Story posted April 25, 2012
Image above: students mapping lithologies and structures out at Pemaquid Point (Karl Koehler ’14 and Evan Kulak ’14)
When most people think of strike-slip faults, they think of the San Andreas Fault in California. What most people don’t know is that Maine is home to an older (inactive) strike-slip fault system that rivals the San Andreas Fault in terms of both length and the amount of relative plate motion—it’s called the Norumbega Fault Zone.
On April 14 & 15, Bowdoin College’s EOS 242 – The Plate Tectonics Revolution – traveled to several destinations in Maine to examine firsthand what the Norumbega Fault Zone looks like. Because the fault zone has been differentially exhumed, we can walk along the surface of the Earth today to examine rocks that were faulted at a depths of up to 15 km. Students located minerals that were rotated into alignment in response to strike-slip faulting and traced their fingers along “fossilized” earthquakes and shear zones.
In addition to observing the Norumbega Fault Zone, students also traveled to coastal Maine to unravel the history of rocks that have been deformed by a series of tectonics events. From continental collision to large-scale strike-slip faulting to the rifting apart of continents to form the Atlantic Ocean, students observed and measured evidence of the tectonic history of south-central Maine.