Three Fingered Jack
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Three Fingered Jack is a summit of a shield volcano of the Cascade Range in the U.S. state of Oregon. Formed during the Pleistocene epoch, the mountain consists mainly of basaltic andesite lava and was heavily glaciated in the past. While other Oregon volcanoes that were heavily glaciated—such as Mount Washington and Mount Thielsen—display eroded volcanic necks, Three Fingered Jack's present summit is a comparatively narrow ridge of loose tephra supported by a dike only Template:Convert thick on a generally north–south axis. Glaciation exposed radiating dikes and plugs that support this summit. The volcano has long been inactive and is highly eroded.
Three Fingered Jack has diverse flora, fauna, and fungi. The Molala people, one of the indigenous groups in the northwestern United States, historically inhabited the area around the volcano. Not much is known about Molala culture, other than that the group fished for salmon and collected berries, fruits, obsidian, and dried herbs. David Douglas was the first person of non-indigenous descent to reach the area in 1825, followed by Peter Skene Ogden the following year. The first group to ascend the volcano reached its summit in September 1923. Three Fingered Jack can still be climbed, but climbers can require rescue after becoming disoriented in low visibility conditions.
GeographyEdit
Three Fingered Jack lies in the U.S. state of Oregon, in Linn<ref name="ngs"/> and Jefferson counties.<ref name=gnis/> It has a volume of Template:ConvertTemplate:Sfn and a summit elevation of Template:Convert,<ref name="ngs"/>Template:Efn with a proximal topographic relief of Template:Convert and a draping relief of Template:Convert.Template:SfnTemplate:Efn Its jagged edifice rises between Mount Jefferson and the Three Sisters volcanic complex.Template:Sfn Three Fingered Jack lies within the Mount Jefferson Wilderness and is only accessible on foot by trails such as the Pacific Crest Trail.Template:Sfn Located about Template:Convert northwest of the city of Sisters, it is a prominent landmark in the area.<ref name="ngs"/>
Physical geographyEdit
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Lateral and terminal moraines formed on Three Fingered Jack during the last major advance of glacial ice in the area during the Wisconsin glaciation, along with glacial striations, altered vegetation patterns, and lithologies that suggest glacial transport of material.Template:Sfn Jack Glacier (unofficially-named) is the sole glacier remaining on the volcano, located in a shaded cirque on the northeast side.Template:SfnTemplate:Sfn The glacier resides at an unusually low altitude for the central Oregon Cascades it is protected by tall ridges to the south and west.Template:Sfn Jack Glacier has an area of Template:Convert, though historically it has reached estimated areas of up to Template:Convert.Template:Sfn It is likely stagnant.Template:Sfn During the Little Ice Age, which spanned roughly 1350 to 1850, the glacier produced moraines with heights close to Template:Convert,Template:Sfn which are dotted with Template:Convert of ash from the Sand Mountain cinder cone chain and Template:Convert of ash from the Blue Lake Crater cinder cone.Template:Sfn
The moraine for Jack Glacier dammed a lake with a volume of Template:Convert, a surface area of Template:Convert, and a maximum depth of Template:Convert.Template:Sfn This lake was documented in 1937, although it did not appear on United States Geological Survey topographic maps made during the 1920s.Template:Sfn The lake sits precariously;Template:Sfn moraines on the volcano are steep, unstable, and populated with boulders.Template:Sfn Before September 1960, there was a partial breach of this moraine-dammed lake that covered an area of Template:Convert near the moraine's base.Template:Sfn Since 1960, there have been at least three incidents in which moraine-dammed lakes on the volcano have caused floods down the slopes,Template:Sfn including a significant flood and debris flow in 2012.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Local soil is thin, and it has been buried by a layer of weathered Holocene tephra from Three Fingered Jack, which has a maximum thickness of Template:Convert.Template:Sfn
EcologyEdit
Douglas fir, Alpine fir, blue spruce, mountain hemlock, and bear grass can be found along the volcano and its hiking trails.Template:Sfn Cascade parsley fern grows on Three Fingered Jack between elevations of Template:Convert.Template:Sfn There are also mountain goats in the surrounding wilderness area.<ref name=canyoncreek/>
Carnivorous animals in the surrounding area include American black bears, coyotes, cougars,Template:SfnTemplate:Sfn red foxes, raccoons, American martens, stoats (also known as ermines), long-tailed weasels, American minks, North American river otters, and bobcats.Template:Sfn Deer species include Roosevelt elk, black-tailed deer, and mule deer;Template:Sfn insectivores include vagrant shrews, American water shrews, and coast moles.Template:Sfn Bats at Jefferson include little brown bats and silver-haired bats, and American pikas and snowshoe hares are also present.Template:Sfn Rodents such as yellow-bellied marmots, mountain beavers, yellow-pine chipmunks, Townsend's chipmunks, golden-mantled ground squirrels, western gray squirrels, Douglas squirrels, mountain pocket gophers, North American beavers, deer mice, bushy-tailed woodrats, water voles, Pacific jumping mice, and North American porcupines are present.Template:Sfn
Birds nearby include mallards, northern goshawks, sharp-shinned hawks, red-tailed hawks, dusky grouses, grey partridges, killdeers, spotted sandpipers, California gulls, band-tailed pigeons, great horned owls, mountain pygmy owls, common nighthawks, rufous hummingbirds, Northern flickers, pileated woodpeckers, yellow-bellied sapsuckers, hairy woodpeckers, and white-headed woodpeckers.Template:Sfn Other bird species found in the area consist of Eurasian three-toed woodpeckers, willow flycatchers, olive-sided flycatchers, tree swallows, Canada jays, Steller's jays, common ravens, Clark's nutcrackers, black-capped chickadees, mountain chickadees, chestnut-backed chickadees, red-breasted nuthatches, pygmy nuthatches, Eurasian treecreepers, American dippers, wrens, American robins, varied thrushes, hermit thrushes, Townsend's solitaires, golden-crowned kinglets, ruby-crowned kinglets, water pipits, blue-headed vireos, western tanagers, Cassin's finches, gray-crowned rosy finches, pine siskins, red crossbills, green-tailed towhees, dark-eyed juncos, white-crowned sparrows, golden-crowned sparrows, fox sparrows, and Lincoln's sparrows.Template:Sfn Long-toed salamanders, California giant salamanders, rough-skinned newts, tailed frogs, western toads, Pacific tree frogs, northern red-legged frogs, Oregon spotted frogs, pygmy short-horned lizards, common garter snakes, and northwestern garter snakes make up some of the amphibious and reptilian animals in the vicinity.Template:Sfn
Geology and subfeaturesEdit
Three Fingered Jack is a shield volcano,Template:Sfn<ref name=vw>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=gvp>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>Template:SfnTemplate:Efn and it is part of the group of volcanoes known as Oregon's Matterhorns, whose tall, pinnacle spires resemble the Matterhorn in Switzerland. The volcano (like Mount Thielsen, Mount Bailey, Diamond Peak, and Mount Washington) had a shorter lifespan than larger volcanoes in the Cascade Range, ceasing eruptive activity more than 100,000 years ago.Template:Sfn Three Fingered Jack marks the northernmost point for this group.Template:Sfn South of Mount Jefferson, the High Cascades of Oregon consist of a broad ridge produced by shield volcano activity and eruptions from cinder cones. Vents range from deeply eroded complexes to recently active volcanoes, with most of the region mantled by normally polarized rock produced within the past 730,000 years.Template:Sfn
Three Fingered Jack is part of a group of more than 30 large shield volcanoes and stratovolcanoes that form a segment of Pleistocene-to-Holocene-epoch volcanic vents that produced mafic lava (rich in magnesium and iron).Template:Sfn Three Fingered Jack includes several overlapping cinder cones and composite cones over underlying lava flows from shield volcano activity.Template:Sfn These volcanic edifices and their lava flow deposits cover an area of Template:Convert.Template:Sfn
The major edifice, which consists of light gray, basaltic andesite lava flow deposits, sits Template:Convert to the west of the first tephra cone. Variegated pyroclastic rock is embedded among these flows.Template:Sfn Element abundance analysis suggests that lava in the Three Fingered Jack area can be grouped into discrete units based on its source magma chamber, except for the Jorn Lake basalt produced by the underlying shield volcano and basaltic andesite erupted by Three Fingered Jack. Petrological analysis shows high and low pressures for the crystallization of these lava flow deposits, and that basaltic andesite was distinct from basalt due to longer fractionation times.Template:Sfn
Though Three Fingered Jack does not have a high-level conduit-filling volcanic plug, its summit sits atop a pyroclastic cone.Template:Sfn Another cone lies Template:Convert to the south of the major cone, and there are secondary craters on the sides, as well as radial dikes and volcanic plugs.Template:Sfn Known subfeatures include two shield volcanoes, Maxwell Butte (less eroded than Three Fingered Jack) and Turpentine Peak, which have elevations of Template:Convert and Template:Convert, respectively.<ref name=gvp/> There are six additional known volcanic cones: Duffy Butte, at an elevation of Template:Convert; Hogg Rock (a tuya), at an elevation of Template:Convert; Marion Mountain, at an elevation of Template:Convert; Red Butte, with an elevation of Template:Convert; and Marion Peak and Saddle Mountain, which do not have elevations listed.<ref name=gvp/> Other shield volcanoes and cinder cones that were active during the Pleistocene epoch occur to the northwest and southwest.<ref name=gvp/>
The volcano has a long ridge that trends from north to south. It is highly eroded;<ref name=vw/>Template:Sfn shaped like a sawtooth, it consists of tephra deposits supported by a vertical dike with a thickness of Template:Convert. Erosion has been so extensive that climbers claim that the summit moves in the wind.Template:Sfn During the Pleistocene epoch, glaciers exposed its inner contents, providing evidence for its eruptive history.Template:Sfn Though it has not been dated by radiometric approaches, the volcano is likely between 500,000 and 250,000 years old,Template:Sfn and has been carved out by at least three glacial periods.Template:Sfn
Eruptive historyEdit
Three Fingered Jack has an eruptive history similar to many High Cascade volcanoes.Template:Sfn The first activity was the formation of a pyroclastic cone over shield volcanoes. Later eruptions formed a main volcanic cone from lava flows and more pyroclastic rock. There are dikes that radiate from a micronorite plug, which deformed tephra in the surrounding strata. The northern and southern flanks of Three Fingered Jack feature lava flows made of olivine and augite basalt.Template:Sfn
Three Fingered Jack is estimated to be between 500,000 and 250,000 years old.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It underwent more explosive eruptions as its eruptive history progressed, generating large amounts of tephra which created a loose, unconsolidated summit and upper cone. Lava flows near the summit have an average thickness of Template:Convert. Secondary volcanic craters produced lava flows and pyroclastic material, which traveled both north and south of the volcano. Cone-building eruptions ceased before the Pleistocene epoch's glacial period, allowing the expanded glacial cover to remove most of the cone, especially on the eastern and northeastern sides.Template:Sfn
During the ongoing Holocene epoch, there has been volcanic activity between the Three Sisters volcanoes and Three Fingered Jack. Such eruptive episodes have produced tephra and lava flows that cover several hundred square kilometers in the region. These eruptions occurred after the climactic eruption of Mount Mazama, which took place roughly 6,600 years ago.Template:Sfn
Human historyEdit
The Molala people traditionally inhabited the surrounding area. The Molala fished for salmon and collected berries, fruits, obsidian, and dried herbs. Their culture was not well documented.Template:Sfn The first person of non-indigenous descent to reach the area was David Douglas in 1825, followed by Peter Skene Ogden the following year.Template:Sfn
Sources disagree about the affiliation of the mountain's first ascenders, some calling them "the Boys from Bend,"Template:Sfn others saying they were members of the Mazamas mountaineering club.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Nonetheless, a source written by one of these first ascenders clearly states who was in the party and when they climbed. Ervin McNeal, Phil Philbrook, Armin Furrer, Wilbur Watkins, Leo Harryman, and Ronald Sellars were the first to ascend Three Fingered Jack on September 3, 1923.Template:Sfn
The origins of Three Fingered Jack's name remain unclear.Template:Sfn One account claims that the volcano received its name from Joaquin Murrieta, a gold miner and vaquero during the California Gold Rush also known as Three Fingered Jack.Template:Sfn Others allege that the volcano was named after a trapper with less than five fingers on one of his hands.Template:Sfn
RecreationEdit
Hikers can see Three Fingered Jack on trails surrounding the mountain. The Canyon Creek Meadows hiking trail begins at Jack Lake, progresses through the Mount Jefferson Wilderness, and runs for about Template:Convert. It has an elevation gain of Template:Convert, and is accessible to children and families. An additional connected hiking trail runs for another Template:Convert up the rocky glacial washout plain adjacent to the volcano, becoming steeper as it approaches Three Fingered Jack and gaining Template:Convert in elevation.<ref name=canyoncreek>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The base can also be reached on Pacific Crest Trail which runs for Template:Convert round trip and offers views of the volcano and its summit lake.Template:Sfn Moreover, the Three Fingered Jack loop trail runs for Template:Convert around the volcano, gaining Template:Convert in elevation.Template:Sfn
When Three Fingered Jack's face becomes foggy, climbers have become disoriented due to the low visibility conditions of climbing the mountain, requiring rescue.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>
The summit can be quite dangerous due steep cliffs and poor rock quality which can result in footing and hand holds giving way without warning. One such event occurred on July 19, 2020, resulting in the death of a hiker attempting to reach the summit.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>
NotesEdit
ReferencesEdit
SourcesEdit
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