Inspiration in ancient rocks and simple physics

[a post by Anne Jefferson]
If you ask my mom how I got started in geology, she’d tell you that it began with her taking 3-year-old me to see landslides coming off steep hillslopes during the spring thaw. That makes a nice story, but its not the real reason I got sucked into geology. Truth be told, I picked geology because it was the field of science my parents knew nothing about.
In my hometown public school system, the smart kids were herded towards doing in-depth middle school science fair projects. There was a wonderful teacher who helped us find projects and mentors, and taught us the art of visual displays and public teaching. As the child of two scientists, I was a natural fit for the program. There was only one problem: I didn’t want to do anything with which my parents could help. That was my mild form of early teenage rebellion. With my parents’ expertise in biology, chemistry and computer science, I felt I only had one choice: physics. But physics had too much math for my taste. (Little did I know just how mathy geology can be.)
Then a family friend suggested a geology project, I took it and ran with it, and the rest is history. My family friend was a resident of the Bayfield Peninsula, which juts up into Lake Superior from northern Wisconsin. Our friend was a sailor and nature enthusiast, and he pointed out that all of the rock cliffs along the lakeshore had right-angle fractures. He wanted to know why.

Figure 1. Shoreline at Big Bay State Park, Madeline Island, Wisconsin.
Figure 1. Shoreline at Big Bay State Park, Madeline Island, Wisconsin. Photo by Anne Jefferson, July 2007.

That question was the inspiration for my first real science fair project was “Fracture characteristics and geologic history of the Chequamegon Sandstone (Bayfield Group, Late Precambrian).” I collected dozens of stones from the rocky beaches of Madeline Island, where the Chequamegon Sandstone is exposed. I measured the angles between all sides of the stones, and tried to correlate them with grain size, induration and other characteristics. I made my first and last thin sections and I sieved samples using the same sort of Ro-Tap machine I now teach students to use. I also learned about things like properties of non-crystalline materials, the North American Mid-continental rift sytem, paleocurrents, and Pleistocene glaciations.

Figure 2. More shoreline made of Chequamegon Sandstone in Big Bay State Park, Madeline Island, Wisconsin. Glacial scour marks are visible on some of the rock surfaces.
Figure 2. More shoreline made of Chequamegon Sandstone in Big Bay State Park, Madeline Island, Wisconsin. Glacial scour marks are visible on some of the rock surfaces. Photo by Anne Jefferson, July 2007.

I don’t think my conclusions were particularly startling to people who knew anything about rocks. The rocks generally broke along their bed planes, and then at 90 degrees from their bedding, with more than 50% of the rocks exhibiting fractures between 80 and 100 degrees from bedding. Secondary modes were 60 and 120 degrees from bedding. More tightly indurated rocks had a higher propensity to have obtuse fracture angles.

Figure 3. The young scientist at work.
Figure 3. The young scientist at work. Photo by Carol Jefferson, August 1991.

That first project led to a second project, a year later: “Strength, porosity and fractures in the Chequamegon, Mount Simon, and Eau Claire Formations,” in which I contrasted the material properties of two building stones and an aquifer. Then the Mississippi River floods of 1993 pretty permanently steered my interest from ancient rocks and materials properties towards the more dynamic modern landscape. I’ve never again worked on rocks within an order of magnitude as old as my first rocks, and these days I’m more apt to think about the water flowing over and through rocks than the rocks themselves. But sometimes I’m in the field, and my eyes will be drawn to an outcrop, boulder, or piece of float. And I still find myself silently inspired by the amount of geologic history that rock has experienced to end up in the stream bed, hillslope or lakeshore obeying simple laws of physics.

Figure 4. Perpendicular joints in the Chequamegon Sandstone at Big Bay State Park, Madeline Island, Wisconsin.
Figure 4. The adult scientist still inspired by those perpendicular joints in the Chequamegon Sandstone at Big Bay State Park, Madeline Island, Wisconsin. Photo by James Jefferson Jarvis, July 2007.

Categories: by Anne, fieldwork, geology

Comments (6)

  1. Kim Hannula says:

    I never knew your original project was structural geology… cool!

  2. Diggitt says:

    A great post and a lovely story. Young people should hear more stories like this so they can feel the scientist’s enthusiasm.
    Of course, more young people should only have parents who encourage them to follow their own questions.
    For several years, I was an officer of an inner-city environmental education center right on the Hudson River. When I would take our Beach in a Box and other exhibits and go to Saturday family fairs, it broke my heart to see (usually inner-city) parents slapping their child’s hand away from touching and picking up.
    Every program would find me repeating, dozens of times — These stones/shells/seeds are here to be picked up and held. The parents would be doubtful and the kids wouldn’t know whether to believe me. I don’t think there’s any substitute for seeing things up close and asking every question you can think of, and being able to find the answers for yourself.

  3. Clare Jarvis says:

    Well Anne,
    I don’t think I pressured you toward chemistry or computers. And you did not mention economics. It is no wonder that you became a field scientist though, growing up in such a pretty part of the country with two parents who like the outdoors.
    Keep up the good work.
    Dad.

  4. Kate says:

    Great post by an awesome guest! I agree, more stories in the blogosphere about how scientists got started are instructive. Thanks for sharing!

  5. Mom says:

    Thanks for the memories and insights. I love you, Anne! You forgot to mention your next 4 years (grades 9-12) studying sedimentation and sediment transport in the Upper Mississippi. — and winning many national and international awards! Then on to college and grad school!
    MOM (the field ecologist & professor)

  6. Rod says:

    Please forgive the completely off-topic comment!
    WoGE#167 has been languishing for so long on Ron Schott’s site that the Google imagery has actually changed. I think it’s probably just escaped the attention of the geoblogosphere because the momentum was lost back in early spring, but it’s time to get things rolling again. Ron tried to give a big hint recently, but he did it through Twitter. I thought I’d take the more drastic measure of posting a hint on some previous WoGE winners’ sites: Windley and Allen, 1993.