Mosaic Assemblage
Encyclopedia
The Mosaic Assemblage is a rock unit of the Pacific Ranges
of the Coast Mountains
in southwestern British Columbia
, Canada
. It is the namesake of Mosaic Glacier, which is drained by Mosaic Creek. This geological formation formed 140,000 to less than 90,000 years ago when porphyritic
plagioclase
-augite
-olivine
basalt
and trachybasalt
was erupted in valleys and on mountain ridges. These volcanic rock
s form scoria
ceous lava flows, breccia
s, volcanic bomb
s and pillow lava
s.
The location of the Mosaic Assemblage is sparse, being present just north of the Lillooet River
, south of and in upper Meager Creek
and between Job Creek and Mosaic Creek. Because these four areas are well apart, each area probably has its own volcanic vents. Small patches of the Mosaic Assemblage overlie The Devastator Assemblage
and form minor portions of the Mount Meager
massif
.
Pacific Ranges
The Pacific Ranges are the southernmost subdivision of the Coast Mountains portion of the Pacific Cordillera. Located entirely within British Columbia, Canada, they run northwest from the lower stretches of the Fraser River to Bella Coola, north of which are the Kitimat Ranges.The Pacific Ranges...
of the Coast Mountains
Coast Mountains
The Coast Mountains are 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. They are so-named because of their proximity to the sea coast, and are often...
in southwestern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It is the namesake of Mosaic Glacier, which is drained by Mosaic Creek. This geological formation formed 140,000 to less than 90,000 years ago when porphyritic
Porphyritic
Porphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group...
plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
-augite
Augite
Augite is a single chain inosilicate mineral, 2O6. The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.-Characteristics:Augite is a solid solution in the pyroxene group...
-olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
and trachybasalt
Trachybasalt
Trachybasalt is a volcanic rock with a composition between trachyte and basalt. Minerals included in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and likely very small amounts of leucite or analcime. It contains high alkali content ....
was erupted in valleys and on mountain ridges. These volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...
s form scoria
Scoria
Scoria is a volcanic rock containing many holes or vesicles. It is most generally dark in color , and basaltic or andesitic in composition. Scoria is relatively low in mass as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity...
ceous lava flows, breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
s, volcanic bomb
Volcanic bomb
A volcanic bomb is a mass of molten rock larger than 65 mm in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains...
s and pillow lava
Pillow lava
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava under water, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one metre in...
s.
The location of the Mosaic Assemblage is sparse, being present just north of the Lillooet River
Lillooet River
The Lillooet River is a major river of the southern Coast Mountains of British Columbia. It begins at Silt Lake, on the southern edge of the Lillooet Crown Icecap about 80 kilometres northwest of Pemberton and about 85 kilometres northwest of Whistler...
, south of and in upper Meager Creek
Meager Creek
Meager Creek is a creek in the southern Pacific Ranges of the Coast Mountains in British Columbia, Canada. It flows northeast into the Lillooet River....
and between Job Creek and Mosaic Creek. Because these four areas are well apart, each area probably has its own volcanic vents. Small patches of the Mosaic Assemblage overlie The Devastator Assemblage
The Devastator Assemblage
The Devastator Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Devastator Peak , the lowest and southernmost subsidiary peak of Meager...
and form minor portions of the Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
massif
Massif
In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...
.
See also
- Job AssemblageJob AssemblageThe Job Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Mount Job, a subsidiary peak of Meager. The rock unit was formed during a period of rhyodacite volcanism during the Pleistocene epoch.Around Mount...
- Plinth AssemblagePlinth AssemblageThe Plinth Assemblage, also known as the Plinth Formation, is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located just north of the Lillooet River and on the northern flank of the Mount Meager massif...
- Capricorn AssemblageCapricorn AssemblageThe Capricorn Assemblage is a geological formation comprising the central portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Capricorn Mountain, the third highest subsidiary peak of Meager...
- Pylon AssemblagePylon AssemblageThe Pylon Assemblage is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located about north of Vancouver. It is named after Pylon Peak, a subsidiary summit of the Mount Meager massif...
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
- List of Cascade volcanoes
- List of volcanoes in Canada