What are the current research gaps and opportunities in rock viscosity studies?

1 Laboratory experiments

One of the most common ways to measure rock viscosity is to perform laboratory experiments on rock samples or analog materials, such as wax, ice, or salt. These experiments involve applying controlled stress and temperature conditions to the samples, and measuring their deformation and flow behavior. The viscosity can then be calculated from the stress-strain relationship, using rheological models that describe how different types of rocks behave under different conditions. For example, some rocks exhibit Newtonian behavior, where the viscosity is constant and independent of stress, while others exhibit non-Newtonian behavior, where the viscosity changes with stress or strain rate.

2 Field observations

Another way to measure rock viscosity is to observe how rocks deform and flow in natural settings, such as in mountain ranges, fault zones, or magmatic systems. These observations can provide information on the spatial and temporal variations of rock viscosity, as well as the interactions between different rock types and fluids. Field observations can also be used to validate and calibrate laboratory experiments and rheological models, by comparing the measured and predicted deformation patterns and rates. However, field observations also have some limitations, such as the difficulty of accessing some locations, the uncertainty of the boundary conditions, and the complexity of the geological history.

3 Numerical models

A third way to measure rock viscosity is to use numerical models that simulate the deformation and flow of rocks under various scenarios and parameters. Numerical models can be useful to test hypotheses, explore sensitivities, and extrapolate results beyond the available data. Numerical models can also incorporate different physical processes and mechanisms that affect rock viscosity, such as phase transitions, chemical reactions, fluid migration, or microstructural evolution. However, numerical models also have some challenges, such as the need for reliable input data, the selection of appropriate numerical methods and codes, and the evaluation of the model accuracy and uncertainty.

4 Geophysical methods

A fourth way to measure rock viscosity is to use geophysical methods that detect and measure the physical properties and signals of rocks, such as seismic waves, gravity, magnetism, or heat. Geophysical methods can provide indirect estimates of rock viscosity, by relating the measured properties and signals to the rheological parameters of the rocks. For example, seismic waves can be used to infer the elastic and anelastic properties of rocks, which are related to their viscous behavior. Geophysical methods can also provide information on the depth and spatial distribution of rock viscosity, as well as the temporal changes due to dynamic processes.

5 Rock viscosity research

Rock viscosity research is an active and interdisciplinary field that aims to improve our understanding and quantification of how rocks deform and flow in different geological contexts. Rock viscosity research has important implications for various topics, such as plate tectonics, geodynamics, geohazards, georesources, and geoengineering. However, there are still many challenges and uncertainties in measuring and modeling rock viscosity, such as the effects of heterogeneity, anisotropy, damage, and feedbacks. Therefore, there is a need for more data, experiments, observations, models, and methods to advance our knowledge and capabilities in this field.