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82-444: The range takes its name from a volcanic peak on the west side, named Magdalena Peak, after Mary Magdalene . A talus formation and shrub growth on the east slope of Magdalena Peak is said to resemble a woman's face. According to Julyan's Place Names of New Mexico , one legend about the mountain purports that "a group of Mexicans were besieged by Apaches on the mountain, when the face of Mary Magdalene miraculously appeared, frightening

164-600: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Mexican spotted owl 3, see text The spotted owl ( Strix occidentalis ) is a species of true owl . It is a resident species of old-growth forests in western North America , where it nests in tree hollows , old bird of prey nests, or rock crevices. Nests can be between 12 and 60 metres (39 and 197 ft) high and usually contain two eggs (though some contain as many as four). It

246-484: 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, a mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas

328-595: A 7.2% annual decline across northern Washington and southwestern British Columbia. Fewer than 30 breeding pairs were thought to exist in Canada in 2006, and some experts have predicted the imminent extirpation of the species from Canada. An experiment sanctioned by the USFWS investigated the suitability of protecting the spotted owl by controlling its competitor, the barred owl. Work began in 2009 by removing populations of barred owls in designated areas. The studies found that in

410-665: A battle between two federal agencies, the Bureau of Land Management , and the Fish and Wildlife Service, the committee ruled for the exemption of 1,700 acres from the ESA. The legal battle went on at different levels , creating a complex case study in environmental law. Each subspecies of the spotted owl is a frequent subject of disagreement between conservationists and loggers , cattle grazers , developers , and other organizations whose activities can affect forest conservation. In February 2008,

492-672: A broader diet, and occur in more varied habitats. Though the two species are genetically quite distinct, they may hybridize in areas where displacement is occurring, resulting in an interspecific hybrid owl referred to as a "sparred owl". The Gila Wilderness is home to the largest population of the Mexican subspecies. The northern spotted owl has a nearly contiguous range from southwestern British Columbia south through western Washington and Oregon to Marin County, California . The California spotted owl's range overlaps this range in

574-541: A federal judge reinforced a USFWS decision to designate 8,600,000 acres (35,000 km ) in Arizona, Utah, Colorado, and New Mexico as critical habitat for the Mexican spotted owl. The decision was challenged by the Arizona Cattle Growers' Association , but the decision was upheld on appeal. By 2006, the northern spotted owl was reported to be in rapid decline in the northernmost part of its range, with

656-437: 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,

738-438: A lesser extent, including birds (smaller owls, jays, woodpeckers, and passerines, including various songbirds), amphibians, reptiles, and insects. The IUCN Red List status for the spotted owl is near threatened with a decreasing population trend. NatureServe considers the species Vulnerable . All studies assessing the species' population trend have found populations to be in decline. Habitat loss due to timber harvesting

820-562: A little over 50 mm (2.0 in) long, and are white and smooth with a slightly grainy texture. The spotted owl is similar in appearance to the barred owl , but has cross-shaped markings on the underparts, whereas the barred owl is alternately barred on the breast and streaked on the belly. Barred owls are larger and grayer than spotted owls. In recent years, the California and northern subspecies of spotted owl have been displaced by barred owls ( S. varia ), which are more aggressive, have

902-403: A negative effect on northern spotted owl survival and fecundity . There are also negative effects when Barred owls live in the same area as Spotted Owls. Spotted owls are nocturnal , sit-and-wait predators . They often hunt from a perch and swoop or pounce on prey, or may take arboreal prey from tree boles and limbs. They do occasionally hunt during the day. Although diet varies with location,

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984-443: 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

1066-632: A primary threat to spotted owl population viability, but a systematic review and meta-analysis found fires created more benefits than costs for spotted owls. The northern spotted owl and Mexican spotted owl subspecies are listed as threatened in the United States under the Endangered Species Act (ESA). On February 23, 2023, The California spotted owl was proposed for listing under the Endangered Species Act by

1148-450: A territory increases reproduction. Large trees seem to constitute preferred nesting and roosting habitat for all three subspecies, and canopy cover greater than 40% (often greater than 70%) is generally sought out. Substantial tall shrub cover is a common characteristic of spotted owl habitat. Spotted owls can be found at elevations of 70–6,600 feet (21–2,012 m) for the northern subspecies, at 1,000–8,500 feet (300–2,590 m) for

1230-632: 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

1312-555: 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

1394-465: 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

1476-739: 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

1558-458: Is a nocturnal owl which feeds on small mammals and birds. Three subspecies are recognized, ranging in distribution from British Columbia to Mexico . The spotted owl is under pressure from habitat destruction throughout its range, and is currently classified as a near-threatened species . The spotted owl has an average length of 43 cm (17 in), wingspan of 114 cm (45 in), and weight of 600 g (1.3 lb). Its eggs are

1640-412: 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

1722-565: 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

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1804-584: 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

1886-435: Is generally recognized as the main threat. One study reported that competition with the barred owl is also a major contributor to the decline of the spotted owl. Forest and spotted owl management documents often state that severe wildfire is a cause of recent declines in populations of spotted owls, and that mixed-severity fires (5–70% of burned area in high-severity patches, with >75% mortality of dominant vegetation) pose

1968-537: 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

2050-471: 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

2132-617: 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

2214-626: 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,

2296-783: The Paleoindian period providing glimpses into the peopling of the New World and megafaunal extinction ." Much of the now Magdalena Ranger District was a province of the Apache . Bands of Apache effectively controlled the Magdalena-Datil region from the seventeenth century until they were defeated in the Apache Wars in the late nineteenth century. A mining rush followed the Apache wars – gold, silver, and copper were found in

2378-683: The Sierra Madre Occidental and the Sierra Madre Oriental . Spotted owls occur in a variety of hardwood and coniferous forest habitats, although the species prefers closed-canopy, uneven-aged, late-successional, and old-growth forests. The Mexican subspecies may also make use of chaparral and pinyon woodlands, including areas in deep, steep-walled canyons with little canopy cover. The California subspecies uses unlogged, complex early seral forests created by wildfire for foraging, and more high-severity fire in

2460-593: The U.S. Fish and Wildlife Service (USFWS) after 20 years of attempts by environmental groups to get it listed. The Coastal-Southern California distinct population segment (DPS) is proposed for endangered status, while the Sierra Nevada DPS is proposed for threatened status with a 4D rule exception. The northern spotted owl was one of a few cases where the "God committee", a provision of the Endangered Species Act, has been invoked to decide whether or not to open up more federal forest for commercial logging. In

2542-834: 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

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2624-413: The California subspecies, and rather higher (6,000–8,500 feet (1,800–2,600 m)) for the Mexican spotted owl. All subspecies appear to value the proximity of water sources. Spotted owl home ranges are generally large but of variable size, with extents of 661–14,169 acres (2.67–57.34 km ), depending on subspecies, habitat, and prey availability. Home ranges are smaller in the breeding season than in

2706-786: The Indians away." Most of the Magdalena Mountains are within the Magdalena Ranger District of the Cibola National Forest , and parts are also administered by the Bureau of Land Management . While there are no designated Wilderness areas in the range, the Ryan Hill Inventoried Roadless Area (IRA) is sizeable (up to approximately 35,000 acre). In 1980, Public Law 96-550 established Langmuir Research Site in

2788-848: The Magdalena Livestock Driveway, but more popularly known to cowboys and cattlemen as the Beefsteak Trail. The trail began use in 1865 and its peak was in 1919. The trail was used continually until trailing gave way to trucking and the trail officially closed in 1971. The Magdalena Mountains contain a wide variety of vegetation types, including scrubland, pinyon-juniper woodland, ponderosa pine forest, spruce-fir forest, grassland, and riparian areas. At lower elevations, grasses include black and sideoats grama, poverty threeawn, fluffgrass, burrograss, and galleta grass. Higher up, grass species include blue and hairy grama, little blue stem, and Arizona fescue. Shrubs that are mixed in

2870-470: The Magdalena Mountains is intimately linked with the rich history of the surrounding area. Basham noted in his report documenting the archeological history of the Cibola's Magdalena Ranger District that "[t]he heritage resources on the district are diverse and representative of nearly every prominent human evolutionary event known to anthropology. Evidence for human use of district lands date back 14,000 years to

2952-544: The Magdalena Mountains was chosen "because thunderstorms are initiated by the mountains and the storms are often isolated, stationary, and relatively small" and occur with high frequency. Visiting scientists at Langmuir also study bats, hummingbirds, butterflies and plant life in the area. The same area hosts the Magdalena Ridge Observatory Interferometer , also operated by New Mexico Tech, along with other institutions. The history of

3034-501: The Magdalena Mountains. Congress found the mountains uniquely suited for atmospheric and astronomical research which has been conducted at Langmuir Laboratory near South Baldy since the mid-1960s. The Act designated a 31,000 acre portion of the mountain as essentially roadless, but not wilderness. There is overlap between the Ryan Hill IRA and the congressionally designated Langmuir Research Site management area. Directly adjacent to

3116-657: The Magdalenas. Over half of the trails are in the Ryan Hill Inventoried Roadless Area. The Water Canyon Campground is a developed campsite located at 6,800 ft elevation in the Magdalenas. Significant summits include: At the southern end of the main range crest, just south of South Baldy, lies the Langmuir Laboratory for Atmospheric Research of the New Mexico Institute of Mining and Technology (New Mexico Tech). The Langmuir's location in

3198-883: 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 the core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which

3280-622: 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

3362-613: 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

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3444-510: 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

3526-402: 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

3608-799: 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

3690-431: 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

3772-610: 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

3854-585: 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

3936-466: 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

4018-468: The grasslands include sotol, cholla, yucca, Apache plume, mountain mahogany, shrub live-oak, gambel oak, and alligator juniper. The range of habitat areas available is reflected by the variety of wildlife in the area. The mountains are home to mountain lions, black bears, pronghorns, mule deer, coyotes, red and grey foxes, bald and golden eagles, prairie falcons, kestrel, and Mearn's quail. Several thousand acres of Mexican spotted owl critical habitat lie in

4100-492: 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

4182-700: The majority consists of a few mammalian species. Species taken most often are northern flying squirrels (which may comprise more than 30% of total prey) and woodrats (the most common prey overall), including dusky-footed ( Neotoma fuscipes ), bushy-tailed, ( N. cinerea ), and Mexican woodrats ( N. mexicana ). In some portions of its range, much of the spotted owl's diet is composed of several other mammals such as deer mice ( Peromyscus maniculatus ), pocket gophers ( Thomomys spp.), voles ( Microtus , Clethrionomys , and Phenocomys spp.), snowshoe hares ( Lepus americanus ), rabbits , and several species of squirrels. Bats and non-mammalian prey species are taken to

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4264-419: 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

4346-551: 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

4428-415: 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

4510-400: The mountains. While miners combed the mountains for mineral riches during the late nineteenth and early twentieth centuries, stockmen drove tens of thousands of sheep and cattle to stockyards at the village of Magdalena, then linked by rail with Socorro. In fact, the last regularly used cattle trail in the United States stretched 125 miles westward from Magdalena. The route was formerly known as

4592-438: 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

4674-452: 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

4756-487: The nonbreeding season, and females have larger home ranges than males. Density of spotted owl pairs within suitable habitat also depends on specific habitat quality and location, varying between 0.022 owls/km in pinyon-juniper woodlands of the Sacramento Mountains and 1.049 owls/km . Spotted owls do not build their own nests, instead making use of cavities found in trees, deadwood, and snags, as well as

4838-876: 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

4920-478: The northern range often settling into a wintering range before seeking out breeding territories in the spring. Dispersal range is often less than 19 mi (31 km). Spotted owls are long-lived and maximum ages of 16 or 17 years have been documented in the northern subspecies. The average annual survival rate is usually in excess of 80% for adults, although it is considerably lower for juveniles, which have an average annual survival rate of 21–29%. In New Mexico,

5002-549: 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

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5084-420: 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

5166-471: 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

5248-441: The of one year but two years or older is more common. Normal clutch size is two eggs but may reach four on rare occasions. The female sits on the eggs and cares for the young, while the male provides food for them. Egg incubation times of about a month have been reported from western Oregon; time from fledging to independence of chicks is between three and four months. Once independent, juveniles disperse in late summer to fall, in

5330-468: 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

5412-425: 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

5494-619: 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

5576-504: The range. The Magdalenas provide habitat and an east–west movement corridor for mountain lions, and the area is considered important for species movement across the landscape. The Nature Conservancy identified the Magdalena Mountains as part of a key conservation area due to their ecosystem diversity and species richness. Volcanic A volcano 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

5658-435: 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

5740-492: 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

5822-917: The sites of abandoned raptor or squirrel nests. Some nest sites are used repeatedly. High-quality (consistently occupied and reproductive) breeding sites remain occupied after wildfire and post-fire salvage logging, while lower quality sites that are inconsistently occupied and reproductive are more likely to be abandoned after fire and salvage logging. Spotted owls most often choose the same type of cover selected for nesting sites for daytime roosting. The spotted owl's breeding season occurs from early spring to late summer or fall, with prelaying behaviors such as preening and roosting together starting in February or March. Spotted owl pairs are monogamous and rarely re-nest after failed breeding attempts. The species does not normally breed every year, with average breeding probability being 62%. Young owls may start breeding at an

5904-622: 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

5986-601: The southern Cascade Range , and extends south through the western Sierra Nevada to Tulare County , with discrete populations in mountainous areas of coastal and southern California from Monterey County to northern Baja California . The Mexican spotted owl occurs in disjunct populations in mountain ranges and canyons of the Southwestern US (including Utah , Colorado , Arizona , New Mexico , and extreme western Texas ), as well as in western Mexico ( Sonora , Chihuahua , Nuevo León , and eastern Coahuila ) through

6068-677: The southern boundary of the Ryan Hill IRA lies the Devil's Reach Wilderness Study Area (WSA). The Devil's Reach WSA and its neighboring Devil's Backbone WSA are both managed by the BLM. The Ryan Hill IRA, Devil's Reach WSA, and Devil's Backbone WSA combine to form a 44,050-acre contiguous roadless area on the southern end of the range. A well-established network of trails exists in the Magdalena Mountains, providing abundant hiking, backpacking, hunting, horseback-riding, and stargazing opportunities. The Forest Service notes that there are over 60 miles of trails in

6150-406: 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

6232-665: The survival rate for fledgling Mexican spotted owls can be as low as 11%. The most common causes of mortality are predation, starvation, and possibly disease. Various birds and mammals such as the fisher ( Pekania pennanti ) are among the predators of eggs and young spotted owls, American goshawks ( Accipiter atricapillus ), crows may prey on juvenile spotted owls, while great horned owls ( Bubo virginianus ), red-tailed hawks ( Buteo jamaicensis ), and golden eagles ( Aquila chrysaetos ) are likely predators of both juveniles and adults. Great horned and barred owls compete with spotted owls for food and space in some areas. Barred owls have

6314-434: 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

6396-444: 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

6478-431: 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

6560-492: 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

6642-424: 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

6724-421: 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

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