Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-07-27T19:46:53Z No. of bitstreams: 1 2012 - Alexandre Muselli Barbosa.pdf: 9021333 bytes, checksum: 5ab49dd0b9a0835ab179fedb0302417a (MD5) / Made available in DSpace on 2017-07-27T19:46:53Z (GMT). No. of bitstreams: 1 2012 - Alexandre Muselli Barbosa.pdf: 9021333 bytes, checksum: 5ab49dd0b9a0835ab179fedb0302417a (MD5) Previous issue date: 2012-02-29 / FAPERJ / The objective of this work was the environmental study of the northern flank of the volcano Cotopaxi, Ecuador, with the focus on the acting of weathering processes and climate in the soil formation processes and cryopedogenesis, in a transect ranging from 3979 to 4885m. For the study a survey and zoning of the vegetation was conducted; digital geomorphologic analysis, consisting of elevation, slope, curvature, illumination and radiation exposure, geological study, monitoring of temperatures of air and at five soil depths, in three different elevation points; description and collection of six representative soil profiles, according to the variation of vegetation, topography, presence of snow and elevation; and evaluation of soil composition through analysis of petrographic, mineralogical, physical and chemical properties of soils. The vegetation covering the slope is the P?ramo, varying in size according to elevation and increasing of ice sheets over the soil, which occurs up to 4885 m, and the biota is represented by extremophile organisms. The geology of the Cotopaxi volcano is complex due to the recent volcanic activity, where the ejected material is of Andesite-rhyolite, as identified by the petrography, with large deposits of tephra, and an area of debris deposition. The geomorphology is characteristic of a stratovolcano, with conical and symmetric formations, with broad base and gentle slope, headed for a peak with high altitude and slopes, the slopes are full of drainage systems and erosional features, and in the lower portions of the landscape there are sedimentary deposits of periglacial origin. The registered temperatures showed that the soil are kept warmer than the air temperature for the three elevations, even in the systems that present ice coverage, showing that the soil has thermal insulation properties. The soils are stratified, with layers of ash and lapilli interspersed, with pumices, predominantly coarse texture and low clay content. The mineralogical analyzes indicated the presence of easily weathered minerals such as apatite, olivine, pyroxenes and feldspars. The minerals found influence in the soil chemical data, with high levels of Na, P and K, and the large amounts of Fe, from the ferromagnesian minerals in the parent material. The six profiles described were identified into two systems of soil classification, the WRB - FAO and the USDA - Soils Taxonomy. As for the WRB, three soils were classified as Regosols, two as Leptosols, and one as Cryosol. In the Soil Taxonomy, three were classified as Inceptisols, two as Entisols and one as Gelisol. The coarse texture and presence of pumice material, together with the large presence of easily weathered minerals, show the dominance of physical weathering over chemical reactions in the alteration of parent material of the Cotopaxi volcano. This fact results in poor soil development, also influenced by the climate, type of vegetation, and the recent deposition of material from the volcanic activity. Since the data of soil temperature was only of one year, it is not possible to determine the soil thermal dynamics, requiring continuing the monitoring to acquire data on a longer time scale. / O objetivo deste trabalho foi realizar o estudo ambiental do flanco norte do vulc?o Cotopaxi, Equador, com o enfoque da a??o dos processos intemp?ricos e clim?ticos na forma??o dos solos e processos criopedog?nicos, em um transecto variando entre 3.979 a 4.885m de altitude. Para o estudo foi realizado o levantamento e zoneamento vegetal; an?lise geomorfol?gica digital, composta por eleva??o, declividade, curvatura, face de exposi??o e radia??o; estudo geol?gico; monitoramento das temperaturas em cinco profundidades do solo e do ar em tr?s pontos de eleva??o diferentes; descri??o e coleta de seis perfis representativos, de acordo com a varia??o de vegeta??o, topografia, presen?a de neve e eleva??o; e avalia??o da composi??o do solo, atrav?s de an?lises petrogr?ficas, mineral?gicas, f?sicas e qu?micas dos solos. A vegeta??o que recobre a encosta ? o P?ramo, variando de porte de acordo com a eleva??o e o aumento das camadas de gelo sobre o solo, sendo este presente at? os 4.885m, e a biota ? representada por organismos extrem?filos. A geologia do Vulc?o Cotopaxi ? complexa devido a recentes atividades vulc?nicas, sendo o material expelido Riol?to-Andesito, comprovadas pelas an?lises petrogr?ficas, com grandes deposi??es de tephra, e ?rea de deposi??es de corrida de detritos. A geomorfologia ? caracter?stica de estrato vulc?es, forma??es c?nicas e sim?tricas, com base ampla e declive suave, indo a cumes com elevada altitude e grandes declividades, suas encostas s?o repletas de sistemas de drenagem e fei??es erosivas, e nas por??es mais baixas ocorrem dep?sitos sedimentares de origem periglacial. As temperaturas registradas mostraram que o solo se mantem em n?veis mais elevados que a temperatura do ar para as tr?s eleva??es, mesmo nos sistemas que apresentam cobertura de gelo, mostrando que o solo possui propriedades de isolamento t?rmico. Os solos s?o estratificados, com camadas intercaladas de cinza e lapilli, pedregosos, com textura predominantemente grosseira e baixo conte?do de argila. As an?lises mineral?gicas apontaram a presen?a de minerais facilmente intemperiz?veis, como apatita, as olivinas, os pirox?nios e os feldspatos. Os minerais encontrados refletem nos dados qu?micos dos solos, com teores elevados dos elementos de Na, P e K, al?m dos altos teores de Fe, pelo material de origem de mineral ferromagnesiano. Os seis perfis descritos foram identificados em dois sistemas de classifica??o de solos, o WRB da FAO e o Soil Taxonomy do USDA. Sendo para o WRB, tr?s solos classificados como Regosols, dois Leptosols e um Cryosol. No Soil Taxonomy, tr?s solos s?o Inceptisols, dois Entisols e um Gelisol. A presen?a de textura grosseira e rochas vesiculadas, juntamente com a grande presen?a de minerais facilmente intemperiz?veis, evidenciam o predom?nio do intemperismo f?sico sobre o qu?mico na altera??o do material de origem do Vulc?o Cotopaxi. Este fato resulta no fraco desenvolvimento dos solos, tamb?m influenciado pelo clima, tipo de vegeta??o e as recentes deposi??es de material pela atividade vulc?nica. Como os registros de temperatura do solo foram de apenas um ano, n?o ? poss?vel determinar a sua din?mica t?rmica, sendo necess?ria a continuidade do monitoramento para a obten??o de dados com maior dura??o de tempo.

La première partie consigne les résultats de l'étude de terrain. La deuxième partie aborde la pétrographie classique , l'étude des mélanges de laves et des pegmatoïdes de Neirebrousse. La troisième partie permet de caractériser chaque type pétrographique . En conclusion : un essai de reconstitution historique a été tenté.