Project Info

Evaluating the Terrace-Mound Connection of the Mima Mounds of Puget Lowland, WA, Using GIS and Field Reconnaissance

Danica Roth

Project Goals and Description:

For over a century, Mima Mounds of the Puget Lowland have baffled geologic thought. Numbering in the thousands along proglacial terraces, these elongated dome-like ellipsoids measuring up to 2 m in height fuel both speculation and controversy (Washburn, 1988). With similar “Mimalike” mounds across the US and beyond, a variety of genetic models have been proposed ranging from biotic to seismic. Nonetheless, the shared or discrepant origins of these discrete mound fields remains unresolved, fueling debate along lines of disciplinary and regional bias (Pope, 2021c). Even classification of mound fields appears elusive, yet many Mimalike mound fields appear to be associated with Pleistocene terraces (Pope, 2021b). This raises the question: do terraces represent sites for preservation of mounds or do they play some causal role in the formation of Mimalike mounds? Considering these observations, the proposed study purposes to test the observations of Pope (2021b) to determine the strength of correlating mounds to host terraces and the specific genetic, morphological, and chronostratigraphical relation the mounds of the Puget Lowland hold to their host terraces, thereby constraining the mounds’ origin.

More Information:

Grand Challenge: Not applicable.

Primary Contacts:

Danica Roth,

Student Preparation


Field mapping, GIS mapping, experience with analyzing soil cores, grain sizes, petrology and mineralogy, ability to engage with scientific literature and communicate scientific results.




Following literature review to more robustly assess the association of Mimalike mounds and terraces, GIS mapping will analyze the spatial correlation between the mounds to their host feature, paying heed to indications of constraint by the terrace versus preservation bias along terraces. Meanwhile, the sedimentological association of the mounds and the terraces will be queried through coring the cardinal points of three mounds using PVC piping to collect the cores, similar to Seifert et al. (2009) in the Oklahoma mound fields. Once retrieved, grain size analysis will “map” the distribution of grain sizes throughout the mounds and related to terrace-scale trends (e.g., gradient) using GIS. Examination of the provenance of pebbles within the mounds, as begun by Pope et al. (2020), will be continued first with hand samples to evaluate the composition of the pebbles to narrow the provenance, and thus origin, of the mound diamicton itself. Analysis of grain size, mineralogy, and clast petrology could begin with initial examination in Summer 2023 but may not fully mature until Fall 2023.


Student will have weekly to biweekly meetings to discuss progress, challenges and questions, as well as email, Slack and drop-in availability. The student will also be included in weekly lab group meetings, and will be invited to attend lab journal reading groups, which will provide exposure to a collegial research environment and provide networking and professional development opportunities. Depending on student interests, goals and performance, this project may also lead to student co-authorship on scientific publications and presentation at scientific conferences, and additional research, internship and teaching or field assistantship opportunities with the group going forward.


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