Welcome to GeoUnion, the graduate student body of the Department of Earth, Environmental and Planetary Sciences. GeoUnion strives to supplement the overall graduate student experience at Rice and DEEPS. GeoUnion represents DEEPS in the overall Rice grad student community, acts as a liaison between students and faculty and organizes a number of intra- and inter-departmental events throughout the academic year.
Graduating senior Rachel Marzen receives NSF graduate research fellowship.
New student paper out! Matt Weller, publishing in Earth and Planetary Science Letters, finds that planets migrate through tectonic states over time as their surface temperatures change. A planet even can have multiple stable tectonic states over time! [article]
We use 3D mantle convection and planetary tectonics models to explore the links between tectonic regimes and the level of internal heating within the mantle of a planet (a proxy for thermal age), planetary surface temperature, and lithosphere strength. At both high and low values of internal heating, for moderate to high lithospheric yield strength, hot and cold stagnant-lid (single plate planet) states prevail. For intermediate values of internal heating, multiple stable tectonic states can exist. In these regions of parameter space, the specific evolutionary path of the system has a dominant role in determining its tectonic state. For low to moderate lithospheric yield strength, mobile-lid behavior (a plate tectonic-like mode of convection) is attainable for high degrees of internal heating (i.e., early in a planet’s thermal evolution). However, this state is sensitive to climate driven changes in surface temperatures. Relatively small increases in surface temperature can be sufficient to usher in a transition from a mobile- to a stagnant-lid regime. Once a stagnant-lid mode is initiated, a return to mobile-lid is not attainable by a reduction of surface temperatures alone. For lower levels of internal heating, the tectonic regime becomes less sensitive to surface temperature changes. Collectively our results indicate that terrestrial planets can alternate between multiple tectonic states over giga-year timescales. Within parameter space regions that allow for bi-stable behavior, any model-based prediction as to the current mode of tectonics is inherently non-unique in the absence of constraints on the geologic and climatic histories of a planet.
ESCI 334 is one of the Earth Science department’s capstone undergraduate courses. The field trip takes us to a location near San Ysidro, New Mexico, because of the easy access to phenomenal rock exposures, which span approximately one billion years of geological time. Students map in detail rocks that were folded and faulted during the late Cretaceous Period (approximately 70 million years ago), as a consequence of the intense mountain building along the western margin of North America during that time.
During the field campaign, students integrate and apply knowledge they acquired throughout their undergraduate earth science core curriculum. The goal is for students to achieve their full potential in exploring and discovering the geology underfoot. Throughout the field trip students build their confidence in working independently. They make their own scientific observations, which culminate in an interpretive report that transforms their observations into geological understanding.
During the field trip students form bonds and friendships with one another that often extend beyond their studies at Rice. This sort of camaraderie and friendship is in part facilitated by our lodging arrangement. This year the group of students was rather large, but we were able to find a vacation rental on the outskirts of Albuquerque, which had two houses on a single property. Although quarters were tight, this allowed us to share meals and socialize in the evenings, after a hard day’s work in the field.
Department of Earth, Environmental and Planetary Sciences
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