The Itcha Range, also known as the Itchas, is a small isolated mountain range in the West-Central Interior of British Columbia, Canada. It is located 40 km (25 mi) northeast of the community of Anahim Lake. With a maximum elevation of 2,375 m (7,792 ft), it is the lowest of three mountain ranges on the Chilcotin Plateau extending east from the Coast Mountains. Two mountains are named in the Itcha Range; Mount Downton and Itcha Mountain. A large provincial park surrounds the Itcha Range and other features in its vicinity. More than 15 animal species are known to exist in the Itcha Range area, as well as a grassland community that is limited only to this location of British Columbia. The Itcha Range is within territory which has been occupied by aboriginal peoples for millennia. This area has a relatively dry environment compared to the Coast Mountains in the west. In contrast to most mountain ranges in British Columbia, the Itcha Range represents an inactive shield volcano. This highly dissected volcanic edifice consists of a variety of rock types, including basanite, hawaiite, trachyte, rhyolite, phonolite and alkali olivine basalt. They were deposited by different types of volcanic eruptions characterized by passive lava flows and explosivity. Two stages of eruptive activity have been identified at the volcano along with three sub-phases that are limited only to the first stage of development. The main body of the Itcha Range is between 3.8 and 3.0 million years old and thus over two million years ago it passed the most active shield stage of life. A period of dormancy lasting for almost a million years followed, which was interrupted by the post-shield stage of volcanism 2.2 to 0.8 million years ago. More recent volcanic activity in and around the Itcha Range might have occurred in the last 340,000 years to produce cinder cones. The Itcha Range is part of an east–west trending volcanic zone called the Anahim Volcanic Belt. This consists of large shield volcanoes, small cinder cones, lava domes and lava flows that become progressively younger from west to east. Several explanations have been made regarding the creation of this feature, each citing a different geologic process. If volcanic activity were to resume at the Itcha Range, Canada's Interagency Volcanic Event Notification Plan (IVENP) is prepared to notify people threatened by eruptions.
Geography
Location and terrain The Itcha Range is situated on the northern Chilcotin Plateau, a subdivision of the Fraser Plateau which in turn is one of the main subdivisions of the large Interior Plateau. It is bordered on the west by the Ilgachuz Range, another mountain range on the Chilcotin Plateau. The Itcha Range is located within one of British Columbia's many territorial divisions known as the Range 3 Coast Land District. Stream erosion has played a significant role in dissecting the mountain range, and many of its peaks are dotted with glaciers. This dissection has resulted in a variety of landforms, such as valleys, crags and domes. Small graveled creeks flow from alpine mountains out onto the regional prairies where there are pale blue rock-bottomed lakes, including the so-named Itcha Lake. Three streams drain the Itcha Range, namely Corkscrew Creek, Downton Creek and Shag Creek. Although the Itcha Range has been dissected by stream erosion and subsequently glaciated, its original shape has been largely preserved. Rocks in the Itcha Range are a variety of colours, including red, white and yellow.
Climate The climate of the Itcha Range is influenced by the presence of the Coast Mountains to the west, which disrupt the flow of the prevailing westerly winds and causes them to drop most of their moisture on the western slopes of the Coast Mountains before reaching the Interior Plateau, casting a rain shadow over the Itcha Range. In contrast to the Coast Mountains, the Interior Plateau experiences a precipitation peak in the summer months, reflecting the influence of summer convective storms, and most of winter precipitation falls as snow. The mean annual precipitation for the area ranges from about 40 to 80 cm (16 to 31 in) whereas the mean annual temperature is approximately 3 °C (37 °F), with a summer mean of 12.5 °C (54.5 °F) and a winter mean of −8 °C (18 °F).
Flora and fauna The Itcha Range area is home to a grassland ecosystem that has not been found elsewhere in southern or central British Columbia. It is dominated by communities of Altai fescue and lichen. Extensive and diverse alpine and subalpine vegetation is also present in the area, some species of which are at the northernmost or southernmost of their range. Several animal species inhabit around the Itcha Range. Among them are cougars, wolves, grizzly bears, black bears, moose, mule deers, mountain goats, beavers, coyotes, red foxes, muskrats, martens, river otters, lynx and wolverines. Also present is the largest herd of woodland caribou in southern British Columbia, as well as the most northerly population of California bighorn sheep in North America.
Geology
Background A number of mechanisms have been proposed to interpret the origin of volcanism in the Anahim Volcanic Belt. This includes rift propagation and melting of mantle associated with lithospheric fracturing due to flexuring of the crust along the northern edge of the subducting Juan de Fuca Plate. However, insignificant evidence exists to support these hypotheses. The most common and best mechanism used to explain Anahim Belt volcanic activity is a stationary hotspot. This is supported by a well-defined progression in age of volcanism from west to east along the belt that compares well with the age trend of the Yellowstone hotspot track. The North American Plate moves westward over the hotspot at a rate of between 20 and 30 mm (0.79 and 1.18 in) per year. Nazko Cone, a volcanic cone east of the Itcha Range, is centred near the Anahim hotspot.
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