Complex Shear Wave Velocity Structure Imaged Beneath Africa and Iceland

Area of Science:

• Geophysics
• Seismology
• Earth Sciences

Background:

• Understanding mantle dynamics is crucial for explaining surface geological features.
• Previous models have not fully captured the extent of deep mantle structures influencing volcanism.

Purpose of the Study:

• To model three-dimensional shear wave velocity variations in the Earth's mantle.
• To investigate the deep mantle origins of Cenozoic flood basalt volcanism and active rifting in East Africa.

Main Methods:

• Developed a three-dimensional shear wave velocity model of the mantle.
• Analyzed seismic wave propagation to infer mantle structure and thermal anomalies.

Main Results:

• Identified a tilted low-velocity anomaly extending from the core-mantle boundary (CMB) beneath the southeastern Atlantic to the upper mantle beneath eastern Africa.
• This extensive anomaly suggests a link between Afar volcanism, the East African Rift, and a distant CMB thermal anomaly.
• A distinct low-velocity anomaly beneath Iceland was found to be confined to the upper mantle.

Conclusions:

• Cenozoic flood basalt volcanism and active rifting in the East African Rift are likely driven by a deep thermal anomaly at the CMB.
• The findings highlight the significant influence of deep mantle structures on continental rifting and volcanism.
• Icelandic volcanism appears to have a shallower, distinct origin compared to East African volcanism.