Two aspects that I love about TA’ing geology labs are 1) learning new things and 2) going on field trips (think of field trips as recess for college students and their TA’s/Professors). As part of my graduate work, this semester I TA for the Sed-Strat lab. Sedimentology means the study of sedimentary rocks, where stratigraphy means the order and relative position of formation layers, or strata.
Studying how layers of rocks relate to one another, or any other example of geology, means a student needs to head outdoors. Hence, field trips. This explains how I found myself hiking up a hill on Monday afternoon wearing my cute little flats, a cardigan and pearls.Yes, I knew the Professor intended this lab for Monday afternoon. No, I did not remember it when I got dressed.
Monday’s lesson: how to accurately determine the Belle Fourche Shale formation thickness (conveniently) located at the edge of campus. To do this we used a Jacob’s Staff and a Brunton Compass. Not only did I make it outside for the entire afternoon, I learned something new about Jacob’s Staffs – including how to use them.
A Jacob’s Staff (seen at my feet in the picture above) is a length of wood or nonferrous alloy with a predetermined height and a support for the compass. Possibly named for Jacob and his staff in Genesis 32:10, the staffs make qualitative judgments about the height and angle of an object relative to the user of the staff. Originally designed and used in the 1300’s for astronomical measurements, Jacob’s Staffs soon gained usefulness in ship navigation (but eventually giving way to sextants), and then geology and surveying.
My responsibility as TA was to set the start and end stakes so everyone measured the same distance (TA tip: this makes grading much easier). Our Jacob’s Staffs measure 5′, but they can be any length so long as the person using the staff and compass is tall/short enough to comfortably sight in their compass.
For Sed-Strat lab, students paired off: one student held the staff using the compass as a level sights in a consistent target. The second student, rather the soles of their shoes, acted as the target. As soon as the first student targeted the shoes, s/he would move up to the second student’s location and the second student would make his/her way up to the next 5′ elevation change.
Working from the bottom stake to the top stake, nascent geologists measured the formation thickness in 5′ increments. To get the total thickness, multiple the number of increments by the height of the staff and voila! The height of the formation is known and ready for mapping.
Despite my inappropriate footwear I would not beg off for a minor bipedal inconvenience. I charged right up that hill with my stake and hammer ready to set up the lab. Except when it occurred to me that rattle snakes enjoy the sunshine as much as I do.
Rest assured, dear reader, my shoes suffered no fang punctures that afternoon. Welcome to the new school year and a great reason to buy a new pair of boots!