal Science Advances, has shown
the additional force of heat drawn from Earth's core plays a part
in plate dynamics. The team observed the East Pacific Rise, which
is a divergent tectonic plate boundary which lies along the
Pacific Ocean floor, and also made models of the mantle flow
beneath the surface.
During their observations, they concluded that the movement of
the East Pacific Rise could not be completely explained by
subduction - when one plate moves under the other - and other
forces had to be at play. In the paper, they state that buoyancy
is created by heat rising up from deep within the Earth's core.
The estimate is 50% of plate tectonic movement is driven by this
heat, and about 20 terawatts of heat flows between the core and
the mantle. That's just slightly more than the average total power
consumption of humans on Earth every year.
"We see strong support for significant deep mantle contributions
of heat-to-plate dynamics in the Pacific hemisphere," said
Professor David B. Rowley, an expert of geophysical sciences at
the University of Chicago and lead author of the paper, in a statement. "Heat from the base of the
mantle contributes significantly to the strength of the flow of
heat in the mantle and to the resultant plate tectonics."
When the case on the mantle is heated, this reduces the density
of the material, making it buoyant, which causes it to rise
through the mantle. Plates also cool at the surface, creating
something called negative buoyancy, which is another way of
describing an object that sinks. These two forces move the plates
In other words, hot parts rise and cool parts sink, creating a
sort of churning movement in the mantle that the plates ride on.
"Based on our models of mantle convection, the mantle may be
removing as much as half of Earth's total convective heat budget
from the core," Rowley said. "The implication of our work is that
textbooks will need to be rewritten."