Jorgensen, William Revis (2007-05). A validation of ground penetrating radar for reconstructing the internal structure of a rock glacier: Mount Mestas, Colorado, USA. Master's Thesis. Thesis uri icon

abstract

  • 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.
  • 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.

publication date

  • May 2007