Hoodoo Mountain, sometimes referred to as Hoodoo Volcano, is a potentially active stratovolcano in the Northern Interior of British Columbia, Canada. It is located northeast of the Alaska–British Columbia border on the north side of the Iskut River opposite of the mouth of the Craig River. With a summit elevation of and a topographic prominence of , Hoodoo Mountain is one of many prominent peaks within the Boundary Ranges of the Coast Mountains. Its flat-topped summit is covered by an ice cap more than thick and at least in diameter. Two valley glaciers surrounding the northwestern and northeastern sides of the mountain have retreated significantly over the last hundred years. They both originate from a large icefield to the north and are the sources of two meltwater streams. These streams flow along the western and eastern sides of the volcano before draining into the Iskut River.
Much of Hoodoo Mountain was formed beneath glacial ice and it has been overlain by glaciers or an ice cap throughout much of its history. The main rock types composing the volcano are phonolite and trachyte, which were deposited during six periods of eruptive activity beginning about 85,000 years ago. Most of these eruptive periods were characterized by steady flows of lava, but at least one period of explosive activity occurred as indicated by the presence of pyroclastic rocks. The latest eruptive period began about 10,000 years ago with the eruption of extensive lava flows that cover the north–central, northwestern and southeastern mountain slopes. A lava flow covering the southwestern slope may have been produced by a more recent eruption within the last couple of hundred years. Although no historical eruptions are known at Hoodoo Mountain, there have been periods of seismic activity since at least the mid-1980s, indicating possible future eruptions and volcanic hazards.
Hoodoo Mountain lies in a remote area of Cassiar Land District that has undergone mineral exploration since at least the early 1900s. This exploration led to the discovery of copper, silver and gold within the Iskut River floodplain where two underground mines operated between 1988 and 1999. Geological studies have been conducted at Hoodoo Mountain since at least the 1940s; the most detailed studies occurred in the 1990s and 2000s. The area has a mostly cool and wet climate with heavy precipitation. As a result, a limited number of mammals live around Hoodoo Mountain. Trees of the pine and willow families form forests in the regional river valleys and on the lower slopes of the volcano. They compose one of many ecoregions that occur throughout British Columbia. Due to its remoteness, Hoodoo Mountain can only be accessed by air, by water or by trekking great distances on foot. The closest communities are more than away from the mountain.
Geography Biogeography Hoodoo Mountain lies within the Boundary Ranges Ecoregion, a mountainous region of the Coast Mountains in southeastern Alaska and northwestern British Columbia characterized by rugged, largely ice-capped mountains of granitic and metamorphic rocks. Mountain hemlock, western hemlock and Sitka spruce form forests on valley bottoms and lower valley slopes. They are overlooked by an extensive alpine tundra zone consisting primarily of large icefields, glaciers and barren rock. Several large river valleys with wide braided channels penetrate the Boundary Ranges Ecoregion; black cottonwood occur on their floodplains. A limited number of mammal species thrive in this ecoregion, such as hoary marmots and mountain goats, which inhabit the alpine tundra zone. The Boundary Ranges Ecoregion is part of the Coast and Mountains Ecoprovince which forms part of the Humid Maritime and Highlands Ecodivision.
The Boundary Ranges Ecoregion is subdivided into three ecosections, the Southern Boundary Ranges Ecosection being the main ecosection at Hoodoo Mountain. This ecosection is cut by several streams, including the Salmon, Bear and Unuk rivers, which drain directly into marine channels or sounds. The only settlements in the Southern Boundary Ranges Ecosection are Kincolith, Stewart and Hyder, the latter two of which are connected by the Stewart Highway. There is no human population within of Hoodoo Mountain, but 2,330 people live within . Forests of this ecosection grow on the lower slopes of Hoodoo Mountain except for its northeastern flank where rock and ice are dominant. Much of this forest cover lies at elevations below .
Climate Hoodoo Mountain has a maritime glacial climate that is intermediate between fully coastal maritime and continental climates. Moist air from the Pacific Ocean brings intense precipitation over the region while simultaneously allowing cold Arctic air to pass down through the Portland Canal into the Dixon Entrance where it flows into British Columbia's North Coast. Therefore, the regional climate is mostly cool and wet with snowpacks and heavy precipitation. About of precipitation falls during the summer months of June, July and August whereas up to of precipitation can be expected during the winter months of December, January and February. In summer the average temperature is whereas the average winter temperature sits at . The annual average temperature is .
Glaciers
Two valley glaciers wrap partially around the base of Hoodoo Mountain, both of which are actively retreating. Hoodoo Glacier surrounding its northwestern base is the source of the Hoodoo River which flows south into the Iskut River. It has lost about of its total thickness over the last 700 years and its terminus has retreated at least since the 1920s. At the terminus of Hoodoo Glacier is a roughly long and wide lake which may occupy a previously drained depression. The western side of the glacier contains a small possibly drained ice-marginal lake. Twin Glacier surrounds the northwestern base of Hoodoo Mountain and is the largest of the two valley glaciers. It is the source of the Twin River which also flows south into the Iskut River. Several changes have taken place at this double-lobed glacier since the 1920s. Its terminus has retreated about , having formerly flowed around both sides of a north–south trending ridge. A small moraine-dammed lake lies along the southwestern margin of Twin Glacier.
The Hoodoo and Twin glaciers are separated by a ridgeline extending north of Hoodoo Mountain. They have cut deep valleys into the older regional bedrock and have interacted with Hoodoo Mountain intermittently since the Pleistocene. Both glaciers originate from the Andrei Icefield centered northeast of Hoodoo Mountain. This large glacial field is informally named after the son of Olav Mokievsky-Zubok, a glaciologist who carried out significant glaciological work in the Coast Mountains from the 1960s to the 1970s.
The summit of Hoodoo Mountain contains an ice cap that persists at elevations greater than . It varies from thick and has a diameter of , attaining a minimum volume of . Its circular shape and higher elevation have made it relatively stable to climate change, having undergone minor retreat and thinning only at its very edges. It therefore maintains at least partial snow cover during all months of the year. At the north–central end of the ice cap lies a prominent nunatak called The Horn or Horn Nunatak which consists of pyroclastic rock surrounding a core of lava.
Geology Background Hoodoo Mountain is part of the Northern Cordilleran Volcanic Province (NCVP), a broad area of shield volcanoes, lava domes, cinder cones and stratovolcanoes extending from northwestern British Columbia northwards through Yukon into easternmost Alaska. The dominant rocks that make up these volcanoes are alkali basalts and hawaiites, but nephelinites, basanites and peralkaline phonolites, trachytes and comendites are locally abundant. These rocks were deposited by volcanic eruptions from 20 million years ago to as recently as a few hundred years ago. Volcanism 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.
Hoodoo Mountain is part of a subdivision of the NCVP called the Stikine Subprovince. This subprovince, confined to the Stikine region of northwestern British Columbia, includes three other volcanic centres: Heart Peaks, Level Mountain and Mount Edziza. The four volcanic centres differ petrologically and/or volumetrically from the rest of the NCVP. Heart Peaks, Level Mountain and Mount Edziza are the largest NCVP centres by volume, the latter two of which have experienced volcanism for a much longer timespan than any other NCVP centre. Hoodoo Mountain, Level Mountain and Mount Edziza are the only NCVP centres that contain volcanic rocks of both mafic and intermediate to felsic composition. The highest of the four complexes is Mount Edziza at , followed by Level Mountain at , Heart Peaks at and Hoodoo Mountain at .
Hoodoo Mountain is one of ten volcanoes composing the Iskut volcanic field. This is a group of NCVP volcanoes scattered along the Iskut River and its main tributaries. They consist of both subaerial and glaciovolcanic deposits, the latter of which are in the form of pillow lavas, tuff breccias and hyaloclastite. All of these volcanoes were active in the last 150,000 years; the latest eruption occurred from The Volcano about 150 years ago. The remaining Iskut volcanoes are Cinder Mountain, Little Bear Mountain and the Cone Glacier, Iskut Canyon, Second Canyon, Snippaker Creek, King Creek and Tom MacKay Creek cones.
Structure
Hoodoo Mountain is one of the largest peralkaline volcanoes in the NCVP. It is a stratovolcano composed primarily of peralkaline phonolite and trachyte lava flows and hyaloclastites, although some pyroclastic rocks are also present. Its peralkalinity is unique among other volcanoes in the Iskut volcanic field, which range in composition from alkali basalt to hawaiite. Hoodoo Mountain has also been designated as a subglacial volcano due to much of the mountain having formed subglacially in the last 85,000 years. Its involvement with glaciation has resulted in several interactions with glacial ice as much as thick, affording multiple examples of glaciovolcanic processes. This includes the formation of ice-marginal lava flows and the interlayering of glacial till with volcanic deposits.
Hoodoo Mountain's constant struggle with surrounding and overlying ice is attested by its nearly flat summit, which attains an elevation of . Lava flows from Hoodoo Mountain partially bury Little Bear Mountain, a much smaller and older basaltic volcano immediately to the north. Both volcanoes are underlain by plutonic rocks and metamorphosed volcanic and sedimentary rocks of Stikinia. These basement rocks are of Paleozoic-to-Mesozoic age; pyroxene-bearing syenite composes a significant portion of the Mesozoic basement. Intruding the basement rocks are 1.8-million-year-old trachyandesite dikes, which represent the earliest known manifestations of Quaternary magmatism in the Iskut region.
Hoodoo Mountain has been described as "one of the most magnificent and interesting mountains in northern British Columbia". This is because it has a different lithological and topographical structure than most glaciated mountains in the Canadian Cordillera. In contrast to its rugged counterparts, Hoodoo Mountain is symmetrical and circular in form. It has a basal diameter of around , a volume of and a topographic prominence of , making it the smallest of the four volcanoes composing the Stikine Subprovince. Hoodoos, pillar-like rock formations after which the volcano is named, are as much as in height and give the mountain a unique appearance. In 1919, a landslide removed lava rock from a wide section on the western side of Hoodoo Mountain.