Resumo

JIMENEZ, Wilmer; LOAYZA, Verónica  e  METZLER, Eric. Mapeo de cangahuas mediante teledetección en el Ecuador. Siembra [online]. 2018, vol.5, n.1, pp.38-50. ISSN 2477-8850.  https://doi.org/10.29166/siembra.v5i1.1426.

Thousands of years ago, certain section of the Ecuadorian sierra experienced strong volcanic activity. During these volcanic events, igneous material and ash were ejected, forming a zone of volcanic mud that fused and hardened. Afterwards, this material was covered by volcanic ash that further affected the surface soil. Local residents call this hardened material cangahua, which in Kichwa means “hard land”. Bad soil management practices promoted by land pressure have unleashed erosive processes that have removed the surface soil and exposed the lower cangahua layer. By its nature, cangahua is a poor agricultural substrate. Today, farming in the cangahua region is very difficult, and farmers often abandon their impoverished lands. The goal of this study was to generate a 1:25.000 scale map of the cangahua zones in Ecuador. This map helped to pinpoint the location of both exposed cangahua and cangahua layers up to 60 cm deep covered by soils and other materials. The study analyzed the factors that determined cangahua exposure, including volcanic system dynamics, altitude, topography, erosion patterns and deposition, soils and visible cover. The analysis of these factors led to the modelling of cangahua behavior and its role on the landscape. This project relied on orthophotography and high-resolution satellite images from space taken from the Google Earth Pro and ArcGIS Earth applications, including the DigitalGlobe and Airbus Defense and Space’s CNES catalogues. It was supported by collecting field data using GPS, and deriving secondary data from soil survey maps, geopedology, digital terrain modeling (DTM), contour line maps and Google Street View images. The study concluded that, at national level, the total area covered by cangahua deposits is of 181.487 ha, of which 13.162 ha are exposed cangahua and 168.325 ha are deposits of cangahua located up to a depth of 60 cm.

Palavras-chave : soil; volcanic limestone; erosion; satellite images; geographic information system.

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