At the end of last year Peruvian volcanologists had made an announcement that installing a permanent monitoring system to this high-risk volcano was finished… wait, high risk?… I never knew that Nevado Coropuna was that dangerous, more reason to get acquainted with this volcano. Please meet my newest friend:
At the start of the 20th c. Mt. Coropuna was thought to be the highest mountain on the double continent. The first to find that this was not the case, was, to his chagrin, Hiram Bingham (the “discoverer” of the Inca city Machu Picchu; more about him in “Besides…” below). With time, and more accurate measurements, Coropuna’s ranking fell to only the 5th highest within Peru. However, with 6377* m a.s.l. Coropuna is the highest, and the most voluminous, of the 16 active volcanoes in the country.
*Most sources give Coropuna’s highest peak with 6425 m, but the IGP has the parameter I cited. So, probably newest measurements brought some changes?)
Coropuna has also one of the northernmost glaciers south of the equator. It is covered by thick layers of permanent ice, which, like all Andean glaciers, are rapidly getting smaller lately. Its area has been shrinking at an average loss rate of 0.4 km² per year since 1980. Going on at this rate, the glacier will have completely disappeared in abt. 100 years. This would be an unprecedented disaster for the population, because it could deprive them of their only source of water in this otherwise semi-arid landscape.
Nevado Coropuna is located approximately 150 km NW of Arequipa. It was considered a sacred mountain by the Inca and was frequently mentioned by chroniclers of the 16th and 17th centuries as an oracle, worshipped since pre-Inca times. The architectural complex Mawk’allaqta, in its southern foothills, still has the foundations of more than 200 stone buildings and tombs, an usnu and three other huge ceremonial platforms, made of stones and earth. It may be considered the most important Inca site discovered in “Kuntisuyu”, the fourth quarter of the Inca Empire. The Inca also built the highest irrigation system in the world on Coropuna at 5600 m a.s.l..
As with many long-time dormant volcanoes, the tourist industry often wrongly describe Coropuna as an extinct volcano. Even websites where people look for advice and guidance, like the or the Andes.org.uk, have it as being extinct. Some travel agencies even forget to mention that it is a volcano.
Correct is that Coropuna is an active stratovolcano, which is presently in a dormant status.
However, Coropuna is not that deep in a coma that volcanologists would ignore it: it is even classed as a high risk volcano. This is mainly due to the possibility of lahars and glacier runs. It doesn’t need a full-blown eruption – just a slight heating up of the interior could cause melting on the underside of the glacier.
A HUMONGOUS VOLCANO
in a very volcanic neighborhood
Nevado Coropuna is a large, mainly andesitic stratovolcano, one of the northernmost volcanoes in Peru. It is part of the northern Central Volcanic Zone (CVZ) and, along with Ampato–Sabancaya–Hualca Hualca, Chachani, and El Misti, forms a part of the main volcanic arc. It lies on a contiguous line of volcanoes that runs from Solimana to Sabancaya.
Its direct neighbors are Nevados Firura and Solimana volcanoes to the NW and N, two old stratovolcanoes with distinct traces of glacial erosion; no data are available about their activity. Only 20 km to the NE lies the Andahua-Orcopampa volcanic field. This contains extremely youthful cinder cones and lava flows that reportedly have destroyed buildings in historic times and may be only a few hundred years old. The area was reported to have been active during the reign of the Incas, and to have “become active again” in 1913.
The Coropuna stratovolcano complex can be recognized from the air as a bent line of E-W orientation, 20 km long and 12 km wide. Ten strato cones, scoria cones and lava domes form the massif, six of them rise over 6,000 m a.s.l.. The flanks of the volcano are carved by ravines and deep valleys, partly filled with alluvial and/or lahar deposits. Two main summits are found in the western part of the massif, aligned N-S. The eastern part has a central edifice with an ice-filled crater, and the eastern cone which has generated the most recent lava flows.
It is thought that the tertiary ignimbrites of rhyo-dacitic composition found in the wider area stem from large caldera-forming eruptions. They are testimony to violently explosive times. The ignimbrites cover the previously folded mountains to form a plateau which was then easily eroded and cut by rivers. Today we have, as a result, a dramatic landscape with steep great gorges such as the Colca Canyon.
The cones of Coropuna are built on top of the ignimbrites, mainly of dark-coloured andesites. In the mid-Pliocene (~5.3-1.8 Ma) the activity became more effusive. Since then, eruptions have been of Vulcanian nature, with large andesitic lava flows. Two consecutive phases have formed the edifices: Coropuna I is now mostly buried beneath Coropuna II. The lavas that made up the older Coropuna appear completely eroded by ice masses or are deeply dissected by glacier valleys today.
Older ash layers gave ages of ~37 ka and ~27 ka. It is thought that these would probably have come from the same fissure that also generated three more recent lava flows. Glaciological studies found that a reactivation of eruptive activity might have started about 11-10 ka, with an apparent migration from the NW to the East of the volcanic complex. Also, the lava chemistry has obviously changed back to more dacitic products.
The three flows of fresh looking trachy-dacitic blocky AA lava lie on the NE, SE and West flanks. These flank vents are thought to postdate activity from the summit craters: their lavas have flown over Holocene glacier moraines. Úbeda et al., 2012, determined their age to be 6000, 2000 and less than 1000 years. The head of the recent Coropuna project at the Volcano Observatory, engineer Jersy Mariño, mentioned that the last eruption was only 700 years ago, which would have been about the same time as the last Misti eruption. This makes it clear that Nevado Coropuna is indeed a potentially active volcanic center.
Reports of Coropuna’s latest eruptions do not exist. No solfataras or gas emitting vents have been found, however, a chain of warm springs along a fault to the S, with temperatures of 21–51°C, can be seen on the geo map (below), and several more on other faults around the volcano. There are numerous faults cutting through the area, best visible south and southwest of Coropuna where ground shifts of 10 m and more have occurred. An earthquake swarm and associated ground deformation were observed near Coropuna and Sabancaya in 2001. Also, the June 2001 southern Peru earthquake (M 8.4) caused seismic swarms at Coropuna.
IS THIS DORMANT VOLCANO INDEED DANGEROUS?
According to a study of the “Evaluation of volcanic risk in Peru”, carried out in 2016, Coropuna is one of the four very high risk volcanoes in the country. (For the “Relative Volcanic Risk” all possible dangers a certain volcano *could* pose are assessed and evaluated in a score system, to arrive at comparable values.)
In 2018, the IGP installed a permanent surveillance network on this volcano. Five seismic stations now identify seismicity in its interior, and a surveillance camera watches possible changes on the outside. Rumblings can be caused inside by volcanic earthquakes or outside by the dynamics of the glacier (ice quakes). While at this time nobody expects Coropuna to blow suddenly, several volcano-tectonic EQs have been recorded that indicate rock fracturing inside. So it sure is a good idea to keep an eye on it for all possible risk scenarios.
In case of an eruption, it can affect many thousands of residents and thousands of hectares of crops. Especially, there is the hazard of lahars from the melting ice cap. The danger becomes worse if one considers the extreme relief near the volcano: a hight difference of 4,000 m within a horizontal distance of only 15 kilometres. Any powerful lahar that enters the Colca/Majes/Camaná valleys may shoot all the way down to the coast (115km), thereby endangering many small villages & towns, incl. Camaná at the mouth of the river with 20 k residents. But there are also villages higher up in the foothills of Coropuna. For understandable reasons they are always in the pathways of water streams – which equal pathways of pyroclastic flows, ice & debris avalanches or lahars. Geological evidence of frequent lahars has been found in the Majes river valley. Also, some explosions have tossed lava bombs up to 7 km away.
In their report for the second half of December 2018, the volcano observatory say that on average per day 13 VT earthquakes of low magnitude were recorded in Coropuna (but no LP quakes) – similar as in the previous period. The highest number in a day was 33. Only slight seismicity related to the glacier was measured, also the coverage of snow/ice has not changed much.
Looking back through earlier reports there were in total since July 2018 only a handful of very small Long Period quakes, related to fluid movements inside (can be hydrothermal or magmatic). The highest numbers of Volcano-Tectonic quakes usually reached 20 to less than 40 in a single day.
Other, less known volcanoes in the area
There are still more volcanoes in southern Peru that represent a possible high risk. Tutupaca, Yucamane and Chachani for example. Tutupaca and Yucamane are located in the Tacna region, near the city of Candarave. Chachani is located 22 km from the Plaza de Armas of Arequipa, bordering the town area of Cerro Colorado. The latter has a population close to 200 k, and it has the highest population growth in the country. These three volcanoes also have, since 2018, their own geophysical monitoring networks. Because they had never been monitored in real time before, their internal earthquakes have been analyzed in detail to determine a baseline of *normal* behavior for each. From there it will be possible to recognise any *abnormal* behaviour in case of some unrest.
HOW HIRAM BINGHAM CLIMBED THE “TOP OF THE AMERICAS”
Hiram Bingham was the leader of several archaeological expeditions to Peru, and he was a man of his time. Anne Smith Peck was an avid mountaineer and adventuress. Having climbed Mt. Huascaran, also in Peru, she boasted that she had reached an altitude “greater than any man or woman before her”. Both were Americans.
He must have read her account with great distaste and his male pride was undoubtedly offended – thus writes his son Alfred Bingham in an article about his father, “Raiders Of The Lost City”. This article is highly interesting and quite amusing. Among others, it also comments on the story of Hiram Bingham climbing to the “top of the Americas”:
Once, Bingham saw mentioned that “a mountain in southern Peru named Coropuna, with an estimated elevation of more than twenty-three thousand feet, was now presumed to be the ‘culminating point of the continent’!“. This gave him the idea that he somehow could top that feisty woman Annie Peck’s claims… He would climb the highest point in the Americas himself, that would show her!
He managed to squeeze in, among his many travels to the hidden places of ancient Peru, his quest to be the first on top of Coropuna. The problem was, Coropuna had six very high peaks, each looking highest from a different angle, depending on your standpoint… Annie, of course, had quickly beaten him to it a few weeks earlier, but turned out to have climbed a lower peak. In Oct. 1911 Bingham’s party went up another chosen Coropuna summit, but were very much in doubt whether or not they were on the “right” one: did not the next snowy dome look still higher from here?
“My father was worried by that neighboring peak, but after sighting along a pocket level, he persuaded himself that the bothersome dome was really 250 feet below him. Convinced that he had climbed the highest peak, he put up an American flag. He felt he had achieved a major climb, perhaps the greatest feat of his expedition. The American Alpine Club, to his satisfaction, denied Miss Peck’s claim and gave him credit for a first ascent.”
Well…, much later, after his death, an official survey by the Peruvian government found that that next snowy dome – which neither he, Bingham, nor Miss Peck had climbed – was the true summit of Coropuna. It was not 250 ft. lower but 50 ft. higher than the one he was on. The true summit was finally mastered in 1952 by an Italian, Piero Ghiglione.
Video by Jaime Baldeon, 2014, on YT (6 min)
Disclaimer: I am not a scientist, all information in this (and any of my other posts) is gleaned from the www and/or from books I have read, so hopefully from people who do get things right! 🙂 If you find something not quite right, or if you can add some more interesting stuff, please leave a comment.
Enjoy! – GRANYIA
SOURCES & FURTHER READING
– GVP, Coropuna
– […] y la evolución volcánica y glaciar del Nevado Coropuna (2013)
– OVS/IGP report No.11-2018
– Ingemmet: Bol. No. 25: Mapa Preliminar […]
– Archaeological and Glacial Geologic Investigations of the Nevado Coropuna
– Improved estimates of glacier change rates […] (2018)
– SummitPost.org, Coropuna
– Very detailed Map (IGM Inst. Geogr. Mil.) on GVP
– Raiders Of The Lost City (on Hiram Bingham, by his son)
– About Annie Smith Peck
– Climbing Coropuna (Hiram Bingham, from INCA LAND)