It rains a lot in British Columbia. Here is where the Pacific Ocean dumps its excess moisture. The mountains are covered with trees; the lichen-covered branches drip in the seemingly perpetual rain or drizzle. The summers are mild and dry but don’t last long enough. The everlasting days soon end, and the autumn rains and winter snows take over. But always sunshine makes a desert and British Columbia shows how attractive the alternative can be. A green, lush rainforest has grown up. The rain feeds the rivers, the rivers attract the fish, and the fish feed the bears and the people. The salmon runs here are famous. Fishing in this sparsely populated land requires wilderness experience. This land still belongs to the original settlers, the first people. Visitors tread carefully here: they need to respect the land, its First Nation owners, their traditions and their memories.
One of the many rivers is the Nass, named the Ḵ’alii-aksim Lisims by the local Nisga’a people. One if its many minor tributaries is the Ksi Sii Aks river. Later arrivals called these the Nass and the Tseax river. Tseax is a fearful name; the memories of the events here run deep.
There are many ancient sites along the Nass river, prehistoric villages with their totem poles. One of these is Gitwinksihlkw (and no, I don’t know how to pronounce that either). It was settled in the 1700’s but the site at the shore of a canyon was problematic. It was badly damaged by two major fires around 1890, and surrounding villages were destroyed by a big flood in 1917. None of the totem poles survive. The people who settled here had been in a hurry and in bad shape. They were fleeing from another disaster, which had wiped out the ancient villages upstream. But the village still exists, one of four main villages along the river in which some 2500 Nisga’a still live. They are tough survivors. Their oral traditions go back a long time. They tend not to publish these traditions. Each of the four main families keeps their own distinct memories. Those oral traditions show the reality of Canada’s volcanic dangers.
Although Canada has a significant number of volcanoes, it lacks the grandeur of the volcanoes of the western US, or those of Alaska. By reputation, it forms a quiescent gap between those areas. There are some impressive looking volcanoes, such as Mount Meager, Mount Baker, and Mount Edziza. But volcanic activity is so low that one of the minor peaks, the one with possibly the most recent activity, is just called The Volcano. There have been large eruptions: Mount Meager suffered a large explosion, St-Helens size, 2350 year ago. But Canada’s volcanoes have long repose times and eruptions are therefore infrequent.
The sparse large volcanoes are supplemented by a large number of smaller cones. These may erupt only a few times or even once, before the magma finds another outlet. They may not be as eye-catching, but Canadian cones carry the past and future of its volcanism. Canada is not as brash as its southern or western neighbour; its volcanoes mirror the nation’s diversity, and here, the little ones matter. They out-trump the big volcanoes, their noisy, seemingly dominant, but ultimately harmless neighbours. The largest numbers of volcanic cones are in the northwest of British Columbia, close to the Northwest Territories and Alaska. (British Columbia perhaps is an outdated name, but ‘Canada’s Columbia’ lacks in abbreviation: who wants to be a ‘CC’?) Here, in BC’s sparsely populated north, is the Stikine volcanic belt, oriented north-south and containing over 50 locations which have had eruptions since the ice age. The activity is different from that elsewhere in Cascadia. This is a zone where extension has taken place, and this is causing the magma melt. The magma melting is dispersed over many small areas rather than a few large magma chambers. This tends to build up small cones rather than large mountains, and thus the volcanic nature of the region may not be as obvious as it is say near Seattle. The rugged deeply forested terrain further hides the evidence. The lava is basaltic. Over time, as the plate junction between the Pacific and North American plate migrated north, extension had slowed and volcanic activity has diminished. But it has not gone away.
Here, at the southern end of the Stikine belt, close to the southernmost border of Alaska, is where the Nass River flows. And this was the location of the worst volcanic disaster known to have happened in Canada, the third worst environmental event in the nation’s history. The Nisga’a still remember.
The Tseax eruption
One of the southern tributaries to the Nass river is the Tseax. It runs through a lake, which begins at a volcanic cone just east of the river, 300 meter wide and 100 meter high; the cone is build on an older and slightly larger cone. The lake has the suggestive name ‘Lava lake’. Indeed, 300 year ago, lava came from here. The lava flowed from the crater, which is likely to have contained its own lava lake during the eruption. It flowed into the narrow Tseax river valley: five kilometer downstream, it dammed the valley. The resulting lake is the appropriately called Lave Lake; it is still here. But the lava did not stop: it went down further, exited the tributary and flowed into the Nass valley. This is a fairly flat region, and this allowed the lava to spread out more. It fanned out and covered an area 3 kilometer wide and 10 kilometer long. The total length of the flow is 22 kilometer. It covers and area of 38 km2, and the average depth is over 10 meter. The volume is some 0.4 km2. It was a sizable eruption! The Nass River lost its bed and had to relocate 1 mile to the north. The valley was inhabited, and the local population was badly, perhaps surprisingly badly, affected by the eruption. The survivors fled and settled downstream, in Gitwinksihlkw.
The lava field is still there and is now a memorial monument. The Nisga’a consider it a burial site, and for good reason. The Nisga’a Memorial Lava Bed Park (which also carries several less memorable names) was established in 1992 and is the only BC provincial park jointly managed with a First Nation. It is not difficult to get to, and there is a small camp site, but be prepared to drive on unpaved roads. The lava beds contain a mixture of smooth pahoehoe and rough a’a. There are lava tubes and tree casts, the latter vertical holes where trees were burned after the lava passed. The lava has developed a coat of green moss, courtesy of the climate. Tseax is the main and youngest cinder cone, but there are other cones in the area. This is one of the more accessible places in Canada to witness it volcanic history.
How it unfolded cannot be deduced from the solidified surface flows. The oral traditions provide a better way. The stories were first recorded by Barbeau, and published in 1935. He wrote about an elder called Neesyoq, who told him:
First there was smoke, like that coming out of a house, a big pillar of smoke. It was as if a house was burning on the mountain top. The people saw a big fire. The fire came down the side in their direction, but not as fast as a forest fire. It moved down slowly, very slowly. It was strange and frightful. Invisible fumes pushed ahead of the advancing wall of fire. Those who smelled them were smothered, and stiffened like rock.
According to the stories, about 2000 people died, and two villages were destroyed. The death toll must have amounted to a significant part of the population.
Another version of the story, published by the Nisga’a themselves, runs as follows
Long ago, two children were playing down by the river. One child caught a salmon and slit open its back. The child stuck sticks into the salmon’s back, set them on fire, and returned the fish to the river. The children were amused to see the salmon swim erratically, smoke rising from its back. The other child caught a salmon and slit open its back, inserted a piece of shale, and put it back into the river. The salmon floated on its side, weighed down by the shale. The children laughed at the struggling fish. An elder happened upon the scene and warned the children, “Take care what you do. The salmon will curse you and the Creator will respond in kind.” The ground began to tremble and shake. Nature’s harmony had been upset. A scout was sent to investigate. From the top of Gennu’axwt, he saw smoke and flames and ran to warn the people of their fiery destiny. In panic, some villagers fled up the mountain. Others canoed to the far side of the river but were killed by the lava. As the people watched the lava flow over their villages, Gwaxts’agat (a powerful supernatural being) suddenly emerged to block the lava’s advance. For days, Gwaxts’agat fought back the lava by blowing on it with its great nose. Finally, the lava cooled and Gwaxts’agat retreated into the mountain where it remains to this day.
Another source states that people dug pits for shelter but died from poison smoke.
Dating the disaster
From the stories, it was thought that the eruption would have happened around 1770 and this is the data given in many places, such as Volcanodiscovery. A second line of evidence came from tree trunks in places where the survivors had settled. These trunks showed evidence that bark had been stripped, and this was provisionally dated to 1770. A similar date was obtained from a report by the first modern visitor here was from Peru, Juan Francisco de la Bodega y Quadran. His ship, the Sonora, arrived in Bucareli Bay in 1775. On arrival at the mouth of the Nass he wrote about his young crew They suffered somewhat from the heat, which they attributed to the great flames which issued from four or five mouths of a volcano and at nighttime lit up the whole district, rendering everything visible. This has been used to date the eruption to 1775.
However, none of these lines of evidence are fully convincing. As early as 1924, a geological report mentions that the lava is clearly older than that. As for the 1775 observations from the Sonora, they were much too far from the Tseax volcano to have seen the eruption. A large forest fire is a far more likely explanation. Carbon-14 dating of trees covered by the lava has proven difficult, but gives older dates than the reports above. The most conclusive evidence comes from
the orientation of the magnetic field. The lava records this while it cools and solidifies. But the magnetic north pole moves around, and when as close to it as Canada, the angle towards magnetic north changes significantly. The angles in the lava do not agree with where the magnetic pole was around 1770. The combined evidence indicates that the Tseax eruption happened in 1668–1714, with a smaller possibility that it was a century earlier. This was published by Michael Higgins in 2009, who speculates that the eruption was caused by the megathrust earthquake of 1700, because of the oral tradition that the ground shook before the eruption. But this appears at best unproven.
There is an older lava flow from this cone, for which a C-14 data of 1330+-75 is quoted. This is a so-called ‘uncorrected’ date, which does not take into account natural changes in the C-14 in the atmosphere. Correcting for this gives a ‘corrected’ date (the date for the recent eruption is a corrected date): for the older eruption, this becomes 1240+-67.
The death toll is highly uncertain, based on the oral memories. But it is likely to have been high. It is not the largest environmental disaster of Canada. A hurricane at Newfoundland in 1775 killed an estimated 4000 people, and the death toll of the Cascadia megathrust earthquake in 1700 is unknown but must have been considerable. The Tseax eruption ranks third in this list.
But effusive, basaltic eruptions tend to be relatively safe: the lava flows are slow and people have time to get out of the way. What made this eruption so devastating? That is not known. The narrow river valley may have channeled a mud flow. The mentioned of invisible fumes has lead to suggestions that poisonous gases were the main killer. CO2 has been suggested as the killer, and is indeed invisible, though lacks smell. But the description of stiffened bodies is suggestive of intense heat. Perhaps a pyroclastic-like flow came down the narrow river valley. Against this, there is no evidence of an explosive eruption. Perhaps the narrow Tseax valley amplified an otherwise minor event.
So uncertainty rules. It would be good to resolve this issue: whatever danger is lurking in the mountains could be vastly more destructive nowadays. Canada has few volcanoes and repose times are long, so that eruptions are not considered an important hazard. The monitoring is far less extensive than it is in the US. But even if the monitoring were more comprehensive, this eruption did not come from one of the main volcanoes. This wasn’t Mount Meager. It was a small cone, and there are many of these in Canada. Hiding in the wilderness, how much do we know what they are brooding? And it seems that Tseax is a repeat offender which produced another lava flow around 1240. Neither do we know why so many people were killed. There is danger here.
Canada is not known for its volcanoes. Perhaps it should be.
Update: the image of the Tseax cone has been replaced after it was pointed out the original was wrong cone.