Geography. 250px, Image:Cerro_de_los_siete_colores.jpg.html" ;"title="Cerro de los Siete Colores">Image:Cerro de los siete colores.jpg">250px, , Jujuy Province. The Argentine Northwest comprises very distinct biomes">Cerro de los Siete Colores, Jujuy Province. The Argentine Northwest comprises very distinct biomes, or geographical and climatic regions. From west to east they are: * The Altiplano or Central Andean dry puna, "Puna" * High Mountains of the Andes * Valles Calchaquíes, Fertile valleys * Red-rock canyons and mountain passes * Humid Sub-Andean Sierras * Tropical jungles or Southern Andean Yungas, Yungas * And the ecotone—or transitional zone—between the Yungas and the Gran Chaco, Chaco region. Besides the Southern Andean Yungas, Yungas jungle on the eastern fringe of the region, the only fertile lands are those near the river basins, which have been irrigated extensively. Across millennia the erosive forces of these rivers has gradually created a multitude of red-rock canyons, such as the Quebrada de Humahuaca and the Valles Calchaquíes. West of these valleys the peaks of the Andes reach heights of over and the Altiplano, an extensive 3,500-meter high plateau, dominates the landscape and continues far north into Bolivia and Southern Peru.
Archaeological findsIn February 2021, archaeologists from the University of Buenos Aires–National Scientific and Technical Research Council announced the discovery of 12 graves dated to 6,000-1,300 years ago. Researchers also revealed necklaces and pendants next to some of the bodies. According to archaeologist Leticia Cortés, there were many kinds of burial methods, in individual or collective graves, and also in the posture of the bodies. Some were hyperflexed, like squatting, with the shoulders touching the knees.
ClimateNorthwest Argentina is predominantly dry and hot and classified as subtropical. Owing to its rugged topography, the region is climatically diverse, depending on the altitude, temperature and distribution of precipitation. Consequentially, the vegetation will differ at these different climate types. In general, the climate can be divided into 2 main types: a cold arid climate, arid or semi-arid climate at the higher altitudes and warmer subtropical climate in the eastern parts of the region. Under the Köppen climate classification, the region has 5 different climate types which are semi–arid (''BS''), arid (''BW''), Köppen climate classification#GROUP C: Temperate/mesothermal climates, temperate climate without a dry season and with a dry season (''Cf'' and ''CW'' respectively) and an alpine climate at the highest altitudes. The atmospheric circulation is controlled by the two semi–permanent South Atlantic and South Pacific highs, and a seasonal low pressure system east of the Andes (called the Chaco Low). During summer, the interaction between the South Atlantic high and the Chaco low causes the low pressure system to bring northeasterly and easterly winds that carry moisture to the region, particularly in the northern parts. The movement of moist air into the region during the summer results in very high precipitation. Most of the moisture comes from the east since the Andes block any moisture from the Pacific Ocean. Cold fronts that travel northwards to the region can produce precipitation during the summer months and is more prominent in the southern parts of the region. For example, in Tucuman Province, these cold fronts are responsible for 70% of the rainfall in that province. In contrast, during the winter months, the Chaco low attracts air masses from the South Pacific high, creating a dry and cold wind. This effect is more prominent in the winter months, when the intensity of the cold is more stronger. The Intertropical convergence zone reaches the region during the summer months, leading to low pressure, and unstable air masses due to the relatively high land temperatures compared to the sea during this season. This leads to enhanced precipitation in the form of convective thunderstorms during the summer months. During the winter months, the intertropical convergence zone moves northwards to Ecuador while both the South Pacific and South Atlantic high move northwards, and the Chaco low weakens, all of which result in the suppression of rain during the winter. With the predominant wind being from the west and the Andes blocking most rain bearing clouds from the Pacific Ocean along with atmospheric circulation patterns unfavourable for rain, this results in a dry season during winter. At the highest altitudes, westerly winds from the Pacific Ocean can penetrate during the winter months, leading to snowstorms.
PrecipitationPrecipitation in the region is highly seasonal and is mostly concentrated in the summer months, during which precipitation decreases from east to west. Precipitation is distributed irregularly owing to relief. As moist air reaches the eastern slopes of the mountains, this moist air raises up vertically, cooling Lapse rate, adiabatically, leading to the formation of clouds which generate copious amounts of rain. The eastern slopes of the mountains can receive between of precipitation a year although some places can receive of precipitation per year owing to orographic precipitation. In the south, the orographic effect is enhanced by advancing cold fronts from the south, resulting in enhanced precipitation. The high rainfall on these first slopes creates a thick jungle that extends in a narrow strip along these ranges. Beyond the first slopes of the Andes into the valleys, the air descends vertically, warming adiabatically, creating air that is drier and warmer than on the eastern slopes. Since the mountain ranges are oriented in a north–south direction, increase in altitude to the west, and have a discontinuous orography, this allows valleys to have regions of relatively high precipitation in the west and drier regions in eastern parts of the valleys through orographic precipitation. In the temperate valleys, which include major cities such as Salta and Jujuy, average precipitation ranges from . For example, in the Lerma Valley which is surrounded by tall mountains (only the northeastern part of the valley is surrounded by shorter mountains), precipitation ranges from in Salta to in San Lorenzo, just away. Rainfall in the Lerma valley in Salta and in wetter valleys in Jujuy province, including its San Salvador de Jujuy, provincial capital, is mainly concentrated in the summer months and falls in short but heavy bursts. Valleys in the southern parts of the region are drier than northern valleys due to the mountains on the eastern slopes of both the Andes and the Sierras Pampeanas being taller than the ones in the north (ranging from ), presenting a significant orographic barrier that blocks moist winds from the Atlantic and Pacific oceans. These valleys often receive less than of precipitation per year and are characterized by sparse vegetation adapted to the arid climate. For example, in La Rioja Province, Argentina, La Rioja province, mean annual precipitation ranges from in the easternmost parts to at the foot of the Andes. Similarly in Catamarca province, the mean annual precipitation varies from in the middle of valleys between the Andes mountains to more than in the nearby mountain ranges which form the valleys. In Jujuy province, precipitation in the dry Quebrada de Humahuaca valley ranges from . A similar annual precipitation is found in the dry Calchaquí Valleys, with mean annual precipitation ranging from in Molinos, Salta, Molinos to in Cafayate. Further west in the Puna region next to Bolivia, the average altitude is and the terrain is mostly desert due to the higher altitudes of the mountains on the east from both the Andes and the northwest extension of the Sierras Pampeanas, blocking most of the easterly winds from coming in. Precipitation in the Puna region averages less than a year while potential evapotranspiration ranges from a year, owing to the high insolation, strong winds, and low humidity that exacerbates the dry conditions. Owing to the low precipitation in conjunction with the extreme climatic conditions, the Puna region has a water deficit in all months of the year. Although easterly winds are rare in the Puna region, they bring 88–96% of the precipitation to the area. Snowfall is rare, averaging less than 5 days of snow per year since most of the precipitation falls in the summer in the form of rain. The southeast part of the Puna region is very arid and receives the lowest annual precipitation in the region, averaging . In the northeast part of the Puna region in Jujuy province, mean annual precipitation ranges from . Due to the aridity of these mountains at high altitudes, the snowline can extend as far up as 6,000 m above sea level. The El Niño Southern Oscillation influences precipitation levels in northwest Argentina. During an El Niño year, the westerly flow is strengthened while moisture content from the east is reduced, resulting in a drier rainy season. In contrast, during a La Niña year, there is enhanced easterly moisture transport, resulting in a more intense rainy season. Nonetheless, this trend is highly variable both spatially and temporally.
TemperaturesTemperatures in northwest Argentina vary by altitude. In the temperate valleys which includes the cities of Salta and Jujuy, they have a temperate climate, with mild temperatures in the summer (a mean of in Salta, in Jujuy in January) and extremely dry and cool winters with regular frosts (a mean of in Salta and in Jujuy in July). The Diurnal temperature variation, diurnal range in these cities is fairly large, particularly in the winter. In the Quebrada de Humahuaca valley in Jujuy province, north of Jujuy city, the diurnal range is large with a thermal amplitude between . A major reason for the large thermal amplitude is that during the day, there is intense radiation from the sun, causing the land to heat up while during the night, there is less radiation, causing the land to cool and temperatures to fall down. Mean temperatures in the warmest month in the Quebrada de Humahuaca valley range from in Humahuaca at the higher altitudes to in Volcán (Jujuy), Volcan at the lower altitudes; in the coldest month, the mean temperature ranges from . The mean annual temperatures in the Quebrada de Humahuaca valley ranges from , depending on altitude. In the Calchaquí Valleys in Salta province, the climate is similar to the valleys in La Rioja province and Catamarca province, by being temperate and arid with large thermal amplitudes, long summers, and a long frost free period which varies depending on altitude. Mean temperatures in the warmest month in the Calchaqui valleys range from at the higher altitudes to at lower altitudes; in the coldest month, the mean temperature ranges from . The mean annual temperatures in the Calchaqui valleys ranges from in La Poma at the higher altitudes to in San Carlos, Salta, San Carlos which lies at a lower altitude. In both the Quebrada de Humahuaca and Calchaqui valleys, winters are cold with frosts that can occur between March and September. In the valleys in the south in La Rioja province and Catamarca province along with the southwest parts of Santiago del Estero Province which is part of the arid Chaco ecoregion, the climate is mild year long in terms of temperature. Temperatures during the summer are very high, with a mean temperature of in January, the warmest month. Temperatures can exceed on an average of 20–25 days and can occasionally exceed , particularly in the central valley of Catamarca (Valle Central de Catamarca) and the valley of La Rioja Capital which lie at lower altitudes than other valleys such as Tinogasta. Winters in the valleys of La Rioja province and Catamarca province along with southwest Santiago del Estero province are mild, with a mean temperature of . Cold fronts from the south, bringing cold Antarctic air can cause severe frosts in the valleys of La Rioja province and Catamarca province. Temperatures can fall between during these cold fronts. In contrast, the Zonda wind, which occurs more during the winter months can affect these valleys in La Rioja province and Catamarca province can raise temperatures up to with strong gusts, causing possible crop damage. Further west, in the Puna region next to Bolivia, temperatures are much colder, with a mean annual temperature of less than owing to its high altitude. The Puna region is characterized by being cold but sunny throughout the year. The diurnal range is large with a thermal amplitude that can exceed due to the low humidity and the intense sunlight throughout the year. and the mean annual maximum and minimum temperatures are and respectively with frosts that can occur in any month as night temperatures can regularly fall below freezing. Absolute maximum temperatures in the Puna region can reach up to while absolute minimum temperatures can fall below . In Tucuman province, the eastern parts have an average annual temperature of . Summers are hot with mean temperatures averaging between while in winter, the mean temperatures are between . Easternmost parts of the province, which borders the Chaco region are home to the highest and lowest temperatures in the province where absolute maximum temperatures can exceed while absolute minimum temperatures can reach close to owing to the accumulation of cold air that descends from the mountains. At higher altitudes, the climate is cooler with summer temperatures averaging and winter temperatures averaging . The annual temperature in the higher altitudes is between at an altitude of above sea level. Within the valleys located between the mountains, temperatures are cooler with a mean annual temperature of (summers average while winters average ) in the Tafi valley.
EconomyThe majority of the population—and thus economic activity—of this region is concentrated in the many fertile valleys. In these valleys, the cultivation of sugarcane, tobacco, and citrus is the most important activity, along with cattle and goat raising. Important vineyards are also found in the Valles Calchaquíes in the Cafayate region. Thus most economic activity is associated with agriculture, with the exception of the "Altos Hornos Zapla" steel Blast furnace, furnace. Mining includes lithium, lead, silver, zinc and salt, and hydrocarbons extraction.
TourismThe Argentine Northwest is a popular destination for both domestic and international travelers, attracting neighboring Argentine, Argentinos and vacationing Europeans alike. Some of the most popular destination are Quebrada de Humahuaca and the Cerro de los Siete Colores, Cafayate and the Valles Calchaquíes, Tafí del Valle, and the capital cities of the provinces: San Miguel de Tucumán, San Fernando del Valle de Catamarca, Salta and San Salvador de Jujuy. The National parks of Argentina, national parks of the region are: Baritú National Park, Calilegua National Park, El Rey National Park, Los Cardones National Park and Campo de los Alisos National Park.
Cultural tourismBesides the geography of the area, the culture is also of great interest. It is strongly influenced by Quechua people, Quechua and Aymara people, Aymara cultures, and the region is quite distinct from the more European Buenos Aires. This influence can be seen in the music of Argentina, music, clothing and customs of the people.
See also*1948 Salta earthquake