Jeff discussed the unique Precambrian geology of Glacier Park and its place in the geologic development of the North American continent. A striking and well-exposed sequence of algal stromatolites (fossil algae), red and green argillites, and tan to gray dolomites of the Snowslip and Helena Formations, which we observed earlier.

Most geologists theorize that these rocks are good evidence that the earth's atmosphere was quite different during the Precambrian. An atmosphere rich in CO2 may have allowed for the growth of massive algal colonies such as those preserved in the Precambrian rocks of Glacier National Park. He also discussed plate tectonics and the importance of the Lewis Thrust Fault in Glacier Park's geologic history.