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76-682: Kounugu Mountain is a mountain in the Spectrum Range at the southern end of the Mount Edziza volcanic complex in northwestern British Columbia , Canada. It is southeast of Yeda Peak , west and northwest of the Little Iskut River , south of Stewbomb Creek valley and just north of Little Ball Lake . It has an elevation of 2,267 metres (7,438 feet) and lies at the southeastern end of the Spectrum Range. The mountain

152-479: A caldera or an irregular collapse structure. It occurs within a roughly circular area about 10 kilometres (6.2 miles) in diameter and likely formed by collapse of a shallow magma chamber during eruption of the Spectrum Formation lavas. At least 1 kilometre (0.62 miles) of vertical caldera collapse may have resulted if the magma chamber was similar in diameter to this circular area, but poor exposure of

228-492: A basaltic lava flow but it was later buried under debris from the landsliding. Although volcanic activity at the Spectrum Range continued into the current Holocene epoch , the last eruption is unknown. Alteration of Spectrum Formation rocks caused by fumarolic activity during the formation of the Spectrum Dome occurs at Yeda Peak and elsewhere throughout the Spectrum Range. Fumarolic alteration at Yeda Peak occurs in

304-409: A deeper, hotter and longer lived hydrothermal system than elsewhere in the Spectrum Range, the lava flow fumaroles were small and relatively short-lived. The multi-coloured rocks which give the Spectrum Range its name are partially the result of fumarolic alteration. At the head of Ball Creek valley is a subvolcanic mass of granite with abnormally high soda content that probably intruded into

380-769: 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. Underlying nearly all of the Spectrum Range is the Kounugu Member of the Nido Formation , one of many stratigraphic units comprising

456-466: A group of overlapping shield volcanoes , stratovolcanoes , lava domes and cinder cones that have formed over the last 7.5 million years. It contains an intermontane plateau that is overlain by four central volcanoes along its north–south trending axis; the Spectrum Range is the southernmost and third oldest central volcano. Extending outward from the central portion of this nearly circular group of pyramidal peaks and long, narrow-creasted ridges

532-519: A more moderate climate put an end to the neoglacial period in the 19th century which has resulted in rapid glacial recession throughout the Mount Edziza volcanic complex. This rapid glacial recession is apparent from the lack of vegetation on the barren, rocky ground between the glaciers and their trim lines which are up to 2 kilometres (1.2 miles) apart. Unlike Mount Edziza which has an approximately 70-square-kilometre (27-square-mile) ice cap ,

608-472: A part of the Mount Edziza volcanic complex, the Spectrum Range is drained on all sides by streams within the Stikine River watershed . Kitsu Creek is a northwest-flowing stream originating from the northern side of Kitsu Peak. It contains one named tributary, Nagha Creek , which also flows northwest from the Spectrum Range. Tadekho Creek originates from between Kuno and Yeda peaks and flows to

684-521: A valley between Artifact and Obsidian ridges. Ball and More creeks both flow south from the southern end of the Spectrum Range near Yeda Peak, the former of which contains an east-flowing tributary called Chachani Creek. The Little Iskut River and Ball and More creeks are tributaries of the Iskut River which flows south and then west into the Stikine River. The Spectrum Range is part of

760-471: Is volcanic in origin , consisting of lava flows that are interbedded with volcanic ejecta . These lava flows and the associated ejecta originated from several volcanoes of the Mount Edziza volcanic complex which has been the focus of volcanic activity over the last 7.5 million years. Alkali basalt , hawaiite and trachyte are among some of the volcanic rocks comprising the Kitsu Plateau which

836-444: Is a crudely radial drainage system characterized by deeply incised valleys. Talus and felsenmeer deposits cover large portions of the valley slopes which rise to broad, rounded crests of the interfluvial ridges. These ridges are the eroded remains of a once continuous lava dome whose original surface is only preserved as a few small remnants on the summits of the higher peaks. The ridges and peaks decrease in elevation away from

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912-635: Is also at the southeastern end of Mount Edziza Provincial Park which is southeast of the community of Telegraph Creek . The name of the mountain became official on January 2, 1980, after being submitted to the BC Geographical Names office by the Geological Survey of Canada . Kounugu was the guardian of fresh water in Tahltan folklore "who slept throughout the day on top of the well that contained his treasure". Kounugu Mountain

988-430: Is characterized by warm summers and cold, snowy winters; temperatures are warmest in mid-summer during the day when they may hit the 30 degrees Celsius (86 degrees Fahrenheit) range. However, temperatures can drop below freezing during summer nights, making snow or freezing rain a possibility at any time of the year. The Spectrum Range can be accessed by float plane or helicopter, both of which are available for charter at

1064-555: Is dominated by the Mess Lake Lava Field which extends from Raspberry Creek in the north to Nagha Creek in the south. It covers an area of around 18 square kilometres (6.9 square miles) and contains three pyroclastic cones which were the source of lava flows that travelled westward towards the Mess Creek Escarpment. The oldest cone, sometimes referred to by the numeronym ML-1, is at the northern end of

1140-495: Is drained by many small streams that flow into these neighbouring valleys and, unlike the valleys, it is relatively barren of vegetation . Surrounding the Kitsu Plateau is Mount Edziza Provincial Park which is one of the largest provincial parks in British Columbia. Access to this remote plateau is mainly by aircraft since motorized vehicles are prohibited from entering Mount Edziza Provincial Park. The Kitsu Plateau

1216-423: Is exposed along the Mess Creek Escarpment on the western side of the plateau and at the southern and eastern ends of the plateau. This geological formation largely consists of comendite, pantellerite and pantelleritic trachyte which are in the form of lava domes and lava flows, as well as minor breccia and ash flow deposits. Spectrum trachyte flows on the Kitsu Plateau are relatively thin compared to those forming

1292-536: Is locally covered with iron and manganese oxides . The Spectrum Range lies at the southern end of Mount Edziza Provincial Park , a protected area founded in 1972 to showcase the volcanic landscape. This remote wilderness area of northwestern British Columbia is not accessible by motorized vehicles to help protect the very sensitive environment. Instead, access is mainly via aircraft or unmaintained hiking trails that cross creeks. Mount Edziza Provincial Park covers 266,180 hectares (657,700 acres), making it one of

1368-401: Is not accessible by motorized vehicles to help protect the very sensitive environment. Instead, access is mainly via aircraft or unmaintained hiking trails that cross creeks. Mount Edziza Provincial Park covers 266,180 hectares (657,700 acres), making it one of the largest provincial parks in British Columbia. Hunting, camping, fishing, hiking, wildlife viewing and nature studying are some of

1444-768: Is subdivided into five geological formations , each being the product of a distinct period of volcanic activity. Volcanism on the plateau continued into the current Holocene epoch and created the Mess Lake Lava Field which contains small volcanic cones . The Kitsu Plateau is on the Tahltan Highland east of the Boundary Ranges of the Coast Mountains and west of the Skeena Mountains in Cassiar Land District . Between

1520-462: Is the namesake of the Kounugu Member, a geological member of the Nido Formation which is a geological formation of the Mount Edziza volcanic complex. The base of Kounugu Mountain consists of basaltic lava flows of the Kounugu Member which erupted from multiple volcanoes during the Pliocene epoch. These lava flows are overlain directly by rhyolite of the Spectrum Formation which comprises

1596-477: Is the youngest and uppermost geological formation comprising the Kitsu Plateau, consisting of hawaiite and alkali basalt in the form of lava flows, lava bombs , agglutinate and air-fall tephra . These volcanic rocks were deposited by eruptions during the Holocene and mainly comprise the Mess Lake Lava Field, one of the three Big Raven lava fields of the Mount Edziza volcanic complex. Alkali basalt flows from

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1672-572: The Northern Cordilleran Volcanic Province , a broad area of volcanoes and lava flows extending from northwestern British Columbia northwards through Yukon into easternmost Alaska . 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

1748-610: The Skeena Mountains in Cassiar Land District . To the southwest, the Spectrum Range is surrounded by the Arctic Lake Plateau which includes adjacent volcanic features such as Outcast Hill , Wetalth Ridge , Exile Hill , Nahta Cone and Tadekho Hill . The Kitsu Plateau surrounds the Spectrum Range to the northwest and includes the Mess Lake Lava Field which consists of geologically recent lava flows and tephra from three pyroclastic cones . To

1824-589: The Sustut Group are present in the mouth of Nagha Creek valley at the southwestern end of the Kitsu Plateau and are in the form of conglomerates , sandstones , arkoses , siltstones , shales or minor coal . The name of the plateau was adopted 2 January 1980 on the National Topographic System map 104G/10 after being submitted to the BC Geographical Names office by the Geological Survey of Canada . It means northern lights in

1900-526: The Tahltan language and was likely chosen due to the plateau's association with Kitsu Creek and Kitsu Peak whose names were also adopted 2 January 1980 on the National Topographic System maps 104G/10 and 104G/7, respectively. The Kitsu Plateau lies at the southern end of Mount Edziza Provincial Park , a protected area founded in 1972 to showcase the volcanic landscape. This remote wilderness area of northwestern British Columbia

1976-464: The continental margin of North America during the Jurassic . The Spectrum Range consists mainly of trachyte, comendite and pantelleritic trachyte and rhyolite of the Spectrum Formation, the fifth oldest stratigraphic unit of the Mount Edziza volcanic complex. More than 90% of these volcanic rocks were erupted as lava while less than 10% of them were erupted as pumice and pyroclastic flows ;

2052-416: The second magmatic cycle of the Mount Edziza volcanic complex and was originally more than 25 kilometres (16 miles) wide. Much of the dome consists of massive rhyolite and trachyte lava flows but relatively minor basalt lava flows erupted later during the dome's formation. These lava flows form the nearly circular group of pyramidal peaks and long, narrow-crested ridges comprising the Spectrum Range;

2128-629: The second magmatic cycle . The fifth oldest geological formation comprising the Kitsu Plateau is the Big Raven Formation which was deposited during the fifth magmatic cycle in the last 20,000 years. The Raspberry Formation is exposed on the lower northern, western and southwestern sides of the Kitsu Plateau. It has an elevation of less than 1,310 metres (4,300 feet) along the Mess Creek Escarpment and consists of flat-lying basaltic lava flows interbedded with scoria . More than 180 metres (590 feet) of Raspberry lava flows are exposed in

2204-797: The 30 degrees Celsius (86 degrees Fahrenheit) range. However, temperatures can drop below freezing during summer nights, making snow or freezing rain a possibility at any time of the year. From near the Eastman Creek Rest Area south of Kinaskan Lake on the Stewart–Cassiar Highway , the historic Yukon Telegraph Trail extends about 15 kilometres (9.3 miles) west to the Little Iskut River. From there, it enters Mount Edziza Provincial Park and continues another 15 kilometres (9.3 miles) west along Bourgeaux Creek through Raspberry Pass. The telegraph trail then continues to

2280-670: The 6.3-million-year-old Armadillo Formation are exposed on the northern side of the plateau and along the Mess Creek Escarpment on the western side of the plateau where they overlie basaltic lava flows of the Raspberry Formation. Armadillo basalt flows are interbedded with air-fall pumice and ash flows of trachytic and comenditic compositions and were highly fluid and mobile at the time of their eruption as evidenced by their extreme persistence and relatively narrow thicknesses; individual basalt flows are normally less than 3 metres (9.8 feet) thick. The source of these flows

2356-476: The Arctic Lake Formation which formed during a period of volcanic activity 0.71 million years ago. Volcanism during the Holocene created subaerial cinder cones and lava flows on the northwestern and southwestern sides of the Spectrum Range, all of which are part of the Big Raven Formation . The basaltic Mess Lake Lava Field on the northwestern flank issued from three cinder cones adjacent to

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2432-597: The Boundary Ranges and the Kitsu Plateau is Mess Creek valley which extends more than 30 kilometres (19 miles) to the north where it separates the Zagoddetchino massif from the Big Raven Plateau in the east. The northern end of the plateau is bounded by Raspberry Pass which contains the east-flowing Bourgeaux Creek in the east and the northwest-flowing Raspberry Creek in the west. Between

2508-549: The Kitsu Member which likely issued from multiple eruptive centres on the dome's summit that have since been removed by erosion. These lava flows travelled over a layer of polymict gravel that overlies older volcanic rocks of the Spectrum Formation. Following construction of the Spectrum Dome, lesser activity continued into the Quaternary from parasitic vents in and adjacent to the Spectrum Range. Volcanism during

2584-556: The Kitsu Plateau and the Skeena Mountains is Artifact Ridge and the Little Iskut River , the latter of which flows north in a north–south trending valley and then flows southeast towards the Skeena Mountains into the Iskut River . In the southeast, the Kitsu Plateau is surrounded by the Spectrum Range while in the south the plateau is separated from Yagi Ridge by Nagha Creek valley. This roughly 10-kilometre-long (6.2-mile) and 6-kilometre-wide (3.7-mile) plateau lies at

2660-400: The Kitsu Plateau inside Nagha Creek valley and has been described as a pyroclastic cone or a conical explosion crater. The Kitsu Plateau is subdivided into at least five geological formations , each being the product of a distinct period of volcanic activity. These periods of volcanic activity occurred during three magmatic cycles of the Mount Edziza volcanic complex; each cycle began with

2736-582: The Kitsu Plateau is underlain by the Stikinia terrane . This is a Paleozoic and Mesozoic suite of volcanic, sedimentary and metamorphic rocks that accreted to the continental margin of North America during the Jurassic . The rocks of this terrane are exposed to the south and southwest where they are largely buried under landslide and colluvium deposits, as well as stream gravel, outwash and braided channel deposits. Minor exposures of Cretaceous – Paleocene sedimentary rocks assigned to

2812-424: The Mess Creek Escarpment, most of which were erupted from a shield volcano that formed on a Late Miocene erosion surface . These lava flows travelled westward into the ancestral valley of Mess Creek and originated from vents north of Raspberry Pass which were subsequently buried under younger volcanic deposits. A minimum age for the timing of Raspberry volcanism is 7.4–6.2 million years. Basaltic lava flows of

2888-520: The Mess Creek Escarpment, the Kitsu Plateau rises more than 910 metres (3,000 feet) above Mess Lake in Mess Creek valley; Mess Lake has an elevation below 760 metres (2,500 feet) while the Mess Creek Escarpment reaches an elevation of more than 1,700 metres (5,500 feet). The plateau surface is barren of vegetation but at lower elevations the surrounding valleys contain white spruce , lodgepole pine and trembling aspen forests. The Kitsu Plateau

2964-455: The Mount Edziza volcanic complex. A relatively small initial eruption of pumice and ash was followed by the effusion of massive rhyolite flows that reached 13 kilometres (8.1 miles) long. These rhyolite flows accumulated in rapid succession to form the broad Spectrum Dome which reached a thickness of at least 750 metres (2,460 feet) and a width of more than 25 kilometres (16 miles). The predominantly rhyolitic eruptions were later replaced by

3040-401: The Mount Edziza volcanic complex. Basaltic lava flows of this Pliocene geological member are exposed around the perimeter of the Spectrum Range and are limited only to the area south of the broad east–west valley of Raspberry Pass . They issued from at least four separate eruptive centres that have been either deeply eroded or have been completely destroyed by erosion. Also underlying

3116-530: The Nido Formation comprising the Kitsu Plateau. It consists of basaltic lava flows, flow breccia and agglutinate which were erupted 4.4 million years ago from at least four eruptive centres; these eruptive centres have since been deeply eroded and buried under younger volcanic deposits. At least some of the Kounugu lava flows comprising the Kitsu Plateau may have originated from Swarm Peak further to

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3192-599: The Pleistocene created a number of small volcanoes on the southwestern flank of the mountain range that formed in subaerial and subglacial environments. Subaerial lava fountaining at the extreme northern end of the Arctic Lake Plateau created the Outcast Hill cinder cone which blocked westerly flowing streams to create a temporary lake against its eastern side. About 4 kilometres (2.5 miles) to

3268-540: The Spectrum Range are flat-lying basalt flows of the Raspberry Formation , the oldest unit of the Mount Edziza volcanic complex. This geological formation is of late Miocene age and originated as a composite shield volcano that erupted lava from at least three locations near Raspberry Pass. The Nido and Raspberry formations are underlain by the Stikinia terrane , a Paleozoic and Mesozoic suite of volcanic and sedimentary rocks that accreted to

3344-439: The Spectrum Range is covered with relatively small separate glaciers that occupy cirques on most peaks greater than 2,130 metres (6,990 feet) in elevation. The largest glacier is Nagha Glacier which initiates just northwest of Yeda Peak and terminates at the head of the valley between Yagi Ridge and the Kitsu Plateau. Yeda Glacier, an informally named glacier at the head of Ball Creek , existed south of Yeda Peak in 1988. As

3420-491: The Spectrum Range was covered by a regional ice sheet during the Pleistocene which receded and advanced periodically until about 11,000 years ago when deglaciation was essentially complete in a steadily warming climate. This warming trend ceased about 2,600 years ago, causing glaciers to advance from the Spectrum Range and elsewhere along the volcanic complex as a part of the neoglaciation . The present trend towards

3496-435: The Spectrum Range. As a part of the Mount Edziza volcanic complex, the Kitsu Plateau is drained entirely by streams within the Stikine River watershed . The only named stream on the plateau is Kitsu Creek which originates on the northern flank of Kitsu Peak in the Spectrum Range and flows northwest then north into Mess Creek, a tributary of the Stikine River. Several small unnamed streams flow into Kitsu Creek and

3572-482: The activities available in Mount Edziza Provincial Park. Wildlife in the area includes moose , caribou , mountain goats , stone sheep , wolves , bears , squirrels , owls , ptarmigans , ravens , gyrfalcons , grouse and migratory songbirds . The climate is characterized by warm summers and cold, snowy winters; temperatures are warmest in mid-summer during the day when they may hit

3648-510: The adjacent Spectrum Range but they are the most distal remnants of the main Spectrum Dome . These trachyte flows are overlain by alkali basalt of the Kitsu Member which is mainly exposed at the southern end of the Kitsu Plateau and along the western edge of the plateau. This alkali basalt is in the form of lava flows and likely originated from vents of the Spectrum Dome which have since been destroyed by erosion. The Big Raven Formation

3724-559: The basalt flows mainly cap the higher peaks. Volcanism in the last 2.5 million years has mainly occurred on the northwestern and southwestern sides of the Spectrum Range but the precise age of the latest eruption is unknown. The Spectrum Range was labelled as the Rainbow Mountains on a BC Lands map published in 1929 which was followed by renaming of the mountain range to the Spectrum Mountains in 1945. In 1954,

3800-406: The base of the Spectrum Dome during the explosive Yeda Peak breccia pipe eruption. It lies along the edge of the hypothetical caldera or irregular collapse structure and comprises a series of glacially rounded bluffs along the southwestern side of Ball Creek valley. The soda granite forming this subvolcanic intrusion is lustrous brown and medium to coarse-grained, consisting mostly of feldspar that

3876-468: The breccia pipe comprising this peak and along adjacent fractures; it likely resulted from fumarolic activity after the explosive eruption that formed the Yeda Peak crater. Alteration elsewhere in the Spectrum Range was caused by fumarolic activity during the cooling and degassing of lava flows comprising the Spectrum Formation. In contrast to the fumarolic activity at Yeda Peak which was likely sourced by

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3952-437: The bulk of Kounugu Mountain. The Spectrum Formation is the eroded remains of a large Pliocene lava dome that forms the current pyramidal peaks and ridges of the Spectrum Range. Spectrum Range The Spectrum Range is the eroded remains of a large lava dome whose original surface is only preserved as a few small remnants on the summits of the higher peaks. This dome formed between 3.5 and 2.5 million years ago during

4028-425: The central portion of the mountain range. Among these peaks and ridges are Kitsu Peak , Yeda Peak , Kuno Peak , Kounugu Mountain , Obsidian Ridge and Yagi Ridge . The current, approximately 19-kilometre-wide (12-mile) dome comprising the Spectrum Range originally had a width of more than 25 kilometres (16 miles) as indicated by the existence of erosional remnants around its northern and southwestern edges. It

4104-446: The communities of Iskut and Dease Lake . Private aircraft are prohibited from landing on the Kitsu Plateau lava flows. Mess Lake northwest of the Spectrum Range, 180 Lake southeast of the Spectrum Range, Arctic Lake and Little Arctic Lake southwest of the Spectrum Range and Little Ball Lake just south of Kounugu Mountain at the southwestern end of the Spectrum Range are large enough to be used by float-equipped aircraft. Landing on

4180-423: The depression and of the bounding vertical faults has given fragmentary evidence. The southwestern side of a northwesterly-trending, nearly vertical fault adjacent to Stewbomb Creek has dropped at least 90 metres (300 feet) and is cut by parallel rhyolite dikes . The rocks comprising the Spectrum Range were deposited by volcanic eruptions between 3.5 and 2.5 million years ago during the second magmatic cycle of

4256-539: The east which issued lava that travelled westward; remains of the Swarm Peak eruptive centre are in the form of north-trending fissure swarms. Lava from the Swarm Peak eruptive centre is exposed along the Mess Creek Escarpment where it overlies till and glacial- fluvial gravel derived from the Armadillo Formation. The Kounugu Member is overlain by the 3.1-million-year-old Spectrum Formation which

4332-407: The edge of the Mess Creek Escarpment. Lava from the two oldest cones flowed to the west and probably cascaded over the escarpment into Mess Creek valley. The youngest cinder cone, The Ash Pit , formed at the south end of the Mess Lake Lava Field and was the source of a northeasterly-trending tephra deposit on the Kitsu Plateau. An eruption near the northern edge of the Arctic Lake Plateau created

4408-578: The effusion of alkali basalt and culminated with the eruption of lesser volumes of felsic magma. The two oldest geological formations comprising the Kitsu Plateau are the Raspberry and Armadillo 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 Spectrum formations which were deposited between 6 and 3 million years ago during

4484-436: The effusion of trachyte lava as deeper parts of the underlying magma chamber were tapped. Formation of the Spectrum Dome was followed by evacuation of the magma chamber, resulting in the creation of the caldera which was eventually buried by lava from subsequent eruptions. Yeda Peak, a 2,240-metre-high (7,350-foot) pinnacle in the middle of the Spectrum Range, was the site of a subsequent explosive eruption that resulted in

4560-432: The form of name was changed to the Spectrum Range in accordance to the Geological Survey of Canada memoir 247 published in 1948. These names for the mountain range refer to its multi-coloured rocks; pale green, light grey and white rocks weather to bright hues of orange, yellow and red. The Spectrum Range lies at the southern end of the Tahltan Highland east of the Boundary Ranges of the Coast Mountains and west of

4636-494: The formation of a crater . Some of the ejecta accumulated around the vent to form a low volcanic cone while the more volatile, pumice-rich phases of the eruption sent ash flows down the slopes of the Spectrum Dome. Renewed volcanism at Exile Hill 8 kilometres (5.0 miles) to the west on the Arctic Lake Plateau produced a similar but much smaller eruption that created a roughly 200-metre-wide (660-foot) breccia pipe . Late-stage volcanism also deposited alkali basalt flows of

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4712-424: The isolated Nahta Cone on the southwestern flank of the Spectrum Range which was the source of a narrow, 3-kilometre-long (1.9-mile) basaltic lava flow that travelled northward into the head of Nahta Creek. Volcanic activity on the southern flank of Kuno Peak at the southwestern end of the Spectrum Range created a cinder cone that was subsequently destroyed by landsliding on Kuno Peak. This cinder cone also produced

4788-405: The largest provincial parks in British Columbia. Hunting, camping, fishing, hiking, wildlife viewing and nature studying are some of the activities available in Mount Edziza Provincial Park. Wildlife in the area includes moose , caribou , mountain goats , stone sheep , wolves , bears , squirrels , owls , ptarmigans , ravens , gyrfalcons , grouse and migratory songbirds . The climate

4864-530: The latter two lakes with a private aircraft requires a letter of authorization from the BC Parks Stikine Senior Park Ranger. Mess Lake Lava Field The Kitsu Plateau is a small intermontane plateau in Cassiar Land District of northwestern British Columbia , Canada. It lies on the Tahltan Highland and is surrounded by several valleys, including those of Mess Creek , Nagha Creek and Raspberry Creek . The plateau

4940-409: The lava field while the second oldest cone, ML-2, is at the southern end of the lava field. Both cones are covered by tundra vegetation and have been slightly rounded by erosion, although their craters are still recognizable. The Ash Pit , sometimes referred to by the numeronym ML-3, is the youngest and southernmost eruptive centre of the Mess Lake Lava Field. It lies on the steep southern slope of

5016-430: The lava is in the form of flows that individually reach thicknesses of up to 200 metres (660 feet). These volcanic rocks are overlain locally by eroded remnants of Kitsu Member basaltic lava flows which preserve the unmodified upper surface of the original Spectrum Dome and cap the higher peaks of the Spectrum Range. In the middle of the Spectrum Range at the base of the volcanic pile is a buried depression that may be

5092-495: The neighbouring valleys of Mess Creek, Raspberry Creek and Nagha Creek; Raspberry Creek drains into Mess Creek while Nagha Creek drains into Kitsu Creek just northeast of Mess Lake . The western, northern and southern edges of the Kitsu Plateau are marked by steep cliffs forming the Mess Creek Escarpment , the southern side of Raspberry Creek valley and the northern side of Nagha Creek valley, respectively. At

5168-439: The north and northeast, the Spectrum Range is bounded by Raspberry Pass and Artifact Creek valley, respectively, the latter of which separates Artifact Ridge from the mountain range. The Spectrum Range lies at the southern end of the Mount Edziza volcanic complex which includes the adjacent Arctic Lake and Kitsu plateaus, as well as Mount Edziza and the Big Raven Plateau to the north. This volcanic complex consists of

5244-497: The north-northeast on the Kitsu Plateau. The Ash Pit was also the source of a hawaiitic lava flow that travelled 3.5 kilometres (2.2 miles) to the northwest through Nagha Creek valley towards Mess Lake. Residual heat from The Ash Pit eruption may have resulted in the formation of the Mess Lake Hot Springs 2.5 kilometres (1.6 miles) to the west in Mess Creek valley. As a part of the Mount Edziza volcanic complex,

5320-476: The northwest through Raspberry Creek valley along the northern edge of the Kitsu Plateau for about 15 kilometres (9.3 miles) to Mess Creek valley. Only short segments of the Yukon Telegraph Trail are still passible, having been mostly overgrown since maintenance of the trail ended in 1936. The Kitsu Plateau can be accessed by float plane or helicopter, both of which are available for charter at

5396-445: The northwest. Kitsu and Tadekho creeks both flow into Mess Creek which is a northwest-flowing tributary of the Stikine River. The Little Iskut River originates from Little Ball Lake just south of Kounugu Mountain and flows to the northeast where it collects Stewbomb Creek flowing east from the Spectrum Range. Stewbomb Creek contains one named tributary, Artifact Creek, which originates adjacent to Kitsu Peak and flows through

5472-418: The south, Tadekho Hill formed on top of a 180-metre-high (590-foot) remnant of Spectrum Formation trachyte. Lava from this volcano spread onto the surrounding plateau surface to form a small shield volcano. Subsequent subglacial volcanism near the central portion of the Arctic Lake Plateau formed the subglacial mound of Wetalth Ridge. All three Pleistocene volcanoes are basaltic in composition and are part of

5548-585: The southern end of the Mount Edziza volcanic complex which also includes the Big Raven Plateau to the north, as well as the Spectrum Range and the Arctic Lake Plateau to the south. This volcanic complex consists of a group of overlapping shield volcanoes , stratovolcanoes , lava domes and cinder cones that have formed over the last 7.5 million years. It contains four central volcanoes along its north–south trending axis; from north to south they are Mount Edziza , Ice Peak , Armadillo Peak and

5624-465: The two oldest pyroclastic cones in the Mess Lake Lava Field, ML-1 and ML-2, most likely cascaded over the Mess Creek Escarpment into Mess Creek valley, but no evidence of this phenomenon has been found on or below the escarpment. The Ash Pit, which may be the youngest eruptive centre of the entire Mount Edziza volcanic complex, was the source of a 6.5-kilometre-long (4.0-mile) and 2.5-kilometre-wide (1.6-mile) hawaiitic air-fall tephra deposit that extends to

5700-430: Was also originally higher than its current elevation of 2,430 metres (7,970 feet) as evidenced by the thick, gently dipping lava flows comprising the summit of Kitsu Peak, the highest point of the Spectrum Range. The original volume of the Spectrum Dome is estimated to have been 101 cubic kilometres (24 cubic miles) based on restoration calculations of the original surface. As a part of the Mount Edziza volcanic complex,

5776-429: Was probably a cluster of vents further to the north called Sezill Volcano which may have been active prior to the onset of Armadillo volcanism. In contrast, the air-fall pumice and ash flows probably originated from the more than 4-kilometre-in diameter (2.5-mile) Armadillo Peak caldera northeast of the Kitsu Plateau. Overlying the Armadillo Formation is the Kounugu Member which is the only stratigraphic unit of

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