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2019 Field Studies, Section 1

Oregon’s youngest obsidian lava flow at Newberry Volcano. This flow is ~1,300 years old with a spatial extent of ~1 square mile.

GEOL-406 Field Studies in Volcanology and Geophysics (CRN 41170) 4 credits  Instructors: Thomas Giachetti and Valerie Sahakian.  Graded for Majors; P/NP optional for all other students.  Additional $785 field trip fee beyond normal tuition and UO fees.

The main project of this section will take place at Newberry Volcano, a potentially active stratovolcano and the second largest in the Cascades. Newberry features a number of basaltic lava flows, as well as explosive ash flow and fall deposits. The project in this portion of the module will be to untangle the order and nature of processes during the last eruptive phase of this volcano that took place less than a thousand years ago, using a combination of physical volcanology, geophysical, and surveying techniques.

Students may participate in either the physical volcanology or geophysical components:

Close-up view of the base of the explosive pumice deposits.

Physical volcanology group: this group will quantify the volume and main textural characteristics of the tephra ejected during the explosive phase of the Big Obsidian Flow eruption. To do so, students will dig several 1-to-6-feet deep pits in the tephra fall deposit to obtain the thickness and a detailed description of this phase of the eruption. This will include an analysis of the subsurface extent of the buried sub-units, as well as detailed descriptions of the sub-units themselves (e.g., number of sub-units, thickness of each layer, size, shape, and texture of the different components of the deposit).

Geophysics group: this group may use subsurface imaging techniques on or near the pits dug by the physical volcanology group to corroborate with the observational data. This group will also map out the spatial extent of the obsidian flow and estimate its thickness to get its volume.

The students from both groups will then work together with their collected data and data gathered from the literature and satellite/aerial images to make cross-sections, maps, and provide estimates on volume, extent, and viscosity of the various deposits and eruptive phases. This will allow them to develop a joint interpretation of sequence of events that took place during the last eruption of Newberry Volcano.

The next project of this section will be an extended field trip to the Oregon Basin and Range to examine the relationship between volcanology and tectonics in this region.

Abert Rim, Oregon, uplifted along a normal fault

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