Southeastern Section - 66th Annual Meeting - 2017

Paper No. 12-5
Presentation Time: 1:00 PM-5:00 PM

QUANTIFICATION OF MOGOTE ASYMMETRY: ARECIBO, PUERTO RICO


MADERA, Andreana D. and HUGHES, K. Stephen, Department of Geology, University of Puerto Rico, Mayag├╝ez, PR 00681, andreana.madera@upr.edu

Mogotes are dissolution landscape features that are common in the northern karst terrain of Puerto Rico. Their height mostly ranges from 30 to 50 meters, with some over 50 meters. Since the early 20th century, it has been noted that these features tend to have asymmetrical shapes, most commonly with steeper western slopes. Potential causes for the asymmetry of mogotes that have been suggested include differential solution during daily afternoon showers when the western slopes are heated to a higher temperature or action by trade winds which arrive predominantly from the east. In order to quantify these anecdotal observations to provide context for local mass wasting hazards, we used a 25m2(DEM) to construct North-South and East-West topographic profiles for solitary mogotes in the pilot study area of the municipality of Arecibo.

Profiles were generated for 104 mogotes and the resulting metrics show that there is no consistent topographic asymmetry in the data derived from the DEM, regardless of underlying geologic unit. However, our field observations indicate that the DEM used is likely too coarse to accurately capture the asymmetry of individual mogotes.

To carefully measure the true slope of one target feature, we used the Structure from Motion technique on a mostly unvegetated mogote using over 400 aerial images captured with a drone. The resulting 3D Model was converted to a high-resolution DEM, which was used to construct much more precise topographic profiles. The results of this analysis will be presented and compared with the results from the coarse 25m2 DEM.

Handouts
  • CorrMogMaderaPoster.pdf (8.4 MB)