The dynamic evolution of landscapes reflects the effects of temporal changes in climate as well as tectonics. Geomorphic features preserved in a landscape are some of the youngest markers that can be used to reconstruct the climate and tectonic history of a region.  Place-based studies incorporating local and historical knowledge reveal entanglements between the human and earth proecesses shaping the landscape.

With the advent of robust techniques for dating Quaternary features, we have tools that allow us to quantify the timing of formation or the modification of geomorphic features. With this geochronologic dataset, coupled with high resolution remote and field-based mapping, as well as human historical records, and  we can assess the nature of the processes acting on and modifying these geomorphic features.  

We can quantify the rates of surface uplift or local slip rates along active structures through absolutely dating offset geomorphic markers such as strath terraces, marine terraces, alluvial fans, or pediment surfaces. Using this technique in the forearc of southern Peru, we have found multiple active structures that are a relatively new component of models for understanding how the Andean orogen formed and how it is currently being maintained (Audin et al., 2006; Hall et al., 2008; Saillard et al., 2008; Saillard et al., 2011; Hall et al., 2012; Rodriguez et al., 2013; Saillard et al., 2017; Benavente et al., 2017).

Active Tectonics in the Andes

Geochronologic datasets based on surface exposure dating of glacial geomorphic features such as moraine-crest boulders and radiocarbon ages on peat from lake sediment cores provide important constraints on periods of glacier advance and retreat.  These variations have important implications for understanding the degree of synchronicity of glacial events as well as for understanding the regional impacts of global climate change. My work to date has focused on the north-central Peruvian Andes, which hosts the largest system of tropical glaciers in the world (Hall et al., 2009). Currently, I am working on a glacial chronology from the Cordillera Blanca, Peru.

Glacial Geochronology in the Andes

Landscape Evolution: Orogenesis and Erosion

We can observe the effects of coupled climate and tectonic interactions through tracing the pathways rocks have traveled from depth to the surface of the earth. Using low-temperature (U-Th)/He thermochronology, coupled with stratrigraphic and structural data from the north-central Peruvian Andes, collaborators and I have recorded the timing of rock cooling and have used this to constrain the exhumation history of the Eastern Andean Cordillera (Michalak et al., 2015; Margirier et al., 2015). Further, by coupling low-temperature thermochronologic datasets with basin-averaged erosion rates derived from cosmogenic isotopes, we can begin to compare rates of long-term exhumation with shorter-term erosion (Hodson, 2012; Michalak et al., 2015; Margirier et al., 2015).

The dramatic relief of the coastal region of Maine, the homelands of the Passamaquoddy and Penobscot people, highlights the interaction of long and short timescale geologic processes. By mapping bedrock fractures and topographic lineations coupled with new geochemical and geochronological data, we have identify potential locations of unmapped faults or geologic contacts plausibly correlated with highly fractured rock.  Especially relevant for a local population that relies heavily on private well-water intentionally tapping fractured bedrock, we are curious about the geochemical signature of these fractured and often mineralized zones.

Landscape Evolution: Modern morphologies reflecting ancient processes

Watershed Monitoring in and around Acadia National Park

Training, professional development, and career preparedness of Environmental STEM (ESTEM) students

This is a multipurpose collaborative project building long-term datasets through stream monitoring which provide a foundation for various current and future research projects, resource management decisions, and educational projects. During the high tourist season on Mt Desert Island (MDI), local water sources and other community infrastructure see heavy demand, particularly within and around Acadia National Park (ANP). The primary work of this study is to train student researchers to monitor 8 watersheds within and proximal to the park, particularly those of specific interest to local stakeholders. Through this project, COA students train and network with collaborators at ANP, Friends of Acadia (FOA), and University of Maine.

With an aging STEM workforce and well-documented leaky pipeline (while students are majoring in STEM, they are not always making it into the workforce), it is a critical time to be training STEM students, particularly within the Environmental fields. Fundamental to training the next generation of STEM workers is sparking their interest and dedication to societally relevant problems at a young age and providing students with tranformative field experiences. To that end, I continue to be involved in geoscience eduation projects aimed at undergraduate students and k-16 educators through the producation of curricular resources, offering field opportunities, advising undergraduate research, and through the creation of a Professional Development Program for Environmental STEM (ESTEM) students (NSF GEOPATH inititative).