Publications

The Gold Basin landslide is located along the South Fork Stillaguamish River, within the Mount Baker-Snoqualmie National Forest in western Washington State. Recent concerns related to slope stability after the 2014 State Route 530 Landslide near Oso, Washington, forced the closure of the U.S. Forest Service Gold Basin Campground in May of 2014. In addition to safety concerns for National...

The geology of San Francisco and the surrounding northern and central California area has played a pivotal role in the development of our understanding of Earth processes, especially the process of tectonic accretion at a continental margin and the development of transform plate margins. The Franciscan Complex, which underlies most (or perhaps all) of the City and County of San Francisco...

During the last deglaciation (19,000–9,000 years ago), atmospheric CO2increased by about 80 ppm. Understanding the mechanisms responsible for this change is a central theme of palaeoclimatology, relevant for predicting future CO2 transfers in a warming world. Deglacial CO2 rise hypothetically tapped an accumulated deep Pacific carbon reservoir, but the processes remain elusive as they...

Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North...

Pliocene–Pleistocene glaciation modified the topography and erosion of most middle- and high-latitude mountain belts, because the evolution of catchment topography controls long-term glacier mass balance and erosion. Hence, characterizing how erosion rates change during repeated glaciations can help test hypothesized glacier erosion-landscape feedbacks across a range of settings. To...

A recent study posits that much of the 240-m-deep inner gorge of Grand Canyon was carved between 500 and 400 ka via passage of a migrating knickzone with incision rates of ~1600 m/Ma during that time period; this was based on dating of a ca. 500 ka travertine deposit perched on the rim of the inner gorge, near Hermit Rapid, and a ca. 400 ka travertine drape that extends to within 60 m of...

A horizontal gradient analysis of the isostatic gravity and aeromagnetic anomaly grids of the NewMexico-Arizona-southernCalifornia area was carried out, focused on eastern Arizona and western New Mexico, to define the transitional boundary between the Proterozoic Yavapai province to the west and the Mazatzal province to the east. The two provinces differ substantially in their...

Maps of extreme value, horizontal component geoelectric field amplitude are constructed for the Pacific Northwest United States (and parts of neighboring Canada). Multidecade long geoelectric field time series are calculated by convolving Earth surface impedance tensors from 71 discrete magnetotelluric survey sites across the region with historical 1‐min (2‐min Nyquist) geomagnetic...

A recent report points out where the United States is most dependent on mineral imports and highlights some ways for reducing this dependence.

Most current models for the landscape evolution over geological timescales are based on semi-empirical laws that consider riverbed incision proportional to rock erodability (dependent on lithology) and to the work performed by water flow (stream power). However, the erodability values obtained from these models are entangled with poorly known conditions of past climate and streamflow...

The geologic record of the formation of marine basins during continental rifting is uncommonly preserved. Using GIS-based paleotectonic maps, we show that marine basin formation in the Gulf of California–Salton trough oblique rift (Mexico and the United States) occurred in a stepwise manner as crustal thinning lowered elevations within the Gulf of California Shear Zone, and subsidence...

We use synoptic surveys of stream discharge, stable isotopes, and dissolved noble gases to identify the source of groundwater discharge to the Verde River in central Arizona. The Verde River more than doubles in discharge in Mormon Pocket over a 1.4 km distance that includes three discrete locations of visible spring input to the river and other diffuse groundwater inputs. A detailed...