Understanding the Earth with Topographic Inversions
The Earth’s surface controls the interaction between the solid Earth and the bio- hydro- atmo- and cryo-spheres. Earth’s topography is the largest data set available to us that can help develop our undertsanding of these interactions. Topography records the culmination of processes that have acted on it, and my research hinges on our ability to deconvolve these processes from the shape of the Earth itself.
Rock Uplift Rates in the Wasatch
The Wasatch Range, Utah, is located on the eastern boundary of the Basin and Range, created by slip on the Wasatch Fault. As a seismically active fault located besides Utah’s most populated metropolitan areas, and an important structural boundary of the Basin and Range, undertsanding slip on the Wasatch Fault is interesting from a range of perspectives. Although fault slip has been characterised on the 10s of Millions of year timescales, and the < 1000 year timescales, there is little evidence available that characterises fault behaviour between these timescales.
River network inversions can bridge the gap between these timescales, providing rock uplift rate histories on the million year timescale. We therefore attempted to constrain the million year history of the Wasatch Range by using a river network inversion to infer rock uplift rates through time. We combined this approach with field data, and a number of data sets such as AHe data and erosion rate data derived from cosmogenic nuclides to tightly constrain our model parameters.
Measuring channel width in Big Cottonwood Canyon, Wasatch Range, Utah
Having recovered the rock uplift rate history of the Wasatch Range from 3 river networks draining the Wasatch, we demonstrate that rock uplift rate has increased and decreased over the last million years. Periodic increases in rock uplift rate have coincided with the development of pluvial lakes on the adjacent Bonneville basin, implicating lake rise and fall in controlling fault slip. We therefore provide evidence the the mechanism described by Hetzel and Hampel (2005) has been ongoing throughout the Pleistocene.
The rock uplift rate history of the Wasatch Range inferred from three river networks
Surface Uplift in the Sierra Nevada
Recent Sierra Nevadan surface uplift has been much debated. We used an inversion based on the methdology of Fox (2019) to infer the pattern of surface uplift across the southern Sierra Nevada. We found that the pattern of surface uplift recovered from the networks of the Sierra Nevada shows increased surface uplift in the centre of the range, which could be intepreted as produced by support from buoyant asthenosphere, associated with the Isabella anomaly. Our methodology is advantageous, as we use the entire river network to infer surface uplift, which provides greater resolution on surface uplift parameters. This work has been published in Earth-Science Reviews, available here.
A u* map and surface uplift map created from relict topography in the southern Sierra Nevada. The L-surface shows the chosen parameters used in the inversion