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Landscapes represent a dynamic point of articulation between humans and the environment. While often dichotomized, humans are active participants in the environment and often play a pivotal role in its transformation over time. In this paper, we use case studies from western South America and Australia to illustrate the importance of studying long-term dynamics between humans and the environment. Such investigations can bring significant historical depth to environmental change and the role humans have played in altering courses of landscape evolution and species biodiversity. Humans comprise a critical element in environmental change, and collectively, our results hold strong implications for issues related to sustainability and effective management of our planet's desert resources.

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RESUMEN. La vegetación y las unidades geomorfológicas de una región están relacionadas entre sí, de tal manera que cualquier cambio en una afecta a la otra. El objetivo de este trabajo es el reconocimiento de unidades geomorfológicas y el inventario y cobertura de especies de plantas nativas de la

The evolution of the drainage pattern of the eastern Andes has proven to be a valuable indicator of tectonic phenomena that occurred between the Early Miocene and the Late Quaternary. In this work a 1000-kmlong segment of the central Andes between 27º and 34º S has been studied. This segment has been identifi ed as an area of intense seismic and quaternary tectonic activity. The stage for these neotectonic manifestations is found to the east of the magmatic arc of the Principal Cordillera and the Frontal Cordillera in the western territories of La Rioja, San Juan, and Mendoza provinces (Argentina). The most signifi cant characteristics of the topography of this region are the high mountain ranges that make up the Frontal and Principal Cordilleras, which reach altitudes that exceed 6,000 m. During the past 20 Ma, the deformation advanced from west to east and the mountain ranges began to rise. These mountains consist of fold and fault blocks that obstructed and diverted the rivers that fl owed eastward. Because of this phenomenon a marked concentration of the drainage was produced in a decreasing number of rivers. This process culminated in the total concentration of the surface drainage in a single large trunk collector, the Colorado River, which drains into the Atlantic Ocean. Currently the deformation is still active in the easternmost strip of the Bermejo -Desaguadero valley characterized by high seismicity and movements as tested by geodetic measurements. The ages of the morphotectonic controls decrease from north to south and from west to east.Keywords: Evolution of drainage system, Quaternary tectonic activity, San Juan-Colorado fl uvial System. Resumo Controle tectônico sobre a drenagem desenvolvida na vertente oriental dos Andes centrais deArgentina. A evolução do padrão de drenagem dos Andes orientais tem provado ser um indicador valioso dos fenômenos tectônicos que ocorreram entre o início do Mioceno e Quaternário Tardio. Um segmento de 1.000 km de extensão da Cordilheira dos Andes central, entre 27 o e 34 o S é considerado. Este segmento tem sido identifi cado como uma área de atividade sísmica e tectônica intensa no Quaternário. O palco para essas manifestações neotectônicas é encontrado a leste do arco magmático da Cordilheira Principal e Cordilheira Frontal nos territórios ocidentais das províncias de La Rioja, San Juan e Mendoza (Argentina). As características mais signifi cativas da topografi a desta região são as cadeias de montanhas elevadas que formam a Cordilheira Frontal e Principal, que alcançam altitudes que excedem 6.000 m. Nos últimos 20 Ma, a deformação avançadas do oeste ao leste e as serras começaram a subir. Estas montanhas consistem em pliegues e blocos da falha que obstruído e desviado os rios que fl uíam para o oriente. Devido a esse fenômeno uma acentuada concentração da drenagem foi produzida em uma diminuição do número de rios. Este processo culminou com a concentração total da drenagem superfi cial em um coletor tronco único e grande, o rio Colorado, que desagua no Oc...

We present a 1:50,000 geomorphological map of the Talacasto river alluvial fan (93 km 2 ), located in the Central Andean Precordillera of Argentina. The aim of this map is to identify and classify dynamic and potentially destructive geomorphological processes such as gully erosion, headward erosion, concentrated erosion, laminar erosion and similar features that are present in an alluvial fan, so as to identify unstable sectors for public infrastructure. This map is the result of combining remote sensing data, aerial photographs analysis and fieldwork. Landforms and active geomorphological processes are identified, classified and illustrated for this Quaternary alluvial fan. Four Quaternary landscape subunits were classified, taking into account morphogenetic characteristics and erosional processes such as:(1) Exhumed and erosional landforms inducted by neotectonic activity; (2) Alluvial landforms;(3) Polygenetic landforms covered in glacis; and (4) Playa lake landforms. The presence of desert pavements and salt-hardened subsoil formations contributes to the generation and transmission of surface runoff during summer heavy rains, causing alluvial hazards and damages in routes and roads.

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