Huaynaputina

Huaynaputina lies at an elevation of about 4,850 metres (15,910 ft).[1] It consists of an outer composite volcano[2] (or stratovolcano)[13] and three younger volcanic vents nested within a 2.5-kilometre (1.6 mi) wide[2] and 400-metre (1,300 ft) deep[7] amphitheatre.[2] This horseshoe-shaped[16] structure is set in the older volcano[2] at an elevation of 4,400 m (14,400 ft)[17] and opens eastwards.[18] The amphitheatre lies at the margin of[12] a rectangular[19] high plateau[12] that is covered by about 2-metre-thick (6.6 ft)[20] ash over an area of 50 square kilometres (19 sq mi).[19] In general, the volcano has modest dimensions and rises less than 600 m (0.37 mi) above the surrounding terrain,[21] but the products of the volcano's 1600 eruption cover much of the region to this day[22] especially west, north and south from the amphitheatre;[23] these include pyroclastic flow dunes that crop out from underneath the tephra.[24] Deposits from the 1600 eruption and previous events also crop out within the amphitheatre walls.[25] Another southeastward-opening landslide scar lies just north of Huaynaputina.[26]

One of these funnel-shaped vents[27] is a 70-metre (230 ft) trough that cuts into the amphitheatre, which appears to be a remnant of a fissure vent. The second appears to have been about 400-metre (1,300 ft) wide before the development of the third vent, which has mostly obscured the first two. The third vent is steep-walled, with a depth of 80 m (260 ft), and contains a 200-metre (660 ft) wide pit within a small mound that is in part nested within the second vent. This third vent is surrounded by concentric faults,[28] and at least one of the vents has been described as an ash cone.[29] In addition, a fourth vent lies on the southern slope of the composite volcano outside of the amphitheatre[2] and has been described as a maar.[17] It is about 70-metre (230 ft) wide and 30-metre (98 ft) deep and appears to have formed during a phreatomagmatic eruption.[28] These vents lie at an elevation of about 4,200 m (13,800 ft), making them among the highest vents of a Plinian eruption in the world.[2]

Slumps have buried parts of the amphitheatre.[30] Dacitic dykes crop out within the amphitheatre[31] and are aligned along a northwest–south trending lineament that the younger vents are also located on.[32] These dykes and a dacitic lava dome of similar composition were formed before the 1600 eruption.[28] A number of faults with recognizable scarps occur within the amphitheatre and have offset the younger vents;[33] some of these faults existed before the 1600 eruption while others were activated during the event.[34]

The terrain west of the volcano is formed by the high plateau[2] at an elevation of about 4,600 m (15,100 ft),[21] which north of Huaynaputina features the volcano Ubinas and the depression of Laguna Salinas[7] while the peaks Cerro El Volcán and Cerro Chen are situated south of it.[2] Cerro El Volcán (a lava dome)[35] and Cerro Las Chilcas (another small lava dome[36]) lie 3 km (1.9 mi) south from Huaynaputina.[19] Northeast-east of Huaynaputina,[26] the terrain drops off steeply (2.3 km or 1.4 mi vertically and 6 m or 20 ft horizontally[21]) into the Río Tambo valley, which runs southward and then westward as it rounds Huaynaputina. Some tributary valleys join the Río Tambo from Huaynaputina; clockwise from the east these are the Quebradas Huaynaputina, Quebrada Tortoral, Quebrada Aguas Blancas and Quebrada del Volcán.[2] The Río Tambo eventually flows southwestward into the Pacific Ocean.[10]

The vents of Huaynaputina form a north–northwest-south–southeast trend, which also encompasses the neighbouring volcanoes Ubinas and Ticsani,[2] the former of which is a typical stratovolcano while Ticsani resembles Huaynaputina in structure.[18] The trend also constitutes a volcanic field located behind the major volcanic arc and associated with faults at the margin of the Río Tambo graben[41] as well as regional strike-slip faults.[42] In addition, the volcanic rocks produced by these volcanoes have similar compositions,[8] and recent seismic and volcanic activity at Ubinas and Ticsani indicate that they share a magma reservoir.[43] The faults associated with the volcanic complex have influenced the evolution of the constituent volcanoes including Huaynaputina[42] by acting as conduits for ascending magma especially at fault intersections.[44] A 40-by-60-kilometre (25 mi × 37 mi) magma reservoir may underpin this volcanic system.[45]

The eruption products of the 1600 eruption are dacites, which define a calc-alkaline,[46] potassium-rich suite;[47] the geochemistry of the 1600 rocks has also been described as adakitic.[48] The 1600 rocks also contain rhyolite inclusions[47] and a rhyolite matrix.[49] Phenocrysts include biotite, chalcopyrite, hornblende, ilmenite, magnetite and plagioclase;[49] amphibole, apatite and pyroxene have been reported as well.[50] Aside from new volcanic rocks, Huaynaputina in 1600 also erupted material that is derived from rocks underlying the volcano, including sediments[51] and older volcanic rocks, both of which were hydrothermally altered.[16] Andesite has also been found at Huaynaputina.[52] The Huaynaputina pumices have a white colour.[16]

A large amount of sulfur appears to have been carried in a volatile phase associated with the magma rather than in the magma proper.[49] An even larger amount of sulfur may have originated from a relic hydrothermal system that underpins the volcano, and whose accumulated sulfur would have been mobilized by the 1600 eruption;[53] some contradictions between the sulfur yield inferred from ice core data and these inferred from the magma composition can be resolved this way.[54] The amount of volatiles in the magma appears to have decreased during the course of the 1600 eruption, indicating that the magmas originated either in two separate magma chambers or from one zoned magma chamber. This compositional change may explain changes in the eruption phenomena during the course of the 1600 activity[55] as the "Dacite 1" rocks erupted early during the 1600 event were more buoyant and contained more gas and thus drove a Plinian eruption, while the latter "Dacite 2" rocks were more viscous and only generated Vulcanian eruptions.[56] Crustal interactions and crystal fractionation processes were involved in the genesis of the magmas as well,[57] with the so-called "Dacite 1" geochemical suite forming deep in the crust, while the "Dacite 2" geochemical suite appears to have interacted with the upper crust.[58]

The rocks had a temperature of about 780–815 °C (1,436–1,499 °F) when they were erupted,[59] with the "Dacite 1" being hotter than the "Dacite 2".[60] Their formation may be stimulated by the entry of mafic magmas into the magmatic system;[55] such an entry of new magma in a volcanic system is often the trigger for explosive eruptions.[58] The magmas erupted early during the 1600 event (in the first stage of the eruption) appear to have originated from depths of more than 20 km (12 mi);[53] petrological analysis indicates that some magmas came from depths greater than 15–25 km (9–16 mi) and others from shallower depths of about 4–6 km (2.5–3.7 mi).[39] While an older hypothesis by de Silva and Francis held that the entry of water into the magmatic system may have triggered the eruption,[61] a more recent viewpoint argues that the entry of new dacitic magma into a pre-existent dacitic magma system triggered the 1600 eruption; furthermore movement of deep andesitic magmas that had generated the new dacite produced movements within the volcano.[62]

Tephra and block-and-ash flows deposits from Holocene eruptions can be found within the amphitheatre,[68] and some 7,000–1,000 year-old tephra layers close to Ubinas volcano have been attributed to activity at Huaynaputina.[70] A debris avalanche deposit that crops out on the eastern side of the Río Tambo, opposite to the amphitheatre,[23] may have been emplaced not long before the 1600 eruption.[68] Three eruptions of the volcano have been dated to 9,700 ± 190, less than 7,480 ± 40 years ago[71] and 5,750 years before present, respectively.[72][1] The first two eruptions produced pumice falls and pyroclastic flows,[71] the first event also depositing tephra in Laguna Salinas north of Huaynaputina and producing a block-and-ash flow to its south.[68]

The existence of a volcano at Huaynaputina was not recognized before the 1600 eruption,[2] with no known eruptions of Huaynaputina[73] other than fumarolic activity.[72] As a result, the 1600 eruption has been referred to as an instance of monogenetic volcanism.[67][31] The pre-1600 topography of the volcano was described as "a low ridge in the center of a Sierra,"[2] and it is possible that a cluster of lava domes existed at the summit prior to the 1600 eruption[74] and was blown away during the event.[75]

However, the last eruption may have preceded 1600 by several centuries, seeing as native people reportedly offered sacrifices to the mountain[76] such as birds, personal clothing and sheep,[77] although it is known that non-volcanic mountains were also offered sacrifices in southern Peru.[78] There have been no eruptions since 1600;[79] a report of an eruption in 1667 is unsubstantiated[18] and unclear owing to the sparse historical information and probably reflects an eruption at Ubinas instead.[80][81]

In 1962, there were reportedly no fumaroles within the amphitheatre,[82] though fumaroles occur in the amphitheatre close to the three vents.[31] There is a fumarole on the third vent, and fumaroles occur in association with dykes that crop out in the amphitheatre.[28] These fumaroles produce white emanations and smell of rotten eggs. Vegetation has grown at their vents.[83] Investigations in 2010 gave temperatures of 51.8–78.7 °C (125.2–173.7 °F) for the gases,[84] with seasonal variations.[85] The fumarolic gas composition is dominated by water vapour, with smaller quantities of carbon dioxide and sulfur gases.[86]

Hot springs occur in the region and some of these have been associated with Huaynaputina;[87] these include Candagua[88] and Palcamayo northeast,[89] Agua Blanca and Cerro Reventado southeast from the volcano on the Río Tambo and Ullucan almost due west.[90] The springs have temperatures ranging from 22.8–75.4 °C (73.0–167.7 °F) and contain large amounts of dissolved salts.[91] Cerro Reventado and Ullucan appear to be fed from magmatic water and a deep reservoir,[85] while Agua Blanca is influenced by surface waters.[92]

It is possible that the entry of new magma – known as "Dacite 1" – into a magmatic system containing a magma entity known as "Dacite 2" triggered the eruption by pressurizing the system until magma started ascending to the surface.[56] In the prelude to the eruption, magma moving upwards to the future vents caused earthquakes[98] beginning at a shallow reservoir at a depth of 6 km (3.7 mi) depth;[99] reportedly people in Arequipa fled their houses out of fear that they would collapse.[15] The rising magma appears to have intercepted an older hydrothermal system[98] that existed down to depths of about 3 km (1.9 mi) below the vents,[100] parts of which were expelled during the eruption.[100] Once the magma reached the surface, the eruption quickly became intense.[98]

A volcanic mushroom cloud

A first Plinian stage took place on 19 and 20 February,[101] accompanied by an increase of earthquake activity.[99] The first Plinian event lasted for about 20 hours[102] and formed 18–23-metre-thick (59–75 ft) pumice deposits close to the vent.[101] The pumice was then buried by the ash erupted during this stage, which has been recorded as far as Antarctica.[103] This stage of the eruption produced at least 26 cubic kilometres (6.2 cu mi) of rocks,[104] thus it makes up the bulk of the output from the 1600 eruption.[105] This stage generated a sustained[106] eruption column about 34–46 km (21–29 mi) high,[59] which likely also created a mushroom cloud.[98] The eruption cloud darkened the sky, obscuring the sun and the stars.[107] Afterwards, collapses in the amphitheatre and within the vent enlarged both features and impeded further eruptive activity.[98] A first pyroclastic flow was emplaced already during this time[108] when the column became unstable.[106]

This stage was channelled by a fracture[39] and had the characteristics of a fissure-fed eruption.[1] Possibly, the second vent formed during this stage,[98] but another interpretation is that the second vent is actually a collapse structure that formed late during the eruption.[109] Much of the excavation of the conduit took place during this stage.[99]

Descent of pyroclastic flows on Mayon volcano

After a hiatus the volcano began erupting pyroclastic flows, which were mostly constrained by the topography and were erupted in various stages interrupted by ash fall that extended to larger distances. Most of these pyroclastic flows accumulated in valleys radiating away from Huaynaputina,[103] the flows reaching distances of 13 km (8 mi) from the vents.[1] Winds blew ash from the pyroclastic flows, and rain eroded freshly emplaced pyroclastic deposits.[110] Ash fall and pyroclastic flows alternated during this stage, probably caused by brief obstructions of the vent;[39] at this time a lava dome formed within the second vent.[55] A change in the composition of the erupted rocks occurred, with the "Dacite 1" geochemical suite being increasingly modified by the "Dacite 2" geochemical suite that became dominant during the third stage.[58]

Pyroclastic flows ran down the slopes of the volcano, entered the Río Tambo valley and formed dams on the river course, probably mainly at the mouth of the Quebrada Aguas Blancas;[2] one of the two dammed lakes[21] was about 28 km (17 mi) long.[22] When the dams failed, the lakes released hot water with floating pumice and debris down the Río Tambo.[111] The deposits permanently altered the course of the river.[112] The volume of the ignimbrites has been estimated to be about 2 km³ (0.48 cu mi), without counting the ash that was erupted during this stage,[113] and the pyroclastic flows along with pumice falls covered an area of about 950 km² (370 sq mi).[21]

In the third stage, Vulcanian eruptions took place at Huaynaputina and deposited another ash layer, which is thinner than that produced by the first stage eruption and appears to be partly of phreatomagmatic origin. During this stage the volcano also emitted lava bombs; the total volume of erupted tephra is about 1.5 km³ (0.36 cu mi).[113] This third stage destroyed the lava dome and formed the third vent, which then began to settle along the faults as the magma underneath the vent was exhausted.[55] The fourth vent outside of the amphitheatre formed late during the eruption as well.[39]

The eruption was accompanied by intense earthquakes, deafening explosions[114] and noises that could be heard Lima and as far as one thousand kilometres away.[107] In Arequipa, the sky became dark and at the same time was illuminated by lightning, and ash fell so thick that houses collapsed. The noise of the eruption was perceived as resembling artillery fire.[15] The blasts of the eruption could be heard in the coastal localities of Lima, Chiquiabo and Arica. In these coastal localities it was thought that the sound came from naval engagements, likely with English corsairs. In view of this, the viceroy of Peru sent reinforcement troops to El Callao.[115] Closer to the vents, inhabitants of the village of Puquina saw large tongues of fire rising into the sky from Huaynaputina before they were enveloped by raining pumice and ash.[116]

At first, it was assumed that caldera collapse took place during the 1600 event,[117] as accounts of the eruption stated that the volcano was obliterated to its foundation;[6] later investigation suggested otherwise. Normally very large volcanic eruptions are accompanied by the formation of a caldera, but exceptions do exist.[41] This might reflect either the regional tectonics or the absence of a shallow magma chamber, which prevented the collapse of the chamber from reaching the surface;[55] most of the magma erupted in 1600 originated at 20 km (12 mi) of depth.[58] Some collapse structures did nevertheless form at Huaynaputina, in the form of two not readily recognizable circular areas within the amphitheatre and around the three vents,[118] probably when the magmatic system depressurized during the eruption.[62] Additionally, part of the northern flank of the amphitheatre collapsed during the eruption,[24] with some of the debris falling into the Río Tambo canyon.[119]

The 1600 eruption had a volcanic explosivity index of 6[120] and is considered to be the only major explosive eruption of the Andes in historical time.[121] It is also the largest volcanic eruption during recorded history in the Andes[5] and throughout South America in historical time, as well as one of the largest in the last millennium[122] and the largest historical eruption in the Western Hemisphere.[123] It was larger than the 1883 eruption of Krakatau in Indonesia and the 1991 eruption of Pinatubo in the Philippines.[124] Huaynaputina's eruption column was high enough to penetrate the tropopause[125] and influence the climate of Earth.[126] Stratigraphically, the eruption deposits have been subdivided into five formations.[12]

The total volume of tephra erupted by Huaynaputina was about 30 km³ (7.2 cu mi), in the form of dacitic tephra, pyroclastic flows and pyroclastic surges,[1] although smaller estimates have been proposed as well.[127] It appears that the bulk of the fallout originated during the first stage of the eruption, with the second and third stage contributing a relatively small portion.[128] For comparison, another large Holocene eruption in the Central Andes[129] which exceeded Huaynaputina's in size,[130] the eruption of Cerro Blanco in Argentina about 2,300 ± 60 BCE, erupted a bulk volume of 110 km³ (26 cu mi) of rock, equivalent to a volcanic explosivity index of 7.[131] Various estimates have been made for the dense rock equivalent of the Huaynaputina eruption, ranging between 4.6 and 11 km³ (1.1 and 2.6 cu mi).[132][125]

Ash fall from Huaynaputina reached a thickness of 1 centimetre (0.39 in) within a 95,000-square-kilometre (37,000 sq mi) area of southern Peru, Bolivia and Chile;[126] the tephra was emplaced in a major westerly lobe and a minor northerly lobe,[29] which is an unusual distribution as tephra from volcanoes in the Central Andes is usually carried eastward by winds.[133] The deposition of the tephra was influenced by topography[134] and wind changes during the eruption, which led to changes in the fallout pattern.[106] The ash deposits from the eruption are visible to this day,[135] and several archeological sites are preserved under them.[136]

Some tephra was deposited on the volcanoes El Misti[137] and Ubinas,[138] into lakes of southern Peru,[139] possibly into a peat bog close to Sabancaya volcano where it reached thicknesses of 5–10 cm (2.0–3.9 in),[140] as far south as in the Peruvian Atacama Desert where it forms discontinuous layers[141] and possibly as far north as the Cordillera Vilcabamba.[142] Ash layers about 8–12-centimetre-thick (3.1–4.7 in) were noted in the ice caps of Quelccaya in Peru and Sajama in Bolivia,[122] although the deposits in Sajama may instead have originated from Ticsani volcano,[76] and reports of Huaynaputina-related ashfall in Nicaragua are implausible.[19]

The Huaynaputina ash layer has been used as a tephrochronological marker for the region,[2] for example in archeology[143] and in volcanology, where it was used to date an eruption in the Andagua volcanic field for example.[144] The ash layer, which may have reached as far as[145] East Rongbuk Glacier at Mount Everest in the Himalaya,[146] has also been used as a tephrochronological marker in Greenland[147] and Antarctic ice cores,[148][149] and proposals have been made to use it as a marker for the onset of the Anthropocene.[150]

1615 illustration of the ashfall on Arequipa

The eruption had a devastating impact on the region.[2] Ash falls, pumice falls and pyroclastic flows incinerated everything within their path[151] and buried the surroundings beneath more than 2 metres (6 ft 7 in) of rocks,[22] wiping out vegetation over a large area.[152] Of the volcanic phenomena, the ash and pumice falls were the most destructive.[153] Ash fall, debris flows and pyroclastic flows devastated[80] an area of about 40 by 70 kilometres (25 mi × 43 mi) around Huaynaputina,[16] and both crops and livestock sustained severe damage.[135]

Between 11 and 17 villages within 20 kilometres (12 mi) from the volcano were buried by the ash,[132] among which were Calicanto and Chimpapampa south of Huaynaputina;[12] the "Huayruro Project" that began in 2015 aims at rediscovering these towns.[154] The death toll in villages from toxic gases and ash fall was severe;[155] reportedly, some villages lost their entire populations to the eruption.[116] One of the lost sites, Estagagache, has been deemed the "Pompeii of Peru".[156]

The impact was also noticeable in Arequipa,[157] where up to 1 metre (3.3 ft) of ash fell[158] causing roofs to collapse under its weight.[159] Ash fall was also reported in an area of 300,000 km² (120,000 sq mi) across Peru, Chile and Bolivia mostly west and south from the volcano, including in La Paz,[13] Cuzco, Camana where it was thick enough to cause palm trees to collapse, Potosi, Arica as well as in Lima where it was accompanied by sounds of explosions. Ships observed ash fall from as far as 1,000 km (620 mi) west of the coast.[122]

The local population fled during the eruption[160][161] and wild animals sought refuge in the city of Arequipa.[159] The site of Torata Alta, a former Inka administrative centre, was destroyed during the Huaynaputina eruption and after a brief reoccupation abandoned in favour of Torata.[162] Likewise, the occupation of the site of Pillistay close to Camana ended shortly after the eruption.[163] Together with earthquakes unrelated to the eruption and El Niño-related flooding, the Huaynaputina eruption led to the abandonment of some irrigated land in Carrizal, Peru.[164]

The eruption claimed 1,000[93]–1,500 fatalities,[21] not counting any fatalities from earthquakes or flooding on the Río Tambo.[74] In Arequipa, houses[21] and the cathedral collapsed during mass[165] after an earthquake[72] on 27 February,[94] concomitant with the beginning of the second stage.[75] Reportedly, tsunamis occurred during the eruption as well.[166] Flooding ensued when volcanic dams in the Río Tambo broke,[80] and debris[167] and lahars reached the Pacific Ocean 120[1]–130 km (75–81 mi) away. Occasionally the flows that reached the Pacific Ocean have been described as pyroclastic flows.[168] Reportedly, fish were killed by the flood in the Pacific Ocean at the mouth of the river.[117]

Damage to infrastructure and economic resources of southern Peru was severe.[13] A colonial wine industry in southern Peru was wiped out;[80] chronists tell how all wines were lost during the eruption and tsunamis that accompanied it.[166] Before the eruption the Moquegua region had been a source of good wine, and afterwards the focus of viticulture shifted to Pisco, Ica and Nazca;[169] later sugarcane became an important crop in Moquegua valley.[170] Cattle ranching also was severely impacted by the 1600 eruption.[171] The Arequipa and Moquegua areas were depopulated by epidemics and famine;[167] recovery only began towards the end of the 16th century.[125] Population movements resulting from the Huaynaputina eruption may have occurred as far away as in Bolivia.[172] After the eruption, taxes were suspended for years, and indigenous workers were recruited from as far as Lake Titicaca and Cuzco to aid in the reconstruction.[135] The city of Arequipa went from being a relatively wealthy city to be a place of famine and disease in the years after the eruption.[173] Despite the damage, recovery was fast in Arequipa.[135] New administrative surveys – so-called revisitas – had to be carried out in the Colca Valley in 1604 after population losses and the effects of the Huaynaputina eruption had reduced the ability of the local population to pay the tributes.[174]

Historians' writings about conditions in Arequipa tell of religious processions seeking to soothe the divine anger,[159] people praying all day and those who had lost faith in the church resorting to magic spells as the eruption was underway,[112] while in Moquegua children were reportedly running around and women screaming.[175] In the city of Arequipa church authorities organized a series of processions, requiem masses and exorcisms in response to the eruption.[176] Some indigenous people organized their own rituals which included feasting on whatever food and drink they had and battering dogs that were hanged alive.[177] The apparent effectiveness of the Christian rituals led many previously hesitant indigenous inhabitants to embrace Christianity and abandon their clandestine native religion.[177]

News of the event was propagated throughout the American colonies,[178] and both Christians and native people of Peru interpreted the eruption in religious context.[165] The Spaniards interpreted the event as a divine punishment, while native people interpreted it as a deity fighting against the Spanish invaders;[179] one myth states that Omate volcano (Huaynaputina) wanted the assistance of Arequipa volcano (probably El Misti) to destroy the Spaniards but the latter could not, claiming that he was Christian now, and so Huaynaputina proceeded alone.[180] El Misti had erupted less than two centuries before,[181] and local populations were further concerned that after Huaynaputina, El Misti might erupt next. As a result, natives and Franciscan friars reached the summit of that volcano and threw relics of saints into its crater.[182] Shamans in the Tambo valley urged a return to old customs,[161] and processions and sacrifices to Huaynaputina took place.[77] In Arequipa, a new patron saint, San Genaro,[lower-alpha 1] was named following the eruption and veneration of Martha – who was believed to have power over earthquakes – increased; she became the city's sole patron saint in 1693.[184]

Reportedly, in November 1599 a Jesuit named Alonzo Ruiz had announced in Arequipa that divine punishment would strike the natives for continuing to worship their gods and the Spaniards for poor habits.[185] On the other hand, mythology held that the lack of sacrifices had upset the devil who had sent a large snake to announce "horrifying storms"[78] – which eventually ended up killing the natives anyway.[186] Jesuits interpreted this as a deception attempt by the devil.[187] Such prophecies may reflect prior knowledge about the volcanic nature of Huaynaputina. There are reports that a sacrificial offering was underway at the volcano a few days before the eruption.[78]

It is known that volcanic eruptions alter worldwide climate by injecting ash and gases into the atmosphere, which reduce the amount of sunlight reaching the Earth, often causing cold weather and crop failures.[202] The Huaynaputina eruption[126] decreased the amount on solar energy reaching Earth by about 1.94 W/m².[203] The summer of 1601 was among the coldest in the northern hemisphere during the last six centuries,[80] and the impact may have been comparable to that of the 1815 Tambora eruption.[97] Other volcanoes may have erupted alongside Huaynaputina and also contributed to the weather anomalies;[204] a number of large volcanic eruptions took place in the decades preceding[205] and following the Huaynaputina eruption.[198]

The eruption had a noticeable impact on growth conditions in the Northern Hemisphere, which were the worst of the last 600 years,[2] with summers being on average 0.8 °C (1.4 °F) colder than the mean.[49] The climate impact has been noted in the growth rings of a centuries-old ocean quahog (a mollusc) individual that was found somewhere in Iceland,[206] as well as in tree rings from Taiwan,[207] eastern Tibet,[lower-alpha 2][208] the Urals and Yamal Peninsula in Russia, Canada, the Sierra Nevada[209] and White Mountains both in California[210] and Lake Zaysan in Kazakhstan.[211] Notably, the climate impacts became manifest only in 1601; perhaps in 1600 they were suppressed by a strong El Niño event.[212]

Other climate effects attributed to the Huaynaputina eruption include:

• In climate simulations, after the 1600 eruption a strengthening of the Atlantic meridional overturning circulation is observed along with sea ice growth, followed after a delay by a phase of decreased strength.[213]
• An extraordinarily strong El Niño event in 1607–1608 and a concomitant northward shift of the Southern Hemisphere storm tracks have been attributed to the Huaynaputina eruption.[214]
• Manila galleons reportedly were faster when crossing the Pacific Ocean after 1600, perhaps owing to volcanically-induced wind changes.[215]

Temperatures decreased for a long time after the Huaynaputina eruption in the extratropical Northern Hemisphere.[216] Together with the 1257 Samalas eruption and the 1453 Kuwae eruption, the Huaynaputina eruption may have led to the Little Ice Age.[217] Arctic sea ice expansion and climatic cooling has been noted after these eruptions,[218] and a cooling peak occurred around the time of the Huaynaputina eruption.[219] In general, volcanic sulfate aerosol production was higher during the Little Ice Age than before or after it.[220] In the Andes, the Little Ice Age had already begun before the 1600 eruption,[127] although a major expansion of glaciers in the Peruvian Cordillera Blanca occurred around the time of the Huaynaputina eruption.[221]

The 1600 eruption of Huaynaputina occurred at the tail end of a cluster of mid-sized volcanic eruptions, which in a climate simulation had a noticeable impact on Earth's energy balance and were accompanied by a 10% growth of Northern Hemisphere sea ice[222] and a weakening of the subpolar gyre.[223] Such a change in the ocean currents has been described as being characteristic for the Little Ice Age.[224]

The church of the Jamestown colony, where the eruption appears to have caused a drought and high mortality

Thin tree rings and frost rings[lower-alpha 3] have been found in trees of the Western USA[188] such as in Montana[225] and correlate to the Huaynaputina eruption. 1601 and 1603 tree rings close to the tree line in Quebec indicate cold temperatures,[188] and anomalous tree rings and cooling in Idaho have been linked to the eruption as well.[226] 1601 saw the coldest temperature in a Seward Peninsula, Alaska record of the last 600 years,[227] as well as in other places of northwestern and southeastern Alaska.[228] Noticeable cooling has been inferred for the Western US from tree ring data.[229] In addition, weather in the Arctic Archipelago of Canada was unusually wet.[230]

The Huaynaputina eruption was followed by a drought in the Eastern US and may have hindered the establishment of the colony in Jamestown, Virginia, where mortality from malnutrition was high.[231] In addition, the eruption may have contributed to the disappearance of the Monongahela culture from North America, along with other climate phenomena linked to the El Niño-Southern Oscillation.[232]

A major flooding episode in 1605 ± 5 recorded from sediments of the Santa Barbara Basin has been attributed to the Huaynaputina eruption.[215] A global cooling period associated with the Huaynaputina eruption as well as eruptions of Mount Etna and Quilotoa[233] may have forced storm tracks and the jet stream south, causing floods in the Southwestern United States.[234] At that time, flooding also took place in Silver Lake in the Mojave Desert,[235] and Mono Lake rose to the highest level of the last thousand years. There were also wet spells between 1599 and 1606 in the Sacramento River system, according to analysis of tree rings.[236] Colder temperatures may have contributed to the flooding in Silver Lake, as they would have reduced evaporation.[226]

A 1650 map of California. The belief that it was an island may have been promoted by the flooding caused by the Huaynaputina eruption.

Sebastián Vizcaíno and Juan de Oñate visited the US west coast and the Colorado River Delta in the years following the Huaynaputina eruption. The effects of this eruption and the activity of other volcanoes – namely, large scale flooding – might have induced them to believe that California was an island; this later became one of the most well known cartographic misconceptions of history.[237]

Tree rings indicate unusually cold weather in the Austrian Alps[126] and Estonia, where the 1601–1602 winter became coldest in half a millennium.[238] Tree ring analysis suggested cooling in Greece,[239] Lapland (Finland)[240] central Spain, the Swiss Alps[126] and Switzerland (in 1600) more generally,[241] where reconstructed winter temperatures were the lowest of 1525–1860.[238] Anomalous weather conditions relating to the 1600 eruption, possibly under additional solar influence, have been noted in sediment cores from peat bogs in England and Denmark.[242] In Norway, cooling coinciding with the eruption was probably the reason for the development of palsas in Færdesmyra that for the most part disappeared only in the 20th century.[243]

The winter of 1601 was extremely cold in Estonia,[215] Ireland,[244] Latvia and Switzerland,[215] and the ice in the harbour of Riga broke up late.[238] Climate impacts were also reported from Croatia.[132] Reportedly, the 1601 wine harvest was delayed in France, and in Germany it was drastically lower in 1602.[215] Frost continued into summer in Italy and England.[209] A further cold winter occurred in 1602–1603 in Ireland.[244] In Estonia, high mortality and crop failures from 1601–1603 led to an at least temporary abandonment of three quarters of all farms.[245] Scotland saw the failure of barley and oat crops in 1602 and a plague outbreak during the preceding year.[246]

In Fennoscandia, the summer of 1601 was one of the coldest in the last four centuries.[188] In Sweden, harvest failures are recorded between 1601–1603,[247] with a rainy spring in 1601 reportedly leading to famine.[126] Famine ensued there and in Denmark and Norway during 1602–1603 as well.[245] Finland saw one of the worst barley and rye harvests, and crop yields continued to be poor for some years to follow, accompanied by a colder climate there.[248] It is likely that the 1601 crop failure was among the worst in Finland's history,[249] and it led to changes in the social structure of Ostrobothnia.[250] 1601 was called a "green year" in Sweden and a "straw year" or "year of extensive frosts" in Finland.[251]

A 19th century engraving showing the 1601 famine in Russia

Ice cores in the Russian Altai Mountains noted a strong cooling around 1601,[252] with tree ring data also recording a cooling of 3.5 °C (6.3 °F).[253] Cooling was also noted in tree rings of the Kola Peninsula.[240]

The summer 1601 was wet,[238] and the winter 1601–1602 was severe.[215] In 1601–1603 the eruption led to a famine[254] after crops failed in 1601 and 1602; this is considered to be the worst famine of Russian history and claimed about two million lives, a third of the country's population.[238] The tzar Boris Godunov was overthrown in part owing to the social impacts of the famine,[215] and the time of social unrest known as the Time of Troubles began.[240] This social unrest eventually led to a change in the ruling dynasty and interventions from Sweden and Poland.[255]

Before the Huaynaputina eruption in 1591–1596, severe droughts in Anatolia caused harvest failures. The extremely cold winters that followed, associated with Huaynaputina's eruption and an eruption of Nevado del Ruiz in 1595, caused epizootics that killed large amounts of livestock in Anatolia, Crimea and the Balkans. This weakened the Ottoman Empire just as it was conducting the Long Turkish War and appears to have contributed to the onset of the Celali rebellions in Anatolia.[256]

Chronicles during the reign of Emperor Wanli[257] from northern China mention severe frosts in 1601 and frequently cold weather, including snowfall in Huai'an County[189] and Hebei and severe frost in Gansu,[258] Shanxi and Hebei during summer.[259] The frosts destroyed crops, causing famines[260] severe enough that cannibalism took place.[261] Epidemics in Shanxi and Shaanxi have also been linked to Huaynaputina.[259] The cold snap was apparently limited to 1601, as there are no reports of extremely cold weather in the subsequent years.[262]

Weather was anomalous in southern China as well, with 1601 seeing a hot autumn and a cold summer and abrupt snowfall. Disease outbreaks occurred afterwards.[259] Reports of snowfall and unusual cold also came from the Yangtze River valley,[263] and summer in the Anhui, Shanghai and Zhejiang provinces began unusually with cold and snowy weather and then became hot.[258]

Unusually narrow or entirely missing tree rings formed in 1601 in trees close to Khövsgöl Nuur lake.[264] Severe droughts recorded over the Tibetan Plateau in 1602 may have been caused by the Huaynaputina eruption. The eruption would have decreased the atmospheric water content and thus strength of the monsoonal moisture transport towards the plateau.[265] Likewise, droughts[266] recorded in cave deposits of southern Thailand[267] have been related to the Huaynaputina eruption[268] and may reflect a typical response of tropical rainfall to volcanic events.[266]

In 1601 Japan, Lake Suwa froze up considerably earlier than normal,[215] and flooding and continuous rains were accompanied by harvest failures.[245] Korea in 1601 saw an unusually cold spring and summer, followed by a humid and hot mid-summer. Epidemics ensued,[269] although the epidemics in East Asia erupted under different weather conditions and linking them to the Huaynaputina eruption may not be straightforward.[270] On the other hand, temperatures were not unusually cold in Nepal.[271]

• McCoy, Floyd W.; Heiken, Grant, eds. (2000). Volcanic Hazards and Disasters in Human Antiquity. Geological Society of America Special Paper.
• González-Ferrán, Oscar (1995). Volcanes de Chile (in Spanish). Santiago, Chile: Instituto Geográfico Militar. p. 640 pp. ISBN 978-956-202-054-1.
• Hildreth, Wes; Grunder, Anita L.; Drake, Robert E. (January 1984). "The Loma Seca Tuff and the Calabozos Caldera: A Major Ash-flow and Caldera Complex In The Southern Andes of Chile". Geological Society of America Bulletin. Geological Society of America. 95 (1): 45–54. Bibcode:1984GSAB...95...45H. doi:10.1130/0016-7606(1984)95<45:TLSTAT>2.0.CO;2. ISSN 0016-7606.
• Thouret, Jean-Claude; Dávila, Jasmine. "Huaynaputina Volcano, Southern Peru, AD 1600: Eruption Phases and Mechanisms" (PDF). Archived from the original (PDF) on 19 December 2008. Retrieved 29 December 2008.
• Thouret, Jean-Claude; Juvigné, Étienne.; Gourgaud, Alain; Boivin, Pierre; Dávila, Jasmine (30 June 2002). "Reconstruction of the AD 1600 Huaynaputina eruption based on the correlation of geologic evidence with early Spanish chronicles". Journal of Volcanology and Geothermal Research. 115 (3–4): 529–570. Bibcode:2002JVGR..115..529T. doi:10.1016/S0377-0273(01)00323-7.
• Verosub, Kenneth L.; Lippman, Jake (8 April 2008). "Global Impacts of the 1600 Eruption of Peru's Huaynaputina Volcano". Eos Trans. AGU. 89 (15): 141–148. Bibcode:2008EOSTr..89..141V. doi:10.1029/2008EO150001.

• Jara, L. A.; Thouret, Jean-Claude; Siebe, Claus; Dávila, Jasmine (2000). "The Ad 1600 Eruption of Huaynaputina as described in Early Spanish Chronicles". Bibliovirtual | Sociedad Geológica del Perú. Geotecnia y riesgos geológicos.
• Paredes, Japura; Blanca, Saida (30 October 2018). "Estudio estratigráfico y sedimentológico del depósito de caída pliniana de la erupción del año 1600 d.C. del volcán Huaynaputina". Universidad Nacional del Altiplano.