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80-489: Traces of ancient volcanic activity can be seen in rock outcrops near Red Rock Lake and several other sites. For more than 2000 years, this was long an area of occupation by various cultures of indigenous peoples. The oldest artifacts found here date to approximately 500 BC. At Agawa Rock, near the mouth of the Agawa River , there are pictographs created by the early Ojibwe people of this region. The figures are painted on

160-563: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Voyageur Hiking Trail The Voyageur Hiking Trail is a public hiking trail between Sudbury and Thunder Bay in Northern Ontario , Canada . The name honours the early European fur traders of the region who travelled largely by canoe and were known as 'voyageurs’ and ‘coureurs des bois’ (runners of

240-842: A mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift , the Wells Gray-Clearwater volcanic field , and the Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from

320-495: A collection of individual clubs; members are responsible for the footpaths within their areas. Each active club is represented on an elected Coordinating Council that oversees the affairs of the Association. Clubs offer scheduled outings as a way to meet fellow hikers and explore new trails. The Association is one of 27 formal hiking organizations across Ontario represented by Hike Ontario , the provincial voice for hikers. Portions of

400-437: A graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories. The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater. While there is no international consensus among volcanologists on how to define an active volcano,

480-766: A meeting of ‘persons interested in establishing a hiking trail along the precipice of the Cambrian Shield’ from Gros Cap on Lake Superior to Hiawatha Park, just north of Sault Ste. Marie . One of those in attendance, Dr. Paul D. Syme, a Sault Ste. Marie forest research scientist and member of the Bruce Trail Association, immediately saw the possibility of extending this concept to extend northward to Thunder Bay and eastward to Espanola, then south across Manitoulin Island to link up with southern Ontario’s Bruce Trail. The vision has since evolved to link eastward with trails in

560-443: A paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism . It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma , as defined for that body, and/or magmatic gas is erupted.' This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information. The word volcano

640-522: A park trail, without a work permit. After trying to negotiate with the band, the Ministry of Natural Resources (MNR) filed charges against it in 2008, saying that the First Nation had damaged park property. The First Nation contended this was a traditional fishing and ceremonial area and construction of the road was necessary to exercise their Treaty rights. In March 2015 Justice Logan dismissed all but one of

720-607: A teacher in Espanola, invited guests to hike the trail, which became the first organized outing on the Voyageur Hiking Trail. The Saulteaux was the first Voyageur Hiking Trail Club formally established in 1974 and the Saulteaux Section officially opened for hiking at a ceremony on September 21, 1975. The trail system continues to be a work-in-progress, with new development centring around communities. The Voyageur Trail News,

800-632: A volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases. Lava can be broadly classified into four different compositions: Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced [ˈʔaʔa] ) and pāhoehoe ( [paːˈho.eˈho.e] ), both Hawaiian words. ʻAʻa

880-555: A volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behaviour of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus . Vents that issue volcanic material (including lava and ash ) and gases (mainly steam and magmatic gases) can develop anywhere on

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960-465: A volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometres (240 cu mi) of volcanic deposits in a single explosive event. Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera -forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivalling those of flood basalts . Supervolcano eruptions, while

1040-727: Is a volcanic field of over 60 cinder cones. Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon. Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and tephra in alternate layers, the strata that gives rise to the name. They are also known as composite volcanoes because they are created from multiple structures during different kinds of eruptions. Classic examples include Mount Fuji in Japan, Mayon Volcano in

1120-445: Is a rupture in the crust of a planetary-mass object , such as Earth , that allows hot lava , volcanic ash , and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism . On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example,

1200-412: Is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse. More silicic lava flows take the form of block lava, where

1280-554: Is derived from the name of Vulcano , a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan , the god of fire in Roman mythology . The study of volcanoes is called volcanology , sometimes spelled vulcanology . According to the theory of plate tectonics, Earth's lithosphere , its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in

1360-567: Is expressed using the volcanic explosivity index (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions. As of December 2022 , the Smithsonian Institution 's Global Volcanism Program database of volcanic eruptions in the Holocene Epoch (the last 11,700 years) lists 9,901 confirmed eruptions from 859 volcanoes. The database also lists 1,113 uncertain eruptions and 168 discredited eruptions for

1440-519: Is greatly moderated by its location on Lake Superior. Weather in the Park is highly variable depending on the location. Along the shore of Lake Superior, summer temperatures are significantly cooler than inland locations. During the winter, areas along Lake Superior are considerably milder than inland. Winters in Lake Superior Provincial Park are very cold with significant snowfall. February is

1520-517: Is one comfort station located within the campground equipped with showers, laundry facilities and flush toilets. The campground is located beside Rabbit Blanket Lake. Firewood and ice can be purchased at the Rabbit Blanket gatehouse or the park office. ‹The template Manual is being considered for merging .›   The Agawa Bay Beach is a 3 km long beach located at the Visitor Centre and

1600-524: Is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analysed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near

1680-466: Is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland , as well. Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens , but can also form independently, as in

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1760-600: The Cascade Volcanoes or the Japanese Archipelago , or the eastern islands of Indonesia . Hotspots are volcanic areas thought to be formed by mantle plumes , which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off

1840-792: The core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. Mars has significant volcanoes. In 2009,

1920-824: The landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō in New Zealand. Some volcanoes can be low-relief landform features, with the potential to be hard to recognize as such and be obscured by geological processes. Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter , Saturn , and Neptune ; and mud volcanoes , which are structures often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when

2000-645: The Agawa Bay Campground. This beach features an abrupt drop off and on wavy days, can have a dangerous undertow. The water temperature here is usually cold, particularly in June and early July. By mid august, the lake has reached its peak surface temperature at around 20 °C (68 °F). Old Woman Bay is located in the Northern portion of the park. This beach has views of the nearby cliffs. The old Woman River also flows out into Lake Superior here. Old Woman Bay has

2080-528: The Agawa Bay gatehouse. Agawa Bay is also the location of the park's visitor centre where information can be obtained about the park and surrounding areas. There are washrooms and a gift shop open to the public from May through September. The visitor centre has a display area orchestrating the history of the park and the influence that Lake Superior Park had on the fur trade, the Group of Seven artists and shipwrecks in

2160-485: The Agawa Rock Pictographs. They are located on a sheer rock face on Lake Superior. Several of the pictographs can be seen only from the water. The park office is located in the northern part of the park at Red Rock Lake. Senior staff, including the superintendent, can be reached at the park office between 9 am and 4 pm during summer months. Agawa Bay has 152 campsites. There are two comfort stations located in

2240-579: The Nokomis trail, a 5 km loop that overlooks the Bay. The water temperature here is typically a few degrees colder than Agawa Bay. Katherine Cove is one of the most popular beaches in Lake Superior Provincial Park. This beach is located around 15 km north of Agawa Bay and is very shallow. Due to being shallow, Katherine Cove is often warmer than most other beaches in Lake Superior Provincial Park. Located 1 km south of Katherine Cove, this large sandy beach stretches to

2320-582: The Ojibwe people, aided by his wife Jane Johnston Schoolcraft , who was half-Ojibwe and the daughter of a major fur trader in the city. While the Ojibwe were forced to cede their lands to the Canadian government under an 1850 Treaty in exchange for reserves and annuities, they have preserved hunting and fishing rights to former territory. In the 1940s, the Lake Superior Provincial Park was established, and it took over an Ojibwe fishing village known as Nanabozhung within

2400-612: The Philippines, and Mount Vesuvius and Stromboli in Italy. Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like

2480-609: The Sudbury region. Dr. Paul Syme was the leader of the group, which on October 24, 1973 chose the name “Voyageur Trail Association (VTA)” for their newly established group. He was the first elected president of the VTA. Syme met with officials of the Bruce Trail Association, seeking advice and trail building training, and bringing that knowledge back to the Sault visionaries. The group adopted

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2560-609: The USGS defines a volcano as active whenever subterranean indicators, such as earthquake swarms , ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present. The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again. Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in

2640-479: The beautiful Lake Superior coastline. It is very demanding and can take between 5 and 7 days to complete. The Coastal Trail is part of the long-distance Voyageur Hiking Trail . The 11 trails offer a wide variety of distances and difficulty from short half-hour hikes to multi-day trips. Orphan Lake Trail is a moderate difficulty trail that has a variety of terrain over an 8 km loop and takes approximately 2–4 hours to complete. Pictographs A short trail leads to

2720-572: The boundaries. From the late 20th century, the Batchewana First Nation , whose traditional territory included the village, also known as Gargantua Harbour, had long agitated to regain road access to the village. One of its reserves is Rankin Location 15D in Ontario and members have fished at Gargantua Harbour. In 2007 some 200 members, led by Chief Dean Sayers, restored a road to the village along

2800-503: The boundary with the Yukon Territory . Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity. The largest structures are 10 kilometres in diameter and reach 700 meters high. The material that is expelled in a volcanic eruption can be classified into three types: The concentrations of different volcanic gases can vary considerably from one volcano to

2880-423: The campground equipped with showers, laundry facilities and flush toilets. An amphitheatre is located in the campground, and presentations here by park staff are a common occurrence in the summer months. All the campsites are within walking distance to Lake Superior. There is a premium for campsites located beside the beach. Permits are obtained at the Agawa Bay gatehouse. Firewood and ice is available for purchase at

2960-402: The case of Lassen Peak . Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent. Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down

3040-469: The cold winds off Lake Superior. Summer is often slow to start due to the water on Lake Superior being so cold during May and June. During June and July, water temperatures are usually below 15 °C (59 °F) and as a result fog is frequent. August is the warmest month with an average high of 20 °C (68 °F). August is when water temperatures on Lake Superior peak, with an average maximum of 19 °C (66 °F). Recreational activities in

3120-524: The coldest month in Lake Superior provincial Park with an average temperature of −12.5 °C (9 °F). Being located on the eastern shore of Lake Superior, snowfall is abundant during winter months. The park receives an average of 432 centimetres (170 in) annually. Spring is a very short transition season in Lake Superior Provincial Park with snow often remaining on the ground into May. Summers in Lake Superior Provincial Park are often cool due to

3200-547: The eleven counts in the case. In his decision, Logan upheld that a Treaty right existed for the Batchewana First Nation to use Gargantua Harbour for commercial fishing and agreed that the road was necessary to get to the shore. He upheld one charge against Sayers and the Band for obstruction, requiring a fine to be paid. Lake Superior Provincial Park has a humid continental climate ( Köppen climate classification Dfb ) that

3280-772: The enormous area they cover, and subsequent concealment under vegetation and glacial deposits, supervolcanoes can be difficult to identify in the geologic record without careful geologic mapping . Known examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States); Lake Taupō in New Zealand; Lake Toba in Sumatra , Indonesia; and Ngorongoro Crater in Tanzania. Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas in

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3360-431: The flow is covered with angular, vesicle-poor blocks. Rhyolitic flows typically consist largely of obsidian . Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface . These violent explosions produce particles of material that can then fly from

3440-592: The formation of a submarine volcano off the coast of Mayotte . Subglacial volcanoes develop underneath ice caps . They are made up of lava plateaus capping extensive pillow lavas and palagonite . These volcanoes are also called table mountains, tuyas , or (in Iceland) mobergs. Very good examples of this type of volcano can be seen in Iceland and in British Columbia . The origin of the term comes from Tuya Butte , which

3520-568: The future. In an article justifying the re-classification of Alaska's Mount Edgecumbe volcano from "dormant" to "active", volcanologists at the Alaska Volcano Observatory pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in

3600-461: The glossaries or index", however the USGS still widely employs the term. Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the Chaitén volcano in 2008. Modern volcanic activity monitoring techniques, and improvements in

3680-492: The interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split. A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen ), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites . Examples include

3760-419: The mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland . Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. The oceanic plate subducts (dives beneath the continental plate), forming a deep ocean trench just offshore. In a process called flux melting , water released from the subducting plate lowers the melting temperature of

3840-545: The modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale. For example, the Yellowstone volcano has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius

3920-415: The most dangerous type, are very rare; four are known from the last million years , and about 60 historical VEI 8 eruptions have been identified in the geologic record over millions of years. A supervolcano can produce devastation on a continental scale, and severely cool global temperatures for many years after the eruption due to the huge volumes of sulfur and ash released into the atmosphere. Because of

4000-678: The mouth of the Sand River. Bathtub island is located around 50 meters offshore in the shallow water. This island features a pool in the rock that fills with waves and is then heated by the sun. Due to its size and location, the park lies in both the Eastern forest-boreal transition ecoregion and the Central Canadian Shield forests region. Its rugged landscape is wooded with a mix of coniferous and deciduous trees such as pine , maples and birch . Sugar maple dominates many forests in

4080-438: The mud volcano is actually a vent of an igneous volcano. Volcanic fissure vents are flat, linear fractures through which lava emerges. Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle effusive eruptions . Since low-viscosity magma

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4160-452: The next. Water vapour is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide . Other principal volcanic gases include hydrogen sulfide , hydrogen chloride , and hydrogen fluoride . A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen , carbon monoxide , halocarbons , organic compounds, and volatile metal chlorides. The form and style of an eruption of

4240-867: The north side of the mountain. Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 metres (100 to 1,300 ft) high. Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings . Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico , Caja del Rio

4320-541: The ocean surface as new islands or floating pumice rafts . In May and June 2018, a multitude of seismic signals were detected by earthquake monitoring agencies all over the world. They took the form of unusual humming sounds, and some of the signals detected in November of that year had a duration of up to 20 minutes. An oceanographic research campaign in May 2019 showed that the previously mysterious humming noises were caused by

4400-420: The ocean surface, due to the rapid cooling effect and increased buoyancy in water (as compared to air), which often causes volcanic vents to form steep pillars on the ocean floor. Hydrothermal vents are common near these volcanoes, and some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break

4480-471: The ocean's surface. In the deep ocean basins, the tremendous weight of the water prevents the explosive release of steam and gases; however, submarine eruptions can be detected by hydrophones and by the discoloration of water because of volcanic gases . Pillow lava is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form underwater. Even large submarine eruptions may not disturb

4560-462: The one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars . Large pieces of tephra are called volcanic bombs . Big bombs can measure more than 1.2 metres (4 ft) across and weigh several tons. A supervolcano is defined as

4640-425: The overlying mantle wedge, thus creating magma . This magma tends to be extremely viscous because of its high silica content, so it often does not reach the surface but cools and solidifies at depth . When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs . Typical examples are the volcanoes in the Pacific Ring of Fire , such as

4720-449: The park include canoeing (especially in the interior lakes of the park), camping and hiking, fishing, swimming, boating, hunting, educational programs, wildlife viewing, cross-country skiing and snowshoeing. Hiking Trails The 11 hiking trails located throughout the park can be accessed from Agawa Bay, Crescent Lake, or Rabbit Blanket Lake campgrounds, or from Highway 17. The Coastal Trail stretches 65 kilometres (40 mi) and reveals

4800-398: The park include: During the summer months, the park provides habitat for warblers and other birds of the northern forests. In addition to its namesake, the park has numerous smaller lakes in its interior. A number of rivers also flow from the park's interior: Several waterfalls on these rivers can be seen from the road or reached via hiking trails. Volcanic A volcano

4880-595: The plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain , with the Yellowstone Caldera being part of the North American plate currently above the Yellowstone hotspot . However, the mantle plume hypothesis has been questioned. Sustained upwelling of hot mantle rock can develop under

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4960-415: The region. There are trailer storage opportunities available, but arrangements must be made with senior staff located in the northern part of the park at the park office. The visitor centre has received a number of awards for its design. Crescent Lake (now closed) had 46 campsites and was located approximately 2 kilometres off of Highway 17 beside Crescent Lake. Rabbit Blanket Lake has 60 campsites. There

5040-460: The rock with a mixture of powdered hematite and animal fats and are estimated to be 150–400 years old. The records are visual representations of both historical events and legendary figures. The first written description of these pictographs was published in 1851 by American ethnologist, Henry Rowe Schoolcraft . As United States Indian agent in Sault Ste. Marie, he conducted extensive studies about

5120-454: The route including Spanish , Elliot Lake , Iron Bridge , Wawa , Marathon , Terrace Bay , Schreiber , Rossport and Nipigon . While most of the trail has been built and maintained by volunteer members, portions within Provincial and Federal Park lands have been included with the consent of those agencies. The Voyageur Trail Association was created as a not-for-profit entity consisting of

5200-435: The same time interval. Volcanoes vary greatly in their level of activity, with individual volcanic systems having an eruption recurrence ranging from several times a year to once in tens of thousands of years. Volcanoes are informally described as erupting , active , dormant , or extinct , but the definitions of these terms are not entirely uniform among volcanologists. The level of activity of most volcanoes falls upon

5280-485: The same way; they are often described as "caldera volcanoes". Submarine volcanoes are common features of the ocean floor. Volcanic activity during the Holocene Epoch has been documented at only 119 submarine volcanoes, but there may be more than one million geologically young submarine volcanoes on the ocean floor. In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above

5360-622: The solidified erupted material that makes up the mantle of a volcano may be stripped away that its inner anatomy becomes apparent. Using the metaphor of biological anatomy , such a process is called "dissection". Cinder Hill , a feature of Mount Bird on Ross Island , Antarctica , is a prominent example of a dissected volcano. Volcanoes that were, on a geological timescale, recently active, such as for example Mount Kaimon in southern Kyūshū , Japan , tend to be undissected. Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions. The intensity of explosive volcanism

5440-469: The southern Ontario model of dividing the trail into sections and assigning responsibility for trail building, landowner relations, maintenance, public hikes, promotion, etc. to local Voyageur Hiking Trail Clubs. A draft constitution was presented on November 15, 1973. On this basis, an interim board of directors was installed (President, Paul Syme; Vice President, Ralph Yanni; Treasurer, Ralph Wood). Ian Morrison acted as general secretary at this meeting and

5520-502: The southern two-thirds of the park. The predominantly rocky coastline is interrupted by sandy beaches in a few locations. The park is situated within the Great Canadian Shield , dominated by exposed rocks or a thin layer of soil over rock. The park supports a large moose ( Alces alces ) population. The best time for viewing moose is in the months of April, May, and June when the spring melt occurs. Other large animals found in

5600-406: The surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes that were once thought to be extinct, before springing back into eruptive activity were the long-dormant Soufrière Hills volcano on the island of Montserrat , thought to be extinct until activity resumed in 1995 (turning its capital Plymouth into

5680-434: The theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region. At the mid-ocean ridges , two tectonic plates diverge from one another as hot mantle rock creeps upwards beneath

5760-444: The thinned oceanic crust . The decrease of pressure in the rising mantle rock leads to adiabatic expansion and the partial melting of the rock, causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new seafloor . Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where

5840-535: The trail are part of the Trans Canada Trail . A trail guidebook provides trail users with up-to-date maps and descriptions of the available trails. In addition, digital maps that can be downloaded to GPS units for on-trail navigation are available. Planning of the Voyageur Hiking Trail began on March 23, 1973 when the then Commissioner of Parks and Recreation for the City of Sault Ste. Marie, Harold Brain, convened

5920-431: The underlying ductile mantle , and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created). During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in

6000-503: The vast privately and publicly owned forests of this rugged wilderness. The largest city on the completed trail is Sault Ste. Marie , situated between two of the Great Lakes – Lake Superior and Lake Huron – and bordering on the state of Michigan . The route parallels these two great bodies of water, frequently touching on the shoreline or affording glimpses from distant promontories. The trail passes through many other communities along

6080-492: The volcano. Solid particles smaller than 2 mm in diameter ( sand-sized or smaller) are called volcanic ash. Tephra and other volcaniclastics (shattered volcanic material) make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record. The production of large volumes of tephra is characteristic of explosive volcanism. Through natural processes, mainly erosion , so much of

6160-424: The volcanoes of the East African Rift . A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice , typically a volcanic cone or mountain. The most common perception of

6240-466: The woods) The trail is used by all ages and levels of experience, from the day hiker and trail runner to the hardy backpacker . The trail dates to 1973, and is a work in progress that has involved hundreds of volunteers, private sector and government supporters. It is designed for foot traffic in summer and snowshoe/ski traffic in winter Over half the linear trail has been completed (some 600 km) plus numerous side trails. The hiking trail crosses

6320-421: Was described by Roman writers as having been covered with gardens and vineyards before its unexpected eruption of 79 CE , which destroyed the towns of Herculaneum and Pompeii . Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness. Pinatubo was an inconspicuous volcano, unknown to most people in

6400-443: Was elected general secretary shortly thereafter. On July 3, 1974, the association was formally chartered as a corporation without share capital. Dieter Ropke was the longest-serving member of the board of directors, holding the position of treasurer for over 30 years. The Rainbow Section (now abandoned owing to the folding of the local club) near Espanola was the first hikeable Voyageur Trail Section in 1973. In 1974, George Morrison,

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