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Rock glaciers are dynamic landforms and , as such , exhibit interesting and welldeveloped
structural features , which translate to surface morphology in the form of ridges
and furrows . These distinguishing features have led researchers to study the physics
behind the movement and internal deformation of rock glaciers . For years researchers
had no access to the internal makeup of rock glaciers . Thus , proposed models and
discussion have been based on theoretical concepts of electromagnetic (EM ) wave
propogation . With the application of ground penetrating radar (GPR ) to provide a view
of the interior structure of a rock glacier , researchers had “real” data to verify their
models . However , no comparison has been made between a GPR profile and an actual
cross -section of a rock glacier . The purpose of this thesis is to validate the fidelity of
GPR in showing the actual structure of a rock glacier .
A trench that was excavated through the toe of a rock glacier on Mount Mestas in
south central Colorado provided a view of the actual structure of the landform . The
structure in the trench was compared with GPR and EM data . The GPR study was
conducted using a PulsEKKOTM 100A subsurface imaging radar with 25 , 50 , and 100 MHz antennas , to detect dielectric contrasts within the rock glacier . A frequency domain
EM34 by Geonics LtdTM was also used to supplement the GPR data by measuring the
rock glacier’s conductivity at various depths .
This thesis proved , by utilizing statistics , that GPR is a useful tool in visualizing
the interior structure of rock glaciers . The 100 MHz antennas clearly show small scale
reflection horizons caused by changes in clast orientation and subsurface material
composition . These events coincide with structures seen in the trench . Individual clasts
greater than 0 .375 m were also recognized as point sources in the GPR profiles . Large
continuous bedding layers were observed with the 25 and 50 MHz antennas , which
reflect the structure seen in the trench . A large scale thrust fault was also located with the
GPR . However , this was not visible in the panoramic photograph because the fault
occurs below the base of the trench . |
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