Introduction to Physical Geology (Geology 101)
Fall 2006 with Professor Rachel Beane.
The Geology 101 class took an all-day field trip to Vinalhaven Island on Sunday, September 17, 2006. The class arrived early in the morning to drive to Rockland, then enjoyed a ferry ride over to Vinalhaven. The first stop was to the Lane Island Nature Preserve where students observed gabbro and a composite dike. A composite dike consists of "pillows" of basalt within granite, and is significant because it shows injection of the basaltic magma into partially crystallized granite.
The next stop was to Smith Point where students divided into 5 project groups. Their projects were:
1) measure width and orientation of fine grained dikes,
2) measure and photograph orientation of feldspar in granite,
3) measure orientation, length and width of mafic enclaves in granite,
4) photograph and locate contacts between granite dikes and porphyry and
5) observe and sketch field relations within and between gabbro and porphyry.
These projects contributed to ongoing research into the geologic history of Vinalhaven Island (two Bowdoin students have completed honors projects on Vinalhaven Island geology). Students continued to work on the projects, using rocks they collected, throughout the semester culminating in conference-style presentations. The great exposures and field relations of the igneous rocks, along with excellent examples of magma pipes and mingling, make the geology of Vinalhaven special - not only for Maine, but worldwide.
For further information on the geology of Vinalhaven, please see:
Gates, O., 2001. Bedrock Geology of Northhaven and Vinalhaven Islands, map 01-352 and open file 01-37: Maine Geological Survey.
Hawkins, D.P. and Wiebe, R.A., 2004. Discrete stoping events in granite plutons: A signature of eruptions from silicic magma chambers? Geology, v. 32, p. 1021-1024.
Wiebe, R.A., Manon, M.R., Hawkins, D.P., and McDonough, W.F., 2004. Late-stage mafic injection and thermal rejuvenation of the Vinalhaven Granite, Coastal Maine. Journal of Petrology, v. 45, p. 2133-2153.
Wiebe, R.A., Frey, H., and Hawkins, D.P., 2001. Basaltic pillow mounds in the Vinalhaven Intrusion, Maine. Journal of Volcanology and Geothermal Research, v. 107, p. 171-184.