Virginia Tech Department of Geosciences doctoral student J. Robert Jones (above) uses a Global Navigation Satellite installed near Tanzania’s Ol Doinyo Lengai volcano, otherwise known as the Mountain of God.
Expanded and updated version
Virginia Tech Department of Geosciences doctoral student J. Robert Jones used an analytical modeling approach when studying the link between continental faulting and deep Earth movements in a part of Africa that is slowly breaking apart.
Published in Geochemistry, Geophysics, and Geosystems in spring 2019, Jones said such modeling tools have been available to geoscientists since the late 1990s. “Beyond the computer modeling aspect, the applications of math in the program to earthquake processes is based on studies developed in the early 1990s,” Jones said of the study, carried out in northern Tanzania and focusing on the active volcano Ol Doinyo Lengai -- the Mountain of God -- and its mid-2007 to late-2008 eruption. (The volcano is unique because it erupts natroncarbonatite lava, and it’s within a region where the Earth’s surface is just beginning to tear apart.)
“I used an updated version of the program allowing me to do more than the original modeling code and used newly processed geodetic data, but the evaluations and steps are very similar,” added Jones, who hails from Yorktown, Virginia. “Because this is such an established method, we have confidence in our modeling results and interpretations.”
What Jones found: An unexpected parallel motion on the fault bounding a continental rift in its early phases of breaking apart, versus a typical perpendicular rift motion. “This paper changes how we understand the dynamics of continental rifting,” said D. Sarah Stamps, an assistant professor of geosciences and co-author of the study. “Previously, the influence of volcanic activities on border faults was unknown. Now we have evidence that border faults can move in an unexpected direction as a consequence of volcanic activities.”
According to Jones and Stamps, continental rifting breaks up continents and leads to the development of new oceans. The physical processes that make it possible to rupture the Earth’s lithosphere remain elusive, however. Jones’ paper brings scientists closer to an answer, Stamps said.
During the 2007-2008 eruptions, melted rock from Ol Doinyo Lengai’s magma chamber was forced into the crust from deeper parts of the Earth and caused changes in the local stress field. Jones’ research found that these magmatic activities caused a major regional fault to slip. Jones used numerical simulations to test the magmatism’s influence on a fault adjacent to Ol Doinyo known as the Natron Fault.
“We found that magmatic activity from a volcano may promote observable fault slip on major rift border faults in an immature continental rift. We also found that the volcanic activity has the potential to influence slip on the neighboring fault,” Jones said.
The team modeled the stress transferred during the 2007-2008 eruption/rifting events and processed high-precision GPS data recording from the region after the initial events and looked for distinct slip events occurring in 2008. Stamps added that these findings “challenge our current conceptual model of continental rifting.”
What’s next for Jones, Stamps, and their collaborators? They would like to solve how activity on the major border fault can influence volcanic activity, and they want to address how different geomaterials and regional geophysical parameters influence results found during their modeling.
“This future work would utilize new geodetic data to assess the modern-day interactions between Ol Doinyo Lengai and the nearby border fault with our new modeling approach,” Jones added.