University of California-Santa Cruz
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Paleoclimate Reconstruction: Walker Lake-Bloody Canyon Moraines of Mono Basin, California part of NAGT:Teaching Resources:Teaching in the Field:Field Trip Collection
In this activity students map and describe glacial geomorphic features related to Quaternary glaciations in the Sierra Nevada of central California. In this region, multiple sets of glacial moraines and corresponding bogs and lakes are evidence of various advances during the Pleistocene. With time, glacial features are modified by erosional processes resulting in morphological changes that we can use to relatively date the various features. Using cross-cutting relationships, moraine morphology, boulder description/counting, and various other relative dating techniques students will "date" the moraines. In this locality there are three main moraine crests that are well-preserved and available for students to hike along and gather data (classified as Tioga-Tenaya, Tahoe, and Mono Basin moraines). At a locality along each of the three different moraine crests, students will observe the boulders along the ridge crest (within ~5m of the crest) within a known area. The students will record the number of boulders, the degree of weathering of the boulders, the lithology, the size (~diameter), roundness, presence of lichen (describe), and the presence of striations on each boulder. They will also note the style and amount of vegetation on the moraine and soil characteristics (amount of gruss around boulders?) The students should make a table in their field notebooks so that it is easy to compile the data at the end of the day. Generally students work in groups of 2 or 3. Since many of these observations are somewhat qualitative it works well for them to be able to discuss their thoughts while gathering data. It is helpful to use a few boulders as examples to set some ground rules before starting the activity – this will help the class be the same page with regard to the techniques.