Salar de Punta Negra facts for kids
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The Salar de Punta Negra is a huge, flat area covered in salt in the Antofagasta Region of Chile. It's about 230 square kilometers, which is like 23,000 football fields! This salt flat is surrounded by dry riverbeds that come down from the Western Mountains. These dry riverbeds, like those from the Llullaillaco volcano, only have water sometimes. But there are also natural springs that provide water more regularly at Salar de Punta Negra.
Long ago, when the Holocene era began, this area was much wetter. Even though some thought it used to be a big lake, scientists now believe it wasn't. Early humans came here to use the wet areas. They left behind tools like projectile points and other signs of their lives. Today, people dig for copper in this region.
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Where is Salar de Punta Negra?
The Salar de Punta Negra is in the eastern part of the Antofagasta Region in Chile. This region is very important for Chile because it has a lot of copper and nitrate. Before 1981, it was hard to get to this area. That's when a big mine opened up. The name "Punta Negra" means "Black Point." It comes from a black lava flow on the eastern side of the salt flat. This lava came from a volcano a very long time ago.
The salt flat itself is about 230 square kilometers. It's a flat, salty area with a surface that looks like a puzzle of shapes. In some places, the ground is raised, and there are small canals and ponds filled with salty water. The salt is mostly made of gypsum, halite (which is like table salt), and ulexite. These salts form wavy edges and small ridges. The salt flat is a bit uneven, lower in the northwest. This is probably because of cracks in the Earth's crust called faults.
The Salar de Punta Negra is at the center of many dry riverbeds. It's surrounded by a gentle slope called a bajada. This slope often gets steep where it meets the salt flat. It's also crossed by channels that start high up in the mountains. Four of these dry riverbeds in the Western Mountains carry water only during certain seasons. They are called Quebrada Zorros, Quebrada Zorritos, Quebrada Tocomar, and Quebrada Llullaillaco. Sometimes, heavy rains cause flash floods in these riverbeds. These floods can send mud down to the salt flat. Other valleys include Quebrada El Salto and Quebrada El Salado. The Río Frio river flows into the Salar from the south. Most of the water from these areas sinks underground before it reaches the salt flat. But some springs, like Barrancas Blancas, and water seeps on the eastern edge of the Salar, also bring water.
This whole area is part of a large basin, about 77 kilometers long and 30 kilometers wide. It sits between the Western Mountains (with their volcanoes) and the Cordillera Domeyko. This basin formed over millions of years due to Earth's movements. Then, it filled up with rocks and dirt. The Llullaillaco volcano in the Western Mountains is very tall, reaching 6,725 meters. This makes it one of the highest volcanoes in the world! The basin itself is about 3,000 meters high on average. The entire basin covers about 4,263 square kilometers. To the east of Salar de Punta Negra are flat areas called Pampa El Salado, Pampa San Eulogio, and Pampa del Chino. To the north is a smaller salt flat called Salar de Imilac.
Was there a big lake here?
People once thought that Salar de Punta Negra used to have a huge lake. They believed it was about 55 kilometers long, 20 kilometers wide, and at least 125 meters deep. They found what they thought were signs of this old lake, like lake mud, river deltas, old shorelines, and lake terraces. During the last Ice Age and early Holocene, a river called Quebrada de las Zorras was thought to carry water from the mountains around Llullaillaco to Salar de Punta Negra. It was even believed that this lake overflowed into the smaller Salar de Imilac to the north, and then into the Salar de Atacama.
However, newer research suggests there is no strong proof of such a large lake. Scientists haven't found clear lake mud or old shorelines. What were thought to be shorelines might actually be natural ridges formed by the ground sinking or by faults. Also, the fine mud usually found in lakes is only on the eastern side of Salar de Punta Negra, where the springs are active. The idea that there was no big lake here fits with the fact that old lakes with clear shorelines in this region are usually only found at very high places, over 3,500 meters. Farther south, other salt flats like Salar de Aguas Calientes and Salar de Pajonales do show clear signs of having had lakes in the past.
Climate and animals
The area around Salar de Punta Negra has a cold desert climate. The average temperatures range from 8 to 18 degrees Celsius. It gets very little rain, only about 14 to 30 millimeters per year. Most of the rain falls during the summer months, which causes the dry riverbeds to flow sometimes. The temperature can change a lot between day and night, sometimes by 30 degrees Celsius! It's also a very windy place, with winds reaching up to 90 kilometers per hour.
Today, there's almost no plants close to Salar de Punta Negra. The only exceptions are small wetlands along its edges. These wetlands are home to some special moths, including three new kinds that scientists discovered! Animals like flamingos also visit the Salar de Punta Negra. Shrubs grow below 4,100 meters, and grasses grow at higher places. Many different kinds of mammals and birds live in this region.
In the past, there were more wetlands at Salar de Punta Negra. These wetlands had grasses, shrubs, and sedges. Scientists have even found old snail shells in the remains of these wetlands. These wetlands formed during two wet periods, about 15,900 to 13,800 years ago and again from 12,700 to 9,700 years ago. These wet periods are known as the Central Andean Pluvial Events (CAPE). The wetlands disappeared around 9,700 to 8,100 years ago.
Human history
People once thought the Atacama Desert was too harsh for humans to live in. But many signs of past human activity have been found there! Between 12,800 and 9,700 years ago, a time called the "Central Andean Pluvial Event" caused large lakes to form in the Altiplano and wetlands in the lower areas. These wetlands were like oases of life. They also helped early humans spread across the land. Later, the climate became drier again, and many of these lakes and wetlands disappeared.
During the late Ice Age and early Holocene, humans had moved into almost all parts of South America. In the Atacama region, they used the wetlands that existed back then. There are about 36 archeological sites at Salar de Punta Negra. Human tools and other items have been found at places like the "SPN-1" site, which was a former wetland at the northern end of Salar de Punta Negra. Human activity was very connected to the presence of these wetlands. When the wetlands shrank early in the Holocene, human activity also decreased.
Even after the climate became drier, humans continued to be active at Salar de Punta Negra. One site near a waterhole is about 4,970 to 4,830 years old. However, most of the older sites were left empty.
At the ancient sites of Salar de Punta Negra, scientists have found furnaces with camelid (like llama or alpaca) bones, different kinds of tools, and projectile points (like arrowheads). The things found at Salar de Punta Negra are similar to those found at other ancient sites in Peru, Ecuador, Chile, and Argentina. This suggests that people from the Archaic or pre-Paleo-Indian times lived here. The objects belong to the Fell, Tuina, and Punta Negra archaeological traditions. At Punta Negra, hunter-gatherer groups used the local plants and camelid animals. The tools found there were used for hunting and preparing animals.
Other ancient sites in the area include stone walls called pircas, rock art, and Inca roads. A major Inca highway was built in 1485 to help the Inca empire take over this land. Stone piles called cairns mark the road at Tocomar and Vaquillas. For the Inca, this region was a source of minerals like copper, gold, and turquoise.
Copper mining continues today. However, this mining uses a lot of underground water, which has caused the remaining wetlands to dry up. Because of this, rules were put in place in 2005 to limit how much underground water could be taken. In 2020, the Chilean government even filed a complaint. The problems caused by water use at Salar de Punta Negra have made local communities fight against similar water projects in the Salar de Atacama.
See also
In Spanish: Salar Punta Negra para niños
