The Bridge River Cones, sometimes referred to as the Lillooet Cones and Salal Creek Cones, is the name given to a

volcanic field A volcanic field is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes ...

located on the north flank of the upper Bridge River, about west of the town of

Gold Bridge Gold Bridge is an unincorporated community in the Bridge River Country of British Columbia, Canada. Although numbering only around 40 inhabitants, Gold Bridge is the service and supply centre for the upper basin of the Bridge River Valley, which i ...

. The cones are in the lee of the

Lillooet Icecap The Lillooet Icecap, also called the Lillooet Icefield or the Lillooet Crown, is a large icefield in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It is about northwest of the towns of Pemberton and Whistl ...

and sit astride a group of passes between the Bridge River, which flows W-E to their south, and the Lord River, which flows north to the

Taseko Lakes The Taseko Lakes are a pair of lakes, Upper Taseko Lake and Lower Taseko Lake, which are expansions of the upper Taseko River in the southern Chilcotin District of the Central Interior of British Columbia, Canada. Their name is based on the orig ...

in the

Chilcotin District The Chilcotin () region of British Columbia is usually known simply as "the Chilcotin", and also in speech commonly as "the Chilcotin Country" or simply Chilcotin. It is a plateau and mountain region in British Columbia on the inland lee of the Co ...

Geology

The Bridge River Cones consist of small

trachybasalt Trachybasalt is a volcanic rock with a composition between trachyte and basalt. It resembles basalt but has a high content of alkali metal oxides. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and li ...

ic and

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

ic eruptive centers. Sham Hill (), a high steep-sided

volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged mag ...

, is the oldest volcano in the field with a potassium-argon date of one million years. The plug is approximately wide and its bare glaciated surface, strewn with

glacial erratic A glacial erratic is glacially deposited rock differing from the type of rock native to the area in which it rests. Erratics, which take their name from the Latin word ' ("to wander"), are carried by glacial ice, often over distances of hundred ...

s, consists of large subhorizontal columns formed within the central conduit of an eroded

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...

. The

Salal Glacier volcanic complex The Salal Glacier volcanic complex is a complex volcano in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada, located near the upper Bridge River. It is part of a volcanic group called the Bridge River Cones which ...

(), with a potassium-argon date of 0.97 to 0.59 million years, contains subaerial tephra and thin scoriaceous flows in the upper part of the pile are surrounded by ice-ponded flows up to thick.

Tuber Hill Tuber Hill is a small 600,000-year-old basaltic stratovolcano that was constructed on the Bridge River highlands when nearby valleys were packed with ice. Tuber Hill is part of the Garibaldi segment of the Canadian Cascade Arc, but is not in the g ...

(), a small basaltic stratovolcano with a potassium-argon date of 0.6 million years, was constructed on the Bridge River upland when neighboring valleys were filled by ice. Where distal flows violated on the glaciers a marginal meltwater lake was created in which less than of interbedded

hyaloclastite Hyaloclastite is a volcanoclastic accumulation or breccia consisting of glass (from the Greek ''hyalus'') fragments (clasts) formed by quench fragmentation of lava flow surfaces during submarine or subglacial extrusion. It occurs as thin margin ...

debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...

s, and lacustrine

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...

were deposited. The youngest volcanic rocks in the Bridge River volcanic field lie east of Tuber Hill and are remnants of valley-filling basalt flows. The age of these valley-filling basalt flows is unknown but the presence of unconsolidated glacial until under the flows suggest they are less than 1,500 years old.

References

External links

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"NASA/JPL satellite images"
location only * {{Garibaldi Volcanic Belt Volcanoes of British Columbia Volcanic fields of Canada Garibaldi Volcanic Belt Bridge River Country Pacific Ranges Pleistocene volcanoes Holocene volcanoes Inactive volcanoes

Geology

See also

References

External links