LONQUIMAY (🇨🇱) and its Christmas Crater

Lonquimay volcano behind the Christmas crater, or Cráter Navidad. Photo taken towards the SW. (© Andeshandbook, Alvaro Vivanco)

Although not for the faint-hearted and wobbly legged, Lonquimay’s summit is a favorite destination with climbers. The reward for their pains is a stunning view all around: In clear weather, up to 14 volcanoes can be seen within a radius of 250 km:

Stunning view from Lonquimay’s summit crater: The next volcano behind it is Tolhuaca. 02/01/2017. (Explore the full 8.4 MB photo on AndesHandbook – © Felipe Lechuga)

Detail of the previous image: On the upper right one can see Antuco, 110 km away, and Nev. de Chillan at 170 km. Beyond and between the two, it is either S. Pedro Pellado or the higher Cerro Azul peeking through from an impressive distance of 277 km. Left of the group, Nev. de Longavi, 245 km.

Lonquimay is a nice symmetrical volcano, and located about 130 km NE of Temuco in the north of the Araucanía region of Chile. Its name goes back to the ancient Mapuche inhabitants of the area, meaning “great ravine” in reference to a wide, 120 m deep gorge on its east face. Eruptions of Lonquimay were recorded in 1853, 1887, 1933, 1940(?) and 1988.

Two more details from the first image, of the rocks at the Lonquimay crater rim: Left, a layer of jointed columns can be seen where a lava flow had cooled. Right, soft hot spatter splotches that had been thrown out during an eruption built up on the crater rim.

The Lonquimay Volcano is part of the small but beautiful Malalcahuello National Reserve. Quite self-contradictory, it is also located within a touristic concession area and has recently been heavily commercialized. This means that both in the National Reserve and in the Corralco ski center mandatory registration, entrance and ascent fees must be paid. It also means that, in case of a possible eruption, there will always be *somebody* to argue against the potential severity of threats or against suggested safety measures – because times of restrictions for safety = big loss of money.

One ski-related website advertises Lonquimay skiing: “The mountain dominates its surroundings, and it is possible to ski all aspects of it, depending upon snow and weather conditions” – but does not mention ‘…and on volcanic activity’. (© chilemountaintours.com)

While, apparently, it is by far not as bad yet as around Nevados de Chillan, associated infrastructure as roads, hotels, ski lifts, restaurants, night bars, swimming pools etc. never go well with a protected area… as already bemoaned by visitors. On the other hand, Lonquimay lies in a very poor part of the country. Who would not want for the people to get business, get industries, mining, lots of tourists and whatnot – to better their lives? It’s the old conflict between man and nature; we have not yet learned to agree upon a life style that benefits both, without man or nature being exploited.

 

THE VOLCANO and its “CHRISTMAS ERUPTION” 1988

Tectonic setting of the Lonquimay volcano. (B. Ugarte et al, 2010, cropped)

Lonquimay is a small, flat-topped, 2865 m high and symmetrical stratovolcano of late-Pleistocene to dominantly Holocene age in the Southern Volcanic Zone of the Andes. Its immediate neighbor to the SE is the largely Pleistocene Tolguaca (Tolhuaca) volcano. It is located in the northernmost part of the Liquiñe-Ofqui Fault Zone. Here it sits over a NE-SW oriented fault that comes off this zone (a so-called tail crack): The Cordón-Fissural-Oriental fissure zone cuts across the entire volcano, and then extends ~10 km NE of Lonquimay. This is the geological feature that had produced a series of vents and cinder cones – the source of voluminous lava flows of the 1887-90 and 1988-90 eruptions. Lonquimay is dominantly andesitic, but basalt and dacite lavas are also found.

Onset of the eruption

Lonquimay in summer, seen from the neighboring volcano Tolhuaca. (© fundolagunablanca.com)

From 07/12/1988 on people living near the volcano began to hear strange noises from underground. An earthquake swarm with some of quite substantial magnitude for a volcano (>M 4) rattled their houses. One was felt at Temuco, 110 km from the volcano, on Christmas Eve. Then, in the afternoon of Christmas Day, all hell broke loose.

It began with strong ejections of gas and water vapor. Early in the eruption, about eight small vents opened along a fissure ~800 m long, 3.5 km from the summit. This took a similar path as previous Holocene and historic monogenetic eruptive centers which had produced lava domes and andesitic/dacitic block lava flows before. Moderate Strombolian activity from several vents was reported on 26/12. The next day, gas and tephra rose several thousand meters from the two main vents. Viscous lava began to flow N and NE from the fissure.

This east-looking view shows the ice-filled summit crater of Lonquimay at the lower right. The dark area extending to the left from the eruptive vent, which formed along a fissure system trending NE from the summit, is the lava flow that originated on December 27, 1988. (© Jeffrey Post, via GVP)

Eruption in full swing

In the evening of that day a second, more violent phase started with strongly explosive phreatomagmatic activity. An impressive dark column of gas and tephra reached 9 km of altitude within 5 minutes. The activity was concentrated in the upper vent, at 1680 m elevation, which became the principal eruptive center. Within one day, a cone over the main vent had reached 50 m height and 80 m in diameter. This was later to become the famous Cona Navidad – the Christmas Cone – as it had started on Christmas day. As the crater grew, it developed a horseshoe shape, open to the NE (downslope), and by 4 January already measured over 200 m high and 300 m wide.

Contemporary sketch made by volcanologist O. González-Ferrán.

The erupting Navidad Cone seen from the slope of Lonquimay. (© Manfred Mornhinweg)

Some 60 hours after the large explosions on 27/12, the third phase began with substantial lava production and strong magmatic degassing. Vigorous explosions produced shock waves and a large amount of ash, while a blocky lava flow crept very slowly NNE. The rate of lava effusion was estimated at ~40k m³/day through 04/01/1989, with a 10m-thick flow advancing 20-25 m/hour. This explosive and effusive activity kept on with vigorous emission of gas and ash, generating a column that nearly continuously remained at 5000-7000 m altitude. On 04/01, during a period of increased atmospheric humidity, geologists observed that the plume became cauliflower-shaped and a thunderstorm developed within. An acidic rain began to fall, probably of pH 3-4.

A decline in eruptive activity from 06/01 brought a sequence of strong earthquakes instead. These were interpreted to be caused by collapse of the roof of the magma chamber. On 12/01 an M 4.6 shock caused landslides, slumping of roads, and broken windows in houses. Another one registered 24 hours later reached M 5.0 – larger than the events at the onset of the eruption.

The author’s comment: “A bomb! Quite often it happened that a porous rock came up, that had lots of high-pressure gas stored in its pores. When such a rock comes up, as soon as it leaves the high-pressure environment of the chimney, the internal pressure tears it apart! So the rocks explode right above the crater. During daytime we had to run several times, when such a bomb send fragments whirling all over the area. But as it got dark, such bombs produced a display more beautiful than any human-made fireworks!” (© Manfred Mornhinweg)

A week later the activity was back to explosions that caused strong shock waves. Lava block flow and spatter emissions had changed from the more viscous and silicic (andesite-dacite) initial phase to a more fluid andesite. The flow advanced in two lobes down the Rio Lolco valley.

Panoramic view of the Lonquimay eruption from the NE on 10 March 1989 showing the block lava flow along the Lolco river valley and tephra emission from Navidad cone. Contemporary sketch by volcanologist O. González-Ferrán.

By early April the Lolco front had reached 35 m height, with a temperature of 1040°C. It was advancing over a swampy area, causing soil deformation, squeezing the soft sediments, and contaminating the water of the Lolco river. Nearly 0.8 km² of wild Araucaria forest have been destroyed along this valley. In several patches the rough lava surface shows yellowish iron chlorides due to the high HCl content of the volcanic gases.

The velocity of the slow-moving flow front decreased exponentially with distance from the vent. But it still moved on and on until January 1990. By the end of the eruption the lava flow stopped at 10 km from the vent and had a volume of 0.23 km³.

(© Manfred Mornhinweg)

Right: The photographer, who had experienced the lava bombs flying during the eruption, returned to the spot 12 years later: “After twelve years exposed to snow and sun, it has started to crack up. In a few decades it will be just volcanic rubble. This one was found about 400 meters higher than the highest altitude the Navidad’s crater ever reached, and at no less than two kilometers distance! Its elongated axis points exactly at the Navidad, a proof that it landed in partly liquid state and assumed its present shape on impact!”

 

DURING AND AFTER

The Escorial or Lolco lagoon. Several of these lagoons were formed when the lava flow blocked the natural water course of the Lolco river. Their water is affected by the different minerals dissolved from the lava, they have beautiful colors and an interesting chemistry. Some lagoons have submerged part of the adjacent forests, while other trees and plants have withered and died from the volcanic fumes. (© Albert Graell, cropped screen grab from G-Maps)

It was not a strong, great, or super-eruption. Just an ordinary VEI 3 with abundant ash and lava flows. But for some it was the end of the world as they knew it.

Health Problems and Damages to Farming

Although this is not exactly a remote area, people who live here in the mountains get very isolated in the winters. That means they have to store the supplies for themselves, and more importantly, fodder for their animals, during the summers. Only – that year, 1989, had for them been a year without summer. Constant ash emissions made the air actually unbreathable. Yet, despite good preparation campaigns, the people of Lonquimay and surrounding areas had inhaled a lot of volcanic ash, and this affected their respiratory systems. During winter time things became so bad that the children were evacuated, separated from their families. What a disaster!

The Araucanía region takes its name from the proud Araucaría, the Chilean national tree, which can reach an age of more than a thousand years. Together with another archaic giant, the Coigüe, it can form dense forests in an impressive scenery. (© Tamara Nef, via whiteout.ch/2018/04/27/)

A contemporary report describes the damage caused by the eruption: Nearly all of the families dwelling in this mountain area depend for their livelihoods on animal raising. About 10,000 cattle have been suffering the effects of ashfall since December. Many of them have lost more than 100 kg in weight and are dying. Analyses by specialists at the Univ Austral determined that the animals are being affected by overdoses of fluorine from the ash. Losses are estimated at about $2,000,000 (US). Local authorities and the Ministries of Agriculture and Health are taking emergency measures. Also, fires have burned valuable native trees, including coigüe (Nothfogus dombeyi, a native beech) and araucaria (Araucaria araucana) forests.

It was a tragedy that, as usual, once again hit the most vulnerable, the poorest of the country.

The 1989 lava flow seen on G-Earth satellite images. Some cinder cones from former eruptions of the fault are also visible.

 

IS THE NAVIDAD CRATER STILL ACTIVE?

As for the present activity, Lonquimay volcano has just been in the volcano news on 11 August this year. An M 3.0 Hybrid type earthquake had been recorded, suggesting fracturing rocks as well as fluid dynamics inside the volcano. Later followed three Long Period earthquakes which are associated especially with fluid dynamics. Nevertheless, the volcano’s activity status remains at Normal, or Green.

Crater Navidad with Volcan Lonquimay in the background. (© Reserva Nacional Malalcahuello, via TripAdvisor)

Cráter Navidad, “Christmas cone”, vent. 02 May 2010. (© AndyUrbina)

As with Paricutin in Mexico, the appearance of Cráter Navidad allowed Chilean volcanologists for the first time to measure and analyze the complete process of the birth of a volcano until its extinction. Having said that, there may be some doubts allowed: Tourists lately report strong smelly gas emissions from the vent at times, strong enough to even produce a hissing sound. It could be re-heated rain water, but would this also have that strong sulfuric smell? Perhaps so. Even though generally such cinder cones are monogenetic, here they belong to this long-established eruptive fissure zone of the volcano. There still must be cracks reaching down to the hydrothermal system which may be exploited by a future rising magma. Sure there will be more eruptions on this fissure. Whether it will be the Navidad cone again – or it stays monogenetic and another one comes up – remains everybody’s guess.

 

BESIDES… Re: ARAUCANIA

Mapuche groups in Araucanía around 1850. De facto Chilean territory in blue.

“Between two Chilean provinces [Concepción and Valdivia] there is a piece of land that is not a province, its language is different, it is inhabited by other people and it can still be said that it is not part of Chile. Yes, Chile is the name of the country over where its flag waves and its laws are obeyed…” (D.F. Sarmiento)

Like me, some of you might be interested in the surroundings of a volcano, the type of landscape, culture, traditions or its history. Reading up on various volcanoes in the Araucania province, without fail one will see mention of the “Ránquil massacre”.

Following up on this, one is beamed back in time one and a half century, when this part of the Andes was the land of various groups of the indigenous Mapuche. These peoples had been an annoying thorn in the flesh of the Chilean government for a long time. A series of military campaigns, agreements and penetrations by the Chilean army eventually led to the incorporation of Araucanía into Chilean national territory. The Chilean authorities called this process “Pacification” of Araucanía.

There was, however, nothing peaceful about any of this, and not about the following politics. Up to 1914 the government had invited many thousands of foreign settlers (Germans, French, Swiss, Bohemians, etc.) to settle on land “bought” (or rather confiscated) from the natives. The former began to engage in much needed industries, by way of exploiting the latter (as well as poor Chilean settlers) as their work horses. Understandably, this would lead to discontent and unrest. There were uprisings in several places, including the gold panners of Lonquimay.

Ránquil massacre 1934

The Ranquil Massacre took place in June and July 1934, when groups of Mapuche peasants and indigenous people from the Malleco province revolted in unsuspected proportions against the abuses of their bosses. The government, in panic, had sent in corps of Carabineros and the army “to restore order”. However, instead of settling the issues, they murdered half a thousand of the Mapuches and Chilean workers, and another half thousand were thrown in prison.

~~~

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, Lonquimay
– SERNAGEOMIN, Lonquimay
– Surface crust strength during the flow of the 1988–1990 andesite lava of Lonquimay (2007, PDF)
– The Lonquimay Volcanic Complex and the Liquiñe-Ofqui Fault Zone:[…] (2010, PDF download)
– The Lonquimay volcano – never trust a sleeping beauty!
– Article on the Ránquil massacre