The Eastern Hills (Spanish: Cerros Orientales) are a chain of hills forming the eastern natural boundary of the Colombian capital Bogotá. They are part of the Altiplano Cundiboyacense, the high plateau of the Eastern Ranges of the Colombian Andes. The Eastern Hills are bordered by the Chingaza National Natural Park to the east, the Bogotá savanna to the west and north, and the Sumapaz Páramo to the south. The north-northeast to south-southwest trending mountain chain is long and its width varies from . The highest hilltops rise to over the western flatlands at . The Torca River at the border with Chía in the north, the boquerón (wide opening) Chipaque to the south and the valley of the Teusacá River to the east are the hydrographic limits of the Eastern Hills.
Geologically, the Eastern Hills are the result of the westward compression along the Bogotá Fault, that thrust the lower Upper Cretaceous rocks of the Chipaque Formation and Guadalupe Group onto the latest Cretaceous to Eocene sequence of the Guaduas, Bogotá, Cacho and Regadera Formations. The fold and thrust belt of the Eastern Hills was produced by the Andean orogeny with the main phase of tectonic compression and uplift taking place in the Pliocene. During the Pleistocene, the Eastern Hills were covered by glaciers feeding a large paleolake (Lake Humboldt) that existed on the Bogotá savanna and is represented today by the many wetlands of Bogotá.
The main tourist attractions of the Eastern Hills of Bogotá are the Monserrate and Guadalupe Hills, the former a pilgrimage site for centuries. Other trails in the Eastern Hills follow the creeks of La Vieja, Las Delicias and others. The busy road Bogotá – La Calera crosses the Eastern Hills in the central-northern part and the highway between Bogotá and Villavicencio traverses the southernmost area of the hills. The eastern side of the Eastern Hills is part of the municipalities La Calera, Choachí, Ubaque and Chipaque.
The Eastern Hills were sparsely populated in pre-Columbian times, considered sacred by the indigenous Muisca. The native people constructed temples and shrines in the Eastern Hills and buried their dead there. The Guadalupe and Monserrate Hills, important in Muisca religion and archaeoastronomy, are the hilltops from where Sué, the Sun, rises on the December and June solstices respectively, when viewed from the present-day Bolívar Square. The construction and expansion of the Colombian capital in Spanish colonial times caused excessive deforestation of the Eastern Hills. Reforestations were executed in the 1930s and 1940s.
Large parts of the Eastern Hills are designated as a natural reserve with a variety of flora and fauna, endemic to the hills. Despite its status as a protected area, the Eastern Hills lie in an urban setting with more than ten million inhabitants and are affected by mining activities, illicit construction, stream contamination, and frequent forest fires. Several proposals to fight the environmental problems have been written in the past decades.
Description
The Eastern Hills cover an area of approximately , are oriented north-northeast to south-southwest along a length of , have a width between and range in elevation from . They border the Colombian capital Bogotá to the east. The main hills are Cerro Guadalupe at and Monserrate at . Cerros Orientales – Alcaldía Bogotá Cerro Monserrate – official website Cerro de Guadalupe Other hills are Aguanoso, Pico del Águila, El Cable, El Chicó, El Chiscal, La Laguna, Pan de Azúcar and La Teta. From north to south, the rural areas of the localities of Usaquén, Chapinero, Santa Fe, San Cristóbal and Usme are part of the Eastern Hills.Audiencia CAR, 2006, p.42 Of the area of Santa Fe, 84.5% is rural area, located in the Eastern Hills.Martínez Montoya, 2010, p.29 The municipalities Chía, La Calera, Choachí, Ubaque and Chipaque are partly in the Eastern Hills. The Cerros Orientales are an important water source for the Colombian capital. The San Rafael Reservoir, administered by the municipality La Calera, is east of the Eastern Hills.
Etymology Bogotá, and as a result the Eastern Hills of Bogotá, are named after the original main settlement of the Muisca; Bacatá. Bacatá in Muysccubun means "(enclosure) outside of the farmfields" or "limit of the farmfields",Correa, 2005, p.213 referring to the seat of the zipa in present-day Funza on the right bank of the Bogotá River. Bacatá is a combination of bac or uac, uac - Muysccubun Dictionary online ca, ca - Muysccubun Dictionary online and tá, ta - Muysccubun Dictionary online meaning "outside", "enclosure" and "farmfield(s)" respectively.
Alternative spellings are Muequetá, or Muyquytá, Muyquytá - Muysccubun Dictionary online and the word is transliterated in Epítome de la conquista del Nuevo Reino de Granada as Bogothá.Epítome, p.85
Geography
Geographically, the Eastern Hills form part of the Altiplano Cundiboyacense, the high plateau in the Eastern Ranges of the Colombian Andes. The natural boundaries of the Eastern Hills are the Bogotá savanna in the north and west, the hills of Chingaza National Natural Park in the east and the mountains of Sumapaz Páramo in the south. The northern hydrographic limit is the Torca River at the border with Chía, the southern limit the boquerón Chipaque and the eastern hydrographic boundary is formed by the Teusacá River.
Geology
The rocks forming the Eastern Hills range in age from Late Cretaceous to Paleogene and are covered by sub-recent sediments of the Pleistocene and Holocene. The contact between the Maastrichtian to Lower Paleocene Guaduas and Late Paleocene Cacho Formations is discordant, indicating the first uplift of the Andes. Between the Eocene and Pleistocene a hiatus is present, where the Pleistocene formations are followed by Holocene unconsolidated sediments.Geological Map Bogotá, 1997
The Cenomanian–Turonian Chipaque Formation got its name from the village Chipaque and is the oldest stratigraphical unit outcropping in the eastern flank of the Eastern Hills. It comprises laminated organic to highly organic shales and mudstones with intercalated sandstone beds. The overlying Guadalupe Group, of Campanian to Maastrichtian age, consists of four formations, from base to top: Arenisca Dura, Plaeners, Arenisca de Labor, and Arenisca Tierna. Some authors define the Guadalupe Group as a formation and call the individual formations, members.Guerrero Uscátegui, 1992, p.4 The thickness of the Guadalupe Group in its type localities Guadalupe and El Cable Hills is .Guerrero Uscátegui, 1992, p.5 The competent hilltops of the Eastern Hills are represented by the resistant members of the Guadalupe Group; in the northern parts of the Cerros Orientales they comprise the Labor and Tierna members and are in the southern area represented by the Arenisca Dura.
Concordantly overlying the Guadalupe Group is the Maastrichtian to Early Paleocene Guaduas Formation, composed of well-laminated compacted grey shales and calcitic claystones with sandstone banks and in the lower parts of the stratigraphical sequence numerous coal beds. In the synclinal of the Bogotá savanna, the thickness of Guaduas varies between . The Late Paleocene Cacho Formation, a relatively thin stratigraphical unit following the Guaduas Formation, white, yellow and reddish in colour, is represented by thick sandstone banks with intercalations of thin shale beds.
The Bogotá Formation, named after the capital, is a Paleocene to Lower Eocene argillaceous unit, concordantly overlying the lower Paleogene sequence. The formation is composed of grey, purple and red shales with micaceous sandstone beds towards the top of the stratigraphical unit. The thickness in the subsurface of the Bogotá savanna ranges from and outcrops at the edges of the flatlands. In this formation fossils of the ungulate Etayoa bacatensis, named after the name for the savanna and its main settlement in present-day Funza, used by the native Muisca; Bacatá, have been found.Villarroel, 1987, p.241Etayoa bacatensis at Fossilworks.org The estimated size of the South American hoofed mammal was that of a dog. Un xenungulado del Paleoceno de la Sabana de Bogotá – Paleontología en Colombia Other fossilised fragments found in the Bogotá Formation are molds of Stephania palaeosudamericana and Menispina evidens.Stephania palaeosudamericana – Paleobiology DatabaseMenispina evidens 1 – Paleobiology DatabaseMenispina evidens 2 – Paleobiology Database
Discordantly overlying the Lower Eocene is the Middle Eocene Regadera Formation, consisting of quartzitic and feldspar-rich thick medium- to coarse-grained to conglomeratic sandstone beds intercalated with thin pink claystones. The total thickness of the Regadera unit is very variable throughout the area. Following the Regadera Formation is the discordant Late Eocene Usme Formation, named after the locality in southeastern Bogotá, for the most part located in the Eastern Hills. The unit with a total thickness of consists of a lower member composed of grey shales with occasional fine-grained sandstone layers and an upper member of coarse-grained quartzarenites and conglomerates. The Usme Formation represents the last Paleogene stratigraphic unit before the hiatus of approximately 30–35 million years.Guerrero Uscátegui, 1992, p.6
While the Bogotá savanna contains two other formations; the Pliocene Tilatá and Plio-Pleistocene Sabana formations, the Eastern Hills lack these late Neogene stratigraphical units. The basal unit of the Quaternary sequence is the fluvio-lacustrine Subachoque Formation, present in the subsurface of the foreland area of the Eastern Hills. The Tunjuelo Formation, named after the Tunjuelo River that is fed by the Eastern Hills creeks in the south and the Sumapaz Mountains to the southeast, is the last consolidated stratigraphical unit. Coarse-grained Quaternary fluvio-glacial deposits as a result of the Eastern Hills run-off through the San Cristóbal, San Francisco and Arzobispo rivers and the many creeks, intercalate with clays and conglomerates. The Tunjuelo Formation has a maximum thickness of .Guerrero Uscátegui, 1996, p.12 This Pleistocene sequence is followed by poorly consolidated to unconsolidated sediments of lacustrine origin, Pleistocene–Holocene in age, mixed with the erosional products of the Eastern and Suba Hills and Sumapaz mountains that form the alluvium.Guerrero Uscátegui, 1992, p.7
Code Formation Age Lithologies Type locality Qdp Alluvium Pleistocene to Holocene Sands, shales and conglomerates Qcc Tunjuelo Pleistocene Conglomerates with sandstones and lime Tunjuelo Valley Qsu Subachoque Early Pleistocene Fluvio-lacustrine shales with sand and gravel intercalations Subachoque Synclinal Tsu Usme Late Eocene Shales and siltstones Usme Synclinal Tpr Regadera Middle Eocene Cross-laminated sandstones and conglomerates Regadera Valley Tpb Bogotá Late Paleocene to Early Eocene Mudstones and shales with intercalated sandstones and coal Ciudad Bolívar Tpc Cacho Paleocene Coarse-grained sandstones and conglomerates Soacha Ktg Guaduas Maastrichtian to Early Paleocene Intercalated sandstones and shales, coalbeds Guaduas Ksg Guadalupe Campanian to Maastrichtian Grey sandstones and shales Guadalupe Hill Ksch Chipaque Cenomanian–Turonian Organic shales with sandstone banks Chipaque
Soils