NASA: Chile - Lluta River - 11.07.13
Posted by Ricardo Marcenaro | Posted in NASA: Chile - Lluta River - 11.07.13 | Posted on 9:04
acquired July 19, 2012
download large image (9 MB, JPEG, 5551x11341)
acquired July 19, 2012
Editor’s Note: Today’s caption is the answer to Earth Observatory’s October Puzzler.
A remote plateau in far northern Chile is not a place you want to be
without water. Large sections of the Atacama Desert—often called the driest place on Earth—receive less than a millimeter of rain per year.
The town of Arica—which lies
along the Pacific coast, about 15 miles (24 kilometers) west of the area
shown here—has the lowest average precipitation of any city in the
world. Arica survives on just .03 inches (0.8 millimeters) of rain per year, about 75 times less than what California’s Death Valley receives.
The barren nature of the landscape was on full display on July 19, 2012, when the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite acquired this image. Although a few types of cacti
and other drought-tolerant species can survive in the Atacama, surfaces
appear vegetation-free from ALI’s perspective, leaving a veneer of tan
to dominate the image.
The exceptions, of course, are the explosions of green
in the canyons, which were carved by the Lluta and San José rivers.
Both rivers flow toward the Pacific Ocean and have headwaters to the
east, in the foothills of the Andes. Glaciers on Tacora,
a stratovolcano to the northeast, provide enough water for the Lluta to
flow year round, making it one of the few rivers in the area that does.
Distinct blocks of green color the bottom of the Lluta and Apaza
Valleys, the product of irrigation by residents of the small farming
villages nestled in the canyon bottoms. Despite the seemingly lush
fields, farmers in the Lluta Valley face serious water quality problems.
In addition to being quite saline and acidic, the Lluta River contains
dangerously high levels of boron, arsenic, sulfate, and other
undesirable substances that flow into the river from natural geothermal
springs and upstream mining operations.
Due to the poor water quality, farmers who irrigate with Lluta River
water can only use it for pastureland or for a few tolerant crops, such
as onions and potatoes. The water woes have left the area struggling
economically and reliant on bottled drinking water from the Chilean
government. In contrast, the clean waters of the San José River a few
kilometers to the south, which carved Apaza Valley, support a broad
range of high-quality crops, particularly olives.
The steep slopes, or scarps, that form the Lluta Valley’s walls make
reaching the valley floor from the plateau a challenge. Route 11
provides one of the few access points near the village of Churina. The
complicated network of drainage channels that join the river from the
east lessened the slope on the southern wall, making it easier to build
the road.
Water running off a massive amphitheater-shaped scarp a few kilometers east—the product of a giant landslide known as the Lluta Collapse—created
the distinctive drainage pattern. The landslide, one of the oldest
known slides in the world, occurred at least 2.5 million years ago and
displaced 25 cubic kilometers of material.
References
- Arizona State University World: Longest Recorded Dry Period. Accessed October 31, 2013. World: Longest Recorded Dry Period. Accessed October 31, 2013.
- Goddard Earth Sciences Data and Information Services Center Northern Chile. Accessed October 31, 2013.
- Hoke, G. (2007, October 31) Geomorphic evidence for 1 post–10 Ma uplift of the western flank of the Central Andes 18°30–22°S. Tectonics, 26 (5).
- Kober, F. & Schlunegger, F. (2006, July) Surface uplift and climate change: The geomorphic evolution of the Western Escarpment of the Andes of northern Chile between the Miocene and present. GSA Special Papers, (398) 75-86.
- Northwestern Engineering (2011, September 19) Engineers for a Sustainable World Students Conduct Water Research in Chile. Accessed October 31, 2013.
- Shi, J. et al (2011, September 19) Arsenic and Boron Removal from the Lluta River, Chile. Accessed October 31, 2013.
- Strasser, M. & Schlunegger, F. (2005, July) Erosional processes, topographic length-scales and geomorphic evolution in arid climatic environments: the “Lluta collapse,” in northern Chile. International Journal of Earth Sciences, 94 (30) 43-44.
- Worner, G. (2002, February 15) Evolution of the West Andean Escarpment at 18S (N. Chile) during he last 25 MA: uplift, erosion and collapse through time. Tectonophysics, 345 (1-4) 183-198.
- Window to the Universe Atacama Desert. Accessed October 31, 2013.
NASA Earth Observatory image by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Adam Voiland. Congratulations to Jaimen W. for solving the October Puzzler the fastest. Congratulations also to Javier Canete, Alan W, and Juan Pablo Joui for offering some interesting details about the area.
- Instrument:
- EO-1 - ALI
NASA: Chile - Lluta River - 11.07.13
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