Big Raven Plateau
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The Big Raven Plateau is an intermontane plateau in
Cassiar Land District Cassiar Land District is a cadastral survey subdivision of the province of British Columbia, Canada, created with rest of those on Mainland British Columbia via the Lands Act of the Colony of British Columbia (1858–1866), Colony of British Columb ...
of northwestern
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
, Canada. It lies on the
Tahltan Highland The Tahltan Highland is an upland area of plateau and relatively lower mountain ranges in British Columbia, Canada, lying east of the Boundary Ranges and south of the Inklin River (the east fork of the Taku River). Its eastern boundary is formed ...
and is surrounded by several valleys, including those of Mess Creek, Kakiddi Creek, Chakima Creek, Walkout Creek and the Klastline River. The plateau is drained by many small streams that flow into these neighbouring valleys and, unlike the valleys, it is relatively barren of vegetation. Stream erosion has resulted in the creation of
canyon A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...
s with intervening
ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...
s on the eastern and western sides of the plateau, resulting in the creation of rugged
terrain Terrain (), alternatively relief or topographical relief, is the dimension and shape of a given surface of land. In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientati ...
. The plateau is in
Mount Edziza Provincial Park Mount Edziza Provincial Park is a provincial park in Cassiar Land District of northern British Columbia, Canada. It was established on 27 July 1972 to showcase the Mount Edziza volcanic complex and the surrounding Tahltan Highland. Geography The ...
which is one of the largest provincial parks in British Columbia. Access to the Big Raven Plateau is mainly by aircraft or by a network of
horse trail A bridle path, also bridleway, equestrian trail, horse riding path, ride, bridle road, or horse trail, is a trail or a thoroughfare that is used by people riding horses, riding on horses. Trails originally created for use by horses often now s ...
s from surrounding roads. The Big Raven Plateau is volcanic in origin, consisting mostly of
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
ic lava flows of the
Mount Edziza volcanic complex The Mount Edziza volcanic complex ( ; abbreviated MEVC) is a group of volcanoes and associated lava flows in northwestern British Columbia, Canada. Located on the Tahltan Highland, it is southeast of Telegraph Creek and southwest of Dease Lak ...
that were erupted in the last 7.5 million years. These lava flows are
interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...
with
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
and
trachyte Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanite, aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava (or shallow intrus ...
which are in the form of rock fragments produced and ejected by
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...
s. The dominant feature on the Big Raven Plateau is
Mount Edziza Mount Edziza ( ; ) is a volcanic mountain in Cassiar Land District of northwestern British Columbia, Canada. It is located on the Big Raven Plateau of the Tahltan Highland which extends along the western side of the Stikine Plateau. Mount Ed ...
, an ice-covered
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
reaching an elevation of . Its composition is more diverse, consisting of
alkali basalt Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt i ...
,
hawaiite Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii. It occurs during the later stages of volcanic activity on oceanic islands such as Ha ...
,
trachybasalt Trachybasalt is a volcanic rock with a composition between trachyte and basalt. It resembles basalt but has a high content of alkali metal oxides. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and l ...
, tristanite,
mugearite Mugearite () is a type of oligoclase-bearing basalt, comprising olivine, apatite, and opaque oxides. The main feldspar in mugearite is oligoclase. Mugearite is a sodium-rich member of the alkaline magma series. In the TAS classification of volc ...
,
benmoreite Benmoreite is a volcanic rock of intermediate composition. It is a silica-undersaturated sodium-rich variety of trachyandesite (the other kind is latite) and belongs to the alkaline suite of igneous rocks. It was named after Ben More, a mount ...
, trachyte and rhyolite which are in the form of lava flows,
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s and
breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...
. The Big Raven Plateau is subdivided into at least 10
geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...
s, each being the product of a distinct period of volcanic activity.


Geography and geomorphology


Location

The Big Raven Plateau is on the
Tahltan Highland The Tahltan Highland is an upland area of plateau and relatively lower mountain ranges in British Columbia, Canada, lying east of the Boundary Ranges and south of the Inklin River (the east fork of the Taku River). Its eastern boundary is formed ...
east of the Zagoddetchino
massif A massif () is a principal mountain mass, such as a compact portion of a mountain range, containing one or more summits (e.g. France's Massif Central). In mountaineering literature, ''massif'' is frequently used to denote the main mass of an ...
and west of the mountainous Klastline Plateau in
Cassiar Land District Cassiar Land District is a cadastral survey subdivision of the province of British Columbia, Canada, created with rest of those on Mainland British Columbia via the Lands Act of the Colony of British Columbia (1858–1866), Colony of British Columb ...
. Between the Zagoddetchino massif and the Big Raven Plateau is Mess Creek valley, which extends more than to the south where it separates the
Boundary Ranges The Boundary Ranges, also known in the singular and as the Alaska Boundary Range, are the largest and most northerly subrange of the Coast Mountains. They begin at the Nass River, near the southern end of the Alaska Panhandle in the Canadian pro ...
of the
Coast Mountains The Coast Mountains () are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the British Columbia Coast, Coast of British Columbia sout ...
in the west from the
Spectrum Range The Spectrum Range, formerly gazetted as the Spectrum Mountains and the Rainbow Mountains, is a small mountain range in Cassiar Land District of northwestern British Columbia, Canada. Located at the southern end of the Tahltan Highland, it bord ...
and Arctic Lake Plateau in the east. Between the Big Raven and Klastline plateaus is the north–south trending Kakiddi Creek valley, which includes a number small lakes such as Nuttlude Lake, Kakiddi Lake, Mowchilla Lake and Mowdade Lake. The northern end of the Big Raven Plateau is bounded by the Klastline River valley whereas the southern end is bounded by two relatively small east–west trending valleys; a
mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...
ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...
extends south of the Big Raven Plateau between these valleys. The Big Raven Plateau lies at the northern end of the
Mount Edziza volcanic complex The Mount Edziza volcanic complex ( ; abbreviated MEVC) is a group of volcanoes and associated lava flows in northwestern British Columbia, Canada. Located on the Tahltan Highland, it is southeast of Telegraph Creek and southwest of Dease Lak ...
, which consists of a group of overlapping
shield volcano A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...
es,
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
es,
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s and
cinder cone A cinder cone or scoria cone is a steep, volcanic cone, conical landform of loose pyroclastic rock, pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are forme ...
s that have formed over the last 7.5 million years. Four
central volcano A central volcano is a type of volcano formed by basalts and silica-rich volcanic rocks. They contain very few or no volcanic rocks of intermediate composition, such that they are chemically bimodal volcanism, bimodal. Large silicic eruptions at c ...
es occur along the north–south trending axis of the volcanic complex; the two youngest central volcanoes,
Mount Edziza Mount Edziza ( ; ) is a volcanic mountain in Cassiar Land District of northwestern British Columbia, Canada. It is located on the Big Raven Plateau of the Tahltan Highland which extends along the western side of the Stikine Plateau. Mount Ed ...
and Ice Peak, are on the Big Raven Plateau. In addition to the Big Raven Plateau, the volcanic complex also includes the Arctic Lake and Kitsu plateaus, as well as the Spectrum Range to the south. All of these landforms are in
Mount Edziza Provincial Park Mount Edziza Provincial Park is a provincial park in Cassiar Land District of northern British Columbia, Canada. It was established on 27 July 1972 to showcase the Mount Edziza volcanic complex and the surrounding Tahltan Highland. Geography The ...
, one of the largest provincial parks in British Columbia founded in 1972 to showcase the volcanic landscape.


Drainage

As a part of the Mount Edziza volcanic complex, the Big Raven Plateau is drained entirely by streams within the
Stikine River watershed The Stikine River ( ) is a major river in northern British Columbia (BC), Canada and southeastern Alaska in the United States. It drains a large, remote upland area known as the Stikine Country east of the Coast Mountains. Flowing west and so ...
. The northeastern portion of the Big Raven Plateau is drained by Tsecha Creek, which flows to the northeast. Draining the eastern side of the plateau are a series of east-flowing streams choaked with glacial and landslide debris from rapidly eroding
headwall In physical geography and geology, the headwall of a glacier, glacial cirque (landform), cirque is its highest cliff. The term has been more broadly used to describe similar geomorphic features of non-glacial origin consisting of a concave depress ...
s; from north to south these are Pyramid Creek, Tenchen Creek, Nido Creek, Tennaya Creek,
Sorcery Creek Sorcery Creek is a tributary of Kakiddi Creek and part of the Stikine River watershed in northwest part of the province of British Columbia, Canada. From high peaks just south of Mount Edziza it flows generally east for roughly Lengths and dista ...
and Shaman Creek. Transportation of the glacial and landslide debris into Kakiddi Creek valley has resulted in the formation of several large
alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to Semi-arid climate, semiar ...
s behind which Nuttlude Lake, Kakiddi Lake, Mowdade Lake and Mowchilla Lake have ponded. Nido Creek and Tennaya Creek flow into Nuttlude Lake whereas Sorcery Creek and Shaman Creek flow into Kakiddi Lake. Both lakes are expansions of Kakiddi Creek, which flows north into the Klastline River, a
tributary A tributary, or an ''affluent'', is a stream or river that flows into a larger stream (''main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they ...
of the Stikine River. Elwyn Creek and its tributary,
Kadeya Creek Kadeya Creek is a tributary of Elwyn Creek, which in turn is a tributary of Mess Creek, part of the Stikine River watershed in northwest part of the province of British Columbia, Canada. It flows generally northwest for roughly to join Elwyn Cr ...
, drain the northwestern portion of the plateau; Elwyn Creek flows westward whereas Kadeya Creek flows to the northwest. Northwest-flowing Taweh Creek and its tributary, the westward-flowing Sezill Creek, drain the southwestern and western portions of the plateau, respectively. Elwyn Creek and Taweh Creek are tributaries of Mess Creek, which flows northwestward into the Stikine River. The northern end of the Big Raven Plateau is drained by small, unnamed streams which flow north into the Klastline River; these streams are shallowly incised into the plateau. At the southern end of the Big Raven Plateau is a
drainage divide A drainage divide, water divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighboring drainage basins. On rugged land, the divide lies along topographical ridges, and may be in the form of a single ...
between Chakima Creek, flowing east into the Kakiddi drainage, and Walkout Creek flowing west via Raspberry Creek into Mess Creek.


Structure

The Big Raven Plateau is about long, wide and more than in elevation. It is roughly oval in structure, largely covered with
colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, Sheet erosion , sheetwash, slow continuous downslope creep, or a va ...
and relatively barren of vegetation, which contrasts with the surrounding valleys. Colluvium on the plateau consists of
felsenmeer A blockfieldWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984, pp. 66 and 190. . (also spelt block fieldLeser, Hartmut, ed. (2005). ''Wörterbuch Allgemeine Geographie'', 13th ed., dtv, Munich, pp. 107 and 221 ...
,
till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...
, glacial and
fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...
outwash An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and c ...
, as well as
solifluction Solifluction is a collective name for gradual processes in which a mass moves down a slope ("mass wasting") related to freeze-thaw activity. This is the standard modern meaning of solifluction, which differs from the original meaning given to i ...
deposits. In contrast to the northern end of the Big Raven Plateau which is relatively smooth and uneroded, the eastern side has undergone extensive erosion, which has resulted in the creation of steep spurs with intervening valleys. A handful of these spurs are named on the southeastern side of the plateau; from north to south they are Idiji Ridge,
Sorcery Ridge Sorcery Ridge is a mountain ridge extending east of Tencho Glacier on the southern flank of Mount Edziza in northwestern British Columbia, Canada. It is bounded on the north and south by valleys containing unnamed streams while to the east and no ...
and Cartoona Ridge. Idiji Ridge extends east from the northern end of
Tencho Glacier Tencho Glacier is a mountain glacier in northwestern British Columbia, Canada. It is located inside Mount Edziza Provincial Park on the Tahltan Highland, an upland area of the Stikine Plateau. Tencho Glacier is the source of several small streams ...
and is the namesake of Idiji Glacier, which exists to the northwest. Sorcery Ridge, which shares its name with adjacent Sorcery Creek, extends east from the southern end of Tencho Glacier. Cartoona Ridge lies between Chakima and Shaman creek valleys and shares its name with Cartoona Peak at the westernmost end of the ridge. The western side of the Big Raven Plateau has been moderately dissected by stream erosion, which has resulted in the formation of steep-sided canyons; Elwyn, Sezill and Taweh creek canyons are the most extensive. Elwyn and Sezill creek canyons contain
hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...
s with recorded water temperatures of and , respectively. Discharge at these hot springs may be linked to shallow
hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
systems driven by residual
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...
tic heat as they are adjacent to recently active volcanic centres on the plateau. Forming the southwestern edge of the Big Raven Plateau is the Mess Creek Escarpment, which extends at least to the south where it forms the western edge of the Kitsu Plateau.


Landforms

The Big Raven Plateau is dominated by the ice-covered stratovolcano of Mount Edziza, which rises to an elevation of from the middle of the plateau. Immediately north of Mount Edziza is the
Desolation Lava Field The Desolation Lava Field (DLF) is a volcanic field at Mount Edziza in British Columbia, Canada. It reaches an elevation of on the Big Raven Plateau, but decreases to at Buckley Lake and in the Klastline River valley. The lava field cover ...
, which covers an area of more than and mostly issued from cinder cones near the northern
trim line A trim line, also written as trimline, is a clear line on the side of a valley formed by a glacier. The line marks the most recent highest extent of the glacier. The line may be visible due to changes in color to the rock or to changes in vege ...
of Mount Edziza's
ice cap In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description By definition, ice caps are not constrained by topogra ...
. The
Snowshoe Lava Field The Snowshoe Lava Field (SLF) is a largely buried volcanic field at Mount Edziza in British Columbia, Canada. It reaches an elevation of and engulfs more than of the Big Raven Plateau and adjacent valleys with blocky lava flows. The Snowshoe L ...
immediately southwest of Mount Edziza covers an area of about and mostly issued from cones on the southwestern flank of Ice Peak. Smaller features on the Big Raven Plateau include Hoia Bluff at the southwestern end of the plateau along Taweh Creek, Kaia Bluff and Cartoona Peak at the southeastern end of the plateau, Camp Hill near the southwestern edge of the plateau,
Kana Cone Kana Cone is a red nested cinder cone in northern British Columbia, Canada, located northeast of Eve Cone in Mount Edziza Provincial Park. The name of the cone was adopted 2 January 1980 on National Topographic System map 104G/12 after being submit ...
on the extreme northern side of the plateau, Klastline Cone on the eastern side of the plateau near the
head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...
of Pyramid Creek,
Tsekone Ridge Tsekone Ridge, also called Tsekone Peak and Black Knight Cone, is an isolated ridge on the Big Raven Plateau of the Tahltan Highland in northwestern British Columbia, Canada. It is located southeast of Telegraph Creek at the north side of Mount E ...
at the northwestern end of the plateau near the head of Elwyn Creek canyon and Ornostay and Koosick bluffs near the middle of the plateau adjacent to the head of Sezill Creek canyon.


Mount Edziza

Mount Edziza is a nearly symmetrical volcanic cone containing a nearly flat summit with an ice-filled, in diameter
crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...
. The symmetry of the volcano is broken by several steep-sided lava domes, including Sphinx Dome, Glacier Dome,
Triangle Dome Triangle Dome is a trachytic lava dome in northern British Columbia, Canada. It is thought to have formed in the Pleistocene period.The Pyramid A pyramid is a structure with triangular lateral surfaces converging to an apex. Pyramid may also refer to: Anatomy and medicine * Petrous part of the temporal bone, the pyramid * Pyramid (brainstem), the anterior part of medulla oblongata Gam ...
. Surrounding the summit crater is a circular ridge breached to the east by active
cirque A (; from the Latin word ) is an amphitheatre-like valley formed by Glacier#Erosion, glacial erosion. Alternative names for this landform are corrie (from , meaning a pot or cauldron) and ; ). A cirque may also be a similarly shaped landform a ...
s where the remains of several
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 (sometim ...
s are exposed inside the crater. The ridge is partially exposed above the ice cap as a discontinuous series of spires and serrated
nunatak A nunatak (from Inuit language, Inuit ) is the summit or ridge of a mountain that protrudes from an ice field or glacier that otherwise covers most of the mountain or ridge. They often form natural pyramidal peaks. Isolated nunataks are also cal ...
s; spires forming the southern end of the ridge are the highest. Although the eastern side of Mount Edziza has been deeply dissected by
glacial erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
, less dissection has taken place on the southern and northwestern flanks of the volcano. Extending northwest from the northwestern flank of Mount Edziza is
Pillow Ridge Pillow Ridge is a ridge of the Tahltan Highland in northern British Columbia, Canada, located southeast of Telegraph Creek. It extends northwest from Mount Edziza in Mount Edziza Provincial Park. History As its name suggests, Pillow Ridge was na ...
, which is named after its exposures of
pillow lava Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of discontinu ...
. About south of the summit is Ice Peak, the southern peak of Mount Edziza. This prominent pyramid-shaped horn has an elevation of and is the glacially eroded remains of an older stratovolcano whose northern flank is buried under the younger edifice of Mount Edziza. The southern and western flanks of Ice Peak are approximal to those of the original stratovolcano whereas the eastern flank has been almost completely destroyed by headward erosion of glacial valleys. At its climax, the stratovolcano had a symmetrical profile and contained a small crater at its summit; the current summit is an erosional remnant etched from the eastern crater rim.


Desolation Lava Field

The Desolation Lava Field at the northern end of the Big Raven Plateau consists of blocky
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
ic lava flows and wind-sculptured
ash Ash is the solid remnants of fires. Specifically, ''ash'' refers to all non-aqueous, non- gaseous residues that remain after something burns. In analytical chemistry, to analyse the mineral and metal content of chemical samples, ash is the ...
beds A bed is a piece of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many be ...
that were erupted from at least 10 cinder cones, most of which are clustered near the northern base of Mount Edziza. Lava flows in the Desolation Lava Field range in elevation from more than on the plateau to near the shore of Buckley Lake and in the Klastline River valley. The largest lava flow is about long and travelled to the northeast into the Kakiddi Creek and Klastline River valleys where it temporarily blocked both streams. From oldest to youngest, the cinder cones in this
lava field A lava field, sometimes called a lava bed, is a large, mostly flat area of lava flows. Such features are generally composed of highly fluid basalt lava, and can extend for tens or hundreds of kilometers across the underlying terrain. Morp ...
are Sleet Cone,
Storm Cone Storm Cone is a cinder cone in northern British Columbia, Canada. It is thought to have last erupted in the Holocene period and lies on the Desolation lava field which is part of the Mount Edziza volcanic complex.Triplex Cones The Triplex Cones are a group of three cinder cones in northern British Columbia, Canada. They are thought to have last erupted during the Holocene epoch.Sidas Cone Sidas Cone is a cinder cone on the Big Raven Plateau at the northern end of Mount Edziza Provincial Park in British Columbia, Canada. Its name, meaning "cut oneself with a knife" in the Tahltan language, is descriptive of the breach that has cut ...
, Twin Cone, Moraine Cone,
Eve Cone Eve Cone, sometimes referred to as Eve's Cone, is a cinder cone in Cassiar Land District of northwestern British Columbia, Canada. It has an elevation of and is one of several volcanic cones in the Desolation Lava Field at the northern end of t ...
and Williams Cone which range in elevation from . Williams Cone is the largest, reaching wide at its base and rising about on the northeastern side of Mount Edziza. Eve Cone contains a bowl-shaped crater at its summit and is one of the most symmetrical and best preserved cinder cones in Canada, rising about above the central portion of the Desolation Lava Field.


Snowshoe Lava Field

The Snowshoe Lava Field at the southern end of the Big Raven Plateau consists of blocky basaltic lava flows that issued from at least 12 separate vents, most of which are associated with a cinder cone. Nearly all of these vents are adjacent to the lower edges of broad glaciers projecting from Mount Edziza's ice cap and occur at elevations greater than . Although most of the lava in the Snowshoe Lava Field ponded as thick flows on the gently sloping surface of the Big Raven Plateau, some of it flowed into the upper canyon of Sezill Creek and into the head of Taweh Creek, as well as into the narrow tributary valleys of Walkout and Shaman creeks. Tennena Cone,
Cocoa Crater Cocoa Crater, sometimes called Cocoa Cone, is a cinder cone in Cassiar Land District of northwestern British Columbia, Canada. It has an elevation of and is one of several volcanic cones in the Snowshoe Lava Field at the southern end of the ...
, Coffee Crater, Keda Cone and
The Saucer The Saucer is a cinder cone in northern British Columbia, Canada. It is thought to have last erupted in the Holocene epoch.subglacial volcano A subglacial volcano, also known as a glaciovolcano, is a volcanic form produced by subglacial eruptions or eruptions beneath the surface of a glacier or ice sheet which is then melted into a lake by the rising lava. Today they are most common i ...
that formed on the upper western flank of Ice Peak during the
Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent between 26,000 and 20,000 years ago. Ice sheets covered m ...
between 23,000 and 18,000 years ago, under an expansion of Mount Edziza's ice cap during the
Younger Dryas The Younger Dryas (YD, Greenland Stadial GS-1) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP). It is primarily known for the sudden or "abrupt" cooling in the Northern Hemisphere, when the ...
between 12,900 and 11,600 years ago or during a more recent glacial advance. Cocoa Crater, Coffee Crater and Keda Cone are
subaerial In natural science, subaerial (literally "under the air") has been used since 1833,Subaerial
in the Merriam- ...
cinder cones whereas The Saucer is a low, nearly circular mound of lava roughly in diameter.


Geology


Stratigraphy

The Big Raven Plateau is subdivided into at least 10
geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...
s, each being the product of a distinct period of volcanic activity. These periods of volcanic activity occurred during five magmatic cycles of the Mount Edziza volcanic complex; each cycle began with the effusion of
alkali basalt Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt i ...
and culminated with the eruption of lesser volumes of
felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...
magma. The two oldest geological formations comprising the Big Raven Plateau are the
Raspberry The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...
and
Armadillo Armadillos () are New World placental mammals in the order (biology), order Cingulata. They form part of the superorder Xenarthra, along with the anteaters and sloths. 21 extant species of armadillo have been described, some of which are dis ...
formations, which were deposited by volcanic eruptions during the first magmatic cycle between 7.5 and 6 million years ago. Overlying these two geological formations are the Nido and
Pyramid A pyramid () is a structure whose visible surfaces are triangular in broad outline and converge toward the top, making the appearance roughly a pyramid in the geometric sense. The base of a pyramid can be of any polygon shape, such as trian ...
formations, which were deposited between 6 and 1 million years ago during the second magmatic cycle. The fifth, sixth and seventh oldest geological formations comprising the Big Raven Plateau are the Ice Peak, Pillow Ridge and Edziza formations, which were deposited during the third magmatic cycle between about 1 and 0.8 million years ago. Volcanic eruptions during the fourth magmatic cycle between 0.8 and 0.2 million years ago deposited the Klastline and Kakiddi formations whereas the
Big Raven Formation The Big Raven Formation is a stratigraphic unit of Quaternary age in northwestern British Columbia, Canada. It is the youngest and least voluminous geological formation of the Mount Edziza volcanic complex (MEVC); it overlies at least eight older ...
, the youngest geological formation comprising the Big Raven Plateau, was deposited during the fifth magmatic cycle in the last 20,000 years.


Raspberry Formation

The Raspberry Formation is exposed at the base of prominent escarpments on the western, southwestern and southeastern sides of the Big Raven Plateau. It has an elevation of less than along the Mess Creek Escarpment and consists of flat-lying basaltic lava flows
interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...
with
scoria Scoria or cinder is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackso ...
. More than of Raspberry lava flows are exposed in the Mess Creek Escarpment, most of which were erupted from a shield volcano that formed on a
Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...
erosion surface In geology and geomorphology, an erosion surface is a surface of rock (geology), rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault (geology), fault displacement. Erosional surfaces ...
. These lava flows travelled westward into the ancestral valley of Mess Creek whereas those exposed on and around Cartoona Ridge at the southeastern end of the Big Raven Plateau most likely issued from a smaller volcanic centre northeast of the Raspberry shield. A minimum age for the timing of Raspberry
volcanism Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a he ...
is 7.4–6.2 million years.


Armadillo Formation

Basaltic lava flows of the 6.3-million-year-old Armadillo Formation are exposed in Kadeya Creek canyon on the northwestern side of the Big Raven Plateau, in Sezill Creek canyon on the western side of the plateau and along the Mess Creek Escarpment on the southwestern side of the plateau where they overlie basaltic lava flows of the Raspberry Formation. Armadillo basalt flows form up to thick units at these locations, which are interbedded with air-fall
pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...
and
ash flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot volcanic gas, gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average ...
s of
trachytic Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava (or shallow intrusions) enri ...
and
comenditic Comendite is a hard, peralkaline igneous rock, a type of light blue grey rhyolite. Phenocrysts are sodic sanidine with minor albite and bipyramidal quartz. Iddings, Joseph Paxson, 1913, ''Igneous rocks: composition, texture and classification'', v ...
compositions. The basalt flows were highly fluid and mobile at the time of their eruption as evidenced by their extreme persistence and relatively narrow thicknesses; individual basalt flows of this geological formation are less than thick. The source of these lava flows was probably a cluster of vents further to the east called Sezill Volcano. In contrast, the air-fall pumice and ash flows probably originated from the more than in diameter Armadillo Peak
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
south of the Big Raven Plateau.


Nido Formation

The Tenchen Member is the only
stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features ( facies) that characteriz ...
of the Nido Formation comprising the Big Raven Plateau. It consists of basaltic lava flows and pyroclastic rocks which were erupted 4.4 million years ago from three major volcanoes and several smaller eruptive centres; these eruptive centres have since been deeply dissected by erosion. A lower unit of alkali basalt with minor
hawaiite Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii. It occurs during the later stages of volcanic activity on oceanic islands such as Ha ...
is exposed at the southern, southeastern and southwestern ends of the Big Raven Plateau where it is in the form of lava flows, flow
breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...
and
agglutinate In linguistics, agglutination is a morphological process in which words are formed by stringing together morphemes (word parts), each of which corresponds to a single syntactic feature. Languages that use agglutination widely are called agglut ...
. Alkali basalt and minor hawaiite of the Alpha Peak, Beta Peak and associated satellitic eruptive centres are exposed on Sorcery Ridge and Idiji Ridge on the southwestern side of the plateau. They are in the form of lava flows, agglutinate, flow breccia,
tuff breccia Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
,
pillow lava Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of discontinu ...
and pillow breccia, which are intercalated with gravel. Alkali basalt of the Gamma Peak eruptive centre is in the form of lava flows, tuff breccia and pillow lava, which occur in the upper canyon of Elwyn Creek at the northwestern end of the Big Raven Plateau and overlie alkali basalt of the lower unit at the southeastern end of the plateau. Cartoona Peak and Kaia Bluff at the southeastern end of the Big Raven Plateau both consist of alkali basalt erupted from the Gamma Peak eruptive centre.


Pyramid Formation

Exposures of the 1.1-million year-old Pyramid Formation are limited only to the northeastern, eastern and southeastern ends of the Big Raven Plateau where it is in the form of rhyolite and trachyte domes, flows and pyroclastic breccia. The Pyramid at the northeastern end of the plateau consists of a roughly high trachyte dome whose base is slightly more than wide. Unlike other domes of the Pyramid Formation which have been either buried under younger lavas or greatly modified by erosion, The Pyramid has only been moderately eroded and is completely isolated from adjacent rocks. Sphinx Dome is a partially buried rhyolite dome adjacent to The Pyramid whose southern edge has been largely destroyed by headward stream erosion. Isolated remnants of the rhyolitic
Pharaoh Dome Pharaoh Dome is a lava dome in northwestern British Columbia, Canada, located near Mount Edziza in Mount Edziza Provincial Park. It last erupted during the Pleistocene epoch.pyroclastic surge A pyroclastic surge is a fluidised mass of turbulent gas and rock fragments that is ejected during some volcanic eruptions. It is similar to a pyroclastic flow but it has a lower density or contains a much higher ratio of gas to rock, which makes i ...
deposit of trachytic composition south and east of The Pyramid, both of which are also part of the Pyramid Formation.


Ice Peak Formation

The Ice Peak Formation is the most compositionally diverse geological formation of the Big Raven Plateau, having mostly erupted from the Ice Peak stratovolcano about one million years ago. Most of the Ice Peak rocks are subdivided into two distinct stratigraphic units called the lower and upper assemblages. The lower assemblage consists of alkali basalt, hawaiite and minor
mugearite Mugearite () is a type of oligoclase-bearing basalt, comprising olivine, apatite, and opaque oxides. The main feldspar in mugearite is oligoclase. Mugearite is a sodium-rich member of the alkaline magma series. In the TAS classification of volc ...
, tristanite and
trachybasalt Trachybasalt is a volcanic rock with a composition between trachyte and basalt. It resembles basalt but has a high content of alkali metal oxides. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and l ...
which are in the form of subaerial lava flows and pyroclastic breccia, as well as tuff breccia, pillow lava and pillow breccia that formed in an ice-contact environment. It is widespread throughout the Big Raven Plateau, but is largely buried under
colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, Sheet erosion , sheetwash, slow continuous downslope creep, or a va ...
such as
glacial till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...
and glacial and
fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...
outwash. Alkali basalt, trachybasalt, tristanite, mugearite,
benmoreite Benmoreite is a volcanic rock of intermediate composition. It is a silica-undersaturated sodium-rich variety of trachyandesite (the other kind is latite) and belongs to the alkaline suite of igneous rocks. It was named after Ben More, a mount ...
and trachyte of the upper assemblage are in the form of lava flows, domes and pyroclastic breccia. They comprise the summit of Ice Peak and are exposed to the south and northeast along the southeastern and eastern sides of the Big Raven Plateau. Ornostay and Koosick bluffs on the western flank of Ice Peak consist of thick lobes of trachyte of the upper assemblage and project onto the Big Raven Plateau. Both bluffs are similar in composition and owe their thickness from the ponding of trachyte lava against glacial ice. An isolated occurrence of Ice Peak Formation rocks on the Big Raven Plateau forms Camp Hill, which consists of basaltic tuff breccia, pillow breccia, lava flows and
tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
. Lava from Camp Hill extends to the northwest along the southwestern edge of the plateau, but it is almost completely buried under colluvium deposits. Small exposures of this lava occur along the Mess Creek Escarpment and along Taweh Creek valley just south of Hoia Bluff.


Pillow Ridge Formation

The 0.9-million-year-old Pillow Ridge Formation is limited to Pillow Ridge and Tsekone Ridge at the northern end of the Big Raven Plateau. Pillow Ridge consists of alkali basalt that is in the form of tuff breccia, pillow breccia and pillow lava. The tuff breccia is crudely bedded and comprises much of the lower and central portions of the ridge. Overlying the tuff breccia is an outer mantle of tubular pillow lava, which occurs at the northwestern and southeastern ends of Pillow Ridge. In contrast, Tsekone Ridge consists of a lower and central unit of tuff breccia and an upper unit of fractured, closely jointed pillows and
lava tube A lava tube, more rarely called a pyroduct, is a 'roofed conduit through which molten lava travels away from its vent'. If lava in the tube drains out, it will leave an empty cave. Lava tubes are common in low-viscosity volcanic systems. La ...
s of hawaiitic composition. All of the Tsekone Ridge units are cut by vertical north-trending
dikes Dyke or dike may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), formations of magma or sediment that cut through and across the layering of adjacent rocks * Dike (mythology), ''Dikē'', the Greek goddess ...
, which fed the tuff breccia and pillow lava comprising the ridge. Pillow Ridge and Tsekone Ridge are both products of
subglacial volcanism Subglacial means "formed, or occurring beneath a glacier or other body of ice". It may refer to: * Subglacial eruption * Subglacial lake * Subglacial stream * Subglacial volcano A subglacial volcano, also known as a glaciovolcano, is a volcanic ...
, but they differ in
glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
alteration and
vesicular texture Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many cavities (known as vesicles) at its surface and inside. This texture is common in aphanitic, or glassy, igneous rocks that have come to the surface ...
, suggesting they both formed under slightly different conditions.


Edziza Formation

The Edziza Formation is a 0.9-million-year-old trachyte formation mainly comprising the younger central stratovolcano of Mount Edziza and satellitic domes. The stratovolcano overlies the northern flank of the older Ice Peak stratovolcano and consists of pyroclastic breccia, as well as
lahar A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are o ...
and ash flow deposits. These rocks are well exposed in high cliffs along the northern side of Tenchen Glacier where an active cirque has eroded the eastern side of the volcano. Exposed at the head of this cirque is
hydrothermally altered Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in the chemical comp ...
vent breccia of the central conduit which is overlain by the remains of at least four lava lakes that ponded inside the summit crater. Each lava lake has a thickness of around and are represented by at least four distinct cooling units. Satellitic domes of the Edziza Formation include Glacier Dome on the lower northeastern flank of Mount Edziza, Triangle Dome on the upper western flank of Mount Edziza and Nanook Dome on the southwestern rim of the summit crater, the latter of which is the largest dome of the Edziza Formation. Glacier Dome was the source of a lava flow that travelled along the northern side of Pyramid Creek valley whereas Nanook Dome may have been the source of one or two of the lava lakes inside the summit crater. An unnamed
pyroclastic cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...
on the northwestern flank of Mount Edziza produced two trachytic lava flows that travelled onto the gently sloping surface of the Big Raven Plateau; they are both largely buried under ash and colluvium deposits.


Klastline Formation

The Klastline Formation consists of the remains of thick alkali basalt flows that issued from at least three vents on the northern and eastern sides of the Big Raven Plateau 0.62 million years ago. A lobe of alkali basalt extends eastward from the northern end of the plateau to Buckley Lake as a series of scattered outcrops; much of the lobe is buried under colluvium deposits and younger lava flows. The source of this lobe was probably a pyroclastic cone that has been eroded to a low grassy hill in elevation. Klastline Cone on the eastern side of the Big Raven Plateau near the head of Pyramid Creek was the main source of Klastline Formation lava flows in the Klastline River valley, which have been reduced to small
butte In geomorphology, a butte ( ) is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and table (landform), tablelands. The word ''butte'' comes from the French l ...
s and buttresses.


Kakiddi Formation

The 0.3-million-year-old Kakiddi Formation occurs east and west of Tencho Glacier on the southern flank of Ice Peak, consisting mainly of trachyte in the form of pyroclastic rocks and lava flows. Punch Cone on the southwestern flank of Ice Peak is a roughly long, steep-sided ridge composed of agglutinated Kakiddi spatter and breccia from which a largely buried lava flow extends westward onto the gently sloping surface of the Big Raven Plateau. Erosional remnants of thick Kakiddi lava flows and pyroclastic rocks to the east occur on Ice Peak and in deeply incised valleys on the eastern side of the plateau; lava flow remnants on Ice Peak overlie older volcanic rocks of the Ice Peak Formation. The remnants on Ice Peak originated from a vent near its summit whereas those in the adjacent valleys originated from unknown vents, although Nanook Dome on the summit of Mount Edziza may have been a major source; it consists of similar Edziza Formation trachyte. Trachytic lava flows of the Kakiddi Formation erupted more fluidly than those of the Edziza Formation as evidenced by their greater extant on gently sloping
terrain Terrain (), alternatively relief or topographical relief, is the dimension and shape of a given surface of land. In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientati ...
.


Big Raven Formation

Alkali basalt and hawaiite of the Big Raven Formation is widespread at the northern and southern ends of the Big Raven Plateau; the largest occurrence at the northern end is the Desolation Lava Field whereas the largest occurrence at the southern end is the Snowshoe Lava Field. A
radiocarbon date Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was de ...
of 1340 ± 130 years has been obtained from
willow Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...
twigs preserved within tephra from Williams Cone, the youngest pyroclastic cone in the Desolation Lava Field. Kana Cone is an isolated nested pyroclastic cone on the extreme northern slope of the plateau and is the northernmost occurrence of Big Raven Formation alkali basalt and hawaiite. It was the source of lava flows that forced the Klastline River against the northern valley wall. The Walkout Creek centres on the extreme southern slope of the Big Raven Plateau consist of the remains of two small cinder cones and associated alkali basaltic lava flows on the northern side of Walkout Creek valley. Cinder Cliff, Icefall Cone and Ridge Cone are three isolated occurrences of Big Raven Formation alkali basalt on the eastern flank of Mount Edziza, the latter two of which are on the high eastern rim of Ice Peak and have been significantly modified by
slumping Slumping is a technique in which items are made in a kiln by means of shaping glass over molds at high temperatures. The slumping of a pyrometric cone is often used to measure temperature in a kiln. Technique Slumping glass is a highly techni ...
,
rockfall A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity of Rock (geology), rock that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or wa ...
s and glaciation. The Big Raven Formation also includes the
Sheep Track Member The Sheep Track Member is a stratigraphic unit of the Big Raven Formation, part of the Mount Edziza volcanic complex in northwestern British Columbia, Canada. It consists of pumice from an explosive eruption that fell over an area about . The pu ...
, a
pyroclastic fall A pyroclastic fall deposit is a uniform deposit of material which has been ejected from a volcanic eruption or plume such as an ash fall or tuff. Pyroclastic fallout deposits are a result of: # Ballistic transport of ejecta such as volcanic bloc ...
deposit of unconsolidated comenditic trachyte pumice obscuring much of the surficial details of the Snowshoe Lava Field.


Basement

As a part of the Mount Edziza volcanic complex, the Big Raven Plateau is underlain by the
Stikinia Stikinia, or the Stikine terrane, is a terrane in British Columbia, Canada; the largest of the Canadian Cordillera. It formed as an independent, intraoceanic volcanic arc during the Paleozoic and Mesozoic. Stikinia forms the bedrock of numerous ...
terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its d ...
. This is a
Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...
and
Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
suite Suite may refer to: Arts and entertainment *Suite (music), a set of musical pieces considered as one composition ** Suite (Bach), a list of suites composed by J. S. Bach ** Suite (Cassadó), a mid-1920s composition by Gaspar Cassadó ** ''Suite' ...
of volcanic,
sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...
and
metamorphic Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...
rocks that accreted to the
continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...
of North America during the
Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
. The rocks of this terrane are exposed along the western side of the plateau in Mess Creek valley, the southern side of the plateau in Walkout and Chakima creek valleys, at the extreme northern end of the plateau as inliers and along the eastern side of the plateau where they comprise the lower units of Idiji Ridge, Sorcery Ridge and other neighbouring ridges. Also underlying the Big Raven Plateau are
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
and
Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
conglomerates,
arkose Arkose () or arkosic sandstone is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose. Components ...
s,
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
s,
siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...
s,
shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...
s and minor
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...
of the
Sustut Group The Sustut Group is a geologic group in British Columbia, Canada. It preserves fossils dating back to the Cretaceous period. The leptoceratopsid '' Ferrisaurus'' and the turtle ''Basilemys'' have been recovered from the group. See also * List o ...
, which are exposed along the western side of the plateau.
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
leucogranite Leucogranite is a light-colored, granitic, igneous rock containing almost no dark minerals. Leucogranites have been reported from a variety of orogenies involving continental collisions. Examples include the Black Hills (Trans-Hudson orogeny ...
of the Elwyn Creek Pluton is exposed in Elwyn Creek canyon at the northwestern end of the Big Raven Plateau, as are Eocene rhyolite,
dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
and
andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...
pyroclastic breccias and andesite lava domes and flows. All of these Eocene rocks are part of the Sloko Group and were emplaced by the youngest documented magmatic event before the Mount Edziza volcanic complex started erupting in the Late Miocene.


Name and etymology

The name of the plateau became official on January 2, 1980, and was adopted on the
National Topographic System The National Topographic System or NTS is the system used by Natural Resources Canada for providing general purpose topographic maps of the country. NTS maps are available in a variety of scales, the standard being 1:50,000 and 1:250,000 scales. ...
map 104G after being submitted to the
BC Geographical Names The BC Geographical Names (formerly BC Geographical Names Information System or BCGNIS) is a geographic name web service and database for the Canadian province of British Columbia run by the Base Mapping and Geomatic Services Branch of the Integr ...
office by the
Geological Survey of Canada The Geological Survey of Canada (GSC; , CGC) is a Canadian federal government agency responsible for performing geological surveys of the country developing Canada's natural resources and protecting the environment. A branch of the Earth Science ...
. It is named after Big Raven, a deity in
Tahltan The Tahltan or Nahani are a First Nations people of the Athabaskan-speaking ethnolinguistic group who live in northern British Columbia around Telegraph Creek, Dease Lake, and Iskut. The Tahltan constitute the fourth division of the ''Nahan ...
mythology whose name translates to in the
Tahltan language Tahltan, Tāłtān, also called Tałtan ẕāke ("Tahltan people language"), dah dẕāhge ("our language") or didene keh ("this people’s way") is a poorly documented and endangered Northern Athabaskan language spoken by 235 of the Tahltan, Tah ...
. Several features on the plateau also have names with Tahltan roots that were adopted simultaneously on 104G for
geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
reporting purposes, including Keda Cone, Sidas Cone, Kana Cone, Hoia Bluff, Kaia Bluff and Tsekone Ridge.


Accessibility

The closest roads to the Big Raven Plateau are the
Stewart–Cassiar Highway The Stewart–Cassiar Highway, also known as the Dease Lake Highway and the Stikine Highway, as well as the Kitimat Highway from Kitimat to Terrace, is the northwestern-most highway in the Canadian province of British Columbia. A scenic route th ...
to the east and the Telegraph Creek Road to the northwest, both of which extend within of the plateau. Extending from these roads are
horse trail A bridle path, also bridleway, equestrian trail, horse riding path, ride, bridle road, or horse trail, is a trail or a thoroughfare that is used by people riding horses, riding on horses. Trails originally created for use by horses often now s ...
s that provide access to the Big Raven Plateau. From Telegraph Creek, the Buckley Lake Trail extends about southeast along Mess Creek and Three Mile Lake. It then traverses about 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, the latter of which climbs up onto the gently sloping northern side of the Big Raven Plateau. To the east, the roughly long Klastline River Trail begins at the community of
Iskut Iskut is a small, mostly Indigenous community in the Stikine Country of northwestern British Columbia. It is located on Highway 37, at the north end of Eddontenajon Lake just south of Dease Lake and the crossing of the Stikine River. Communi ...
on the Stewart–Cassiar Highway. It extends northwest and west along the Klastline River for much its length. The trail enters Mount Edziza Provincial Park at about where Kakiddi Creek drains into the Klastline River. After entering Mount Edziza Provincial Park, the Klastline River Trail traverses northwest along the Klastline River for about and then crosses the river north of the Big Raven Plateau. From there, the Klastline River Trail traverses west for about to the northeastern end of Buckley Lake where it meets with the Buckley Lake Trail and Buckley Lake to Mowdade Lake Route. The Big Raven Plateau can also be accessed by float plane or helicopter, both of which are available for charter at the communities of Iskut and
Dease Lake Dease Lake is a small community in the Cassiar Country of the Northern Interior of British Columbia, Canada. It is 230 km south of the Yukon border on Stewart–Cassiar Highway (Highway 37) at the south end of the lake of the same na ...
. Buckley Lake to the northwest, Nuttlude Lake to the east and Kakiddi Lake, Mowchilla Lake and Mowdade Lake to the southeast are large enough to be used by float-equipped aircraft. Alpine Lakes Air and BC Yukon Air are the only air charter companies permitted to provide access to this area via aircraft. Landing on Buckley Lake and Mowchilla Lake with a private aircraft requires a letter of authorization from the
BC Parks BC Parks is an Government agency, agency of the British Columbia British Columbia Ministry of Environment and Climate Change Strategy, Ministry of Environment and Climate Change Strategy that manages all of the, as of 2020, 1,035 List of British C ...
Stikine Senior Park Ranger.


See also

*
List of plateaus in British Columbia This is a list of plateaus and plateau-like landforms in British Columbia, Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the P ...


References


Sources

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External links

* {{Plateaus and highlands of British Columbia Miocene volcanism Pliocene volcanism Pleistocene volcanism Holocene volcanism