Abstract

VELASQUEZ ESPINOZA, Gema de los Ángeles; ALCANTARA AYALA, Irasema; HERNANDEZ SANTANA, José Ramón  and  GARNICA PENA, Ricardo Javier. Volcanic-morphotectonic-zoning in the morphostructural analysis of relief: the case of the municipality of Managua, Nicaragua. Invest. Geog [online]. 2015, n.87, pp.118-140. ISSN 2448-7279.  https://doi.org/10.14350/rig.43549.

The modern Geomorphology has one of the scientific objectives: the morphostructural analysis, which is the set of methods oriented to reveal the structural-tectonic conditions of the earth's crust and its role in the shaping and consolidation of the actual landforms.

Having into account the above mentioned, the main objective in this research is to create a Morpho-Tectonics Volcanic Unit (UMVT) of the Municipality of Managua, Nicaragua, which is represented in a topographic Map to a 1:50 000.00 scale, having as a base, the relationship between the geologic structures and the resulting relief shapes originated by the fragmentation of the Nicaraguan Volcanic Chain and the Graben Formation of Managua.

The following research methods were applied in order to conduct this study: a) Creation of a digital model of elevation and shapes, b) morphometrics analysis, c) interpretation of air photographs to a 1:40 000,00 scale, d) analysis of the lineal morpho-elements and annular relief in order to complement the failure systems and morpho-lineal, e) a correlative structural analysis with the relief litostratigraphy and its lying conditions and the precision between the tectonic-volcanic units, f) interpretation of the structural patterns of the hydrographic network.

The findings obtained from the morphometrics Analysis were: a) the altimeter map that allowed identifying altimetry differences between the main tectonic structures and the volcanic formations of the area. b) The creation of a dissection deep map that identified in a general way, a relationship between the slope and the dissection deep values in the territories: areas with a great number of slopes involves a major dissection and vice versa. c) The slope map which identified that the most important features appreciated, in a general way, were the escarps, which coincide with the mountain sides and erosive deforestation. The minor values are observed in the plains and middle foothills.

In according to the geological-geomorphologic conditions, and the specific criteria stated previously, the Municipality of Managua was divided in twelve zones or morphotectonic volcanic units (UMVT), which are mentioned below:

UMT I: Cuajachillo. This zone is represented by a low plain; UMTV II. Ticomo Los Martínez: This is a crustal weakness zone; UMTV III. San Judas-Tiscapa: This is a zone represented with middle-high plains with notable internal fissures; UMTV IV. San Juan-Unidad de Propósito: This unit is characterized with middle high plains, with presence of low foothills and with notable disjunctives structures; UMTV V. Barrio Nuevo-Esquipulas: In this zone it is middle and high plains are observed with presence of moderate fissures; UMTV VI. Graben el Aeropuerto: This zone is represented by the presence of the Graben Aeropuerto; UMTV VII. Los Madrigales: Low Foothills Zone, form volcanic origin with few presences of notable structural elements; UMTV VIII. Las Cuchillas: It is geomorphologically classified in pre-mountains with some elliptical features in its configuration; UMTV IX. San Isidro: From the geo-morphological perspective, it is classified as a high foothill, with structural evidences of the recent tectonic activity; UMTV X. Cedro Galan-Monte Tabor: This zone is represented by low foothills with some plain sectors; UMTV XI. Berlin: It is characterized by pre-mountain features; UMTV XII. Costa del Lago: This zone is characterized by a low plain.

This classification is a regional characterization and its morphotectonic zoning is constituted from the scientific point of view: as a geo-systemic vision of the structure expression and the geological constitution and the neotectonic activity in the formation, consolidation and differentiation of the tectonic-volcanic relief in Nicaragua, showing the individual characteristics of each of the 12 space units.

In this sense, the morphotectonic-volcanic zoning has a significant holistic strength that allows it to understand the space relationship between the composition of the geological substratum, its structures, and tectonics deformities, and at the same time its role in the relief differentiated formation in complex genetics conditions related with the recent and quaternary volcanism. The definition of the twelve units of this morphotectonic volcanic zoning represent an important input for further studies of the seismic dangerous, volcanic and extreme hydro-meteorological in different weakness sceneries and for designing the suitable programs for an adequate management of its risks.

These aspects are considerably related with the UMTV, for that reason, its analysis in the weakness context due to flooding and its corresponding affections as well as the economic value of the tangible potential damages provoked by a flooding are clear examples of the relevance presented in this research (Velásquez, 2011).

Keywords : Morphostructural analysis; morphotectono-volcanic units; Managua.

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