CLASSROOM EARTH
studies and provide access to that research. Although the state surveys differ in online presence (such as Washington Geological Survey LiDAR files), the USGS provides all USGS publications online in the USGS Publications Warehouse and the National Geologic Map Database co-hosted by the Association of American State Geologists. Memberships in the Geological Society of America (access to a dozen journals) or Geological Society of London (access to almost 80 journals!) also allow free access to a number of non-open access works. Using these resources, I could find almost every publication I needed to complete my research.
Into the field: Mima Mounds, Mount Adams, and Beyond
Figure 2. Breaching the dam along the southeastern margin of the Puget Lobe about 16.5 ka ago, glacial lake Carbon surged into the Tanwax-Ohop Tracts, initiating the late-glacial Tanwax flood. As it flooded westward across the Puget Lowland, debris flow associated with the Tanwax flood deposited sediment along several presently mounded terraces, including Mima Prairie (“Mima Mounds”) and Rocky Prairie. Graphic courtesy of Washington Department of Natural Resources.
flood along the southern limits of the Vashon-age Puget Lobe might explain the mound diamicton (Pringle and Goldstein, 2002; Goldstein and Pringle, 2020). Depositing a mantle of andesite-rich diamicton, the Tanwax flood surged through proglacial channels and incised the andesite-poor Vashon Drift drumlin topography, flowing west into the Chehalis watershed then northwest to the Pacific Ocean (Figure 2) (Goldstein et al., 2010). The deposits left by the Tanwax flood are lithologi- cally and stratigraphically similar to the diamicton composing the Mima Mounds.
With this in mind, my project consisted of sampling the pebbles within the mounds and in the underlying coarse- bedded gravels along several terraces as well as determining the particle mineralogy to ascertain if the mound diamicton was deposited by the Tanwax flood. But alas, such studies require fieldwork! On the cusp of closures, hopes were high that the restrictions would not last long, but the pandemic had only just begun. I began my first week with a detailed litera- ture study, but when the colleges closed so did the libraries, and without the use of library and inter-library loan access I was forced to retrieve articles through alternate means. After all, how may any scientist (or student for that matter) remain current on a subject without reading the literature?
While the pandemic may feel unpar- alleled in recent history, the oppor- tunity to apply technology has been even more so. Because libraries were closed, I shifted to alternative means to obtain the information I needed (see Appendix). Like Facebook or other social media platforms,
ResearchGate.net and
Academia.edu facilitate the dissemina- tion of research products by providing a platform for researchers to post online versions of their writings, while Google Scholar and Scinapse (
scinapse.io) pro- vide online directories to articles, cita- tions/references, and any available full texts. United States Geological Survey (USGS) and state geological surveys have also done much to advance geologic
16 TPG •
Jan.Feb.Mar 2021
Depending on the subject, geological research can only go so far from the literature alone – one must eventually venture into the field. I soon began visiting Mima Prairie Natural Area Preserve on reconnaissance trips and applied for a permit from Washington’s Department of Natural Resources (DNR) to collect samples, but research permits were limited until some restrictions lifted. Until May, my project remained in limbo, giving me time to turn my attention eastward towards Mount Adams. In the heart of the sparsely populated Gifford Pinchot National Forest near my residence, I spent several days exploring unusual poorly sorted terraces deposits along the Cispus River, a stream that flows southward from Goat Rocks Volcanic Complex in the central Cascades until flowing west beyond the northern extremes of the Mount St. Helens hazard zone (Figure 3). Along much of its westerly-bound course, the Cispus River is bordered by terraces over thirty meters above the river, the highest level being the broadest and best developed. These terraces are composed of poorly sorted coarse gravels that are imbricated and reverse graded with a matrix-supported fabric. Early researchers suggested that the terrace gravels were produced by outwash during the Evans Creek Glaciation over twenty thousand years ago (Schuster, 1973; Swanson, 1991), but boulders more than two meters in diameter distributed randomly on several terraces defy this proglacial explanation (figure 4 on page 26). Instead, the poorly sorted terrace gravels were indicative of debris flow deposits such as from a lahar (volcanic mudflow).
With this realization, I quickly consulted my mentor John Berry of AIPG, and began investigating the area. Continued
Figure 3. Flowing from the Goat Rocks Volcanic Field, the Cispus River winds through deformed Oligocene bedrock of the primeval Cascade Range, receiving meltwater from Mount Adams via Adams Creek. Downstream from the Cispus River/Adams Creek junction, the Cispus River is bordered by terraces up to thirty meters above the river and comprised of poorly sorted gravels. Are these gravels remnants of glacial outwash or of an unidentified lahar from Mount Adams?
www.aipg.org
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