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Coordinates: 57°39′0″N 130°40′0″W / 57.65000°N 130.66667°W / 57.65000; -130.66667
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Snowshoe Lava Field
Lava field
A snow-covered plateau with four small cone-shaped mounds in the foreground and a much larger flat-topped mountain in the background
The southern end of the Big Raven Plateau with the Snowshoe Lava Field in the foreground
Relief map of British Columbia pinpointing the location of the Snowshoe Lava Field
Relief map of British Columbia pinpointing the location of the Snowshoe Lava Field
Snowshoe Lava Field
Location in British Columbia
Coordinates: 57°39′0″N 130°40′0″W / 57.65000°N 130.66667°W / 57.65000; -130.66667[1]
LocationBritish Columbia, Canada[2]
Part ofMount Edziza complex[2]
AgeHolocene[2]
Formed byVolcanism[3]
GeologyAlkali basalt, hawaiite[2]
Area
 • TotalMore than 40 km2 (15 sq mi)[4]
Elevation2,390 m (7,840 ft)[5]
DesignationMount Edziza Park[2][6]
Map Location in Mount Edziza Provincial Park

The Snowshoe Lava Field (SLF) is a volcanic field at Mount Edziza in British Columbia, Canada.












Geography

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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.[2][6] 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.[7] The Snowshoe Lava Field reaches an elevation of 2,390 m (7,840 ft) on the plateau, but remnants of the lava field decrease in elevation to 914 m (2,999 ft) near Mess Creek.[2][5][8] 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.[2] Mount Edziza Provincial Park surrounds the Snowshoe Lava Field; it was founded in 1972 to showcase the volcanic landscape.[2][6][9]

The Snowshoe Lava Field consists of more than 40 km2 (15 sq mi) of blocky lava flows that issued from 12 eruptive centres.[10] Most of these eruptive centres are more than 1,800 m (5,900 ft) in elevation and are located on the southwestern flank of Ice Peak, the prominent south peak of Mount Edziza.[4][11] Cocoa Crater, Coffee Crater, Keda Cone, Tennena Cone and The Saucer are the only named eruptive centres in the Snowshoe Lava Field.[12] Tennena Cone on the upper western side of Ice Peak is the highest with an elevation of 2,390 m (7,840 ft), although the Global Volcanism Program gives a lower elevation of 2,350 m (7,710 ft) for the cone.[1][5][13] Cocoa Crater and Coffee Crater attain elevations of 2,117 and 2,000 m (6,946 and 6,562 ft), respectively, and are so-named for their deep colours.[1][9] Keda Cone, 1,980 m (6,500 ft) in elevation, is just south of Coffee Crater on the southern side of upper Taweh Creek.[1] The Saucer is a low, circular mound of lava 1,920 m (6,300 ft) in elevation bounded by concentric ridges of broken lava slabs.[1][3]

As a part of the Mount Edziza volcanic complex, the Snowshoe Lava Field is drained entirely by streams within the Stikine River watershed.[2][14] Taweh Creek flows northwest along the southern edge of the lava field and is a tributary of Mess Creek.[2][15] At the northwestern end of the Snowshoe Lava Field is Sezill Creek, a northwesterly flowing tributary of Taweh Creek.[2][16] Shaman Creek at the southeastern end of the lava field flows east and north into Kakiddi Lake which is an expansion of Kakiddi Creek.[2][17][18] The eastern side of the Snowshoe Lava Field is bounded by Tencho Glacier, the largest glacier of the Mount Edziza volcanic complex.[2][19]

Geology

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Diagram showing the locations of volcanoes and lava fields of a geological formation.
Geological map of the Big Raven Formation showing the extent of the Snowshoe Lava Field

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.[2] 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 18 km2 (6.9 sq mi).[2][20] 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.[2] 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.[2][4] 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.[21][22]

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.[12] 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 period.[2][23] 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.[2][24] They consist of alkali basalt and minor hawaiite which are in the form of subaqueous and subaerial ejecta.[25] SLF-9, SLF-10, SLF-11 and SLF-12 are completely subaerial in origin and consist mainly of hawaiite.[2][26] They are in the form of pyroclastic cones with the exception of the youngest eruptive centre, SLF-12.[27]

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.[12] 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.[2][8]

Subglacial centres

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Tennena Cone (SLF-1), SLF-2, SLF-3

Transitional centres

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SLF-4, SLF-5, SLF-6, Coffee Crater (SLF-7), SLF-8

Subaerial centres

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Keda Cone (SLF-9), Cocoa Crater (SLF-10), SLF-11, The Saucer (SLF-12)

Accessibility

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See also

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References

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  1. ^ a b c d e Global Volcanism Program: Edziza, Synonyms & Subfeatures.
  2. ^ a b c d e f g h i j k l m n o p q r s t u v Souther 1988.
  3. ^ a b Souther 1992, p. 27.
  4. ^ a b c Souther 1992, p. 228.
  5. ^ a b c Hungerford et al. 2014, pp. 41, 56.
  6. ^ a b c Department of Energy, Mines and Resources 1989.
  7. ^ Souther 1990, p. 124.
  8. ^ a b Souther 1992, p. 230.
  9. ^ a b BC Parks: Mount Edziza Provincial Park.
  10. ^ Souther 1992, pp. 228, 229.
  11. ^ BC Geographical Names: Ice Peak.
  12. ^ a b c Souther 1992, p. 229.
  13. ^ Souther 1992, p. 26.
  14. ^ Souther 1992, p. 33.
  15. ^ BC Geographical Names: Taweh Creek.
  16. ^ BC Geographical Names: Sezill Creek.
  17. ^ BC Geographical Names: Shaman Creek.
  18. ^ BC Geographical Names: Kakiddi Lake.
  19. ^ Souther 1992, p. 320.
  20. ^ Souther 1992, p. 235.
  21. ^ Souther 1992, pp. 27, 28.
  22. ^ Global Volcanism Program: Edziza, Eruptive History.
  23. ^ Souther 1992, pp. 36, 228, 230.
  24. ^ Souther 1992, pp. 229, 231.
  25. ^ Souther 1992, p. 231.
  26. ^ Souther 1992, p. 232.
  27. ^ Souther 1992, pp. 232, 233.

Sources

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