Banff National Park
Banff National Park is Canada's oldest national park and was established in 1885. Located in the Rocky Mountains, 110–180 kilometres west of Calgary in the province of Alberta, Banff encompasses 6,641 square kilometres of mountainous terrain, with numerous glaciers and ice fields, dense coniferous forest, alpine landscapes; the Icefields Parkway extends from Lake Louise. Provincial forests and Yoho National Park are neighbours to the west, while Kootenay National Park is located to the south and Kananaskis Country to the southeast; the main commercial centre of the park is the town of Banff, in the Bow River valley. The Canadian Pacific Railway was instrumental in Banff's early years, building the Banff Springs Hotel and Chateau Lake Louise, attracting tourists through extensive advertising. In the early 20th century, roads were built in Banff, at times by war internees from World War I, through Great Depression-era public works projects. Since the 1960s, park accommodations have been open all year, with annual tourism visits to Banff increasing to over 5 million in the 1990s.
Millions more pass through the park on the Trans-Canada Highway. As Banff has over three million visitors annually, the health of its ecosystem has been threatened. In the mid-1990s, Parks Canada responded by initiating a two-year study, which resulted in management recommendations, new policies that aim to preserve ecological integrity. Banff National Park has a subarctic climate with three ecoregions, including montane and alpine; the forests are dominated by Lodgepole pine at lower elevations and Engelmann spruce in higher ones below the treeline, above, rocks and ice. Mammal species such as the grizzly bear, wolverine, bighorn sheep and moose are found, along with hundreds of bird species. Reptiles and amphibians are found but only a limited number of species have been recorded; the mountains are formed from sedimentary rocks which were pushed east over newer rock strata, between 80 and 55 million years ago. Over the past few million years, glaciers have at times covered most of the park, but today are found only on the mountain slopes though they include the Columbia Icefield, the largest uninterrupted glacial mass in the Rockies.
Erosion from water and ice have carved the mountains into their current shapes. Throughout its history, Banff National Park has been shaped by tension between conservationist and land exploitation interests; the park was established on 25 November 1885 as Banff Hot Springs Reserve, in response to conflicting claims over who discovered hot springs there and who had the right to develop the hot springs for commercial interests. The conservationists prevailed when Prime Minister John A. Macdonald set aside the hot springs as a small protected reserve, expanded to include Lake Louise and other areas extending north to the Columbia Icefield. Archaeological evidence found at Vermilion Lakes indicates the first human activity in Banff to 10,300 B. P. Prior to European contact, including the Stoneys, Tsuu T'ina, Kainai and Siksika, resided in the region where they hunted bison and other game. With the admission of British Columbia to Canada on 20 July 1871, Canada agreed to build a transcontinental railroad.
Construction of the railroad began in 1875, with Kicking Horse Pass chosen, over the more northerly Yellowhead Pass, as the route through the Canadian Rockies. Ten years on 7 November 1885, the last spike was driven in Craigellachie, British Columbia. With conflicting claims over the discovery of hot springs in Banff, Prime Minister John A. Macdonald decided to set aside a small reserve of 26 square kilometres around the hot springs at Cave and Basin as a public park known as the Banff Hot Springs Reserve in 1885. Under the Rocky Mountains Park Act, enacted on 23 June 1887, the park was expanded to 674 km2 and named Rocky Mountains Park; this was Canada's first national park, the third established in North America, after Yellowstone and Mackinac National Parks. The Canadian Pacific Railway built the Banff Springs Hotel and Lake Louise Chalet to attract tourists and increase the number of rail passengers; the Stoney First Nations were removed from Banff National Park between the years 1890 and 1920.
The park was designed to appeal to sportsmen, tourists. The exclusionary policy met the goals of sports hunting and game conservation, as well as of those attempting to "civilize" the Indians. Early on, Banff was popular with wealthy European and American tourists, the former of which arrived in Canada via trans-Atlantic luxury liner and continued westward on the railroad; some visitors participated in mountaineering activities hiring local guides. Guides Jim and Bill Brewster founded one of the first outfitters in Banff. From 1906, the Alpine Club of Canada organized climbs and camps in the park. By 1911, Banff was accessible by automobile from Calgary. Beginning in 1916, the Brewsters offered motorcoach tours of Banff. In 1920, access to Lake Louise by road was available, the Banff-Windermere Road opened in 1923 to connect Banff with British Columbia. In 1902, the park was expanded to cover 11,400 km2, encompassing areas around Lake Louise, the Bow, Red Deer and Spray rivers. Bowing to pressure from grazing and logging interests, the size of the park was reduced in 1911 to 4,663 km2, eliminating many eastern foothills areas from the park.
Park boundaries changed several more times up until 1930, when the area of Banff was fixed at 6,697 km2, with the passage of the National Parks Act. The Act, which took effect May 30, 1930 renamed the par
The bobcat is a North American cat that appeared during the Irvingtonian stage of around 1.8 million years ago. Containing 2 recognized subspecies, it ranges from southern Canada to central Mexico, including most of the contiguous United States; the bobcat is an adaptable predator that inhabits wooded areas, as well as semidesert, urban edge, forest edge, swampland environments. It remains in some of its original range, but populations are vulnerable to local extinction by coyotes and domestic animals. With a gray to brown coat, whiskered face, black-tufted ears, the bobcat resembles the other species of the midsized genus Lynx, it is smaller on average than the Canada lynx, with which it shares parts of its range, but is about twice as large as the domestic cat. It has distinctive black bars on its forelegs and a black-tipped, stubby tail, from which it derives its name. Though the bobcat prefers rabbits and hares, it hunts insects, chickens and other birds, small rodents, deer. Prey selection depends on location and habitat and abundance.
Like most cats, the bobcat is territorial and solitary, although with some overlap in home ranges. It uses several methods to mark its territorial boundaries, including claw marks and deposits of urine or feces; the bobcat has a gestation period of about two months. Although bobcats have been hunted extensively by humans, both for sport and fur, their population has proven resilient though declining in some areas; the elusive predator features in the folklore of European settlers. There had been debate over whether to classify this species as Lynx rufus or Felis rufus as part of a wider issue regarding whether the four species of Lynx should be given their own genus, or be placed as a subgenus of Felis; the genus Lynx is now accepted, the bobcat is listed as Lynx rufus in modern taxonomic sources. Johnson et al. reported Lynx shared a clade with the puma, leopard cat, domestic cat lineages, dated to 7.15 million years ago. The bobcat is believed to have evolved from the Eurasian lynx, which crossed into North America by way of the Bering Land Bridge during the Pleistocene, with progenitors arriving as early as 2.6 million years ago.
The first wave moved into the southern portion of North America, soon cut off from the north by glaciers. This population evolved into modern bobcats around 20,000 years ago. A second population arrived from Asia and settled in the north, developing into the modern Canada lynx. Hybridization between the bobcat and the Canada lynx may sometimes occur. Thirteen bobcat subspecies have been recognized based on morphological characteristics: L. rufus rufus – eastern and midwestern United States L. r. gigas – northern New York to Nova Scotia and New Brunswick L. r. floridanus – southeastern United States and inland to the Mississippi valley, up to southwestern Missouri and southern Illinois L. r. superiorensis – western Great Lakes area, including upper Michigan, southern Ontario, most of Minnesota L. r. baileyi – southwestern United States and northwestern Mexico L. r. californicus – California west of the Sierra Nevada L. r. mohavensis – Mojave Desert of California L. r. escuinapae – central Mexico, with a northern extension along the west coast to southern Sonora L. r. fasciatus – Oregon, Washington west of the Cascade Range, northwestern California, southwestern British Columbia L. r. oaxacensis – Oaxaca L. r. pallescens – northwestern United States and southern British Columbia and Saskatchewan L. r. peninsularis – Baja California L. r. texensis – western Louisiana, south central Oklahoma, south into Tamaulipas, Nuevo León, CoahuilaThis subspecies division has been challenged, given a lack of clear geographic breaks in their ranges and the minor differences between subspecies.
The latest revision of cat taxonomy in 2017, by the Cat Classification Taskforce of the Cat Specialist Group recognises only two subspecies, based on phylogeographic and genetic studies, although the status of Mexican bobcats remains under review: Lynx rufus rufus – east of the Great Plains, North America Lynx rufus fasciatus – west of the Great Plains, North America The bobcat resembles other species of the genus Lynx, but is on average the smallest of the four. Its coat is variable, though tan to grayish-brown, with black streaks on the body and dark bars on the forelegs and tail, its spotted patterning acts as camouflage. The ears are pointed, with short, black tufts. An off-white color is seen on the lips and underparts. Bobcats in the desert regions of the southwest have the lightest-colored coats, while those in the northern, forested regions are darkest. Kittens are born well-furred and have their spots. A few melanistic bobcats have been captured in Florida, they may still exhibit a spot pattern.
The face appears wide due to ruffs of extended hair beneath the ears. Bobcat eyes are yellow with black pupils; the nose of the bobcat is pinkish-red, it has a base color of gray or yellowish- or brownish-red on its face and back. The pupils are round, black circles and will widen during nocturnal activity to maximize light reception; the cat has sharp hearing and vision, a good sense of smell. It is an excellent climber, swims when it needs to, but avoids water. However, cases of bobcats swimming long distances across lakes have been rec
The Cariboo Mountains are the northernmost subrange of the Columbia Mountains, which run down into the Spokane area of the United States and include the Selkirks and Purcells. The Cariboo Mountains are within the province of British Columbia, Canada; the range is 7,700 square kilometres in area and about 245 km in length and about 90 km at its widest. East of the range is the Rocky Mountain Trench, in this region the path of the upper Fraser River. To the west the range verges with the Cariboo Plateau through an intermediary "foothill" area known as the Quesnel Highland. Northwestwards the range drops to the Willow River area of the Nechako Plateau, which lies around Prince George. South of the range, northeast of Clearwater a plateau-like mountainous area between the range and the North Thompson River is part of the Shuswap Highland, which crosses the North Thompson and continues into the Shuswap Lake area. N. B; some classification systems assign the Cariboo Mountains to the Cariboo Plateau, which includes the small Marble and Clear Ranges but it is so large and so mountainous a range, with peaks that rival the highest in the Selkirks, that it does not warrant the "plateau" designation.
The Cariboo Mountains subranges include the Mowdish Range. Unlike the other three major subranges of the Columbia Mountains, the Cariboo Mountains have no contact with the Columbia River or its tributaries, but are bounded by the Fraser and its tributary, the North Thompson River (there is a small exception in the Canoe River, which runs into the Rocky Mountain Trench from the eastern end of the range; the Canoe River is on the north side of Albreda Pass, the divide between the North Thompson and the Rocky Mountain Trench. The highest summits in the range are in a group known as the Premier Range whose peaks carry the names of eleven Canadian Prime Ministers, one British Prime Minister, one Premier of British Columbia; the highest peak is Mount Sir Wilfrid Laurier at 3,516 m. The most added name to the group is that of Mount Pierre Elliott Trudeau; the highest peak in the Cariboo Mountains outside the Premiers Range is Quanstrom Mountain 3,038 m, the northernmost peak in the range over 3,000 m.
Mowdish Range Premier Range Wavy Range Much of the Cariboo Mountains lie in Wells Gray Provincial Park, created in 1939 and the 4th largest in British Columbia. Another section is in Bowron Lake Provincial Park, a popular canoeing circuit east of the preserved gold rush town of Barkerville. Another park in the range is Cariboo Mountains Provincial Park, between Wells Gray and Bowron Lake
British Columbia is the westernmost province of Canada, located between the Pacific Ocean and the Rocky Mountains. With an estimated population of 5.016 million as of 2018, it is Canada's third-most populous province. The first British settlement in the area was Fort Victoria, established in 1843, which gave rise to the City of Victoria, at first the capital of the separate Colony of Vancouver Island. Subsequently, on the mainland, the Colony of British Columbia was founded by Richard Clement Moody and the Royal Engineers, Columbia Detachment, in response to the Fraser Canyon Gold Rush. Moody was Chief Commissioner of Lands and Works for the Colony and the first Lieutenant Governor of British Columbia: he was hand-picked by the Colonial Office in London to transform British Columbia into the British Empire's "bulwark in the farthest west", "to found a second England on the shores of the Pacific". Moody selected the site for and founded the original capital of British Columbia, New Westminster, established the Cariboo Road and Stanley Park, designed the first version of the Coat of arms of British Columbia.
Port Moody is named after him. In 1866, Vancouver Island became part of the colony of British Columbia, Victoria became the united colony's capital. In 1871, British Columbia became the sixth province of Canada, its Latin motto is Splendor sine occasu. The capital of British Columbia remains Victoria, the fifteenth-largest metropolitan region in Canada, named for Queen Victoria, who ruled during the creation of the original colonies; the largest city is Vancouver, the third-largest metropolitan area in Canada, the largest in Western Canada, the second-largest in the Pacific Northwest. In October 2013, British Columbia had an estimated population of 4,606,371; the province is governed by the British Columbia New Democratic Party, led by John Horgan, in a minority government with the confidence and supply of the Green Party of British Columbia. Horgan became premier as a result of a no-confidence motion on June 29, 2017. British Columbia evolved from British possessions that were established in what is now British Columbia by 1871.
First Nations, the original inhabitants of the land, have a history of at least 10,000 years in the area. Today there are few treaties, the question of Aboriginal Title, long ignored, has become a legal and political question of frequent debate as a result of recent court actions. Notably, the Tsilhqot'in Nation has established Aboriginal title to a portion of their territory, as a result of the 2014 Supreme Court of Canada decision in Tsilhqot'in Nation v British Columbia; the province's name was chosen by Queen Victoria, when the Colony of British Columbia, i.e. "the Mainland", became a British colony in 1858. It refers to the Columbia District, the British name for the territory drained by the Columbia River, in southeastern British Columbia, the namesake of the pre-Oregon Treaty Columbia Department of the Hudson's Bay Company. Queen Victoria chose British Columbia to distinguish what was the British sector of the Columbia District from the United States, which became the Oregon Territory on August 8, 1848, as a result of the treaty.
The Columbia in the name British Columbia is derived from the name of the Columbia Rediviva, an American ship which lent its name to the Columbia River and the wider region. British Columbia is bordered to the west by the Pacific Ocean and the American state of Alaska, to the north by Yukon Territory and the Northwest Territories, to the east by the province of Alberta, to the south by the American states of Washington and Montana; the southern border of British Columbia was established by the 1846 Oregon Treaty, although its history is tied with lands as far south as California. British Columbia's land area is 944,735 square kilometres. British Columbia's rugged coastline stretches for more than 27,000 kilometres, includes deep, mountainous fjords and about 6,000 islands, most of which are uninhabited, it is the only province in Canada. British Columbia's capital is Victoria, located at the southeastern tip of Vancouver Island. Only a narrow strip of Vancouver Island, from Campbell River to Victoria, is populated.
Much of the western part of Vancouver Island and the rest of the coast is covered by temperate rainforest. The province's most populous city is Vancouver, at the confluence of the Fraser River and Georgia Strait, in the mainland's southwest corner. By land area, Abbotsford is the largest city. Vanderhoof is near the geographic centre of the province; the Coast Mountains and the Inside Passage's many inlets provide some of British Columbia's renowned and spectacular scenery, which forms the backdrop and context for a growing outdoor adventure and ecotourism industry. 75% of the province is mountainous. The province's mainland away from the coastal regions is somewhat moderated by the Pacific Ocean. Terrain ranges from dry inland forests and semi-arid valleys, to the range and canyon districts of the Central and Southern Interior, to boreal forest and subarctic prairie in the Northern Interior. High mountain regions both north and south subalpine climate; the Okanagan area, extending from Vernon to Osoyoos at the United States border, is one of several wine and cider-produci
International Selkirk Loop
The International Selkirk Loop is a 280-mile-long scenic highway in the U. S. states of Idaho and Washington, as well as the Canadian province of British Columbia. The loop encircles the Selkirk Mountain Range, offers several side trips aside from the main route. Included on the loop is the Kootenay Lake Ferry, the longest free ferry in the world; the portion of the loop in the United States has been designated an All-American Road by the United States Department of Transportation. The International Selkirk Loop begins on U. S. Route 2 in the community of Newport; the highway proceeds west for a short distance, passing several buildings that make up the twin, before U. S. Route 2 splits off, the Loop designation transfers to Washington State Route 20; the highway proceeds northwest. The road continues, intersecting several small roads before entering the community of Usk and intersecting Washington State Route 211; the roadway bends northward, passing the community of Cusick, continuing parallel to the Pend Oreille.
Continuing northward, the highway intersects several small roads, makes a large northeastward bend, before returning to traveling northward. It proceeds north, passing through a small portion of Colville National Forest, before entering Ione. While traveling through Ione, WA 20 splits off, the Loop designation transfers to Washington State Route 31. Continuing northward, the roadway passes the Ione Municipal Airport, proceeding parallel to the Pend Oreille River, before crossing over the river and entering Colville National Forest; the road proceeds north, intersecting several small forest roads, before reaching the Canada–US border, where the WA 31 designation ends. The loop enters Canada, the designation transfers to British Columbia Highway 6. After entering British Columbia, the Loop proceeds northward. After intersecting several smaller roads, BC 6 intersects British Columbia Highway 3, which runs concurrently with the highway; the highway proceeds north, continuing along the course of the small creek, intersecting several small roads.
After several miles, BC 3 splits off the highway. The route proceeds before proceeding northeast; the road bends northwestward, before zigzagging along a valley floor. The roadway passes to the west of West Arm Provincial Park, enters the community of Nelson. In Nelson, the Loop's designation transfers to British Columbia Highway 3A at a trumpet interchange; the road passes northeast through Nelson, before passing over an arm of the Kootenay Lake, traveling eastward along the arm of the lake. The Loop designation transfers to the Kootenay Lake Ferry at the intersection of BC 3A and BC 31; the ferry is 5.4 miles in length, connects the loop to the eastern shore of the lake. After crossing the lake, BC 3A continues eastward; the road passes through Crawford Bay, before bending south and traveling along one of the arms of the lake. While traveling along the lakeshore, the highway passes through the community of Gray Creek, passes west of Lockhart Creek Provincial Park; the roadway passes before intersecting several small roads.
The road enters Creston, where the Loop's designation transfers to British Columbia Highway 21. The highway continues south, through Creston, passing numerous buildings which make up a portion of the community; the highway proceeds southward, running parallel to a large river, continuing to the Canada–US border, where the BC 21 designation terminates. The Loop reenters the United States, the designation transfers to Idaho State Highway 1; the highway proceeds southeast, through the community of Porthill, before bending northeastward. The road bends back southeast, proceeds through rural area, before reaching an intersection with U. S. Route 95; the designation transfers to U. S. Route 95; the road proceeds southward, through rural area intersecting a small road. After continuing southward, the highway intersects U. S. Route 2; the road proceeds south, crossing over the Kootenai River, before entering the community of Bonners Ferry. The roadway continues southeast, intersecting several small roads, passing several buildings.
The route proceeds southeast, intersecting several small roads, passing west of the Kaniksu National Forest. The road proceeds south, entering the community of Sandpoint, reaching an interchange with Idaho State Highway 200, where U. S. Route 95 splits off from the highway; the roadway continues westward, traveling parallel to the Pend Oreille River, intersecting the occasional small road. It enters the community of Priest River, passes the Priest River Municipal Airport; the highway intersects Idaho State Highway 57, before continuing west out of the town. The highway continues eastward, crossing over the Pend Oreille River, reaching the Washington-Idaho state line, where the Loop begins again. Official website On the FHWA Byways page
Copper is a chemical element with symbol Cu and atomic number 29. It is a soft and ductile metal with high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, constantan used in strain gauges and thermocouples for temperature measurement. Copper is one of the few metals; this led to early human use in several regions, from c. 8000 BC. Thousands of years it was the first metal to be smelted from sulfide ores, c. 5000 BC, the first metal to be cast into a shape in a mold, c. 4000 BC and the first metal to be purposefully alloyed with another metal, tin, to create bronze, c. 3500 BC. In the Roman era, copper was principally mined on Cyprus, the origin of the name of the metal, from aes сyprium corrupted to сuprum, from which the words derived and copper, first used around 1530.
The encountered compounds are copper salts, which impart blue or green colors to such minerals as azurite and turquoise, have been used and as pigments. Copper used in buildings for roofing, oxidizes to form a green verdigris. Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found in the liver and bone; the adult body contains between 2.1 mg of copper per kilogram of body weight. Copper and gold are in group 11 of the periodic table; the filled d-shells in these elements contribute little to interatomic interactions, which are dominated by the s-electrons through metallic bonds.
Unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are weak. This observation explains the low high ductility of single crystals of copper. At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is supplied in a fine-grained polycrystalline form, which has greater strength than monocrystalline forms; the softness of copper explains its high electrical conductivity and high thermal conductivity, second highest among pure metals at room temperature. This is because the resistivity to electron transport in metals at room temperature originates from scattering of electrons on thermal vibrations of the lattice, which are weak in a soft metal; the maximum permissible current density of copper in open air is 3.1×106 A/m2 of cross-sectional area, above which it begins to heat excessively. Copper is one of a few metallic elements with a natural color other than silver.
Pure copper acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells – the energy difference between these shells corresponds to orange light; as with other metals, if copper is put in contact with another metal, galvanic corrosion will occur. Copper does not react with water, but it does react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the rust that forms on iron in moist air, protects the underlying metal from further corrosion. A green layer of verdigris can be seen on old copper structures, such as the roofing of many older buildings and the Statue of Liberty. Copper tarnishes when exposed to some sulfur compounds, with which it reacts to form various copper sulfides. There are 29 isotopes of copper. 63Cu and 65Cu are stable, with 63Cu comprising 69% of occurring copper. The other isotopes are radioactive, with the most stable being 67Cu with a half-life of 61.83 hours.
Seven metastable isotopes have been characterized. Isotopes with a mass number above 64 decay by β−, whereas those with a mass number below 64 decay by β+. 64Cu, which has a half-life of 12.7 hours, decays both ways.62Cu and 64Cu have significant applications. 62Cu is used in 62Cu-PTSM as a radioactive tracer for positron emission tomography. Copper is produced in massive stars and is present in the Earth's crust in a proportion of about 50 parts per million. In nature, copper occurs in a variety of minerals, including native copper, copper sulfides such as chalcopyrite, digenite and chalcocite, copper sulfosalts such as tetrahedite-tennantite, enargite, copper carbonates such as azurite and malachite, as copper or copper oxides such as cuprite and tenorite, respectively; the largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock is subjected to pressure, causing profound physical or chemical change; the protolith may be igneous, or existing metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface, they are classified by chemical and mineral assemblage. They may be formed by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it, they can form from tectonic processes such as continental collisions, which cause horizontal pressure and distortion. They are formed when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior; the study of metamorphic rocks provides information about the temperatures and pressures that occur at great depths within the Earth's crust. Some examples of metamorphic rocks are gneiss, marble and quartzite.
Metamorphic minerals are those that form only at the high temperatures and pressures associated with the process of metamorphism. These minerals, known as index minerals, include sillimanite, staurolite and some garnet. Other minerals, such as olivines, amphiboles, micas and quartz, may be found in metamorphic rocks, but are not the result of the process of metamorphism; these minerals formed during the crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process. However, all minerals are stable only within certain limits, the presence of some minerals in metamorphic rocks indicates the approximate temperatures and pressures at which they formed; the change in the particle size of the rock during the process of metamorphism is called recrystallization. For instance, the small calcite crystals in the sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble. Both high temperatures and pressures contribute to recrystallization.
High temperatures allow the atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. The layering within metamorphic rocks is called foliation, it occurs when a rock is being shortened along one axis during recrystallization; this causes the platy or elongated crystals of minerals, such as mica and chlorite, to become rotated such that their long axes are perpendicular to the orientation of shortening. This results in a banded, or foliated rock, with the bands showing the colors of the minerals that formed them. Textures are separated into non-foliated categories. Foliated rock is a product of differential stress that deforms the rock in one plane, sometimes creating a plane of cleavage. For example, slate is a foliated metamorphic rock. Non-foliated rock does not have planar patterns of strain. Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive growth habits, will not be foliated.
Where a rock has been subject to differential stress, the type of foliation that develops depends on the metamorphic grade. For instance, starting with a mudstone, the following sequence develops with increasing temperature: slate is a fine-grained, foliated metamorphic rock, characteristic of low grade metamorphism, while phyllite is fine-grained and found in areas of low grade metamorphism, schist is medium to coarse-grained and found in areas of medium grade metamorphism, gneiss coarse to coarse-grained, found in areas of high-grade metamorphism. Marble is not foliated, which allows its use as a material for sculpture and architecture. Another important mechanism of metamorphism is that of chemical reactions that occur between minerals without them melting. In the process atoms are exchanged between the minerals, thus new minerals are formed. Many complex high-temperature reactions may take place, each mineral assemblage produced provides us with a clue as to the temperatures and pressures at the time of metamorphism.
Metasomatism is the drastic change in the bulk chemical composition of a rock that occurs during the processes of metamorphism. It is due to the introduction of chemicals from other surrounding rocks. Water may transport these chemicals over great distances; because of the role played by water, metamorphic rocks contain many elements absent from the original rock, lack some that were present. Still, the introduction of new chemicals is not necessary for recrystallization to occur. Contact metamorphism is the name given to the changes that take place when magma is injected into the surrounding solid rock; the changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a contact metamorphism aureole. Aureoles may show all degrees of metamorphism from the contact area to unmetamorphosed country rock some distance away.
The formation of important ore minerals may o