Explaining mid-ocean ridge topography with magma viscosity

Mid-ocean ridges are areas of tectonic creation, where the planet’s plates pull apart and new crust is formed. The topography of these ridges can be highly varied, with peaks, valleys, and plateaus that result in a unique landscape at every ridge. This variability is often explained with factors such as the spreading rate and magma availability, but the observed topography is not always consistent with these suspected causes.

Sen et al. developed an alternative model to explain this discrepancy in ridge topography.

The team identified the viscosity of sub-crustal melt complexes as a key factor in the creation of tall peaks versus flat plateaus. By employing a two-step suspension and solid-melt mixture rheology calculation, they determined the viscosity of these complexes as a function of their constituting materials. They used this viscosity calculation to inform a numerical model of ridge formation and compared it to observations.

“Our model shows a fascinating match with several natural ocean ridges, such as the East Pacific Rise and the South East Indian Ridge,” said author Nibir Mandal. “Some of them display elevations of a kilometer or so. In contrast, some are absolutely flat. These contrasting relief features are nicely reproduced in this model.”

The authors plan to apply this approach to ridge formation on other worlds.

“We intend to extrapolate our model and its findings to other terrestrial planets like Venus, which show similar tectonic manifestations on their surfaces,” said Mandal. “This kind of study will help us understand their crust-forming processes — a major challenge in planetary sciences.”

Source: “Control of mush complex viscosity on mid-ocean ridge topography: A fluid-structure model analysis,” by Joyjeet Sen, Shamik Sarkar, and Nibir Mandal, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0152667 .