The study area is located in the Cerros de Escazú, province of San José, which is a mountain range in central Costa Rica located southwest of the city of San Jose. The climate is predominantly tropical and rainfall occurs mostly from May to November; abrupt changes between sunny and rainy weather are common. It borders the Central Valley to the south, and along with the Cedral massif forms the Fila de la Candelaria, which is considered the northernmost part of the Cordillera de Talamanca.
The area is located 12 km SW of San José, and extends for approximately 277 km2 with elevations from 400 m along the Pacacua River flood plain to 2,428 m (7,966 feet) at Cerro Rabo de Mico.
The orogenic process that formed the mountain range is the same that caused the lifting of the Cordillera de Talamanca. For this reason, the same geological materials (igneous, sedimentary and metamorphic) are present. The surface formations, especially in areas that are subject to large landslides, expose igneous rocks. In the mountains of Escazú, for example, outcrops of magmatic rock types (intrusive) are located in the hills of San Miguel, Pico Alto Blamco and Burío. The lithology of the Cerros de Escazú has aged rocks from the Tertiary to Quaternary. In a sequence from the oldest to the most recent rocks are the following formations: Pacacua Formation (clastic rocks, volcanic, shale and sandstone, altered and fragmented by the presence of intrusive Escazú); Peña Negra Formation (black shales, siltstones, tuffaceous sandstones and conglomerates, also fragmented, interbedded and mixed with each other, making them susceptible to landslides); Intrusive Escazú (pluton in whose composition can be distinguished granodiorites, monzodiorites, monzonites and micro granodiorites) and Quaternary sediments (colluvium, blocks, cones of debris and recent deposition materials transported by rivers or by gravitational processes).
In the case of the Cerros de Escazú, tectonics is complex, since the materials that compose the Cerros have been affected by a process of internal uprising associated with magmatic intrusions. These magmatic intrusions generated a profuse fault system which gives an unstable condition to the hills, visible especially in the surface materials, which are highly fractured. The area has four main faults of considerable length and countless smaller secondary faults. The four major faults form a trapezoid whose center is dominated by the Intrusive Escazú, which may be the evidence of the formation of a granitic body surrounded by sedimentary formations of marine origin. This system of major and minor faults has an active dynamic that is responsible for the many landslides that are located in different parts of the orographic whole.
Land use is chiefly focused on livestock, horticulture, urbanization and the few remaining forest areas. Human intervention on the landscape, as areas of recent deforestation and the opening of roads, often triggered large landslides. Additionally hurricane events and intense seasonal rainfall events trigger floods and landslide events producing human losses and damages to structures and infrastructures. 2nd-8th November 2010 the intense rainfall caused by Thomas Hurricane triggered numerous landslides and flooding resulting in human fatalities (26) and damages to buildings (2450) and infrastructures (roads, transmission towers).
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