Reconstruction of the Indo-Atlantic Ocean 63 million years ago, during the time of the superfast motion of India which Scripps scientists attribute to the force of the Reunion plume head. The arrows show the relative convergence rate of Africa (black arrows) and India (dark blue) relative to Eurasia before, during and after (from left to right) the period of maximum plume head force. The jagged red and brown lines northeast of India show two possible positions of the trench (the subduction zone) between India and Eurasia depending on whether the India-Eurasia collision occurred 52 million years ago or 43 million years ago.
fresh insight into long-standing debates about how powerful geological
forces shape the planet, from earthquake ruptures to mountain
formations, scientists at Scripps Institution of Oceanography at UC San
Diego have identified a new mechanism driving Earth’s massive tectonic
who study tectonic motions have known for decades that the ongoing
“pull” and “push” movements of the plates are responsible for sculpting
continental features around the planet. Volcanoes, for example, are
generally located at areas where plates are moving apart or coming
together. Scripps scientists Steve Cande and Dave Stegman have now
discovered a new force that drives plate tectonics: Plumes of hot magma
pushing up from Earth’s deep interior. Their research is published in Nature.
analytical methods to track plate motions through Earth’s history,
Cande and Stegman’s research provides evidence that such mantle plume
“hot spots,” which can last for tens of millions of years and are active
today at locations such as Hawaii, Iceland, and the Galapagos, may work
as an additional tectonic driver, along with push-pull forces.
new results describe a clear connection between the arrival of a
powerful mantle plume head around 70 million years ago and the rapid
motion of the Indian plate that was pushed as a consequence of overlying
the plume’s location. The arrival of the plume also created immense
formations of volcanic rock now called the “Deccan flood basalts” in
western India, which erupted just prior to the mass extinction of
dinosaurs. The Indian continent has since drifted north and collided
with Asia, but the original location of the plume’s arrival has remained
volcanically active to this day, most recently having formed Réunion
island near Madagascar.
Images of the satellite derived gravity field over the Central Atlantic (top) and Southwest Indian Ridge (right) showing the zones of rough topography and sharp bends in the fracture zones that were caused by the slowing of Africa’s motion as the Reunion plume head reached its maximum force. The inset globe shows the location of the gravity maps as well as the extent of the parallel zones of rough topography (outlined in red) on the flanks of the Mid-Atlantic and Southwest Indian ridges caused by the change in Africa’s motion.
team also recognized that this “plume-push” force acted on other
tectonic plates, and pushed on Africa as well but in the opposite
to the plume’s arrival, the African plate was slowly drifting but then
stops altogether, at the same time the Indian speeds up,” explains
Stegman, an assistant professor of geophysics in Scripps’ Cecil H. and
Ida M. Green Institute of Geophysics and Planetary Physics. “It became
clear the motion of the Indian and African plates were synchronized and
the Réunion hotspot was the common link.”
is a dramatic slow down in the northwards motion of the Indian plate
around 50 million years ago that has long been attributed to the initial
collision of India with the Eurasian plate,” says Cande, a professor of
marine geophysics in the Geosciences Research Division at Scripps. “An
implication of our study is that the slow down might just reflect the
waning of the mantle plume-the actual collision might have occurred a
A view of the bends of the fracture zones on the Southwest Indian Ridge caused by the slowdown of Africa in response to the Reunion plume head. The image shows the gravity field.
Funding for the research was provided by the National Science Foundation.