Canadians expect all kinds of natural disasters to befall them including floods, hurricanes, landslides, gale winds and forest fires. I would wager my mother-in-law (honestly, a very nice woman) that not many Canadians are aware of the volcanic activity that is in Canada, never mind that Canada's second worst natural disaster in terms of lives lost, was due to a volcanic eruption.
The folklore and legends of the Nisga'a people's have long told of a period of unrest by a volcano that included the complete destruction of two villages and approximately two thousand of their people and those affected most by it – the Nisga'a people - had weaved it into their folklore and oral history despite the loss of life, villages and disruption to way of life.
The legend, abounds with variations but generally speaking, goes a little like this:
Two male children playing near the waters of the Nass caught themselves a salmon. As is the nature of boys sometimes, they slit open the fish's back and inserted two lit pieces of wood and released the fish, both finding great amusement in the hectic swimming and smoking fish. The caught yet another and this time shoved a piece of shale into its back and watched it struggle too, to their mirth.
An elder walked by and warned the children to 'take care what you do ... for the salmon will curse you and the creator will respond in kind' he said. It was then the ground began to shake and tremble under their feet, the children ran for home and the elder sent out scouts. Natures harmony has been upset he thought with a glance to the now dead salmon.
From the tops of a nearby small mountain the scout seen smoke and flames moving closer. He ran back to warn the people of the impending fiery doom. Panicked some ran up the mountain and others to the Nass River. They were all killed by the lava.
Watching broken-hearted at the destruction of their homes, a powerful supernatural being called Gwaxts'agat emerged from the mountain. For days he fought the lava using his great nose to blow on it and cool it. Once he succeeded he simply returned to the mountain where the being remains to this day.
Science has verified their legend or folklore as more truthful than fanciful story telling, which is a first in Canada. For this particular eruption, over the last million or so years many eruptions have shaped the lands, the legend and some science of the existing cooled rock left behind is the only record of it happening.
Sometime during the mid to late eighteenth century (some sources say no earlier than 1750 and no later than 1775; Oregon State University lists the eruption as happening in 1730), the Tseax Cone, which is a smaller volcano almost a thousand feet in diameter, erupted or perhaps more accurately vented a major lava flow.
Our volcanoes may erupt politely but it's trail of destruction was no joking matter. The lava released travelled towards and eventually into the Tseax River forming Lava Lake by damming the river. The flow then carried on north to the Nass River eleven kilometre away and for an additional ten kilometre filled the flat valley floor of the Nass River system.
Along the way it destroyed two villages of the Nisga'a – oral traditions name them as Wii Lax K'abit and Lax Ksiluux. The Nisga'a people's of the time had tried to prepare for what they thought was coming and dug pits for shelter, at the time of the 'eruption' as word spread people panicked and some ran up the mountain and others ran for the River.
The original explosion or eruption would have released poisonous gases and carbon dioxide. It was these gases that likely killed the victims of this event and not the lava. The entire lava flow is considered by the First Peoples has a headstone for a grave and consider taking pieces of the now hardened lava flow as desecration of their dead.
The Nass River Valley shows lava tubes and tree casts, which gives researchers a clearer idea of what kind of eruption this was, what type of lava and the types of gases that would have preceded the lava flow. The lava beds, in some areas, are thirty-nine feet above the roads helping to estimate the amount or volume of lava that erupted.
The Northern Cordilleran Volcanic Province or as it was once called, Stikine Volcanic Belt, is a geological province - which is an area with similar geological attributes such as basins - whose similarity lies in volcanoes from two periods of geological history - twenty million years ago and right up to today.
Essentially it's a belt of land or a corridor of land hundreds of kilometres wide consisting of very old to very young volcanoes running north through the provinces of British Columbia and Yukon in Canada and passing into United States Alaska's eastern territory. This belt of land formed due to extensional (pulling apart) cracking of tectonic plates of the continent North America.
The term Stikine Volcanic Belt was first defined by two members of the Geological Survey of Canada in 1991 – Christopher Yorath and Jack Souther. As more research, with regards to mapping, dating and understanding the area known as Western Cordillera, the Stikine Volcanic Belt expanded to include areas further from its original geographic area (southern British Columbia). Some of the further areas ended up getting renamed, the northern area of the Stikine was now called the Northern Cordilleran Volcanic Province(northern British Columbia).
The Northern Cordilleran Volcanic Province is viewed by many academics as part of the Pacific Ring of Fire, which many know is the area in the Pacific Ocean with volcanic activity and earthquakes. It's technically part of a gap in the Ring of Fire, and many of the volcanoes in the Ring of Fire were formed by ocean crusts where as the Cordilleran Province origins are found in continental rifting.
The northern area tends to have smaller volcanoes than the southern area, but Level Mountain Range is the oldest and largest of these northern volcanoes. It also has a large number of smaller, connected 'volcanoes ' throughout the area, these smaller volcanoes are called cinder cones.
Cinder Cones are 'mini volcanoes' formed by accumulation of lava around a vent found on the surfaces of a surrounding larger volcanic area. They form when ash and other volcanic materials are thrown outwards from an explosive event.
The Aiyansh Volcano is a young, active cinder cone a part of Level Mountain Range, known today as the Tseax Cone located near the Nass Range and Nass River in British Columbia. This cinder cone is the one behind the legend of the Nisga'a as well as being the site of some of the youngest volcanic eruptions in Canada.
The Tseax cone is 951 ft in diameter from the base and is a part of an earlier (dated to about the twelfth century) and larger, broken up cone that is 1,059 ft in diameter and at its summit - a lava lake, created when the volcano overflowed during the eighteenth century.
There is some argument among the geological academics of whether this cone-in-a-cone is the result of the twelfth century eruption or one created closer to the eighteenth century eruption. The activity at this site is caused by rifting of the North American Plate and the Pacific Plate, which cause earthquakes as well and an earthquake is known to have happened in the early eighteenth century.
The Science Behind The Killer Flow
We see huge chunks of rocks jutting from the earth, but all the exciting parts of a volcano are inside and deep under the earth. In the very pits of a volcano is where the pressure builds, the core is where the enormous amount of heat and other forces combine to create lava, the action of tectonic plates create the disruption that start the process of pressure building and thus eruption.
Lava is the rock, heated and melted, that's expelled during eruptions. Eruptions happen during periods of unrest with the Earth's tectonic plates (such as an earth quake) causing a build-up of heat and pressure that needs to be released, thus the tip of volcanoes spewing lava (tips are the weakest parts).
The viscosity of lava helps to determine how it will behave. Lavas with high viscosity such as basaltic lava, tend to flow slower, form semi-solid blocks that resist flow, clog easier, they tend to entrap gases which can be released (almost all at once) as they rise to the surface and has shown by the Tseax Cone Eruption can kill quickly.
Low viscosity lava travels quicker and tends to form channels, rivers and puddles of molten rock, it tends to release the gases as they are formed and less risk of concentrated amounts that can kill and they form on broad shields rather than steep cones.
One would think that a lava flow is the flow of lava from the spewing and erupting volcano. But you would be wrong. Lava flows are indeed the outward poring of lava, but they are created during non explosive eruptions. More akin to a pot boiling over rather than say a pressure cooker exploding.
There is a wealth of information to be obtained from volcanic morphology, the behaviour of lavas and of eruptions, even if buried or very old. For example knowing the Tseax Cone is basaltic, tells us it would have travelled slowly, taking the path of least resistance and capable of releasing large amounts of deadly gases.
The cooled lava at the volcano site shows two different types of flows that were emitted - both are basalt and fluid in nature, or mafic lava, yet each leave distinctive and highly different looking rocks behind.
Mafic (basaltic) lavas are known by their high ferromagnesian content and are known to erupt at temperatures over 950 degrees Celsius. Any geologist just looking at the cooled lava flows will recognize the signs or left overs of mafic lava since they tend to produce flood basalt fields and travels a far distance from the originating vent. Most mafic lava flows are pahoehoe or 'A'a type of lava.
As the thicker lava moves slowly the clinkers (the rubbley outside surface) have cooled fragments at the leading edge and tumble-down ahead of the lava flow only to be reburied when the lava catches up. This will produce lava fragments both top and bottom of the flow but also leads to the creation of up to ten feet big balls of ... well rock. This angular and sharp texture makes an 'A'a flow easily seen from a orbiting satellite due to it being a strong radar reflector.
The second type of flow seen at the Tseax Cone eruption site is Pahoehoe, again we can thank Charles Dutton for the Hawaiian word, but it is suitable as it accurately reflects the appearance of the lava, it means smooth or unbroken. And Pahoehoe lava flows appear quite smooth and billowy; a little like gentle waves on land.
While both the 'A'a and the Pahoehoe style of flows conceals lava beneath a surface crust – the difference being that the surface crust is much smoother and the lava in the core of it is more fluid like than the 'A'a lava flows. It also tends to form lava tubes, create bizarre shapes that are often called lava sculptures.
A Pahoehoe can turn into a thicker and slower 'A'a flow as it moves further away from the source and cools while picking up new rocks and sediment. This smooth rock is a very poor reflector and is difficult to see from orbiting satellites, even if it is larger than a more easily seen rough surfaced lava flow.
Today, the area has been converted into a 17,893 square kilometre provincial park called the Nisga'a Memorial Lave Beds Provincial Park, it was established in 1992, expanded in 1995, in 2000 it was included in the Nisga'a Treaty, and is jointly managed by both the Canadian Government and the Nisga'a peoples, which is a first in Canada. It is not the only co-managed park in Canada today – The Gwaii Haanas National Park is another example of First Nations and Government working together.
The volcano is in the parks grounds but sits quietly today only showing light activity in the form of gases emitted. But it could reawaken at any time and Canada could suffer a repeat of history. Knowing more today about not just volcanoes in general but the areas they are found in allows an opportunity to both monitor and implement strategies to minimize loss of property and life.
If the cone were to erupt again – I say if as some cones only erupt once – we would likely see the poisonous gas effect again, maybe forest fires, the damming of rivers in the way of the flow (as seen with Tseax and Nass River in the mid-eighteenth century) and short-term damage to the salmon fisheries on the Nass River system.
Due to the general lack of historical data on earlier eruptions, the missing modern monitoring and studies of the volcano and its gases today, pose problems for those attempting to safeguard Canadians living down slope the volcano, with a warning system of some types. The people of the area still have a limited understanding of the dangers of the Tseax Cone (or other volcanoes in the area) should it become active or worse, erupt again.
It can be hard to understand how a slow-moving, non erupting volcanic eruption, could kill upwards of two thousand people. We really do not know all the details and can only piece together what we believe they did or went through using Nisga'a folk-lore and science, both of which are limited.
Open to the public, there are a number of attractions and features in the park besides volcanic based features such as cinder cones, tree casts and lava tubes. It also boasts waterfalls, pools, caves, stunning scenery, an interpretive centre in a traditional Nisga'a longhouse and houses the cultural history and traditions of the Nisga'a peoples.