Geophysical
Electrical Resistivity study of a thrust fault with two 9th graders, Wendy Simpson, Dr. Ed
Simpson, Dr. Sarah
Tindall, and Dr. Paul Quinn (and me, of course!)
Wendy Simpson, a
local high
school teacher and friend of mine, had some 9th grade
students who were
interested in doing a geophysical project for their science fair
project. One of the student (Hannah) came up with the idea
because she liked both physics and geology and thought there might be a
way to tie the two together! She is a very smart young woman!
After some discussion, we
decided to see if we could detect a thrust fault that shows up in a
farmer's field on the geologic map of the area. A fault is a big
fracture in the bedrock where two giant blocks of rock slide past one
another. A thrust fault is a special kind of fault that forms
when the land is compressed and one block of rock is pushed up over the
top of the other - our particular fault probably formed when the
Appalachian Mountains formed about 275 million years ago and has long
since stopped moving. (click
here for a summary of the geologic history of the area).
Wendy, Doc Simpson, and I went out
with Hannah and Xin Chi to collect the data on one cold, cold January
weekend. We inserted four copper electrodes into the ground in a
line called a Wenner array. We connected the electrodes to a
battery and to an instrument that measures electrical current (amp
meter). Measuring the electrical current allows us to determine
the electrical resistance of the rocks using Ohm's Law.
By changing the spacing between
the electrodes, we could determine the electrical resistivity of
progressively deeper and deeper rocks. Our goal was to find the
contact between the shale in the upper plate and the limestone in the
lower plate by detecting a change in the electrical resistivity of the
rocks.
Each of us helped out by
performing a different job.
Wendy, Doc Simpson, and I
were in charge of pushing electrodes into the ground (weight can be an
advantage sometimes!)
Hannah was in charge of
operating the instrument and reading off the data.
Xin Chi took notes.
Hannah enjoyed being in charge of
the operation and clearly loves applied geology/physics. I think
she'll discover a new oil field someday.
We marked where we took our measurements on the ground with spray paint
so I could come back a week later to use the high precision Global
Positioning System (GPS) to determine our exact locations.
A couple weeks later, we met at
Kutztown University in the science student lounge with Dr. Sarah
Tindall and Dr. Paul Quinn. Dr. Tindall is a
structural geologist, which means she specializes in studying how rocks
fold and break - a very, very
important branch of geology because it is the key to studying
earthquakes, finding oil, predicting landslide susceptibility,
determining the strength of the ground on which people build houses,
etc. Dr. Quinn is a physicist who loves anything dealing with
math, physics, and nature, preferably all three combined!
Hannah and Xin Chi plotted up the
data with a spreadsheet and we debated the results for the better part
of an afternoon. In the end, the boundary was pretty clear to see
from the data and Hannah and Xin Chi wrote their work up for their 9th
grade school science fair project.
Hannah is interested in following up the resistivity study with a
seismic refraction study of the same area so she can compare results.
Here's a photo of the whole group
(except Doc Simpson). Back row: Paul Quinn and Sarah
Tindall. Front row from left to right: Kurt Friehauf, Hannah, Xin
Chi, and Wendy Simpson.
Wendy, Doc Simpson, and I went out
with Hannah and Xin Chi to collect the data on one cold, cold January
weekend. We inserted four copper electrodes into the ground in a
line called a Wenner array. We connected the electrodes to a
battery and to an instrument that measures electrical current (amp
meter). Measuring the electrical current allows us to determine
the electrical resistance of the rocks using Ohm's Law.
By changing the spacing between
the electrodes, we could determine the electrical resistivity of
progressively deeper and deeper rocks. Our goal was to find the
contact between the shale in the upper plate and the limestone in the
lower plate by detecting a change in the electrical resistivity of the
rocks. 
Each of us helped out by
performing a different job.
Hannah enjoyed being in charge of
the operation and clearly loves applied geology/physics. I think
she'll discover a new oil field someday.
A couple weeks later, we met at
Kutztown University in the science student lounge with Dr. Sarah
Tindall and Dr. Paul Quinn. Dr. Tindall is a
structural geologist, which means she specializes in studying how rocks
fold and break - a very, very
important branch of geology because it is the key to studying
earthquakes, finding oil, predicting landslide susceptibility,
determining the strength of the ground on which people build houses,
etc. Dr. Quinn is a physicist who loves anything dealing with
math, physics, and nature, preferably all three combined!
Hannah and Xin Chi plotted up the
data with a spreadsheet and we debated the results for the better part
of an afternoon. In the end, the boundary was pretty clear to see
from the data and Hannah and Xin Chi wrote their work up for their 9th
grade school science fair project.
Here's a photo of the whole group
(except Doc Simpson). Back row: Paul Quinn and Sarah
Tindall. Front row from left to right: Kurt Friehauf, Hannah, Xin
Chi, and Wendy Simpson.