Experimental physical volcanology
We developed a new methodology for investigating lava flow dynamics and lava
properties using experiments, video analysis, and flow models. At the Lava Project experimental facility at Syracuse university, we melt natural basalts at temperatures over 1350°C. We then pour the lava onto sand, steel, and even ice, and study the behavior. The flows are documented using video and infrared cameras, allowing us to study the physical properties of the lava.
Video velocimetry of lava flows
We use computer vision methods to extract detailed surface velocity fields of flowing lavas.
This information is then used to constrain the mechanical properties of lava. We applied this
technique to experimental and natural flows alike.
The image shows the velocity field of cascading lava flow at Hawaii's Puu O'o volcano.
Channelization in a'a lava flows
Lava are capable of creating their own channels, whioch allow them to travel to great distances.
These channels can get blocked, eroded and overflow. This photo
shows a shaded image made by Adam Soule (WHOI) using airbourne LiDAR.
Flow in image is the 1984 flow on Mauna Loa, Hawai'i.We study the process of channellization by focusing on the rheolgoy of lava, and by developing numerical tools to model flow behavior.
Anisotropy in subduction zones
We examine the effect of anisotropic viscosity on the
thermal structure of subduction zone mantle wedges. Abundant
observations of seismic anisotropy in subduction zones suggest that the
material in the mantle wedge has a strong fabric and may be
mechanically anisotropic. Using two-dimensional finite-element
kinematic models we find that anisotropic viscosity causes three
substantial changes:(1) a hotter slab-wedge interface
(2) a smaller partially molten region
(3) time variability of the melt production rate and excess temperatures
A hotter slab-wedge interface can change the depth extent of the seismogenic zone, limit the depth to which hydrous minerals can carry water, and influence flux melting. Time-variability, a result of heterogeneity in material alignment,
can explain temporal changes in subduction zone magmatism without invoking a change in the wedge geometry, slab age or composition. We therefore recom mend that anisotropic viscosity, as well as time-dependence, be considered in future models of wedge thermal structure.
Shear localization in the upper mantle
The degree of anisotropic viscosity
and the grain size of upper mantle minerals are two important
rheological parameters that are generally poorly constrained.
We use numerical models of asthenospheric flow to determine the grain
size and anisotropic viscosity required to explain the observed confinement of seismic anisotropy to a layer at the top of the convecting upper mantle. We find that a grain size larger than 10mm gives the best fit to the observations. The ratio of shear viscosity to normal viscosity is 0.3 or higher (less anisotropic), depending on the grain size.
We use numerical models of asthenospheric flow to determine the grain
size and anisotropic viscosity required to explain the observed confinement of seismic anisotropy to a layer at the top of the convecting upper mantle. We find that a grain size larger than 10mm gives the best fit to the observations. The ratio of shear viscosity to normal viscosity is 0.3 or higher (less anisotropic), depending on the grain size.