Diagnóstico Físico-Conservacionista do Astroblema da Serra da Cangalha sob a ótica da Geoconservação

Abstract

Impact craters are rare structures with great scientific and educational value distributed throughout the planet. It is estimated that just under 200 astroblems are catalogued, of which 12 are on Brazilian soil: Domo de Araguainha – MT/GO, Vargeão – SC, Colônia – SP, Vista Alegre – PR, Cerro do Jarau – RS, Riachão – MA, São Miguel Tapuio – PI, Piratininga -SP, Santa Marta – PI, Inajah – PA, Curuçá – AM and Serra da Cangalha – TO. Serra da Cangalha is located in the northeast region of Tocantins, in Campos Lindos. This region has a large concentration of monoculture crops. Thus, the Serra da Cangalha Astrobleme is located in a context marked by landscape transformations. Therefore, the aforementioned changes put the abiotic diversity of the Impact Crater at risk. Given this scenario, the objective was to investigate the degradation stage of the Serra da Cangalha Impact Crater through the application of Physical-Conservationist Diagnosis (DFC). The study area covers the astrobleme and its surroundings, accounting for 4785.95 km² distributed in the municipalities of Campos Lindos, Riachão, Carolina and Goiatins. This work is divided into Topographic Compartmentation and Application of the DFC. The characterization, the initial part of the compartmentalization, took into account the physical aspects of the landscape. Added to this is the use of morphometric indexes, namely: Relief Dissection Index, Roughness Concentration Index and Topographic Position Index. In this way, the measured data was interpreted taking into account information on geology, geomorphology, pedology, slope, and use and coverage. Subsequently, with a view to conserving and/or preserving Serra da Cangalha, the DFC was applied to assess the conservation conditions of the structure and its surroundings. This done, the results related to topographic compartments indicate a predominance of tabular tops associated with Debris- Lateritic Covers; convex tops in the rough regions of the astrobleme and dissected portions of the edges of Serra da Gado Bravo; terraces and river plains are present in areas with a medium concentration of roughness in Chapada da Cangalha. The application of the DFC proved to be efficient in investigating the stages of landscape degradation. At this stage, the area under study was sectorized based on municipal political limits, so each sector concerns one of the municipalities mentioned above. The DFC results indicate sectors B and C with the highest number of units at risk of degradation, the use and coverage data corroborate this result. Sector A houses the impact crater, and therefore, careful investigation is carried out regarding changes to the landscape. A considerable increase in temporary agriculture and pastures can be noted in the vicinity of the astrobleme, in the compartment of the astrobleme's lowered ring and in Chapada da Cangalha. Serra da Cangalha is located in a context of tension. The sectors that present a higher degree of risk of degradation are arranged in flat compartments, with little roughness and the absence of ridges. On the other hand, the rough and highly dissected compartments show little change in vegetation cover. Given the context, the need to ensure geoheritage is understood. Therefore, this work contributes to understanding the context of degradation of the structure and its surroundings. In this way, we advocate in favor of geoconservationist practices towards Serra da Cangalha. Although there are discussions to implement a Conservation Unit (Natural Monument of Serra da Cangalha), it is extremely important to take into account the context of rapid expansion of human activities and speed up discussions to implement the UC.