Spectrum Range
The Spectrum Range, formerly called the Spectrum Mountains and the Rainbow Mountains, is a subrange of the Tahltan Highland in the Stikine Country of northwestern British Columbia, 20 km west of the Stewart-Cassiar Highway, south of Mount ...
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
, Canada. It is bounded on the west by Nagha Creek valley, on the northwest by the Kitsu Plateau, on the northeast by
Obsidian Ridge Obsidian Ridge is a volcanic mountain ridge in the Spectrum Range of northwestern British Columbia, Canada, located on the south side of Artifact Creek at the southeast end of Mount Edziza Provincial Park. It was named on January 2, 1980 by the G ...
, on the east by Stewbomb Creek valley and on the southwest by Nagha Glacier and Yagi Ridge. It has an elevation of and lies at the northern end of the Spectrum Range.
Kitsu Peak is at the southern end of
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 protect the Mount Edziza volcanic complex and the surrounding Tahltan Highland.
Geography
The p ...
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58volcanic rocks of the Spectrum Formation which consists of
comendite
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 ...
trachyte
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 enriched with silica and al ...
. These rocks are in the form of
lava flow
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...
s as well as minor
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...
and
ash flow
A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...
deposits. The Spectrum Formation is the eroded remains of a large
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 on ...
that forms the current
pyramidal peak
A pyramidal peak, sometimes called a glacial horn in extreme cases, is an angular, sharply pointed mountain peak which results from the cirque erosion due to multiple glaciers diverging from a central point. Pyramidal peaks are often examples o ...
s and
ridge
A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...
s of the Spectrum Range. Truncated remnants of thick, gently dipping trachyte flows at the summit of Kitsu Peak indicate that the summit of the original dome was higher in elevation than it is today.