My research is focused on the evolution of Earth's surface over the last ~ten million years.
I study the processes that shape landscapes, including active tectonics, fluvial incision, glaciation,
extreme meterological events, and landsliding. I approach these problems using a combination of fieldwork, geochronology,
remote sensing, GIS, and modeling.
Active tectonics in the Himalaya of west Nepal
The Himalaya of west Nepal present an interesting problem to the conceptual models of ongoing deformation within the
range. In central Nepal and northwest India, rapid rock uplift is occurring along a 50-100 km-wide belt at the crest of
high Himalaya. This belt has been imaged via maps of topographic indices like slope and relief, repeat ground surveys,
InSAR, river incision rates, and GPS data. This zone of uplift is thought to overlie a ramp in the Main Himalayan Thrust,
the primary detachment between the subducting Indian Plate and the overriding orogenic wedge. In far west Nepal, this single
belt of rock uplift breaks down into two range-parallel bands with unclear mechanical relation to the single band to the
east and west. These bands surround a zone of subdued, low-relief topography. This transition is most apparent as a transition
from a steep, abrupt mountainfront in central Nepal to a more gradual, two-step mountain front in west Nepal.
Topography and shaded relief in west Nepal. Boxes depict swath profiles shown in A) and B) below.
The alluvial records of the southern Colorado Plateau
Streams in the southwestern U.S. are weird. Most of them are dry for most of the year, carrying water only after intense storms or during spring snowmelt. Over centuries, these streams go through cycles of filling with and cutting into the sandy sediments they carry. When a stream is in the 'cut' phase, it is called an arroyo. In the late 19th century, a series of extreme floods initiated the most recent episode of arroyo cutting, causing streams to cut up to 30 meters into their beds. As a result, thousands of acres of farmland were lost to erosion and entire communities had to be abandoned. This regional incision also exposed beautiful cross-sections of alluvial material (in the arroyo walls), allowing us to reconstruct cut-and-fill histories to better understand how these systems respond to changes in climate and land-use.
Buckskin Wash is one of these strange, ephemeral streams. Along much of its length it flows through a deep arroyo cut ~10 meters into the
valley bottom. It then drains into a slot canyon, where the channel is confined between bedrock walls only meters apart. In alcoves
and short expansions within this canyon, tall stacks of sandy deposits are preserved. Previous workers have interpreted these stacks
of sand as paleoflood deposits.
For my Masters thesis, I studied the relationship between these slot canyon paleoflood deposits and the cycles of arroyo cutting and
filling that occurred upstream. That work has resulted in a few publications:
Quaternary geology of Lake Clark National Park, Alaska
While working for the National Park Service, I was tasked with unraveling the Quaternary history of Lake Clark National
Park in south-central Alaska. Situated on the west side of Cook Inlet about 130 miles southwest of Anchorage, the park is only accessible by
small aircraft. It comprises millions of acres of rugged, glaciated mountains that are drained by countless rivers and waterfalls that feed
the bright blue lakes so distinctive of the region. The park is host to two active volcanos (Mt. Redoubt and Mt. Iliamna).
Interestingly enough, the day I took the job, Mt. Redoubt erupted
with a ~50,000 foot high cloud of ash and smoke.
Very few geologists have worked here, in part because of the inaccessibility, but also because of the relatively complex
geology and poor exposure (too much vegetation!). In addition to writing a synthesis report of all relevant research from
surrounding areas, I studied the timing of the major glacial advances and retreats that carved out the landscape
over the past 30,000 years. I also worked with a geologist from the USGS on a map of the surficial deposits of the park.
It is a big project in an even bigger park--my work is only the first of several seasons of effort that will be required to get a
handle on its complex geologic history.
06/06 - 08/06