The Táchira Depression ( es, Depresión de Táchira) is a saddle of land connecting the

Lake Maracaibo Lake Maracaibo (Spanish: Lago de Maracaibo; Anu: Coquivacoa) is a lagoon in northwestern Venezuela, the largest lake in South America and one of the oldest on Earth, formed 36 million years ago in the Andes Mountains. The fault in the northern se ...

basin to the

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wor ...

basin in the state of Táchira, Venezuela. It forms a break in the eastern Andes, separating the Tamá Massif to the west from the Cordillera de Mérida to the east. The depression has been thought to present a barrier to the movement of species between the Colombian and Venezuelan Andes, but this effect may have been relatively low during the recent ice ages. The mountains of the region have potential for coffee farming and hydroelectric power generation, while the lower levels are suitable for farming.

Location

The Eastern Cordillera of the Colombian Andes forks from the Pamplona Node into two long branches. The Cordillera de Periiá extends northward and the Tamá Massif and Cordillera de Mérida extends in a northeast direction. The second branch is divided by the Táchira depression, an area of low lands between the valleys of the Táchira River to the west, the Lobaterita and Torbes rivers to the east and the Quinimarí to the south. The Táchira depression covers an area of about . The depression has a northern slope in the basin of Lake Maracaibo, drained by the Táchira, Lobatera, La Grita, Orope and Escalante rivers, and a southern slope in the Orinoco basin drained by the Uribante, Torbes, Quinimarí, Doradas, Sarare, Piscuri and Narvay rivers.

Formation

More than 50 million years ago the Táchira depression was a strait that connected

with the

basin. Today it separates the Tamá Massif, a prolongation of the Cordillera Oriental of the

Colombian Andes The Andean region, located in central Colombia, is the most populated natural region of Colombia. With many mountains, the Andes contain most of the country's urban centers.Cordillera de Mérida in the Venezuelan Andes. This gap between the Colombian and Venezuelan Andes is a product of orogenic movements in the

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

period that created major faults, raised blocks and formed rifts including the Táchira Depression. There are four faults with northwest-southeast trends aligned in echelon across the Tachira depression between Córdoba in Colombia to the west and Torondoy in Venezuela to the east. This pattern indicates that the region to the south of the depression must have moved westward relative to the region to the north.

Structure

The region may be divided into three main physiographic units: mountains, valleys and piedmont lake and plain. The mountains cover 71% of the total area, characterized by very irregular relief with slopes of more than 35%, with high and low mountains between the Batallón the Negra

páramo Páramo () can refer to a variety of alpine tundra ecosystems located in the Andes Mountain Range, South America. Some ecologists describe the páramo broadly as "all high, tropical, montane vegetation above the continuous timberline". A narrower ...

s (high moors). Soils are generally shallow and have low natural fertility. The valleys that run between the mountains cover 7% of the area, including the valleys of the Torbes, Grita, Quinimarí, Uribante, Venegará and Táchira rivers. The piedmont region that extends to the north and the piedmont in the

Llanos The Llanos (Spanish ''Los Llanos'', "The Plains"; ) is a vast tropical grassland plain situated to the east of the Andes in Colombia and Venezuela, in northwestern South America. It is an ecoregion of the tropical and subtropical grasslands, sav ...

(grassland plain) to the southeast covers the remaining 22%.

Climate

The climate varies considerably depending on the relief of each area, which affects the prevailing winds and precipitation. The climate is tropical in the premontane piedmont and the low mountains, and in some valleys, semi-arid in regions like Lobatera,

San Antonio del Táchira San Antonio del Táchira is a city in the Venezuelan Andean state of Táchira. The busy highway across the Simón Bolívar International Bridge linking the cities of Cúcuta, Colombia, and San Cristóbal, Venezuela, passes through San Antonio d ...

and Ureña, and humid in the upper and middle basins of the Uribante, Dorados and Camburito rivers. On the southeastern slope the influence of air masses from the llanos causes a single rainy season, usually from April to November. On the northwestern slope the influence of Lake Maracaibo causes rainy seasons from April to June and from September to November, and dry seasons from December to March and from July to August. In some areas the lack of water means that agriculture depends on irrigation, while in others the excess rain causes erosion and flooding.

Ecology

The depression is divided between the

Cordillera Oriental montane forests The Cordillera Oriental montane forests (NT0118) is an ecoregion in Venezuela and Colombia along the east slopes of the eastern cordillera of the Andes. The extensive region of submontane and montane forests includes distinctive flora and fauna in ...

ecoregion to the southwest and the Venezuelan Andes montane forests ecoregion to the northeast. It merges into the Catatumbo moist forests ecoregion to the northwest and the Apure–Villavicencio dry forests ecoregion to the southeast. It has been assumed that the Táchira Depression is a barrier to movement of species between the Venezuelan Cordillera de Mérida and the Colombian Cordillera Oriental, since flora and fauna adapted to the cool, moist mountain climate would find the warm, dry conditions in the depression unsuitable. However, during the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...

from around 26,500 to 20,000 years before the present the cooler climate led to upper vegetation belts moving down to lower regions. The cool

mesic Mesic may refer to: * Mesic, North Carolina, a town in the United States * Mesic habitat, a type of habitat See also *Mesić (disambiguation) *Mešić Mešić is a Bosnian surname, a patronymic derived from the masculine given name '' Meša'', it ...

habitats of the Cordillera Oriental and Cordillera de Mérida may have extended across the Táchira depression during this period. A 2015 study that compared the vulnerable Merida brocket (''Mazama bricenii'') of the Venezuelan cordillera to its relative the little red brocket (''Mazama rufina'') of the Colombian cordillera found that ''Mazama bricenii'' should not be considered a separate species. The two populations would have exchanged genes until the start of the present Holocene interglacial period, and may still be doing so. This may apply to other mammal species thought to be endemic to the Venezuelan cordillera. The only Venezuelan endemic species that clearly met the conditions of being restricted to cloud forest and/or páramo, and of being distinctive from relatives in the Colombian cordillera, were

Reig's montane mouse Reig's montane mouse (''Aepeomys reigi'') is a species of rodent in the family Cricetidae. It is found only in Venezuela. It is named after Argentine biologist Osvaldo Reig Osvaldo Alfredo Reig, (14 August 1929 – 13 March 1992), was an Arg ...

(''Aepeomys reigi''),

Merida small-eared shrew The Merida small-eared shrew (''Cryptotis meridensis'') is a species of shrew that is endemic to Venezuela. Description ''C. meridensis'' is one of the largest small-eared shrews, with a head-body length of and a tail long. Males and females a ...

(''Cryptotis meridensis'') and eastern mountain coati (''

Nasuella meridensis The eastern mountain coati or eastern dwarf coati (''Nasuella meridensis'') is a small procyonid found in cloud forest and páramo at elevations of in the Andes of western Venezuela. Until 2009, it was included as a subspecies of the western ...

'').

Economy

The depression is important in giving access from Lake Maracaibo to the southern llanos and to Colombia. The mountains from have good potential for coffee cultivation. There are coffee plantations and fruit trees in some very localized areas of the mountains, and there are areas with agroforestry potential. Typically the soil in the short and narrow valleys is alluvial, caused by flooding, and valuable for farming. The piedmont region also has high agricultural potential. The valleys and piedmont areas are suitable for cultivation of flowers, fruit and livestock for milk. As of 1983 the Uribante-Caparo hydroelectric complex was being built. with several dams on the Uribante, Doradas, Camburito and Capero rivers, designed to produce 1,350 Mw of power. Micro-generating plants were planned on watercourses where dams are not practical. The region, with its dramatic landscape, diverse climate and traditional cultures has considerable tourism potential. Coal mining in the Táchira depression may threaten the Venezuelan Andes montane forests ecoregion in the adjacent Tamá Masif.

Notes

Sources

* * * * * * {{DEFAULTSORT:Tachira depression Valleys of Venezuela Geography of Táchira