Spring 2019 Colloquia

Spring 2019 colloquia

Title: A Quest across Hemispheres: Understanding the Linkage between Vegetation Change and Alluvial Fan Aggradation in Arid Regions

Abstract: A widely used model for occurrence of alluvial fan aggradation in arid regions states that at timescales of tens of thousands of years timescales, changes between climate states causes hillslope vegetation change, driving a disequilibrium in the hillslope sediment transport system that ultimately generates aggradation in alluvial fans downstream. The discrete sedimentation pulses observed in Late Quaternary alluvial fans of arid southwestern North America have been explained by invoking this mechanism. Extensive research during the past decades has tried to test this hypothesis not only in the arid southwestern continent, but also in other arid regions.

In this talk, I will focus on how our understanding on alluvial fan sedimentology, timing, and the relation with paleoenvironmental change has improved over the last decade in areas across North and South America, and how this has enabled us to develop new hypotheses that complement the original ideas in the model. I will highlight the critical role that coupled geochronology tools like optically stimulated luminescence and cosmogenic exposure dating have played along with quantitative techniques for soil chronosequence analysis, drawing examples from research in Mexico, the Mojave and the arid Andes.

Title: Chemical Role of Fluids and Mechanical Role of Minerals in Fault Zones

Title: Seismic anisotropy in the middle and lower
continental crust: Using rocks to improve seismic interpretations

Title: Using stable isotopes to track migratory animals

Abstract: The conservation of migratory wildlife requires that we link breeding, stopover and wintering sites of regional populations and identify which factors may be operating to limit populations. This is easily said but difficult to achieve, especially for small songbirds and insects that are rarely encountered and which are typically unable to be equipped with satellite transmitters. For the last decades, I have been working on the use of intrinsic chemical fingerprints (stable isotopes of key elements such as C,N,O,H,S) primarily in bird feathers and insect wings to provide geographic information of origins. The advantage to such an approach is that only one capture is required and sampling is not biased to the relatively few locations where organisms can be marked. This approach has provided a breakthrough in the way we can forensically track wildlife by making use of naturally occurring biogeochemical “isoscapes”. I will provide an overview of this technique and provide many examples from birds to butterflies. I will also try to address where the isotope approach now sits given the advent of new and exciting technologies such as miniaturized light-level geolocators and Motus tags.

Title: Decoupling of modern tectonics, climate, and topography in the Greater Caucasus

Title: Tudor Lecture The 2018 rift eruption and summit collapse of Kīlauea Volcano, Hawai'i: What happened and what have we learned?

Title: Earthquakes and Submarine Landslides: the View from Sediment Shear Strength

Title: In the shadow of volcanoes

Abstract: It is clear that ecosystems are devastated after a volcanic eruption coats the landscape with a layer of ash; however, the ecological recovery of the local groups of mammals after eruptions is poorly understood. Volcanic eruptions vary with magnitude and type and only a fraction of them have been analyzed for effects on the groups of mammals that live in the area of devastation. To better understand the recovery of these effected communities, we will look at ecological changes across modern volcanic boundaries in the 1980 Mount St. Helens (MSH), Washington, and 1914-1917 Mount Lassen, California, eruptions. We will then then investigate the fossil record specifically focusing on the extremely volcanically perturbated Oligocene record at John Day Fossil Beds National Monument in central and eastern Oregon. We will also look at some other examples of volcanically perturbated ecosystems throughout the Cenozoic and how mammals have adapted to volcanism across the globe.

Title: Understanding the mechanical impacts of frictional heating during earthquakes: a laboratory approach