Tseax Cone
Encyclopedia
The Tseax Cone also called the Tseax River Cone or alternately the Aiyansh Volcano, is a young cinder cone
and adjacent lava flows associated with the Nass Ranges
and the Northern Cordilleran Volcanic Province
. It is located east of Crater Creek at outlet of Melita Lake, southeast of Gitlakdamix
and 60 kilometres (37 mi) north of Terrace, British Columbia
, Canada
.
The volcano is situated in a valley above and east of the Tseax River
, about 20 kilometres (12 mi) south of the river's junction with the larger Nass River
. The Tseax Cone is one of the most accessible volcanic centres in British Columbia.
The Tseax Cone has been the site of some of the youngest volcanic eruptions in Canada. It has been active at least twice in the past few hundred years and other remnants of lava flows exist in the area. It is 290 m (951 ft) in diameter at its base and rests on the remnants of an earlier and somewhat larger, dissected, 460 m (1,509 ft) diameter cone. The volcano is made of volcanic bomb
s and cinder
s with a crater
at its summit where a churning lava lake
ponded and overflowed its rim during the 18th century.
Volcanism at the Tseax Cone is caused by the rift
ing of the Earth's crust
where two parts of the North American Plate
are breaking apart. The cause of this rifting is the result of the Pacific Plate
sliding northward along the Queen Charlotte Fault
, on its way to the Aleutian Trench
.
The lava
emitted in eruptions at the Tseax Cone is fluid. Its lavas are made of basalt
, a common grey to black or dark brown extrusive volcanic rock
low in silica content (the lava is mafic
) that is usually fine-grained due to rapid cooling of lava on the Earth's surface. Pāhoehoe is found at the volcano, which have a smooth, billowy, undulating, or ropy surface. A pāhoehoe flow typically advances as a series of small lodes and toes that continually break out from a cooled crust. It also forms lava tube
s where the minimal heat loss maintains low viscosity. However, there is also basaltic lava at the volcano characterized by a rough or rubby surface composed of clinker called 'a'ā. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface.
The Tseax Cone was the source for a major lava flow eruption around the years 1750 or 1775 that travelled into the Tseax River
, damming it and forming Lava Lake
. The flow subsequently travelled 11 km (7 mi) north to the Nass River
, where it filled the flat valley floor for an additional 10 km (6 mi), making the entire lava flow approximately 22.5 km (14 mi) long.
The Nass River valley contains abundant tree casts and lava tube
s. The tree casts were formed when the hot lava flow burned out tree trunks leaving holes in the lava. Lava tubes formed when the low-viscosity hot alkali basalt
ic lava travelled beneath the surface which eventually flowed out leaving the crust as the roof and walls of the tubes.
Native legends of the Nisga'a
people tell of a prolonged period of disruption by the volcano, including the destruction of two Nisga'a villages. Several Nisga'a people dug pits for shelter but approximately 2,000 Nisga'a people died due to volcanic gas
es and poisonous smoke (most likely carbon dioxide
). The Nisga'a story of the destruction is Canada's worst known geophysical disaster.
The lava beds, which reach 12 m (39 ft) above the road in some places, are the burial ground of these people. It is the only eruption in Canada for which legends of First Nations
people have been verified. The lava flow can also be found near modern Nisga'a villages, such as Gitlakdamix
. This eruption is just one of hundreds that have modified the landscape of western Canada over the past million years.
It has recently been suggested that the Tseax eruption was triggered by the Cascadia earthquake
of 26 January 1700. This was the most powerful earthquake during the last 1000 years in the Pacific Northwest. If this theory is substantially correct, then another hazard must be added to those risks associated with major megathrust earthquakes.
quietly rests in the 17,683-hectare Nisga'a Memorial Lava Beds Provincial Park
. But the Tseax Cone could reawaken at any time. Before the tragic 18th century eruption, the volcano erupted in 1325. The gases emitted by the volcano are evidence that the volcano is still active and potentially dangerous. Signs of unrest will almost certainly precede any future eruptive activity from the Tseax Cone, and its past activity is an extremely important factor for hazard assessment.
If the Tseax Cone erupts again, there may be a repeat of the poisonous gas disaster (as happened to the Nisga'a
people). It could cause forest fire
s and could potentially dam local rivers (as happened to the Tseax and Nass River) if the volume of the lava flows are large enough. If the lava flows again reach the Nass River, it could have disastrous short-term consequences for the important salmon fisheries on the Nass River
system.
People living in the region still have limited knowledge of the dangers of the Tseax Cone should it become active or erupt. The relative lack of knowledge on the previous eruptions would require modern monitoring and include studies of the gases emitted by the volcano. Warning systems for people living downslope from the volcano would need to be created.
Cinder cone
According to the , Cinder Cone is the proper name of 1 cinder cone in Canada and 7 cinder cones in the United States:In Canada: Cinder Cone In the United States:...
and adjacent lava flows associated with the Nass Ranges
Nass Ranges
The Nass Ranges are a mountain range north of the Skeena River, west of Hazelton, and northeast of Terrace, British Columbia, Canada. It is associated with the Hazelton Mountains, which in turn form part of the Interior Mountains.-Volcanic eruption:...
and the Northern Cordilleran Volcanic Province
Northern Cordilleran volcanic province
The Northern Cordilleran Volcanic Province , formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America...
. It is located east of Crater Creek at outlet of Melita Lake, southeast of Gitlakdamix
Gitlakdamix, British Columbia
Gitlakdamix or Gitlaxt'aamiks or New Aiyansh is a Nisga'a Village about 100km north of Terrace, in the heart of the Nass River valley, Canada. It is one of four Nisga'a villages...
and 60 kilometres (37 mi) north of Terrace, British Columbia
Terrace, British Columbia
Terrace is a city on the Skeena River in British Columbia, Canada. The Kitselas people, a tribe of the Tsimshian Nation, have lived in the Terrace area for thousands of years. The community population fell between 2001 and 2006 from 12,109 with a regional population of 19,980 to 11,320 and...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
The volcano is situated in a valley above and east of the Tseax River
Tseax River
The Tseax River, also known as Ksi Sii Aks in the Nisga'a language, is a tributary of the Nass River in northwestern British Columbia, Canada. It is most notable as the namesake of Tseax Cone, a volcano within its basin that was responsible for an eruption that killed 2,000 Nisga'a people. Prior...
, about 20 kilometres (12 mi) south of the river's junction with the larger Nass River
Nass River
The Nass River is a river in northern British Columbia, Canada. It flows from the Coast Mountains southwest to Nass Bay, a sidewater of Portland Inlet, which connects to the North Pacific Ocean via the Dixon Entrance...
. The Tseax Cone is one of the most accessible volcanic centres in British Columbia.
Geology
Volcanic bomb
A volcanic bomb is a mass of molten rock larger than 65 mm in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains...
s and cinder
Cinder
A cinder is a pyroclastic material. Cinders are extrusive igneous rocks. Cinders are similar to pumice, which has so many cavities and is such low-density that it can float on water...
s with a crater
Volcanic crater
A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...
at its summit where a churning lava lake
Lava lake
Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified...
ponded and overflowed its rim during the 18th century.
Volcanism at the Tseax Cone is caused by the rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ing of the Earth's crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
where two parts of the North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
are breaking apart. The cause of this rifting is the result of the Pacific Plate
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
sliding northward along the Queen Charlotte Fault
Queen Charlotte Fault
The Queen Charlotte Fault is an active transform fault, located between the North American Plate and the Pacific Plate, Canada's equivalent of the San Andreas Fault. The Queen Charlotte Fault forms a triple junction on its south with the Cascadia subduction zone and the Explorer Ridge...
, on its way to the Aleutian Trench
Aleutian Trench
The Aleutian Trench is a subduction zone and oceanic trench which runs along the southern coastline of Alaska and the adjacent waters of northeastern Siberia off the coast of Kamchatka Peninsula. It is classified as a "marginal trench" in the east as it runs along the margin of the continent, and...
.
The lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
emitted in eruptions at the Tseax Cone is fluid. Its lavas are made of basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
, a common grey to black or dark brown extrusive volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...
low in silica content (the lava is mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
) that is usually fine-grained due to rapid cooling of lava on the Earth's surface. Pāhoehoe is found at the volcano, which have a smooth, billowy, undulating, or ropy surface. A pāhoehoe flow typically advances as a series of small lodes and toes that continually break out from a cooled crust. It also forms lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
s where the minimal heat loss maintains low viscosity. However, there is also basaltic lava at the volcano characterized by a rough or rubby surface composed of clinker called 'a'ā. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface.
18th century eruption
Tseax River
The Tseax River, also known as Ksi Sii Aks in the Nisga'a language, is a tributary of the Nass River in northwestern British Columbia, Canada. It is most notable as the namesake of Tseax Cone, a volcano within its basin that was responsible for an eruption that killed 2,000 Nisga'a people. Prior...
, damming it and forming Lava Lake
Lava Lake
Lava Lake is a lava dammed lake located in northwestern British Columbia, Canada. The lake lies within the Nisga'a Memorial Lava Beds Provincial Park, which includes fishing, hiking and other features.-Formation:...
. The flow subsequently travelled 11 km (7 mi) north to the Nass River
Nass River
The Nass River is a river in northern British Columbia, Canada. It flows from the Coast Mountains southwest to Nass Bay, a sidewater of Portland Inlet, which connects to the North Pacific Ocean via the Dixon Entrance...
, where it filled the flat valley floor for an additional 10 km (6 mi), making the entire lava flow approximately 22.5 km (14 mi) long.
The Nass River valley contains abundant tree casts and lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...
s. The tree casts were formed when the hot lava flow burned out tree trunks leaving holes in the lava. Lava tubes formed when the low-viscosity hot alkali basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic lava travelled beneath the surface which eventually flowed out leaving the crust as the roof and walls of the tubes.
Native legends of the Nisga'a
Nisga'a
The Nisga’a , often formerly spelled Nishga and spelled in the Nisga’a language as Nisga’a, are an Indigenous nation or First Nation in Canada. They live in the Nass River valley of northwestern British Columbia. Their name comes from a combination of two Nisga’a words: Nisk’-"top lip" and...
people tell of a prolonged period of disruption by the volcano, including the destruction of two Nisga'a villages. Several Nisga'a people dug pits for shelter but approximately 2,000 Nisga'a people died due to volcanic gas
Volcanic gas
|250px|thumb|right|Image of the [[rhyolitic]] [[lava dome]] of [[Chaitén Volcano]] during its 2008-2010 eruption.Volcanic gases include a variety of substances given off by active volcanoes...
es and poisonous smoke (most likely carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
). The Nisga'a story of the destruction is Canada's worst known geophysical disaster.
The lava beds, which reach 12 m (39 ft) above the road in some places, are the burial ground of these people. It is the only eruption in Canada for which legends of First Nations
First Nations
First Nations is a term that collectively refers to various Aboriginal peoples in Canada who are neither Inuit nor Métis. There are currently over 630 recognised First Nations governments or bands spread across Canada, roughly half of which are in the provinces of Ontario and British Columbia. The...
people have been verified. The lava flow can also be found near modern Nisga'a villages, such as Gitlakdamix
Gitlakdamix, British Columbia
Gitlakdamix or Gitlaxt'aamiks or New Aiyansh is a Nisga'a Village about 100km north of Terrace, in the heart of the Nass River valley, Canada. It is one of four Nisga'a villages...
. This eruption is just one of hundreds that have modified the landscape of western Canada over the past million years.
It has recently been suggested that the Tseax eruption was triggered by the Cascadia earthquake
Cascadia earthquake
The 1700 Cascadia earthquake was a magnitude 8.7 to 9.2 megathrust earthquake that occurred in the Cascadia subduction zone on January 26, 1700. The earthquake involved the Juan de Fuca Plate underlying the Pacific Ocean, from mid-Vancouver Island in British Columbia, Canada, south along the...
of 26 January 1700. This was the most powerful earthquake during the last 1000 years in the Pacific Northwest. If this theory is substantially correct, then another hazard must be added to those risks associated with major megathrust earthquakes.
Future and present
As of 1993, the volcanoVolcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
quietly rests in the 17,683-hectare Nisga'a Memorial Lava Beds Provincial Park
Nisga'a Memorial Lava Beds Provincial Park
Nisga'a Memorial Lava Bed Provincial Park is a provincial park in the Nass River valley in northwestern British Columbia, Canada, about 80 kilometres north of Terrace, and near the Nisga'a Villages of Gitlakdamix and Gitwinksihlkw.The park was established by Order in Council on April 29, 1992,...
. But the Tseax Cone could reawaken at any time. Before the tragic 18th century eruption, the volcano erupted in 1325. The gases emitted by the volcano are evidence that the volcano is still active and potentially dangerous. Signs of unrest will almost certainly precede any future eruptive activity from the Tseax Cone, and its past activity is an extremely important factor for hazard assessment.
If the Tseax Cone erupts again, there may be a repeat of the poisonous gas disaster (as happened to the Nisga'a
Nisga'a
The Nisga’a , often formerly spelled Nishga and spelled in the Nisga’a language as Nisga’a, are an Indigenous nation or First Nation in Canada. They live in the Nass River valley of northwestern British Columbia. Their name comes from a combination of two Nisga’a words: Nisk’-"top lip" and...
people). It could cause forest fire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
s and could potentially dam local rivers (as happened to the Tseax and Nass River) if the volume of the lava flows are large enough. If the lava flows again reach the Nass River, it could have disastrous short-term consequences for the important salmon fisheries on the Nass River
Nass River
The Nass River is a river in northern British Columbia, Canada. It flows from the Coast Mountains southwest to Nass Bay, a sidewater of Portland Inlet, which connects to the North Pacific Ocean via the Dixon Entrance...
system.
People living in the region still have limited knowledge of the dangers of the Tseax Cone should it become active or erupt. The relative lack of knowledge on the previous eruptions would require modern monitoring and include studies of the gases emitted by the volcano. Warning systems for people living downslope from the volcano would need to be created.
See also
- Northern Cordilleran Volcanic ProvinceNorthern Cordilleran volcanic provinceThe Northern Cordilleran Volcanic Province , formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America...
- List of volcanoes in Canada
- List of Northern Cordilleran volcanoes
- Volcanism of Canada
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
- List of disasters in Canada
- List of Canadian disasters by death toll
- List of volcanic eruptions by death toll