Misplaced Pages

#599400

83-656: 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

166-509: A nomadic lifestyle. They did not build permanent structures in which to live, as they moved from region to region to find food and resources. Animals such as martin, moose and caribou were hunted and trapped by the Dakelh and Tsilhqot'in tribes. In summer, these people gathered roots, plants and a volcanic glass called obsidian . Anahim obsidian was traded widely throughout the Interior and up and down

249-436: A broad, gently sloping structure typical of shield volcanoes. It is mainly composed of 70 to 150 m (230 to 490 ft) thick felsic lava flows that were erupted from a central vent. These are overlain by 1 to 4 m (3.3 to 13.1 ft) thick mafic alkaline lava flows and at least 30 small cinder cones. Hawaiite is the dominant rock type, but alkali olivine basalt and spinel lherzolite -bearing basanite

332-563: 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. 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

415-422: A few glassy dikes at the summit of the shield volcano. These consist of alkali-feldspar porphyritic quartz-trachyte and trachyte. Alkali-feldspar quartz-trachyte plugs formed in rhyolites and trachytes of the pre-explosive phase, as well as pyroclastic deposits and feldspar trachyte lava flows of the explosive phase. Later activity produced trachyte and phonolite plugs and lava flows. This volcanism occurred mainly at

498-734: A few thin hawaiite lava flows. This activity was concentrated at the summit of the volcano as shown by the increasing thickness of volcanic material towards the summit. A hydrothermally altered aphyric trachyte dike , which forms a narrow ridge linking Mount Downton and Itcha Mountain, might have been the source for these eruptions. After the basal trachytes were erupted, the explosive phase produced alkali- feldspar porphyritic trachytes, which erupted as pyroclastic deposits with minor, small lava flows and domes. The explosive eruptions produced pumice flows, bedded tuffs, debris flows , reworked polymict debris flows and lava flows less than 20 m (66 ft) thick. The porphyritic trachytes erupted at

581-676: A large mass of igneous rock , creating a new continental margin. This large mass of igneous rock is the largest granite outcropping in North America. The final event began when the Farallon Plate continued to subduct under the new continental margin after the Insular Plate and Insular Islands collided with the old continental margin, supporting a new continental volcanic arc called the Coast Range Arc about 100 million years ago during

664-687: A major mountain range in the Pacific Coast Ranges of western North America , extending from southwestern Yukon through the Alaska Panhandle and virtually all of the Coast of British Columbia south to the Fraser River . The mountain range's name derives from its proximity to the sea coast, and it is often referred to as the Coast Range . The range includes volcanic and non-volcanic mountains and

747-525: A pre-existing continental margin and coastline of North America. These volcanic islands, known as the Insular Islands by geoscientists, were formed on a pre-existing tectonic plate called the Insular Plate by subduction of the former Farallon Plate to the west during the early Paleozoic era. This subduction zone records another subduction zone to the east under an ancient ocean basin between

830-453: A pre-explosive phase, an explosive phase and a post-explosive phase. Analysis of the first trachyte magmas to erupt during the pre-explosive phase suggest they were relatively fluid as shown by their areal extent. Eruptions became more viscous during the explosive phase, followed by more viscosity during the post-explosive phase. As a result, the volume of erupted material became smaller over time. The increasing viscousness of felsic lava during

913-659: 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

SECTION 10

#1733084921600

996-593: Is also present. They merge laterally with lavas of the much older Chilcotin Group , which surrounds the Anahim Volcanic Belt. However, the exact nature of the relationship between the Anahim Volcanic Belt and the Chilcotin Group is unknown. Exposed in the middle of the mountain range is an assemblage of deformed andesite to dacite lava flows and volcanoclastic sediments. These basement rocks were created during

1079-525: Is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains. The early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet (3,000 m) of mostly Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to

1162-585: 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

1245-417: Is of local concern only and includes the possibility of forest fires by lava flows and the disruption of local air traffic if an eruption column is produced. Volcanic ash reduces visibility and can cause jet engine failure, as well as damage to other aircraft systems. Mountain range Mountain ranges are usually segmented by highlands or mountain passes and valleys . Individual mountains within

1328-409: 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. 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

1411-638: Is the smallest shield volcano in the Anahim Volcanic Belt in terms of area covered. Unlike the Rainbow and Ilgachuz ranges, the Itcha Range is composed of small coalescing volcanic units rather than a stratiform volcanic pile. It is, in many respects, similar to the small alkaline shields found in Kenya and Ethiopia along the East African Rift . About 60% of the shield is exposed while roughly 40% of it remains buried under glacial drift deposits. This suggests that

1494-441: Is too far away to provide an accurate indication of activity under the range. It may sense an increase in seismic activity if the Itcha Range becomes highly restless, but this may only provide a warning for a large eruption; the system might detect activity only once the volcano has started erupting. If the Itcha Range were to erupt, mechanisms exist to orchestrate relief efforts. The Interagency Volcanic Event Notification Plan (IVENP)

1577-823: The Alpide belt . The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera , the Aleutian Range , on through Kamchatka Peninsula , Japan , Taiwan , the Philippines , Papua New Guinea , to New Zealand . The Andes is 7,000 kilometres (4,350 mi) long and is often considered the world's longest mountain system. The Alpide belt stretches 15,000 km across southern Eurasia , from Java in Maritime Southeast Asia to

1660-538: The Annamite Range . If the definition of a mountain range is stretched to include underwater mountains, then the Ocean Ridge forms the longest continuous mountain system on Earth, with a length of 65,000 kilometres (40,400 mi). The position of mountain ranges influences climate, such as rain or snow. When air masses move up and over mountains, the air cools, producing orographic precipitation (rain or snow). As

1743-572: The Blackwater Trail between the Ilgachuz and Itcha ranges to carry supplies and cattle to be sold at cattle sales in the small city of Quesnel . Remains of this ranch are still present, as well as many trails that were used as supply routes. The Itcha Range and the surrounding area were designated as a Class A provincial park in 1995 to protect the alpine grasslands, wetlands and wildlife habitats. This 111,977 ha (276,700 acres) protected area

SECTION 20

#1733084921600

1826-724: The British Columbia Interior from the Pacific weather systems, resulting in dry warm summers and dry cold winters. Beyond the eastern slopes is a 154,635 km (59,705 sq mi) plateau occupying the southern and central portions of British Columbia called the Interior Plateau . Included within the Interior Plateau is a coalescing series of layered flood basalt lava flows. These sequences of fluid volcanic rock cover about 25,000 km (9,700 sq mi) of

1909-667: The Fraser River and the Interior Plateau while its far northwestern edge is delimited by the Kelsall and Tatshenshini Rivers at the north end of the Alaska Panhandle, beyond which are the Saint Elias Mountains, and by Champagne Pass in the Yukon Territory . Covered in dense temperate rainforest on its western exposures, the range rises to heavily glaciated peaks, including the largest temperate-latitude ice fields in

1992-772: The Iberian Peninsula in Western Europe , including the ranges of the Himalayas , Karakoram , Hindu Kush , Alborz , Caucasus , and the Alps . The Himalayas contain the highest mountains in the world, including Mount Everest , which is 8,848 metres (29,029 ft) high. Mountain ranges outside these two systems include the Arctic Cordillera , Appalachians , Great Dividing Range , East Siberians , Altais , Scandinavians , Qinling , Western Ghats , Vindhyas , Byrrangas , and

2075-597: The Late Cretaceous period. Magma rising from the Farallon Plate under the new continental margin ascended through the newly accreted Insular Belt, injecting huge quantities of granite into older igneous rocks of the Insular Belt. At the surface, new volcanoes were built along the continental margin. Named after the Coast Mountains, the basement of this arc was likely Early Cretaceous and Late Jurassic intrusions from

2158-600: The Mithrim Montes and Doom Mons on Titan, and Tenzing Montes and Hillary Montes on Pluto. Some terrestrial planets other than Earth also exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars . Jupiter's moon Io has mountain ranges formed from tectonic processes including the Boösaule , Dorian, Hi'iaka and Euboea Montes . Coast Mountains The Coast Mountains ( French : La chaîne Côtière ) are

2241-726: The Saint Elias Mountains and the Chugach Mountains . The Coast Mountains are also part of the American Cordillera —a Spanish term for an extensive chain of mountain ranges—that consists of an almost continuous sequence of mountain ranges that form the western backbone of North America , Central America , South America and Antarctica . The Coast Mountains are approximately 1,600 kilometres (1,000 mi) long and average 300 kilometres (190 mi) in width. The range's southern and southeastern boundaries are surrounded by

2324-507: The Satah Mountain volcanic field is not part of the Itcha Range, it is linked to the range by a volcanic ridge. The felsic shield-building stage began with the eruption of phonolite, trachyte, phonolitic trachyte, quartz -trachyte and rhyolite lava. Subsequent volcanism of the pre-explosive phase produced a basal sequence of aphyric trachyte lava flows and domes with minor altered flow-banded rhyolite, sulfide -bearing rhyolitic tuffs and

2407-699: The Stikine Icecap , which lies between the lower Stikine River and the Whiting River . Because the Coast Mountains are just east of the Pacific Ocean , they have a profound effect on British Columbia's climate by forcing moisture-laden air off the Pacific Ocean to rise, dropping heavy rainfalls on the western slopes where lush forests exist. This precipitation is among the heaviest in North America. The eastern slopes are relatively dry and less steep and protect

2490-401: The 1930 BC Gazetteer. This form of name remained official until March 13, 1947, when it was changed to its current form, Itcha Range , as part of an official government policy. Larger mountain ranges throughout British Columbia, such as the Coast Mountains, retained their gazetted names whereas smaller ones, especially ranges of larger groupings, were subjected to renaming. In more casual speech,

2573-681: The Bridge River Ocean, the Insular Islands drew closer to the former continental margin and coastline of western North America, supporting a pre-existing volcanic arc on the former continental margin of North America called the Omineca Arc . As the North American Plate drifted west and the Insular Plate drifted east to the old continental margin of western North America, the Bridge River Ocean eventually closed by ongoing subduction under

Itcha Range - Misplaced Pages Continue

2656-532: The Bridge River Ocean. This subduction zone eventually jammed and shut down completely 115 million years ago, ending the Omineca Arc and the Insular Islands collided, forming the Insular Belt . Compression resulting from this collision crushed, fractured and folded rocks along the old continental margin. The Insular Belt then welded onto the pre-existing continental margin by magma that eventually cooled to create

2739-573: The Coast Mountains and the highest that lies entirely within British Columbia, located northeast of the head of Knight Inlet with an elevation of 4,019 metres (13,186 ft). The Coast Mountains consists of three subdivisions known as the Pacific Ranges , the Kitimat Ranges , and the Boundary Ranges . The Pacific Ranges are the southernmost subdivision of the Coast Mountains, extending from

2822-506: The Coast Range Arc were then deformed under the heat and pressure of later intrusions, turning them into layered metamorphic rock known as gneiss . In some places, mixtures of older intrusive rocks and the original oceanic rocks have been distorted and warped under intense heat, weight and stress to create unusual swirled patterns known as migmatite , appearing to have been nearly melted in the procedure. Volcanism began to decline along

2905-510: The Coast from the community of Bella Coola . Arrowheads and knives were made from obsidian because when it breaks with a characteristic conchoidal fracture , it creates very sharp edges. A modified form of this lifestyle is practiced by some indigenous people to this day. Settlers arrived in the area from Bella Coola in the early 1900s to establish ranches . One particular ranch, the Home Ranch, used

2988-559: The Insular Islands and the former continental margin of North America called the Bridge River Ocean . This arrangement of two parallel subduction zones is unusual in that very few twin subduction zones exist on Earth; the Philippine Mobile Belt off the southeastern coast of Asia is an example of a modern twin subduction zone. As the Insular Plate drew closer to the pre-existing continental margin by ongoing subduction under

3071-625: The Insular Islands. One of the major aspects that changed early during the Coast Range Arc was the status of the northern end of the Farallon Plate, a portion now known as the Kula Plate . About 85 million years ago, the Kula Plate broke off from the Farallon Plate to form a mid-ocean ridge known to geoscientists as the Kula-Farallon Ridge . This change apparently had some important ramifications for regional geologic evolution. When this change

3154-604: The Interior Plateau and have a volume of about 1,800 km (430 cu mi), forming a large volcanic plateau constructed atop of the Interior Plateau. North of the Interior Plateau on the range's northeastern slopes lies a huge mountainous area known by geographers as the Interior Mountains , which includes the neighbouring Skeena , Cassiar and Hazelton Mountains . The Coast Mountains consist of deformed igneous and metamorphosed structurally complex pre- Tertiary rocks. These originated in diverse locations around

3237-412: 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

3320-539: The Itcha Range is referred to as the Itchas . The name Itcha is indigenous in origin, coming from the local Tsilhqot'in people. Mount Downton was named by D. M. MacKay, a member of the British Columbia Land Surveyors (BCLS) who conducted topographical surveys in the area. He named it after Geoffrey M. Downton, another BCLS member who is credited for first noting the hydroelectric potential inherent in

3403-476: The Itcha Range is related to a hotspot, this temporal and spatial evolution would suggest a waning heat source. The main body of the shield erupted over an area of about 300 km (120 sq mi) . Volcanic activity associated with the Itcha Range extended 20 km (12 mi) south to the Satah Mountain area where lavas erupted along a north-northwest trending fault system and covered an additional area of 250 km (97 sq mi) . Although

Itcha Range - Misplaced Pages Continue

3486-413: The Itcha Range is the lowest of the three Anahim shield volcanoes. Its highest point is Mount Downton, which is situated in the middle of the shield. Just to the northeast is Itcha Mountain, the second highest peak with an elevation of 2,290 m (7,510 ft) . These peaks are situated on top of the shield, which has a topographic prominence of about 690 m (2,260 ft) . The Itcha Range has

3569-485: 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

3652-488: The Itcha Range was glaciated repeatedly during the Pleistocene epoch . Glacial striae on polished surfaces of some of the oldest volcanic rocks in the eastern part of the shield and the local presence of drift deposits throughout the stratigraphy indicate that glaciation and volcanism were contemporaneous through much of the volcanic history of the Itcha Range. With a maximum elevation of 2,375 m (7,792 ft) ,

3735-610: The Itcha Range. However, a cinder cone in the middle of the shield could be much younger, perhaps as young as the basanites at Nazko Cone to the east, which were erupted 340,000 to 7,100 years ago. The older basanites in the Itcha Range may have been erupted contemporaneously with the late feldspar hawaiites. Parasitic cones of the Itcha Range shield were formed mainly during the Early Pleistocene mafic capping stage between 2.2 and 0.8 million years ago. These secondary vents are monogenetic in nature, meaning each cone

3818-426: 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

3901-510: The Juan de Fuca slab. Coupled with the well documented temporal progression of surface volcanism, this has led to the conclusion that the Anahim hotspot is supplied by a mantle plume over slab edge flow. A small high-velocity anomaly east of Nazko Cone marks the eastern extent of the Anahim hotspot track. Magmatism in the Anahim Volcanic Belt can be traced as far back as 10–14 million years ago with

3984-854: The Nass River in the south to the Kelsall River in the north. It is also the largest subdivision of the Coast Mountains, spanning the British Columbia-Alaska border and northwards into Yukon flanking the west side of the Yukon River drainage as far as Champagne Pass , north of which being the Yukon Ranges . The Boundary Ranges include several large icefields, including the Juneau Icefield between Juneau, Alaska and Atlin Lake in British Columbia, and

4067-632: The North American Plate's movement, 6.1 million years ago to construct the Ilgachuz Range shield volcano. Renewed volcanic activity southeast of the Ilgachuz Range starting 3.5 million years ago led to the creation of the Itcha Range, the youngest of the three Anahim shield volcanoes. The Itcha Range continued to be an area of Anahim hotspot volcanism well into the Quaternary period (2.58 million years ago to present). The Itcha Range

4150-575: The air descends on the leeward side, it warms again (following the adiabatic lapse rate ) and is drier, having been stripped of much of its moisture. Often, a rain shadow will affect the leeward side of a range. As a consequence, large mountain ranges, such as the Andes, compartmentalize continents into distinct climate regions . Mountain ranges are constantly subjected to erosional forces which work to tear them down. The basins adjacent to an eroding mountain range are then filled with sediments that are buried and turned into sedimentary rock . Erosion

4233-405: The alkali olivine basalt flows cooled, they formed well-developed columnar joints . Feldspar- phyric , highly vesiculated hawaiites and benmoreites were later erupted from several vents on the summit of Itcha Mountain. In the northwestern and northeastern parts of the shield volcano, basanite lava flows were erupted and are volumetrically subordinate . These represent the youngest known lavas of

SECTION 50

#1733084921600

4316-420: The early Eocene period. Volcanism along the entire length of the Coast Range Arc shut down about 50 million years ago and many of the volcanoes have disappeared from erosion. What remains of the Coast Range Arc to this day are outcrops of granite when magma intruded and cooled at depth beneath the volcanoes, forming the present Coast Mountains. During construction of intrusions 70 and 57 million years ago,

4399-485: The east. This mass of rock was removed as the range was actively undergoing uplift. The removal of such a mass from the core of the range most likely caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment. Computer simulation has shown that as mountain belts change from tectonically active to inactive,

4482-444: The elevation differential between the Bridge River and Seton Lake on opposing sides of Mission Ridge above Shalalth in December 1912. This name for the mountain was adopted on February 7, 1947. The name Itcha Mountain was adopted on March 4, 1954, for the range's second highest peak. Indigenous people of the Dakelh and Tsilhqot'in tribes have inhabited the area for hundreds of years. In pre-contact times, these people lived

4565-461: The emplacement of dike swarms and plutons as well as the eruption of rhyolite flows and breccias on the British Columbia Coast . The slow continuous westward motion of the North American Plate during the late Neogene positioned the Anahim hotspot further east at the Chilcotin Plateau where volcanic activity built the Rainbow Range shield volcano 8.7 to 6.7 million years ago. Volcanism then shifted eastwards, in displacement contrary with

4648-415: The explosive phase. Mount Downton and Itcha Mountain were formed during this eruptive period. The final volcanic event of the post-explosive phase produced 7 to 10 m (23 to 33 ft) thick trachyte lava flows on the western flank. During the mafic capping stage, basanite, alkali olivine basalt and hawaiite erupted mainly from small parasitic cones , tuff rings and fissures in the eastern half of

4731-412: The extensive ice fields of the Pacific and Boundary Ranges , and the northern end of the volcanic system known as the Cascade Volcanoes . The Coast Mountains are part of a larger mountain system called the Pacific Coast Ranges or the Pacific Mountain System, which includes the Cascade Range , the Insular Mountains , the Olympic Mountains , the Oregon Coast Range , the California Coast Ranges ,

4814-407: The globe: the area is built of several different terranes of different ages with a broad range of tectonic origins. In addition, oceanic crust under the Pacific Ocean is being subducted at the southern portion of the range to form a north–south line of volcanoes called the Garibaldi Volcanic Belt , a northern extension of the Cascade Volcanoes in the northwestern United States , and contains

4897-417: The highest mountain of the Coast Mountains, lies in the Waddington Range of the Pacific Ranges. Just north of the Pacific Ranges lies the central subdivision known as the Kitimat Ranges. This subdivision extends from the Bella Coola River and Burke Channel in the south to the Nass River in the north. The third and northernmost subdivision of the Coast Mountains is the Boundary Ranges , extending from

4980-419: 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 . The Anahim hotspot is underlain by a low-velocity anomaly that extends approximately 400 km (250 mi) into the mantle north of the Juan de Fuca slab . However, this low-velocity anomaly may extend deeper southward beneath

5063-605: The last 340,000 years. Alkali olivine basalts of the mafic capping stage were derived from the fractionation of a clinopyroxene , olivine and oxide assemblage. However, the associated hawaiite lavas may have derived from an alkali olivine basalt parent by the fractionation of a clinopyroxene-dominated assemblage at higher pressures. As volcanic activity waned during the mafic capping stage, lava flows became more viscous and decreased in volume. This suggests that parental magmas may have been derived by increasingly smaller degrees of partial melting with time. If volcanic activity of

SECTION 60

#1733084921600

5146-430: The late Mesozoic era , long before the Itcha Range formed. They are similar to rocks found in the Hazelton Group , situated north of the Itcha Range, and the Ootsa Lake Group of the Intermontane Belt . Two stages of volcanic activity constructed the Itcha Range. The first stage, referred to as the felsic shield-building stage, occurred between 3.8 and 3.0 million years ago. Three phases comprise this stage;

5229-409: The length of the arc about 60 million years ago during the Albian and Aptian faunal stages of the Cretaceous period. This resulted from the changing geometry of the Kula Plate, which progressively developed a more northerly movement along the Pacific Northwest . Instead of subducting beneath the Pacific Northwest, the Kula Plate began subducting underneath southwestern Yukon and Alaska and during

5312-417: The lower stretches of the Fraser River to Bella Coola . Included in this subdivision is four of the five major coastal icecaps in the southern Coast Mountains. These are the largest temperate-latitude icecaps in the world and fuel a number of major rivers . Other than logging and a large ski resort at the resort town of Whistler , most of the land in the range is completely undeveloped. Mount Waddington ,

5395-427: The most explosive young volcanoes in Canada. Further north the northwesterly structural trend of the Coast Mountains lies partly in a large continental rift responsible for the creation of several volcanoes. These volcanoes form part of the Northern Cordilleran Volcanic Province , the most volcanically active area in Canada. The first event began 130 million years ago when a group of active volcanic islands approached

5478-457: 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

5561-516: The rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System, including the Moon , are often isolated and formed mainly by processes such as impacts, though there are examples of mountain ranges (or "Montes") somewhat similar to those on Earth. Saturn 's moon Titan and Pluto , in particular, exhibit large mountain ranges in chains composed mainly of ices rather than rock. Examples include

5644-440: 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. The climate of

5727-419: The same mountain range do not necessarily have the same geologic structure or petrology . They may be a mix of different orogenic expressions and terranes , for example thrust sheets , uplifted blocks , fold mountains, and volcanic landforms resulting in a variety of rock types . Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or

5810-441: The shield's summit and on its western flank. Massive lava flows from this volcanic activity have a thickness of about 100 m (330 ft) while three successive lava flows at the summit have a combined thickness of more than 200 m (660 ft) . Lava from the western flank flowed over basement rocks and trachytes of the pre-explosive phase. In contrast, lava from the summit flowed over pyroclastic rocks and lava flows of

5893-474: The shield-building stage suggests a maturing plumbing system underneath the Itcha Range, which may have consisted of multiple, isolated, cupola -type magma chambers . A 900,000‑year‑long period of quiescence followed after the felsic shield-building stage, during which time erosion ate away at the shield's gentle slopes. This quiescence was followed by a mafic capping stage between 2.2 and 0.8 million years ago, but renewed activity might have occurred in

5976-408: The shield. Eruptions occurred subglacially , subaqueously and/or subaerially as shown by a wide range in the degree of vesicularity , freshness and glass content of the lavas. In most cases, each parasitic cone produced three or four lava flows from breaches in the cone walls. These were erupted as pāhoehoe and ʻaʻā , but the tops of the lava flows are commonly missing due to erosion. Hawaiite

6059-419: 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) while 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) . The Itcha Range area

6142-414: The summit of the shield and flowed towards the northeast and east. Because the porphyritic pyroclastic deposits are buried by younger volcanic rocks and glacial drift deposits, the maximum thickness of them is unknown. The felsic shield-building stage ended with the post-explosive phase. This phase of activity created small volcanic plugs , lava flows, minor pyroclastic flows , channelized debris flows and

6225-474: 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

6308-665: 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

6391-513: The world. On its eastern flanks, the range tapers to the dry Interior Plateau and the subarctic boreal forests of the Skeena Mountains and Stikine Plateau . The Coast Mountains are part of the Pacific Ring of Fire —the ring of volcanoes and associated mountains around the Pacific Ocean —and contain some of British Columbia's highest mountains. Mount Waddington is the highest mountain of

6474-431: The zone of Cretaceous dextral thrust faulting appears to have been widespread. It was also during this period when massive amounts of molten granite intruded highly deformed ocean rocks and assorted fragments from pre-existing island arcs, largely remnants of the Bridge River Ocean. This molten granite burned the old oceanic sediments into a glittering medium-grade metamorphic rock called schist . The older intrusions of

6557-525: Was completed, Coast Range Arc volcanism returned and sections of the arc were uplifted considerably in latest Cretaceous time. This started a period of mountain building that affected much of western North America called the Laramide orogeny . In particular a large area of dextral transpression and southwest-directed thrust faulting was active from 75 to 66 million years ago. Much of the record of this deformation has been overridden by Tertiary age structures and

6640-610: Was created to outline the notification procedure of some of the main agencies that would respond to an erupting volcano in Canada, an eruption close to the Canada–United States border or any eruption that would affect Canada. Because of the remote location of the Itcha Range, future eruptions are not a major hazard. Future volcanism is most likely in the form of basaltic cinder cones, but eruptions of felsic magma can not be ruled out. The most immediate hazard relating to future eruptions

6723-525: Was named Itcha Ilgachuz Provincial Park after the Itcha and Ilgachuz ranges, the latter of which is also in the park. Like other volcanoes in the Anahim Volcanic Belt, the Itcha Range is not monitored closely enough by the Geological Survey of Canada to ascertain how active its magma system is. The Canadian National Seismograph Network has been established to monitor earthquakes throughout Canada, but it

6806-465: Was only active for a single eruption sequence before becoming extinct . The duration of volcanic activity at these cones can last from hours to years. Parasitic cones of the Itcha Range are small cinder cones situated at the summit and flanks of the shield volcano. The Itcha Range has had at least two forms of names throughout its history. It was originally named the Itcha Mountains as identified in

6889-523: Was the most extensively erupted lava of the mafic capping stage, occurring mostly at the southern end of the Itcha Range but also in its interior. Volcanism of the mafic capping stage began with the eruption of aphyric hawaiite lava flows. These were extruded from dikes and dissected cinder cones in the central and southeastern parts of the Itcha Range. Alkali olivine basalts were erupted contemporaneously from younger better preserved cinder cones and form lava flows reaching 30 m (98 ft) thick. Once

#599400