Volcanoes of Peru 2: Nevado Sabancaya

Photo: IGP

As I have layed out in the previous Peru article, there are quite a handfull of interesting volcanoes in Peru; it’s hard to choose the next one to introduce here. I take Sabancaya, because it is one of the two currently rumbling (beside Ubinas), and we might get to hear more of it in the near future. However, as it is not a well researched volcano, and no devastating disasters have made the worldwide headlines in the last centuries, there is not a lot to find on the internet – other than travellogs about the nearby tourist attraction Colca Canyon, which indeed would be one of the first and most affected places in case of an eruption.

NEVADO SABANCAYA

Sabancaya stratovolcano is a complex edifice located ~70 km NW of Arequipa, part of the Ampato volcanic group (or Ampato-Sabancaya Complex) and the most active volcano in southern Peru. Located on the saddle between 6288-m-high Ampato and 6025-m-high Hualca Hualca volcanoes, it is the youngest of these volcanic centers and the only one to have erupted in historical time.

Three Volcanoes Photo: Marie Thérèse Hébert

Image NASA. Lava flows around Sabancaya.

Both Nevado Ampato and Nevado Sabancaya consist of a series of lava domes aligned along a NW-SE trend. The name of 5967-m-high Sabancaya, whose Quechua name is “Sahuancqueya” (meaning Spewing Volcano), first appeared in records in 1595 CE, suggesting historic activity prior to that date. Holocene activity has consisted of plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano. Records of historical eruptions date back to 1750, with the largest in 1990 (a VEI 3).

1990-1998 ERUPTION

Photo: IGP

With unrest and phreatic explosions beginning in 1987, Sabancaya had a violent eruption in 1990, continued by vulcanian and phreatic explosions for the following eight years with relatively low lava output. The period of greatest activity was recorded between May 28 and June 5, 1990. Residents living near the volcano reported an explosive eruption from Sabancaya that began on May 28, 1990. Initially, several explosions occurred per day, producing plumes to about 2 km height. Activity intensified on June 4, and by the 8th explosions occurred at intervals of 5-10 minutes and ashfall covered a radius of 20 km. More-or-less constant ash emission continued until 1998. In this period the eruption column reached between 3 and 5 km above the crater, ejecting material a few hundred meters to 1 km height above the crater, with lapilli falling between 3 and 5 km from the crater and ash scattered between 20 and 30 km east of the volcano, covering about 250 km 2 (Thouret et al., 1994). The juvenile material ejected was estimated to be a volume of 25 million m3.

The initial eruption originated from a dacitic magma body, while repeated upwelling of more mafic (from Mg/Fe) magmas led to magma mixing and subsequent eruption of Andesites (tephra analysis showed 60-64 wt% silica content). This repeated recharge of juvenile magma, together with interaction of ground water and magma, was the basis for the sustained activity of very explosive nature. (M-C. Gerbe, J-C. Thouret, 2004)

In this series of vulcanian eruptions (1990-1998), ash falling onto the ice fields of Nevado Hualca Hualca (just north of Sabancaya volcano) melted the ice and produced small lahars that flowed toward the town of Maca near the Rio Colca Valley. This brought to attention the need to evaluate potential hazards from an eruption of Sabancaya in connection with the other volcanoes of the Ampato group, concerning snow and ice fields, drainage channels, and volcanic products. The greatest area of ice and snow is located atop Hualca Hualca, and she has the only drainages that flow to the north into the Rio Colca Valley. Melt water from atop Sabancaya and Ampato would flow south into the Rio Sihuas Valley. (A. Rankin, 2012).

The seismic and volcanic activity observed at and around Sabancaya indicated that its magma chamber is small in volume. The eruptions were fed from NE-SW oriented conduits in the region E of Hualca Hualca (or 10 km from Sabancaya), and the observed superficial deformation was caused by magma movement toward Sabancaya from there. (Antayhua et al., 2001). Sabancaya’s magma chamber may be located 8 km NNE of its summit at a depth of 8-18 km b.s.l. (Pritchard and Simmons, 2004)

An ash-rich vulcanian eruption plume, viewed from the SE, rises above Sabancaya volcano in northern Perú on April 15, 1991. Strong vulcanian explosions were observed at intervals of 20-30 minutes during an April 13-19 visit to the volcano. The explosions lasted about a minute and produced 3-4 km high ash clouds. Explosive activity at Sabancaya began in May 1990 and was continuing in 1995. Photo by Pierre Vetsch, 1991.

LATEST UNREST

On 22./23. Febr. 2013 an orange alert was called for Sabancaya, as an earthquake swarm of abt. 550 quakes was seen by the scientists as the possible beginning of a new eruptive episode. Some of the quakes were strong enough to destroy walls and bridges of the Majes Canal, an important regional water supply that depends mainly on the meltwaters from the glaciers.

The latest unrest started on 13 Aug. 2014 and is still ongoing. In Sept./Oct. 2014 pilots reported ash emissions from Sabancaya which were probably very small, as they could not be confirmed on satellite images. (GVP)

Video: A group of volcanological specialists from IGP visited Crater Sabancaya on 03 and 06 Nov.2014. In this inspection, staff observed the intense emission of magmatic gases at the crater, indicating that magmatic fluids are constantly moving within the volcano.

RISKS in case of an eruption proper

In an IGP report he investigator called to pay special attention to the care of the Majes Canal aqueduct that supplies around 20 thousand hectares of crops and that, if damaged, would deprive water to more than 100,000 residents of El Pedregal-Majes. Macedo Sanchez recalled that in the previous eruptive period of Sabancaya (1990-1998), this important channel was in danger of being damaged by heavy lahars (mudflows) in the sector Pinchollo, so it was necessary to consider it in this scenario. (IGP, 2014-08-12)

Screenshot taken from a recent IGP video

Majes Canal: Through a system of 88 km of tunnels and 13 km of canals, melt- and rain water from the Colca River reaches the plains of Majes. (Photo: INADE)

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More Ellbow Grease to Them!
“Here as in other Andean areas, clashes between local, often ritualized, systems of water distribution and the centralized monetary model adopted by the state led to cases of direct “peasant resistance” by indigenous communities in the highlands. They disputed the state’s control over their water and refused to alter traditional irrigation practices. One case occurred in response to the construction of the Majes Canal, a major internationally financed development project built in the late 1970s, which channels water from the highlands to the desert and coastal areas, and which was constructed on land inhabited by thousands of people. The community of Cabanaconde originally tolerated the disruption caused by the project because they had been promised an off-take of water from the canal and subsequently an increase in irrigated land. When these promises repeatedly failed to materialize despite consistent imploring of the local authorities, the community took matters into their own hands and drilled an unauthorized hole in the canal. They collectively stood their ground and in the end were officially granted an off-take from the canal.”

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To the east and northeast of the Colca River canyon, many inhabited locations would be affected to varying degrees by the emission of lava, ash scattering, ejected incandescent rocks, pyroclastic flows and acid rain, all of them dangerous to crops and people. Much like many Andean volcanoes, the largest threat from Sabancaya would be explosive eruptions that produce pyroclastic flows – but lahars and other debris flows moving up to 30 km down into the surroundings would also be significant hazards. The 1991 eruption of Sabancaya did produce a number of lahars and landslides that resulted in 20 casualties. Over 15,000 people live in villages around the volcano and 250 families living in Maca might need to be evacuated if the unrest continues as they live only ~13 km from the volcano. (E. Klemetti) During an 1988 eruption, cattle died in nearby areas either directly from poisonous volcanic gases or from eating contaminated vegetation. Another unwelcome effect of Sabancaya eruptions would be the melting of glacier caps of the surrounding mountains. The 1990 eruption layed an ash blanket over 250 square km, which has already caused rapid melting of the glaciers. This would lead to droughts and shortage of household and irrigation water in the lower regions of the area.

Agricultural terraces cling to steep slopes high on mountain flanks, and gravity irrigation systems are carved into the steep, harsh, arid mountain terrain, channeling glacial meltwater to fields far below. Photo Morail, Flickr

HYDROTHERMAL ACTIVITY

There are many places in the area where hydrothermal activity plays a role in daily life. The most commonly used are hot spring pools and bath huts, where the waters have high contents of sulfur and iron, and flow from the interior of the hills at a temperature of 80ºC. In addition to this, a little geyser can just as well jump up on the mountain side as you are walking past.  One of the most important geysers of the canyon is known as “Infiernillo”, or “Devil’s Shower,” located at the foot of Mount Hualca Hualca at 4250 m. Here, small “volcanoes” can be seen that eject streams of hot water, with craters of all sizes.  The largest have a diameter of up to 60 cm, and there are smaller geysers where you can cook eggs in less than 10 minutes. All the geysers emit steam and water that boils at 80 º C.

CAMELIDS AND CONDORS IN THE COLCA CANYON

Condor Photo: abehm.de, Wikipedia

No article about Sabancaya and the land it belongs to would be complete without mentioning THE two species of animals that catch the attention of every visitor to the area. The Colca Canyon is one of the sites recognized worldwide as the condor’s habitat, where you can observe the flight of this magnificent bird. The Condor has no larynx and therefore doesn’t make sounds or sing as do other species of birds. Its imposing presence, longevity, and ability to glide for hours were a source of inspiration in primary Andean arts such as cave paintings, ceramics, and sculptures, making this bird an icon within the religious and spiritual beliefs of Andean peoples. –

All four kinds of these loveable camel-sheep (or sheepy camels?) can be found in this National Reserve: Lamas, Alpacas, Vicuñas and Guanacos.

 

AND A MUMMY AGAIN…

Sorry for going on with this, but I find it fascinating… On the summit next to Sabancaya, Ampato, the most famous mummy has been found by archeologists, frozen in time – a twelve-year-old Inca girl which they named Juanita. It was uncovered after the heat of Sabancaya’s eruptions had partially melted the otherwise almost permanent snow and ice cap there.

Juanita the mummy; an Incan sacrificial offering discovered on Ampato volcano in 1995 by archaeologist Johan Reinhard after the eruption of Sabanacaya Volcano. Photo: Museo Santuario de Altura del Sur Andino, Arequipa

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“…The archeologists also found nineteen types of plants -with corn and legumes standing out- and dried llama meat (charqui), which made them think that the girl, was a young ‘Aclla’, a maid that belonged to the Inca that would have been offered in sacrifice to the god Wiracocha to appease the volcano activity in the area. Investigations determined that by the time of her death, Juanita had perfect teeth, strong bones, that she had not suffered from any kind of disease and that she died from a blow in her head. Close to the day of the offering, she was under strict fast and about 6 to 8 hours before the sacrifice was performed, she ate a meal of vegetables. Likewise, she was prepared with plants and coca leafs to numb her. – It is known that those who were chosen by the Inca for sacrifices were prepared from an early age on. This is why Juanita must have been the object of important rituals that started in her homeland and continued through her pilgrimage towards Ampato. Today, her mummified body is in the Museo Santuario de Altura del Sur Andino of the University Católica de Santa María in Arequipa.” (Roxana Guerrero) – [After imposing Catholicism on the native people] …colonial institutions controlling land tenure and resources were put into place. It is easy to imagine how precious any surviving mummies would be after the Extirpación [of the olden beliefs]. This is evident even in modern times, considering the stir that the discovery of La Momia Juanita caused when she was discovered on the heights of Ampato Volcano in 1995.

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No more mummies from now on, I promise! 🙂
Enjoy!  – GRANYIA

MONITORING
– Webcam OVI
– http://volcams.malinpebbles.com/pubweb/Peru.htm
– Observatorio Vulcanológico Arequipa (dept. of IGP)
– Observatorio Vulcanológico INGEMMET
– Seismogram in real-time
– IGP Twitter page

SOURCES & FURTHER READING
– Andean Volcanism: N. Hualca Hualca Volcano, S. Peru, and El Reventador Volcano, Ecuador Burkett, 2008
– Role of magma mixing in the […] 1990–98 explosive activity of Nevado Sabancaya, […] (paywalled)
– IGP Report 2014-08-12
– Global Volcanism Program/Sabancaya
– UNESCO (-Green Cross): Water Security and Peace
– High Mountain Melt-Down: Local Perceptions of Global Warming in the Andes and Himalayas (PDF)
– Mediengerechte Aufbereitung geographischer Forschungsarbeit […] in Peru… (in German)
– UCSM, Museo Santuario de Altura del Sur Andino, Arequipa
– Juanita the Ice Girl
– Investigation of active Volcanoes in Southern Peru