The Aleutian Range is a major mountain range located in southwest Alaska. It extends from Chakachamna Lake to Unimak Island, at the tip of the Alaska Peninsula, it includes all of the mountains of the Peninsula. The Aleutian Range is special because of its large number of active volcanoes, which are part of the larger Aleutian Arc; the mainland part of the range is about 600 miles long. The Aleutian Islands are a submerged western extension of the range that stretches for another 1,600 km; however the official designation "Aleutian Range" includes only the mainland peaks and the peaks on Unimak Island. The range is entirely roadless wilderness. Katmai National Park and Preserve, a large national park within the range, must be reached by boat or plane; the core Aleutian Range can be divided into three mountain groups. Listed from southwest to northeast, they are: Mountains of the Alaska Peninsula and Unimak Island Chigmit Mountains Neacola MountainsSee Aleutian Islands for the continuation of the range to the west of Unimak Island.
Just to the north of the Aleutian Range are the Tordrillo Mountains, the southeasternmost extent of the Alaska Range. Selected mountains: Mount Redoubt, Chigmit Mountains Iliamna Volcano, Chigmit Mountains Mount Neacola, Neacola Mountains Mount Shishaldin, Unimak Island Mount Pavlof, Alaska Peninsula Mount Veniaminof, Alaska Peninsula Isanotski Peaks, Unimak Island Mount Denison, Alaska Peninsula Mount Griggs, Alaska Peninsula Mount Douglas, Alaska Peninsula Mount Chiginagak, Alaska Peninsula Double Peak, Chigmit Mountains Mount Katmai, Alaska Peninsula Pogromni Volcano, Unimak Island Mount Okmok, Fox Islands Two volcanoes erupted during the summer of 2008 on the eastern Aleutian Islands. On July 12, 2008, Mount Okmok erupted, it continued to erupt for a month. A giant moving ash and gas cloud shot up to a height of 15,240 m as a result of this eruption. Mount Kasatochi was home to the other eruption, which occurred on August 7 and 8; this eruption sent up a gas cloud about 15,000 high. Together, these two power volcanic eruptions deposited emissions of trace gases an aerosols into the atmosphere.
These emissions formed a sulfate aerosol layer that totaled a transfer of 1.6 Tg of SO2 into the stratosphere and disturbed flights over this area for a short period following the eruptions. The 7.9 Mw Aleutian Islands earthquake occurred in June 2014 at an intermediate depth of 107 km. The quake was caused by oblique normal faulting along the Aleutian Trench, a convergent boundary where the Pacific plate is subducting underneath the North American plate at around 59 mm/year. List of earthquakes in Alaska U. S. Geological Survey Geographic Names Information System: Aleutian Range
Mount Whitney is the tallest mountain in California, as well as the highest summit in the contiguous United States and the Sierra Nevada—with an elevation of 14,505 feet. It is in Central California, on the boundary between California's Inyo and Tulare counties, 84.6 miles west-northwest of the lowest point in North America at Badwater Basin in Death Valley National Park at 282 ft below sea level. The west slope of the mountain is in Sequoia National Park and the summit is the southern terminus of the John Muir Trail which runs 211.9 mi from Happy Isles in Yosemite Valley. The east slope is in the Inyo National Forest in Inyo County; the summit of Mount Whitney is on the Great Basin Divide. It lies near many of the highest peaks of the Sierra Nevada; the peak rises above the Owens Valley, sitting 10,778 feet or just over two miles above the town of Lone Pine 15 miles to the east, in the Owens Valley. It rises more on the west side, lying only about 3,000 feet above the John Muir Trail at Guitar Lake.
The mountain is dome-shaped, with its famously jagged ridges extending to the sides. Mount Whitney has an alpine climate and ecology. Few plants grow near the summit: one example is the sky pilot, a cushion plant that grows low to the ground; the only animals are transient, such as the butterfly Parnassius phoebus and the gray-crowned rosy finch. The mountain is the highest point on the Great Basin Divide. Waterways on the west side of the peak flow into Whitney Creek; the Kern River terminates in the Tulare Basin. During wet years, water overflows from the Tulare Basin into the San Joaquin River which flows to the Pacific Ocean. From the east, water from Mount Whitney flows to Lone Pine Creek, which joins the Owens River, which in turn terminates at Owens Lake, an endorheic lake of the Great Basin; the estimated elevation of the summit of Mount Whitney has changed over the years. The technology of elevation measurement has become more refined and, more the vertical coordinate system has changed.
The peak was said to be at 14,494 ft and this is the elevation stamped on the USGS brass benchmark disk on the summit. An older plaque on the summit reads "elevation 14,496.811 feet" but this was estimated using the older vertical datum from 1929. Since the shape of the Earth has been estimated more accurately. Using a new vertical datum established in 1988 the benchmark is now estimated to be at 14,505 ft; the eastern slope of Whitney is far steeper than its western slope because the entire Sierra Nevada is the result of a fault-block, analogous to a cellar door: the door is hinged on the west and is rising on the east. The rise is caused by a normal fault system that runs along the eastern base of the Sierra, below Mount Whitney. Thus, the granite that forms Mount Whitney is the same as the granite that forms the Alabama Hills, thousands of feet lower down; the raising of Whitney is due to the same geological forces that cause the Basin and Range Province: the crust of much of the intermontane west is being stretched.
The granite that forms Mount Whitney is part of the Sierra Nevada batholith. In Cretaceous time, masses of molten rock that originated from subduction rose underneath what is now Whitney and solidified underground to form large expanses of granite. In the last 2 to 10 million years, the Sierra was pushed up which enabled glacial and river erosion to strip the upper layers of rock to reveal the resistant granite that makes up Mount Whitney today. In July 1864, the members of the California Geological Survey named the peak after Josiah Whitney, the State Geologist of California and benefactor of the survey. During the same expedition, geologist Clarence King attempted to climb Whitney from its west side, but stopped just short. In 1871, King returned to climb what he believed to be Whitney, but having taken a different approach, he summited nearby Mount Langley. Upon learning of his mistake in 1873, King completed his own first ascent of Whitney, but did so a month too late to claim the first recorded ascent.
Just a month earlier, on August 18, 1873, Charles Begole, A. H. Johnson, John Lucas, all of nearby Lone Pine, had become the first to reach the highest summit in the contiguous United States; as they climbed the mountain during a fishing trip to nearby Kern Canyon, they called the mountain Fisherman's Peak. In 1881 Samuel Pierpont Langley, founder of the Smithsonian Astrophysical Observatory remained for some time on the summit, making daily observations on the solar heat. Accompanying Langley in 1881 was another party consisting of Judge William B. Wallace of Visalia, W. A. Wright and Reverend Frederick Wales. Wallace wrote in his memoirs that "The Pi Ute Indians called Mt. Whitney "Too-man-i-goo-yah," which means "the old man." They believe that the Great Spirit who presides over the destiny of their people once had his home in that mountain." The spelling Too-man-i-goo-yah is a transliteration from the indigenous Paiute Mono language. Other variations are Tumanguya. In 1891, the United States Geological Survey's Board on Geographic Names decided to recognize the earlier name Mount Whitney.
Despite losing out on their preferred name, residents of Lone Pine financed the first trail to the summit, engineered by Gustave Marsh, completed on July 22, 1904. Just four days the new trail enabled the first recorded death on Whitney. Having hiked the trail, U. S. Bureau of Fisheries employee Byrd Surby was struck and killed by lightning while eating lunch
Denali is the highest mountain peak in North America, with a summit elevation of 20,310 feet above sea level. With a topographic prominence of 20,156 feet and a topographic isolation of 4,629 miles, Denali is the third most prominent and third most isolated peak on Earth, after Mount Everest and Aconcagua. Located in the Alaska Range in the interior of the U. S. state of Alaska, Denali is the centerpiece of Preserve. The Koyukon people who inhabit the area around the mountain have referred to the peak as "Denali" for centuries. In 1896, a gold prospector named it "Mount McKinley" in support of then-presidential candidate William McKinley. In August 2015, following the 1975 lead of the State of Alaska, the United States Department of the Interior announced the change of the official name of the mountain to Denali. In 1903, James Wickersham recorded the first attempt at climbing Denali, unsuccessful. In 1906, Frederick Cook claimed the first ascent, proven to be false; the first verifiable ascent to Denali's summit was achieved on June 7, 1913, by climbers Hudson Stuck, Harry Karstens, Walter Harper, Robert Tatum, who went by the South Summit.
In 1951, Bradford Washburn pioneered the West Buttress route, considered to be the safest and easiest route, therefore the most popular in use. On September 2, 2015, the U. S. Geological Survey announced that the mountain is 20,310 feet high, not 20,320 feet, as measured in 1952 using photogrammetry. Denali is a granitic pluton lifted by tectonic pressure from the subduction of the Pacific Plate beneath the North American Plate; the forces that lifted Denali cause many deep earthquakes in Alaska and the Aleutian Islands. The Pacific Plate is seismically active beneath Denali, a tectonic region, known as the "McKinley cluster". Denali has a summit elevation of 20,310 feet above sea level, making it the highest peak in North America and the northernmost mountain above 6,000 meters elevation in the world. Measured from base to peak at some 18,000 ft, it is among the largest mountains situated above sea level. Denali rises from a sloping plain with elevations from 1,000 to 3,000 ft, for a base-to-peak height of 17,000 to 19,000 ft.
By comparison, Mount Everest rises from the Tibetan Plateau at a much higher base elevation. Base elevations for Everest range from 13,800 ft on the south side to 17,100 ft on the Tibetan Plateau, for a base-to-peak height in the range of 12,000 to 15,300 ft. Denali's base-to-peak height is little more than half the 33,500 ft of the volcano Mauna Kea, which lies under water. Denali has two significant summits: the South Summit is the higher one, while the North Summit has an elevation of 19,470 ft and a prominence of 1,270 ft; the North Summit is sometimes counted as sometimes not. Five large glaciers flow off the slopes of the mountain; the Peters Glacier lies on the northwest side of the massif, while the Muldrow Glacier falls from its northeast slopes. Just to the east of the Muldrow, abutting the eastern side of the massif, is the Traleika Glacier; the Ruth Glacier lies to the southeast of the mountain, the Kahiltna Glacier leads up to the southwest side of the mountain. With a length of 44 mi, the Kahiltna Glacier is the longest glacier in the Alaska Range.
The Koyukon Athabaskans who inhabit the area around the mountain have for centuries referred to the peak as Dinale or Denali. The name is based on a Koyukon word for "high" or "tall". During the Russian ownership of Alaska, the common name for the mountain was Bolshaya Gora, the Russian translation of Denali, it was called Densmore's Mountain in the late 1880s and early 1890s after Frank Densmore, an Alaskan prospector, the first European to reach the base of the mountain. In 1896, a gold prospector named it McKinley as political support for then-presidential candidate William McKinley, who became president the following year; the United States formally recognized the name Mount McKinley after President Wilson signed the Mount McKinley National Park Act of February 26, 1917. In 1965, Lyndon B. Johnson declared the north and south peaks of the mountain the "Churchill Peaks", in honor of British statesman Winston Churchill; the Alaska Board of Geographic Names changed the name of the mountain to Denali in 1975, how it is called locally.
However, a request in 1975 from the Alaska state legislature to the United States Board on Geographic Names to do the same at the federal level was blocked by Ohio congressman Ralph Regula, whose district included McKinley's hometown of Canton. On August 30, 2015, just ahead of a presidential visit to Alaska, the Barack Obama administration announced the name Denali would be restored in line with the Alaska Geographic Board's designation. U. S. Secretary of the Interior Sally Jewell issued the order changing the name to Denali on August 28, 2015, effective immediately. Jewell said the change had been "a long time coming"; the renaming of the mountain received praise from Alaska's senior U. S. senator, Lisa Murkowski, who had introduced legislation to accomplish the name change, but it drew criticism from several politicians from Pres
San Jacinto Peak
San Jacinto Peak is the highest peak of the San Jacinto Mountains, of Riverside County, California. It lies within Mount San Jacinto State Park. Naturalist John Muir wrote of San Jacinto Peak, "The view from San Jacinto is the most sublime spectacle to be found anywhere on this earth!"San Jacinto Peak is one of the most topographically prominent peaks in the United States. It is ranked sixth among peaks in the 48 contiguous states. According to John W. Robinson and Bruce D. Risher, authors of The San Jacintos, "No Southern California hiker worth his salt would miss climbing'San Jack' at least once."Known for its spectacular north escarpment, the peak rises 10,000 feet above San Gorgonio Pass. It plays host to the famous Cactus to Clouds Trail. To the east, the peak towers over the city of Palm Springs; the peak is frequently called Mount San Jacinto. The steep escarpment of its north face, above Snow Creek, climbs over 10,000 feet in 7 miles; this is one of the largest gains in elevation over such a small horizontal distance in the contiguous United States.
From the peak, San Gorgonio Mountain can be seen across the San Gorgonio Pass. Visible below is the Coachella Valley and the Salton Sea. In addition, much of the Inland Empire, including Ontario to the west, can be viewed on a clear day. Mount San Jacinto is one of the "Four Saints," a name used to describe the high points of the four mountains over 10,000 feet named for Catholic saints in Southern California: San Jacinto Peak, Mount San Gorgonio, San Bernardino Peak, Mount San Antonio. To the Cahuilla Indians, the peak was known as I a kitch, meaning "smooth cliffs." It was the home of the meteor and legendary founder of the Cahuilla. In 1878, a Wheeler Survey topographical party led by rancher Charles Thomas of Garner Valley climbed the peak; the Wheeler Survey gave the mountain the name "San Jacinto Peak" The earliest recorded ascent of the peak was made in September, 1874 by "F. of Riverside," according to a description of his ascent in the San Diego Union. The first successful ascent of the difficult northeast escarpment was made in 1931 by Floyd Vernoy and Stewart White of Riverside.
The peak is flanked by Marion Mountain. These peaks were named in 1897 by USGS topographer Edmund Taylor Perkins, Jr. Perkins named Jean Peak for his sweetheart and future bride, Jean Waters of Plumas County, whom he married in 1903, he named Marion Mountain after Marion Kelly, his girlfriend, a teacher for the Indian Bureau at the Morongo Valley Reservation. According to a local legend, Perkins spent the summer of 1897 deciding which woman to marry while he conducted his topographical survey of San Jacinto Peak and its environs. Nearby Cornell Peak is named for the alma mater of geologist Robert T. Hill. Perkins and Hill were camping in Round Valley when Hill remarked that the peak looked like the campanile tower at Cornell. Perkins named the peak Cornell Peak. In 1931 and 1932, the San Jacinto Mountain Chamber of Commerce sponsored a Labor Day footrace from Idyllwild to San Jacinto Peak and back, a distance of 18 miles and 5,300 feet; the 1931 race was won by Tom Humphreys, a Hopi, in 3:36:30.
Humphreys won the race again in 1932 with a time of 3:12. Near the summit of San Jacinto peak is a stone hut, built in 1935 by the Civilian Conservation Corps under the direction of Serbo-Croatian immigrant Alfred Zarubicka, a stonemason known in Idyllwild as "Zubi." San Jacinto Peak is accessible, as many trails penetrate the Santa Rosa and San Jacinto Mountains National Monument. The most popular route starts with a ride on the Palm Springs Aerial Tramway from Valley Station at 2,643 feet near Palm Springs up to Mountain Station at 8,516 feet. From there, one can climb the mountain face via trails. Another route is to hike the Marion Mountain Trail from near the mountain town of Idyllwild. There is a reproducing but introduced population of Sequoiadendrons planted in 1974 located here hundreds of miles from native populations; the Cactus to Clouds Trail involves an arduous climb of 10,700 feet from the desert floor in Palm Springs to the summit at 10,834 feet. This trail has no water sources until 8,500 feet, so early starts are advised to avoid the temperatures which soar above 100 °F.
List of highest points in California by county List of Ultras of the United States "Mount San Jacinto State Park". California State Parks. Retrieved 2009-08-17. Mount San Jacinto State Park map. Mount San Jacinto State Park. Retrieved 2015-11-24. "San Jacinto Peak". SummitPost.org. Retrieved 2011-05-07. "Cactus to Clouds Hiking Guide". Mt. San Jacinto Message Board. Archived from the original on 2009-10-25. Retrieved 2009-08-17. "Main page". Riverside Mountain Rescue Unit. Retrieved 2009-08-17. "Forum Index". Mt. San Jacinto Outdoor Recreation. Retrieved 2009-08-17. Howser, Huell. "Mt. San Jacinto – California's Gold". California's Gold. Chapman University Huell Howser Archive
Mount Rainier known as Tahoma or Tacoma, is a large active stratovolcano located 59 miles south-southeast of Seattle, in the Mount Rainier National Park. With a summit elevation of 14,411 ft, it is the highest mountain in the U. S. state of Washington, of the Cascade Range of the Pacific Northwest, it is the second topographically prominent mountain in the continental United States and the first in the Cascade Volcanic Arc. Mt. Rainier is considered one of the most dangerous volcanoes in the world, it is on the Decade Volcano list; because of its large amount of glacial ice, Mt. Rainier could produce massive lahars that could threaten the entire Puyallup River valley. "About 80,000 people and their homes are at risk in Mount Rainier’s lahar-hazard zones." Mount Rainier was first known by Tacoma or Tahoma. One hypothesis of the word origin is, in the Lushootseed language spoken by the Puyallup people. Another hypothesis is that "Tacoma" means "larger than Mount Baker" in Lushootseed: "Ta", plus "Koma", Mount Baker.
Other names used include Tahoma and Pooskaus. The current name was given by George Vancouver, who named it in honor of his friend, Rear Admiral Peter Rainier; the map of the Lewis and Clark expedition of 1804-1806 refers to it as "Mt. Regniere". Although "Rainier" had been considered the official name of the mountain, Theodore Winthrop, in his posthumously published 1862 travel book The Canoe and the Saddle, referred to the mountain as "Tacoma" and for a time, both names were used interchangeably, although "Mt. Tacoma" was preferred in the city of Tacoma. In 1890, the United States Board on Geographic Names declared that the mountain would be known as "Rainier". Following this in 1897, the Pacific Forest Reserve became the Mount Rainier Forest Reserve, the national park was established three years later. Despite this, there was still a movement to change the mountain's name to "Tacoma" and Congress was still considering a resolution to change the name as late as 1924. In the lead-up to Super Bowl XLVIII, the Washington State Senate passed a resolution on Friday, January 31, 2014, temporarily renaming the mountain Mount Seattle Seahawks until the midnight after the Super Bowl, February 3, 2014, in response to the renaming of 53 mountains in Colorado after the 53 members of the Denver Broncos by Governor of Colorado John Hickenlooper.
After the 2015 restoration of the original name Denali from Mount McKinley in Alaska, debate over Mount Rainier's name intensified. Mount Rainier is the tallest mountain in the Cascade Range; this peak is located just southeast of Seattle and Tacoma. Mount Rainier is ranked third of the 128 ultra-prominent mountain peaks of the United States. Mount Rainier has a topographic prominence of 13,210 ft, greater than that of K2, the world's second-tallest mountain, at 13,189 ft. On clear days it dominates the southeastern horizon in most of the Seattle-Tacoma metropolitan area to such an extent that locals sometimes refer to it as "the Mountain." On days of exceptional clarity, it can be seen from as far away as Corvallis and Victoria, British Columbia. With 26 major glaciers and 36 sq mi of permanent snowfields and glaciers, Mount Rainier is the most glaciated peak in the lower 48 states; the summit is topped by two volcanic craters, each more than 1,000 ft in diameter, with the larger east crater overlapping the west crater.
Geothermal heat from the volcano keeps areas of both crater rims free of snow and ice, has formed the world's largest volcanic glacier cave network within the ice-filled craters, with nearly 2 mi of passages. A small crater lake about 130 by 30 ft in size and 16 ft deep, the highest in North America with a surface elevation of 14,203 ft, occupies the lowest portion of the west crater below more than 100 ft of ice and is accessible only via the caves; the Carbon, Mowich and Cowlitz Rivers begin at eponymous glaciers of Mount Rainier. The sources of the White River are Winthrop and Fryingpan Glaciers; the White and Mowich join the Puyallup River, which discharges into Commencement Bay at Tacoma. The broad top of Mount Rainier contains three named summits; the highest is called the Columbia Crest. The second highest summit is Point Success, 14,158 ft, at the southern edge of the summit plateau, atop the ridge known as Success Cleaver, it has a topographic prominence of about 138 ft, so it is not considered a separate peak.
The lowest of the three summits is Liberty Cap, 14,112 ft, at the northwestern edge, which overlooks Liberty Ridge, the Sunset Amphitheater, the dramatic Willis Wall. Liberty Cap has a prominence of 492 ft, so would qualify as a separate peak under most prominence-based rules. A prominence cutoff of 400 ft is used in Washington state. High on the eastern flank of Mount Rainier is a peak known as Little Tahoma Peak, 11,138 ft, an eroded remnant of the earlier, much higher, Mount Rainier, it has a prominence of 858 ft, it is never climbed in direct conjunction with Columbia Crest, so it is considered a separate peak. If considered separately from Mt. Rainier, Little Tahoma Peak would be the third highest mountain peak in Washington. Mount Rainier is a stratovolcano in the Cascade Volcanic Arc that consists of lava flows, debris flows, pyroclastic ejecta and flows, its early volcanic deposits are estimated
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, the natural hazards that threaten it; the organization has four major science disciplines, concerning biology, geography and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility; the USGS is a bureau of the United States Department of the Interior. The USGS employs 8,670 people and is headquartered in Reston, Virginia; the USGS has major offices near Lakewood, Colorado, at the Denver Federal Center, Menlo Park, California. The current motto of the USGS, in use since August 1997, is "science for a changing world." The agency's previous slogan, adopted on the occasion of its hundredth anniversary, was "Earth Science in the Public Service." Since 2012, the USGS science focus is directed at six topical "Mission Areas", namely Climate and Land Use Change, Core Science Systems, Ecosystems and Minerals and Environmental Health, Natural Hazards, Water.
In December 2012, the USGS split the Energy and Minerals and Environmental Health Mission Area resulting in seven topical Mission Areas, with the two new areas being: Energy and Minerals and Environmental Health. Administratively, it is divided into six Regional Units. Other specific programs include: Earthquake Hazards Program monitors earthquake activity worldwide; the National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location and magnitude of global earthquakes. The USGS runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System; the USGS informs authorities, emergency responders, the media, the public, both domestic and worldwide, about significant earthquakes. It maintains long-term archives of earthquake data for scientific and engineering research, it conducts and supports research on long-term seismic hazards. USGS has released the UCERF California earthquake forecast.
As of 2005, the agency is working to create a National Volcano Early Warning System by improving the instrumentation monitoring the 169 volcanoes in U. S. territory and by establishing methods for measuring the relative threats posed at each site. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time; the USGS collaborates with Canadian and Mexican government scientists, along with the Commission for Environmental Cooperation, to produce the North American Environmental Atlas, used to depict and track environmental issues for a continental perspective. The USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online. National Climate Change and Wildlife Science Center implements partner-driven science to improve understanding of past and present land use change, develops relevant climate and land use forecasts, identifies lands and communities that are most vulnerable to adverse impacts of change from the local to global scale.
Since 1962, the Astrogeology Research Program has been involved in global and planetary exploration and mapping. In collaboration with Stanford University, the USGS operates the USGS-Stanford Ion Microprobe Laboratory, a world-class analytical facility for U--Pb geochronology and trace element analyses of minerals and other earth materials. USGS operates a number of water related programs, notably the National Streamflow Information Program and National Water-Quality Assessment Program. USGS Water data is publicly available from their National Water Information System database; the USGS operates the National Wildlife Health Center, whose mission is "to serve the nation and its natural resources by providing sound science and technical support, to disseminate information to promote science-based decisions affecting wildlife and ecosystem health. The NWHC provides information, technical assistance, research and leadership on national and international wildlife health issues." It is the agency responsible for surveillance of H5N1 avian influenza outbreaks in the United States.
The USGS runs 17 biological research centers in the United States, including the Patuxent Wildlife Research Center. The USGS is investigating collaboration with the social networking site Twitter to allow for more rapid construction of ShakeMaps; the USGS produces several national series of topographic maps which vary in scale and extent, with some wide gaps in coverage, notably the complete absence of 1:50,000 scale topographic maps or their equivalent. The largest and best-known topographic series is the 7.5-minute, 1:24,000 scale, quadrangle, a non-metric scale unique to the United States. Each of these maps covers an area bounded by two lines of latitude and two lines of longitude spaced 7.5 minutes apart. Nearly 57,000 individual maps in this series cover the 48 contiguous states, Hawaii, U. S. territories, areas of Alaska near Anchorage and Prudhoe Bay. The area covered by each map varies with the latitude of its represented location due to convergence of the meridians. At lower latitudes, near 30° north, a 7.5-minute quadrangle contains an area of about 64 square miles.
At 49° north latitude, 49 square miles are contained within a quadrangle of that size. As a unique non-metric map scale, the 1:24,000 scale requires a separate and specialized romer scale for pl
Types of volcanic eruptions
Several types of volcanic eruptions—during which lava and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are named after famous volcanoes where that type of behavior has been observed; some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions; the most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of volcanic eruption, driven by the compression of gas within magma, the direct opposite of the process powering magmatic activity; the third eruptive type is the phreatic eruption, driven by the superheating of steam via contact with magma. Within these wide-defining eruptive types are several subtypes; the weakest are Hawaiian and submarine Strombolian, followed by Vulcanian and Surtseyan.
The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions. Subglacial and phreatic eruptions are defined by their eruptive mechanism, vary in strength. An important measure of eruptive strength is Volcanic Explosivity Index, an order of magnitude scale ranging from 0 to 8 that correlates to eruptive types. Volcanic eruptions arise through three main mechanisms: Gas release under decompression causing magmatic eruptions Thermal contraction from chilling on contact with water causing phreatomagmatic eruptions Ejection of entrained particles during steam eruptions causing phreatic eruptionsThere are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels tephra. Effusive eruptions, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary in strength. On the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are not dangerous.
On the other extreme, Plinian eruptions are large and dangerous explosive events. Volcanoes are not bound to one eruptive style, display many different types, both passive and explosive in the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a single crater near their peak, either; some volcanoes exhibit lateral and fissure eruptions. Notably, many Hawaiian eruptions start from rift zones, some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to take several thousands of years, but Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was triggered by magma that took a nonstop route from the mantle over just a few months. The Volcanic Explosivity Index is a scale, for measuring the strength of eruptions, it is used by the Smithsonian Institution's Global Volcanism Program in assessing the impact of historic and prehistoric lava flows.
It operates in a way similar to the Richter scale for earthquakes, in that each interval in value represents a tenfold increasing in magnitude. The vast majority of volcanic eruptions are of VEIs between 0 and 2. Volcanic eruptions by VEI index Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, they range in intensity from the small lava fountains on Hawaii to catastrophic Ultra-Plinian eruption columns more than 30 km high, bigger than the eruption of Mount Vesuvius in 79 that buried Pompeii. Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of volcanic events, characterized by the effusive eruption of fluid basalt-type lavas with low gaseous content; the volume of ejected material from Hawaiian eruptions is less than half of that found in other eruptive types. Steady production of small amounts of lava builds up the broad form of a shield volcano.
Eruptions are not centralized at the main summit as with other volcanic types, occur at vents around the summit and from fissure vents radiating out of the center. Hawaiian eruptions begin as a line of vent eruptions along a fissure vent, a so-called "curtain of fire." These die down. Central-vent eruptions, meanwhile take the form of large lava fountains, which can reach heights of hundreds of meters or more; the particles from lava fountains cool in the air before hitting the ground, resulting in the accumulation of cindery scoria fragments. If eruptive rates are high enough, they may form splatter-fed lava flows. Hawaiian eruptions are extremely long lived. Another Hawaiian volcanic feature is the formation of active lava lakes, self-maintaining pools of raw lava with a thin crust of semi-cooled rock. Flows from Hawaiian eruptions are basal