I am interested in understanding the impacts of mantle convection on geological processes at the Earth’s surface. Hot, upwelling plumes and cold, sinking slabs deflect both the gravity field and surface topography. This transient vertical motion is known as dynamic topography, which has typical amplitudes of ±1 km, varies laterally on 1,000 km lengthscales, and evolves over million year timescales.
Dynamic topography is therefore highly relevant to a diverse field of geologists. Ongoing research has so far explored important links to the formation of mountains and seaways, the morphology of river networks and sedimentary depocentres, and the generation and maturation of hydrocarbon and mineral deposits. These transient vertical motions also impact the pattern of oceanic circulation, the stability of ice sheets and evolution of the Earth’s climate.
Associate of the Department Research Professor at Columbia University
Ben Holtzman is a research professor at Lamont Doherty Earth Observatory, visiting the Mitrovica group. He did his Ph.D. (2003) in geophysics in David Kohlstedt's lab at the University of Minnesota. His research is a mixture of experimental and theoretical rock mechanics, seismology and geodynamics. Much of his work has focused on the coupling of melt migration and deformation and the influences of melt on the mechanical properties of rocks in the deep Earth. Currently, his research has two related fronts: (1) Building computational tools for applying complex time dependent mechanical properties to the interpretation of seismic velocity, attenuation and geodetic measurements, towards constructing more detailed and self-consistent images of the thermal-mechanical structure of plate boundaries and the upper mantle. This work involves the development of new constitutive models for earth materials and applications to a range of settings, in collaboration with Harriet Lau and Jerry Mitrovica. (2) Applying new machine learning methods to earthquake seismicity, with a focus on geothermal reservoirs, towards improving the efficiency of heat extraction. (www.ldeo.columbia.edu/~benh) ... Read more about Ben Holtzman
Since receiving my PhD from the University of Toronto in 2000. I joined Prof. Jerry Mitrovica's group in Canada. After he left for Harvard, the collaboration continued and I became his Harvard group member in October 2017. The focus of my research is on development and application of numerical tools to examine problems related to the ice age geodynamics: visco-elastic deformation, sea level change, tidal response, Earth rotation, stress and gravity field calculation. Generally, we are trying to understand how Earth (or similarly structured planets) would respond to surface and/or potential forcing, given a loading history and an assumed visco-elastic structure, particularly three-dimensional, heterogeneous viscosity, as may be inferred from e.g. seismic tomography. Other important 3-D effects which we include in the models are variations in the lithospheric thickness, plate boundaries, slabs, low viscosity wedges, etc. This list is open-ended. The results are ultimately compared to observables, such as sea level markers or present-day deformation rates, available from satellite measuremets. We can, for example, provide a correction for the glacial isostatic adjustment contribution or assess the impact of a 3-D structure on such predictions, since conventional, radially stratified models are handled in a much more efficient way. The 3-D models require an excessive computer power, even for the forward problem. Currently, the simulations are performed on the Odyssey cluster (Harvard) with a finite volume MPI code, developed in Toronto in the early 2000-s. The latter is an ongoing project, including coding, maintenance, consulting and working with interested researchers on improvements. As a side product, this development has stimulated a strong interest in interpolation techniques and adaprive grid generation.
Post-Doctoral Fellow Junior Fellow, Harvard Society of Fellows Mitrovica Group
I am interested in understanding the large-scale properties of Earth, but in particular, the anelastic/viscous and buoyancy structure of the mantle. My work involves studying processes across different timescales, from solid earth tides (~ hours) to post-glacial rebound (~ 10,000 years), making sure that our theoretical understanding of these dissipative processes is consistent across this broad spectrum. With such a framework, observations may then be used to infer various material properties of the Earth, from the long-wavelength buoyancy structure of the deep mantle to the transient nature of Earth's rheology.
I am interested in understanding the surface expression of deep Earth dynamics and structure. My past research has focused on constraining and modelling the impacts of mantle convection on surface elevations and landscape evolution. This work has helped to reconcile numerical models and observations of this so-called ‘dynamic’ topography, while revealing that convectively driven vertical motions may occur at rates of up to 100 m per million years. These fast-evolving perturbations have significant implications across the Earth Sciences as they may destabilise polar ice sheets, alter ocean circulation via closure of ocean gateways, and control locations of resource-bearing sedimentary basins. My current work aims to integrate geological observations with numerical models to constrain these dynamic topography signals and remove them from palaeo sea-level estimates. These revised values will serve as useful tie points to calibrate ice sheet models, reducing uncertainty in projections of future sea-level rise.