Mount Edziza volcanic complex
The Mount Edziza volcanic complex 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 Lake. The complex encompasses a broad, steep-sided lava plateau that extends over. Its highest summit is in elevation, making the MEVC the highest of four large complexes in an extensive north–south trending volcanic region. It is obscured by an ice cap characterized by several outlet glaciers that stretch out to lower altitudes.
The MEVC consists of several types of volcanoes, including stratovolcanoes, shield volcanoes, cinder cones and lava domes. These volcanoes have formed over the last 7.5 million years during five cycles of magmatic activity which spanned four geologic epochs. Volcanic eruptions during these magmatic cycles produced a wide variety of volcanic rocks that comprise 13 geological formations. The most recent eruptions took place in the last 11,000 years but none of them have been precisely dated. Current activity occurs exclusively in the form of hot springs which exist along the western side of the volcanic complex. Future eruptions are likely to impact local streams and cause wildfires.
Several streams surround the MEVC, many of which drain the flanks of the volcanic complex. They include the Little Iskut River along the southeastern flank, Kakiddi Creek along the northeastern flank, the Klastline River along the northern flank and Mess Creek along the western flank. The valleys of these streams contain several species of trees, including white spruce, trembling aspen and lodgepole pine. Animal species such as birds, rodents, bears, sheep, goats, moose and caribou inhabit the area. Warm summers and cold, snowy winters characterize the climate at the MEVC; snow and ice remain on the highest volcanoes year-round.
Indigenous peoples have lived adjacent to the MEVC for thousands of years. Historically, the local Tahltan people used volcanic glass from the MEVC to make tools and weaponry. Intermittent geological work has been carried out at the volcanic complex since at least the 1950s, the most detailed studies having been conducted in the 1960s. A large provincial park, which can only be accessed by aircraft or by a network of horse trails, dominates the MEVC.
Names and etymology
The Mount Edziza volcanic complex is sometimes referred to as the Mount Edziza–Spectrum Range complex or the Mount Edziza Plateau. Stratigraphically, it has also been referred to as the Mount Edziza Group or the Edziza Group. A number of explanations have been made regarding the origin of the name Edziza. A 1927 report by J. Davidson of the British Columbia Land Surveyors claims that Edziza means "sand" in the Tahltan language, referring to the deep volcanic ash deposits or pumice-like sand covering large portions of the Big Raven Plateau around Mount Edziza. According to David Stevenson of University of Victoria's Anthropology Department, "sand" or "dust" is instead translated as "kutlves" in the Tahltan language. An explanation listed in the BC Parks brochure is that Edziza means "cinders" in the Tahltan language. Another explanation proposed by Canadian volcanologist Jack Souther is that Edziza is a corruption of Edzerza, the name of a local Tahltan family.Geography and geomorphology
Structure
The geomorphology of the MEVC is in some ways similar to that of the Eyjafjallajökull volcano in Iceland. This includes its overall elongated structure, its flanking basaltic lava fields and its summit ice cap surrounded by silica-rich volcanic rocks. The elongated structure of the MEVC is about long and wide. It comprises a broad, steep-sided, intermontane plateau that rises from a base elevation of. Its sides tower above adjacent valleys that serve as drainageways for several streams. The edges of the plateau have been deeply incised by creeks that flow eastward and westward into Mess Creek, Kakiddi Creek and the Iskut River. A northerly-trending, elliptical, composite shield volcano consisting of multiple flat-lying lava flows forms the plateau.Location
The MEVC is surrounded on the east by the Skeena Mountains and the Klastline Plateau whereas to the west it is flanked by the Coast Mountains. It lies on the eastern edge of the Tahltan Highland, a southeast-trending upland area extending along the western side of the Stikine Plateau between the Boundary Ranges in the west and the head of the Iskut River in the east. The width of the Tahltan Highland varies from about in the north to about in the south where the Stikine River crosses the highland.The MEVC is in the Southern Boreal Plateau Ecosection which consists of several upland summits as well as wide river valleys and deeply incised plateaus. It is one of seven ecosections comprising the Boreal Mountains and Plateaus Ecoregion, a large ecological region of northwestern British Columbia encompassing high plateaus and rugged mountains with intervening lowlands. Boreal forests of black and white spruce occur in the lowlands and valley bottoms of this ecoregion whereas birch, spruce and willow form forests on the mid-slopes. Extensive alpine altai fescue covers the upper slopes but barren rock is abundant at higher elevations.
Landforms
Four central volcanoes dominate the MEVC, Mount Edziza being the highest with an elevation of. It is a large ice-covered stratovolcano rising well above the general level of the Tahltan Highland. Ice Peak is a composite stratovolcano in elevation that has been reduced to a steep-walled pyramidal peak with active cirques on all of its sides. The Spectrum Range has an elevation of and consists of a nearly circular, more than wide dome with a thickness of up to. Armadillo Peak represents the eroded remains of a small caldera whose summit is capped by a thick sequence of ponded lava flows. Various stages of erosion have modified these central volcanoes; in some cases, only a few small remnants of their original surface remain. The degree of erosion becomes less pronounced on those that have more recently formed.Several cinder cones dotting the plateau surface rise up to above the surrounding terrain, most of which occur in three lava fields. The Desolation Lava Field on the northern slope of Mount Edziza contains 10 cinder cones, namely Eve Cone, Storm Cone, Moraine Cone, Williams Cone, Sleet Cone, Twin Cone, Sidas Cone and the three Triplex Cones. Five named cones occur in the Snowshoe Lava Field on the southwestern flank of Ice Peak: Tennena Cone, Keda Cone, Coffee Crater, Cocoa Crater and The Saucer. The Ash Pit is the only named cinder cone in the Mess Lake Lava Field which lies at the south-central end of the MEVC. Isolated cinder cones include Icefall Cone and Ridge Cone on the eastern slope of Mount Edziza, Nahta Cone at the extreme southern end of the MEVC, Kana Cone on the extreme northern flank of the MEVC and two unnamed cones in Walkout Creek valley.
The MEVC contains three named subplateaus, the largest and northernmost of which is the Big Raven Plateau. Its dominant feature is Mount Edziza which rises from within the middle of the plateau. Two lava fields are present on the Big Raven Plateau; the Desolation Lava Field at the northern end of the plateau covers more than whereas the Snowshoe Lava Field covers about at the southern end of the plateau. At the northwestern end of the Spectrum Range is the Kitsu Plateau; its dominant feature is the even smaller Mess Lake Lava Field which covers. The Arctic Lake Plateau is the southernmost of the three subplateaus; it consists of a nearly flat upland containing Outcast Hill, Tadekho Hill, Wetalth Ridge, Nahta Cone, Source Hill, Thaw Hill and Exile Hill.
In the north fork of Tenchen Creek is Cinder Cliff, a high barrier of volcanic rocks. Koosick Bluff and Ornostay Bluff are just southwest of Mount Edziza near the head of Sezill Creek. Northwest and east of Coffee Crater are Hoia Bluff and Kaia Bluff, respectively. Hoia Bluff is a prominent west-facing cliff whereas Kaia Bluff is a steep-sided hill. On the northwestern side of Raspberry Pass is an isolated, flat-topped hill with steep sides called Gnu Butte. The Mess Creek Escarpment is a long, often cliff-like feature forming the western edge of the MEVC. It runs along the eastern side of Mess Creek and exposes thick, flat-lying lava flows. Artifact Ridge is a crescent-shaped mountain ridge east of the Kitsu Plateau and just north of Artifact Creek. Just south of Artifact Ridge and Artifact Creek is Obsidian Ridge, a mountain ridge containing high-quality obsidian.
Destell Pass is a narrow rock cleft northwest of Artifact Ridge that provides access between the broad upland valleys of Artifact Creek and Raspberry Creek. It is one of two named mountain passes in the MEVC, the other being Raspberry Pass between the heads of Bourgeaux Creek and Raspberry Creek. Raspberry Pass is a broad east–west valley separating the Spectrum Range in the south from the Mount Edziza area in the north.
Lakes
The eastern side of the MEVC is flanked by Mowdade Lake, Kakiddi Lake, Mowchilla Lake and Nuttlude Lake in Kakiddi Valley; the last three drain north into the Klastline River. Buckley Lake is the main lake bordering the northern side of the MEVC whereas Mess Lake is the main lake bordering the western side of the MEVC. Southeast of the MEVC is 180 Lake, so-named because it is large enough for the Cessna 180 Skywagon to safely operate. The southern end of the MEVC is flanked by Arctic Lake which gets its name from the surrounding barren and treeless landscape.Two small lakes are named on the southern portion of the MEVC. At the head of the Little Iskut River is Little Ball Lake, also called Kounugu Lake after the guardian of fresh water in Tahltan folklore. It lies immediately south of Kounugu Mountain in the Spectrum Range and east of Ball Creek. Little Arctic Lake lies northeast of Arctic Lake near the northeastern flank of Wetalth Ridge.