Snowshoe Lava Field
Template:Short description Template:Use Canadian English Template:Use mdy dates Template:Infobox landform The Snowshoe Lava Field (SLF) is a largely buried volcanic field at Mount Edziza in British Columbia, Canada. It reaches an elevation of Script error: No such module "convert". and engulfs more than Script error: No such module "convert". of the Big Raven Plateau and adjacent valleys with blocky lava flows. The Snowshoe Lava Field is the southernmost of two lava fields on the Big Raven Plateau, the other being the smaller Desolation Lava Field at the northern end of the plateau. It is in Mount Edziza Provincial Park and is part of the Mount Edziza volcanic complex, the latter of which consists of several other volcanic landforms such as shield volcanoes, stratovolcanoes, lava domes and cinder cones. Sezill Creek, Shaman Creek, Taweh Creek and several other unnamed streams in the Stikine River watershed drain the Snowshoe Lava Field. Access to the lava field is only by aircraft or by a network of horse trails from surrounding roads.
The Snowshoe Lava Field issued from several eruptive centres during the Holocene, most of which are clustered on the southern and western flanks of Ice Peak at elevations more than Script error: No such module "convert".. Volcanism in the lava field began with the eruption of three subglacial volcanoes when outlet glaciers of Mount Edziza's ice cap extended to lower elevations during the climax of a glacial advance. This was followed by the creation of four volcanoes whose eruptions were at first subaqueous and then transitioned subaerially. The youngest volcanoes in the Snowshoe Lava Field are completely subaerial in origin and issued most of the blocky lava flows comprising much of the current surface of the lava field. Alkali basalt and hawaiite of the Big Raven Formation are the main volcanic rocks comprising the Snowshoe Lava Field, but most of them are obscured by trachyte pumice of the Sheep Track Member.
Geography
The Snowshoe Lava Field is at the southern end of the Big Raven Plateau which is bounded by Mess Creek valley in the west, Kakiddi Creek valley in the east and the Klastline River valley in the north.Template:SfnTemplate:Sfn This intermontane plateau is one of the principal physiographic features of the Mount Edziza volcanic complex, a group of overlapping shield volcanoes, stratovolcanoes, lava domes and cinder cones that have formed over the last 7.5 million years.Template:Sfn The Snowshoe Lava Field reaches an elevation of Script error: No such module "convert". on the plateau, but remnants of the lava field decrease in elevation to Script error: No such module "convert". near Mess Creek.Template:SfnTemplate:SfnTemplate:Sfn It is one of two lava fields on the Big Raven Plateau, the other being the larger Desolation Lava Field at the northern end of the plateau.Template:Sfn Mount Edziza Provincial Park surrounds the Snowshoe Lava Field; it was founded in 1972 to showcase the volcanic landscape.Template:SfnTemplate:SfnTemplate:Sfn
Landforms
The Snowshoe Lava Field consists of more than Script error: No such module "convert". of blocky lava flows that issued from 12 eruptive centres.Template:Sfn Most of these eruptive centres are more than Script error: No such module "convert". in elevation and are located on the southern and western flanks of Ice Peak, the prominent south peak of Mount Edziza.Template:SfnTemplate:SfnTemplate:Sfn Cocoa Crater, Coffee Crater, Keda Cone, Tennena Cone and The Saucer are the only named eruptive centres in the Snowshoe Lava Field.Template:SfnTemplate:Sfn Tennena Cone on the upper western side of Ice Peak is the highest with an elevation of Script error: No such module "convert"., although the Global Volcanism Program gives a lower elevation of Script error: No such module "convert". for the cone.Template:SfnTemplate:SfnTemplate:Sfn Cocoa Crater and Coffee Crater on the western and southern flanks of Ice Peak attain elevations of Script error: No such module "convert"., respectively, and are so-named for their deep colours.Template:SfnTemplate:Sfn Keda Cone, Script error: No such module "convert". in elevation, is just south of Coffee Crater on the southern side of upper Taweh Creek.Template:Sfn The Saucer is a low, circular mound of lava Script error: No such module "convert". in elevation on the southern flank of Ice Peak bounded by concentric ridges of broken lava slabs.Template:SfnTemplate:SfnTemplate:Sfn
Drainage
As a part of the Mount Edziza volcanic complex, the Snowshoe Lava Field is drained entirely by streams within the Stikine River watershed.Template:SfnTemplate:Sfn Taweh Creek flows northwest along the southern edge of the lava field and is a tributary of Mess Creek.Template:SfnTemplate:Sfn At the northwestern end of the Snowshoe Lava Field is Sezill Creek, a northwesterly flowing tributary of Taweh Creek.Template:SfnTemplate:Sfn Shaman Creek at the southeastern end of the lava field flows east and north into Kakiddi Lake which is an expansion of Kakiddi Creek.Template:SfnTemplate:SfnTemplate:Sfn The source of Sezill Creek, Shaman Creek and several unnamed tributaries of Sezill Creek and Taweh Creek is Tencho Glacier which lies at the northeastern end of the Snowshoe Lava Field.Template:SfnTemplate:Sfn
Geology
The Snowshoe Lava Field is the second largest of the Holocene volcanic features on the Big Raven Plateau, succeeded only by the Desolation Lava Field.Template:Sfn It is also the second largest of three Holocene lava fields in the Mount Edziza volcanic complex; the smaller Mess Lake Lava Field covers about Script error: No such module "convert"..Template:SfnTemplate:Sfn The lava flows and volcanic cones comprising the Snowshoe Lava Field consist mainly of alkali basalt and hawaiite of the Big Raven Formation, the youngest geological formation of the Mount Edziza volcanic complex.Template:Sfn Nearly all of the surficial details of the Snowshoe Lava Field are obscured by pyroclastic fall of the Sheep Track Member; this is the only named geological member of the Big Raven Formation.Template:SfnTemplate:Sfn The pyroclastic fall consists of granular trachyte pumice that was deposited by a small, but violent VEI-3 eruption from the southwestern flank of Ice Peak around 950 CE.Template:SfnTemplate:Sfn
Individual eruptive centres of the Snowshoe Lava Field have been given numeronyms ranging from SLF-1 to SLF-12; greater numbers indicate a younger age.Template:Sfn SLF-1, SLF-2 and SLF-3 are alkali basaltic and formed subglacially when outlet glaciers of Mount Edziza's ice cap extended to lower elevations during the climax of a glacial advance.Template:SfnTemplate:Sfn SLF-4, SLF-5, SLF-6, SLF-7 and SLF-8 are volcanic cones formed when eruptions were at first subaqueous and then transitioned subaerially.Template:SfnTemplate:Sfn They consist of alkali basalt and minor hawaiite which are in the form of subaqueous and subaerial ejecta.Template:Sfn SLF-9, SLF-10, SLF-11 and SLF-12 are completely subaerial in origin and consist mainly of hawaiite.Template:SfnTemplate:Sfn They are in the form of pyroclastic cones with the exception of the youngest eruptive centre, SLF-12.Template:Sfn
The order of eruptions that formed the Snowshoe Lava Field are based on the degree of erosion and vegetation cover of the lava flows and volcanic cones, as well as the order in which the lava flows overlap.Template:Sfn Most of the lava ponded onto the surrounding Big Raven Plateau in the form of broad, thick sheets, but some of it also travelled into neighbouring valleys; the largest of these valley-filling lava flows is located at the head of Taweh Creek.Template:SfnTemplate:Sfn The transition from subglacial to subaerial volcanism in the Snowshoe Lava Field is attributed to retreat of glaciers from lower elevations.Template:Sfn These glaciers are now Script error: No such module "convert". away from their trim lines, but during their maximum advance, they had an ice surface that rose Script error: No such module "convert". above their current levels.Template:Sfn
As a part of the Mount Edziza volcanic complex, the Snowshoe Lava Field lies within a broad area of volcanoes and lava flows called the Northern Cordilleran Volcanic Province, which extends from northwestern British Columbia northwards through Yukon into easternmost Alaska.Template:SfnTemplate:Sfn The dominant rocks comprising these volcanoes are alkali basalts and hawaiites, but nephelinite, basanite and peralkaline phonolite, trachyte and comendite are locally abundant. These rocks were deposited by volcanic eruptions from 20 million years ago to as recently as a few hundred years ago. The cause of volcanic activity in the Northern Cordilleran Volcanic Province is thought to be due to rifting of the North American Cordillera driven by changes in relative plate motion between the North American and Pacific plates.Template:Sfn
Subglacial centres
SLF-1 is Tennena Cone which is one of the few glaciovolcanic features at Mount Edziza that have been investigated in detail.Template:SfnTemplate:Sfn It has been mapped into four subdivisions, all of which are exposed on the eastern, southern and western flanks of the cone.Template:Sfn The first subdivision is massive and crudely bedded tuff breccia exposed in near-vertical cliffs on the flanks of Tennena Cone. Exposed in scarps on the eastern and southern flanks of Tennena Cone is lapilli tuff of the second subdivision which forms Script error: No such module "convert". beds. Two Script error: No such module "convert". wide dikes comprise the third subdivision, both of which consist of fragmented plagioclase-phyric rock.Template:Sfn The first dike forms a Script error: No such module "convert". high remnant and is exposed on the eastern flank of Tennena Cone whereas the second dike is exposed Script error: No such module "convert". to the south. In addition to occurring on the eastern flank, the second dike is also exposed on the western flank and along the summit ridge of Tennena Cone.Template:Sfn The fourth subdivision consists of pillow and fluidal lavas that overlie tuff breccia in the northern section of the cone.Template:Sfn
About Script error: No such module "convert". south of Tennena Cone is SLF-2, a smaller crescent-shaped nunatak protruding through the western portion of Tencho Glacier.Template:SfnTemplate:Sfn It may be the remains of a parasitic cone closely related to Tennena Cone or it may be an extension of Tennena Cone since it consists of similar geology.Template:Sfn SLF-3 at the southern terminus of Tencho Glacier is a crescent-shaped ridge that has been overridden by glacial ice. Crudely bedded tuff breccia and quenched flow fragments comprise the entire ridge, which may be the remains of a tuff ring that formed in a meltwater lake.Template:Sfn In contrast to Tennena Cone which was constructed on a steep slope, SLF-3 is underlain by flat-lying terrain of the Big Raven Plateau.Template:SfnTemplate:Sfn This likely resulted in their differing geomorphology; the Tennena Cone eruption sent both lava and meltwater down the steep western flank of Ice Peak whereas ejecta from the SLF-3 eruption ponded inside a meltwater lake when Tencho Glacier extended onto the flat plateau surface.Template:Sfn
Transitional centres
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SLF-4 and SLF-5 are located on the western and southern margins of Tencho Glacier, respectively.Template:SfnTemplate:Sfn They are within the trim lines of this glacier and have been reduced to low, drumlin-like ridges from glacial ice overriding them. A short distance beyond the trim lines of Tencho Glacier are SLF-6, SLF-7 and SLF-8; SLF-7 is Coffee Crater. These eruptive centres contrast from SLF-4 and SLF-5 in that they have not been overridden by glacial ice, which has allowed them to retain their central craters and their original conical forms. However, their inner structures have been partially exposed due to sufficient erosion. All five eruptive centres consist of a lower succession of brown subaqueous tuff breccia and an upper sequence of subaerial cinders, spatter and bombs which have been stained red due to extreme oxidation.Template:Sfn
Lava flows from the transitional centres have been mostly buried under younger basalt of the subaerial centres, as well as pumice of the Sheep Track Member.Template:Sfn However, they are exposed where streams have eroded the overlying volcanic deposits. The lava flows are also locally exposed along streams that have cut through older lava flows below.Template:Sfn
Subaerial centres
Most of the blocky lava flows comprising much of the current surface of the Snowshoe Lava Field originated from eruptive centres SLF-9, SLF-10 and SLF-11, all of which are pyroclastic cones.Template:Sfn These cones consist of agglutinated lapilli, bombs and spatter which have been stained red due to extreme oxidation.Template:Sfn SLF-9 is Keda Cone at the southern end of the lava field whereas SLF-10 is Cocoa Crater near the centre of the lava field.Template:SfnTemplate:Sfn Cocoa Crater issued a Script error: No such module "convert". wide lava flow that cascaded into upper Sezill Creek canyon, but the most voluminous lava flows originated from Keda Cone and SLF-11.Template:SfnTemplate:Sfn SLF-11 is the only subaerial eruptive centre in the Snowshoe Lava Field with no name.Template:SfnTemplate:Sfn
Lava flows from Keda Cone and SLF-11 engulfed a more than Script error: No such module "convert". wide and Script error: No such module "convert". long area on the Big Raven Plateau prior to entering the upper valley of Taweh Creek. At the head of Taweh Valley, the Keda Cone and SLF-11 flows converged to form a relatively narrow tongue of lava that travelled for at least another Script error: No such module "convert". to near Mess Creek. Erosion has removed nearly all of the final Script error: No such module "convert". of this lava tongue; small remnants are present along the banks of lower Taweh Creek near the junction with Mess Creek.Template:SfnTemplate:Sfn None of the lava flows from these three subaerial eruptive centres display any evidence of having been quenched by water, nor do any of the pyroclastic cones.Template:Sfn
The youngest subaerial eruptive centre, SLF-12, is The Saucer which appears to be the remains of a fissure instead of a pyroclastic cone.Template:Sfn This vent south of Tencho Glacier issued lava that travelled eastward and westward; the Script error: No such module "convert". long eastward lava flow entered the head of Shaman Creek whereas the relatively thick westward lava flow spread onto the Big Raven Plateau in the form of broad lobes.Template:SfnTemplate:Sfn In contrast to the neighbouring Coffee Crater lava flows which are overlain by thick drifts and pockets of Sheep Track pumice, The Saucer and its lava flows are only sparsely covered with very fine pumice of the Sheep Track Member.Template:Sfn The sparsity of this very fine pumice on The Saucer and its lava flows suggests they were extruded sometime after the explosive Sheep Track eruption which may have occurred around 950 CE.Template:SfnTemplate:Sfn Because very fine pumice is susceptible of being blown by wind, it could easily be wind-blown material carried in from neighbouring pumice beds long after the Sheep Track eruption had occurred.Template:Sfn
Accessibility
As part of the Mount Edziza volcanic complex, the Snowshoe Lava Field is in a remote location with no established road access.Template:SfnTemplate:Sfn The closest roads are the Stewart–Cassiar Highway to the east and the Telegraph Creek Road to the northwest, both of which extend within Script error: No such module "convert". of the lava field.Template:SfnTemplate:SfnTemplate:Sfn Extending from these roads are horse trails that provide access to the Mount Edziza volcanic complex.Template:Sfn From Telegraph Creek, the Buckley Lake Trail extends about Script error: No such module "convert". southeast along Mess Creek and Three Mile Lake. It then traverses about Script error: No such module "convert". northeast along Dagaichess Creek and Stinking Lake to the northeastern end of Buckley Lake where it meets with the Klastline River Trail and the Buckley Lake to Mowdade Lake Route.Template:Sfn
To the east, the roughly Script error: No such module "convert". long Klastline River Trail begins at the community of Iskut on the Stewart–Cassiar Highway.Template:Sfn It extends northwest and west along the Klastline River for much its length.Template:Sfn The trail enters Mount Edziza Provincial Park at about Script error: No such module "convert". where Kakiddi Creek drains into the Klastline River.Template:Sfn After entering Mount Edziza Provincial Park, the Klastline River Trail traverses northwest along the Klastline River for about Script error: No such module "convert". and then crosses the river north of the Big Raven Plateau.Template:Sfn From there, the Klastline River Trail traverses west for about Script error: No such module "convert". to the northeastern end of Buckley Lake where it meets with the Buckley Lake Trail and Buckley Lake to Mowdade Lake Route.Template:Sfn
The Buckley Lake to Mowdade Lake Route traverses south from Buckley Lake along Buckley Creek and gradually climbs onto the northern end of the Big Raven Plateau where Tsekone Ridge and landforms of the Desolation Lava Field such as Eve Cone and Sidas Cone are visible along the route.Template:SfnTemplate:SfnTemplate:SfnTemplate:Sfn Most of the Buckley Lake to Mowdade Lake Route is marked by a series of rock cairns from Tsekone Ridge onwards.Template:Sfn At the southern end of the Buckley Lake to Mowdade Lake Route is the Snowshoe Lava Field where Tennena Cone, Coffee Crater and Keda Cone occur. The route continues east through Shaman Creek valley and then turns southeast to the northern end of Mowdade Lake.Template:SfnTemplate:Sfn
The distance between Buckley Lake and Mowdade Lake is about Script error: No such module "convert"., but the hiking length between these two lakes varies depending on the route taken; it can take a minimum of 7 days to hike the Buckley Lake to Mowdade Lake Route. The weather can change extremely fast along this hiking trail.Template:Sfn Buckley Lake is large enough to be used by float-equipped aircraft, but landing on this lake with a private aircraft requires a letter of authorization from the BC Parks Stikine Senior Park Ranger.Template:Sfn Mowdade Lake about Script error: No such module "convert". southeast of the Snowshow Lava Field is also of significant size and does not require a letter of authorization from the BC Parks Stikine Senior Park Ranger to land on it with a private aircraft.Template:SfnTemplate:Sfn Alpine Lakes Air and BC Yukon Air are the only air charter companies permitted to provide access to this area via aircraft.Template:Sfn
See also
References
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Sources
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