{{Short description|Glacially eroded stratovolcano in the US State of Oregon}} {{Use mdy dates|date=January 2025}} {{good article}} {{Infobox mountain | name = Broken Top | image = Broken Top.JPG | image_caption = | elevation_ft = 9177 | elevation_ref = {{NAVD88}}{{sfn|Hildreth|2007|p=7}} | location = Deschutes County, Oregon, U.S. | range = Cascade Range | coordinates = {{coord|44.0828931|N|121.6997595|W|type:mountain_region:US-OR_scale:100000_source:GNIS|format=dms|display=inline,title}} | range_coordinates = | coordinates_ref = <ref>{{cite gnis |id=1138649 |name=Broken Top |access-date=2008-03-31}}</ref> | topo = USGS Broken Top | type = Stratovolcano | age = Pleistocene | volcanic_arc = Cascade Volcanic Arc | last_eruption = About 100,000 years ago<ref name="USDA"> {{cite web | url = http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/brokentop.shtml | archive-url = https://web.archive.org/web/20101109053737/http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/brokentop.shtml | archive-date = 2010-11-09 | title = Broken Top Volcano | work = Deschutes & Ochoco National Forests | publisher = USDA Forest Service | date = 2003-11-26 | access-date = 2008-03-18 }}</ref> | first_ascent = | easiest_route = }}
'''Broken Top''' is a glacially eroded complex stratovolcano. It lies in the Cascade Volcanic Arc, part of the extensive Cascade Range in the U.S. state of Oregon. Located southeast of the Three Sisters peaks, the volcano, residing within the Three Sisters Wilderness,<ref name="USFS_TSW"> {{cite web| title = Three Sisters Wilderness| work = Willamette National Forest| publisher = United States Forest Service| date = 2004-07-29| url = http://www.fs.fed.us/r6/willamette/recreation/tripplanning/wilderness/threesisters.html| access-date = 2008-05-18 | archive-url = https://web.archive.org/web/20100806114202/http://www.fs.fed.us/r6/willamette/recreation/tripplanning/wilderness/threesisters.html | archive-date=2010-08-06}}</ref> is {{nowrap|{{convert|20|mi|km}}}} west of Bend, Oregon, in Deschutes County. Eruptive activity stopped roughly 100,000 years ago, and erosion by glaciers has since reduced the volcano's cone to where its contents are exposed. There are two named glaciers on the peak, Bend and Crook Glacier.
Diverse species of flora and fauna inhabit the area, which is subject to frequent snowfall, occasional rain, and extreme temperature variation between seasons. Broken Top and its surrounding area constitute popular destinations for hiking, climbing, and scrambling.
== Geography == Broken Top lies in the Cascade Volcanic Arc, roughly located at {{coord|44.08|N|121.70|W}}. It is part of the Cascade Range in Oregon,{{sfn|Taylor|1978|p=3}} in the Three Sisters Wilderness, which lies in Deschutes County.{{sfn|Wood|Kienle|1992|p=183}} The mountain has an elevation of {{convert|9177|ft|m|disp=flip}} according to Hildreth (2007).{{sfn|Hildreth|2007|p=7}} left|thumb|300x300px|Wilderness boundary on the south side of Broken Top
=== Wilderness === The Three Sisters Wilderness covers an area of {{convert|281190|acre|km2}}, making it the second-largest wilderness area in Oregon,<ref name="wildernessgen"/> after the Eagle Cap Wilderness area.<ref>{{cite web|url=https://www.wilderness.net/NWPS/wildView?WID=167|title=Eagle Cap Wilderness: General|work=Wilderness Connect|publisher=U.S. Forest Service and the University of Montana|access-date=2018-05-29}}</ref> Designated by the United States Congress in 1964, it borders the Mount Washington Wilderness to the north and shares its southern edge with the Waldo Lake Wilderness. The area includes {{convert|260|mi|km}} of trails and many forests, lakes, waterfalls, and streams, including the source of Whychus Creek.<ref name="wildernessgen">{{cite web|url=http://www.wilderness.net/NWPS/wildView?WID=602&tab=General|title=Three Sisters Wilderness: General|work=Wilderness Connect|publisher=U.S. Forest Service and the University of Montana|access-date=2014-08-15|archive-url=https://web.archive.org/web/20140401085551/http://www.wilderness.net/NWPS/wildView?WID=602&tab=General|archive-date=2014-04-01|url-status=dead}}</ref> The Three Sisters and Broken Top account for about a third of the Three Sisters Wilderness, and this area is known as the Alpine Crest Region. Rising from about {{convert|5200|ft|m}} to {{convert|10358|ft|m}} in elevation, the Alpine Crest Region features the wilderness area's most-frequented glaciers, lakes, and meadows.{{sfn|Joslin|2005|p=34}}
=== Physical geography === Weather varies greatly in the area due to the rain shadow caused by the Cascade Range. Air from the Pacific Ocean rises over the western slopes, which causes it to cool and dump its moisture as rain (or snow in the winter). Precipitation increases with elevation. Once the moisture is wrung from the air, it descends on the eastern side of the crest, which causes the air to be warmer and drier. On the western slopes, precipitation ranges from {{convert|80|to|125|in|cm}} annually, while precipitation over the eastern slopes varies from {{convert|40|to|80|in|cm}} in the east. Temperature extremes reach {{convert|80|to|90|°F|°C}} in summers and {{convert|-20|to|-30|°F|°C}} during the winters.{{sfn|Joslin|2005|pp=32–33}}
Before settlement of the area at the end of the 19th century, wildfires frequently burned through the local forests, especially the ponderosa pine forests on the eastern slopes. Due to fire suppression over the past century the forests have become overgrown, and at higher elevations they are further susceptible to summertime fires, which threaten surrounding life and property. In the 21st century, wildfires have been larger and more common in the Deschutes National Forest.<ref name=centralfire>{{Cite web|url=https://www.fs.usda.gov/r06/deschutes|title=Central Oregon Fire Environment|publisher=U.S. Forest Service|access-date=2017-11-28}}</ref> In September 2012, a lightning strike caused a fire that burned {{convert|41|sqmi|km2}} in the Pole Creek area within the Three Sisters Wilderness, leaving the area closed until May 2013.<ref>{{cite news|url=http://www.oregonlive.com/travel/index.ssf/2015/08/hiking_pole_creek_fire_three_y.html|title=Hiking Pole Creek fire three years after burn in Three Sisters Wilderness|author=Richard, Terry|date=2015-08-30|access-date=November 24, 2017|work=OregonLive.com|publisher=Advance Publications}}</ref> In August 2017, officials closed {{convert|417|sqmi|km2}} in the western half of the Three Sisters Wilderness,<ref name=sj2017>{{Cite news|url=http://www.statesmanjournal.com/story/news/2017/08/15/wildfires-three-sisters-wilderness-obsidian-trial/569554001/|title=11 new wildfires prompt closure of 266,891 acres in Three Sisters Wilderness|author=Urness, Zach|date=2017-08-15|access-date=2017-11-23|publisher=Gannett Company|work=Statesman Journal}}</ref> including {{convert|24|mi|km}} of the Pacific Crest Trail,<ref>{{cite news|url=http://registerguard.com/rg/news/local/35863998-75/lightning-sparked-wildfires-prompt-large-closure-of-three-sisters-wilderness-east-of-eugene.html.csp|title=Lightning-sparked wildfires prompt large closure of Three Sisters Wilderness east of Eugene|work=The Register-Guard|publisher=Guard Publishing Co.|date=2017-08-16|access-date=2017-11-23|archive-date=2017-08-16|archive-url=https://web.archive.org/web/20170816124435/http://registerguard.com/rg/news/local/35863998-75/lightning-sparked-wildfires-prompt-large-closure-of-three-sisters-wilderness-east-of-eugene.html.csp|url-status=dead}}</ref> to the public because of 11 lightning-caused fires, including the Milli Fire.<ref name=sj2017/><ref>{{cite news|url=http://www.bendbulletin.com/localstate/5520811-151/fire-forces-trail-closures-in-three-sisters-wilderness|title=Fire forces trail closures in Three Sisters Wilderness|newspaper=The Bulletin|location=Bend, Oregon|date=2017-08-15|access-date=2017-11-28}}</ref> As a result of the increasing incidence of fires, public officials have factored the role of wildfire into planning,<ref name=centralfire/> including organizing prescribed fires with scientists to protect habitats at risk while minimizing adverse effects on air quality and environmental health.<ref>{{cite web|url=https://www.fs.usda.gov/r06/deschutes|title=Prescribed Fire in Central Oregon|publisher=U.S. Forest Service|access-date=2017-11-28}}</ref>
== Geology == right|thumb|350px|Broken Top as seen from Mount Bachelor, with Mount Jefferson on the left and Mount Hood on the right.|alt=A highly eroded volcano with jagged cliffs, with two steep volcanoes in the background to its left and to its right.
Broken Top is a complex stratovolcano. It lies northwest of Ball Butte and southeast of South Sister (part of the Three Sisters complex volcano), which is located at longitude 121.7° W and latitude 44.08° N. It has an elevation of {{convert|9186|ft|m}}, with a volume of {{convert|10|km3|cumi|disp=flip}}.{{sfn|Hildreth|2007|p=7}} Like other Cascade volcanoes, Broken Top was fed by magma chambers produced by the subduction of the Juan de Fuca tectonic plate under the western edge of the North American tectonic plate.{{sfn|Joslin|2005|p=29–30}} The mountain was also shaped by the changing climate of the Pleistocene Epoch, during which multiple glacial periods occurred and glacial advance eroded local mountains.{{sfn|Joslin|2005|pp=30–31}}
Broken Top joins several other volcanoes in the eastern segment of the Cascade Range known as the High Cascades, which trends from north–south.{{sfn|Joslin|2005|p=30}} This includes the Three Sisters complex, Belknap Crater, Mount Washington, Black Butte, and Three Fingered Jack, and Mount Bachelor.{{sfn|Harris|2005|p=179}} Constructed towards the end of the Pleistocene epoch, these mountains are underlain by more ancient volcanoes that sank within parallel north–south trending faults in the surrounding region.{{sfn|Joslin|2005|p=31}} The Three Sisters form the centerpiece of a region of closely grouped volcanic peaks, an exception to the typical {{convert|40|to|60|mi|km|adj=on}} spacing between volcanoes elsewhere in the Cascades. This vicinity is among the most active volcanic areas in the Cascades and one of the most densely populated volcanic centers in the world,{{sfn|Riddick|Schmidt|2011|p=1}} as well as the second largest volcanic field of silicic rock within the Quaternary Cascades.{{sfn|Hildreth|2007|p=26}} The {{convert|193|sqmi|km2}} area from the Three Sisters to Broken Top and Mount Bachelor features at least 50 eruptive vents for rhyolitic and rhyodacitic lava.{{sfn|Hildreth|2007|p=26}}
East of Broken Top, the c, a {{convert|115.8|sqmi|km2}} area of andesitic and mafic scoria cones, features similarly rhyolitic and rhyodacitic lava deposits. The Tumalo volcano spread ignimbrites and plinian deposits in ground eruptions across the area (Plinian eruptions are similar to the eruption of Vesuvius that destroyed Pompeii). These deposits spread from Tumalo to the town of Bend.{{sfn|Hildreth|2007|p=27}}
=== Eruptive history === thumb|right|350px|Broken Top, with its eroded crater|alt=A volcano with a large crater rises above a forested region.
Broken Top's initial eruptions, beginning about 300,000 years ago during the middle of the Pleistocene epoch<ref name=hazard>{{cite web|url=https://volcanoes.usgs.gov/volcanoes/three_sisters/three_sisters_geo_hist_125.html|title=Eruption History for Broken Top|date=November 15, 2013|access-date=November 15, 2017|publisher=United States Geological Survey|work=Cascades Volcano Observatory}}</ref> and overlapping with eruptions at the North Sister volcano,{{sfn|Hildreth|2007|p=28}} consisted of basaltic andesite lava that contributed to a base shield.{{sfn|Wood|Kienle|1992|p=183}} The center of this edifice consists of oxidized agglomerate that was invaded by intrusive dikes and geologic sills.{{sfn|Wood|Kienle|1992|p=183}} The scoria, dike rocks, and lava that comprised this cone had a uniform composition made up of phenocrysts with plagioclase, olivine, two types of pyroxene, and magnetite.{{sfn|Taylor|1978|p=5}} Erratic eruptions continued afterward, erupting silicic lava off and on{{sfn|Wood|Kienle|1992|p=183}} until 150,000 years ago,<ref name=hazard/> including pyroxene andesites that lacked olivine, as well as obsidian, which was rare among local volcanoes during that time period.{{sfn|Williams|1944|p=45}} Much of the current cone is occupied by flows from eruptions of mafic lava (rich in magnesium and iron) including andesite, dacite, rhyodacite, and pyroclastic flows. These deposits extend from the subordinate volcano to the summit, and reach Todd Lake Volcano as well as rhyodacitic lava at Tam MacArthur rim and Whychus Creek Falls.{{sfn|Williams|1944|p=45}} Another set of rhyodacitic lava domes runs for {{convert|10|km|mi|disp=flip}} from south of Broken Top to Demaris Lake to its north, but they were partially covered by andesitic deposits from eruptions at the South Sister volcano.{{sfn|Taylor|1978|p=5}} In total, throughout its 150,000 years of eruptive activity, Broken Top erupted between {{convert|7|to|10|km3|cumi|disp=flip}} of lava.{{sfn|Hildreth|2007|p=28}} Though most of the material that forms Broken Top's volcanic cone originated from its main vent, the edifice was also built up by auxiliary vents on its flanks and parasitic cones that surrounded the main edifice. The side vents erupted to form fissure vents, producing basalt and andesite, while the parasitic vents erupted scoria.{{sfn|Williams|1944|p=45}}
Broken Top's volcanic crater, now {{convert|0.8|km|mi|disp=flip}} in diameter, was most likely created through subsidence, which created a depression that was filled with thick basaltic andesite lava flows topped by thin lavas. Once the volcano's central conduit congealed, it underwent hydrothermal alteration over time, which has been revealed by several cirques.{{sfn|Wood|Kienle|1992|p=183}}{{Ref|art5|[a]}} The summit cone has also undergone extensive glacial erosion, with embayments and a major cirque on its southern side.<ref name=hazard/> It forms an amphitheatre shape that opens to the southeast.{{sfn|Harris|2005|p=185}} Due to this extensive erosion, the contents of Broken Top's cone are exposed, which allows volcanologists to classify Broken Top as a complex stratovolcano.<ref name = "Wood">Wood and Kienle 1992, p. 183.</ref> Erosion has destroyed the original summit of the mountain, along with its southeastern slope and much of the volcano's interior, revealing purple, red, and black scoria layers that alternate with yellow, brown, and orange pumice and tuffs, along with white pumice interbedded in a matrix with black lava fragments.{{sfn|Harris|2005|p=185}}
=== Glaciation and flash floods === thumb|Icebergs in a small, unnamed glacial lake near the summit of Broken Top.|alt=Small icebergs float in a small lake with volcanic rock in the background During the late Pleistocene, Broken Top and its surroundings were almost entirely covered by glaciers. The only features in the area not buried by glaciers were the summit of Tumalo Mountain and the summit of Broken Top, including the northwest ridge crest. No geologic evidence suggests that any eruptive activity took place subglacially.{{sfn|Taylor|1978|p=8}}
Currently, the Bend and Crook glaciers, located at elevations of {{convert|7762|ft|m}}<ref>{{cite gnis |id=1137916|name=Bend Glacier|access-date=2017-12-11}}</ref> and {{convert|8209|ft|m}},<ref>{{cite gnis |id=1140459|name=Crook Glacier|access-date=2017-12-11}}</ref> respectively, continue to erode the mountain's interior contents. Both small ice streams, they have decreased significantly in size over the past few decades,{{sfn|Harris|2005|p=185}} and retreat continues at a rapid rate.{{Sfn|Marcott|Fountain|O'Connor|Sniffen|2009|p=183}} The pace of glacial retreat from Broken Top's glaciers are reported to be the highest among Oregon Cascade Range glaciers, at over 11% per year. This is up from around 1.9% in annual loss in prior measurements.<ref>https://bendbulletin.com/2026/03/18/half-of-oregons-named-glaciers-have-disappeared-or-are-near-extinction-study-finds/</ref>
When Little Ice Age glaciers retreated during the 20th century, water filled in the spaces left behind, forming moraine-dammed lakes, which are more common in the Three Sisters Wilderness than anywhere else in the contiguous United States.{{sfn|Joslin|2005|p=44}} The local area has a history of flash floods, including at Broken Top itself, where a flash flood took place on October 7, 1966. Analysis of the event by forest ranger David Rasmussen determined that it had originated from a lake on Broken Top, located at an elevation of {{convert|8000|ft|m}} with an area of {{convert|11|acre|km2}}. This lake sits at the foot of Crook Glacier and is fed by Bend Glacier. The event was likely initiated by glacial ice that fell into the lake, spawning a large wave that breached the moraine and drained {{convert|50000000|USgal|L}} of water into a channel underneath the lake.{{sfn|Nolf|1966|p=182}} The resulting flood reached depths of {{convert|10|-|15|ft|m}},{{sfn|Nolf|1966|p=188}} cascading down the eastern and southern flanks of the mountain and reaching the Cascade Lakes Scenic Byway.{{sfn|Nolf|1966|p=182}} The flood moved logs, rocks, and mud to the Sparks Lake meadow basin; it covered between 35 and 45 percent of the lake's basin with silt and deposited at least {{convert|10000|-|20000|ST|t}} of sediment in the lake and surrounding meadow.{{sfn|Nolf|1966|p=182}}
=== Additional cones ===
Todd Lake volcano, which erupted porphyritic andesite (andesite with distinct differences among its crystal size) with a pale gray color, sits at Broken Top's southern foot. Its lava flows have been exposed and are covered with red scoria and agglutinate from a separate volcanic vent. It began to erupt as Broken Top stopped eruptive activity, since the two have overlapping layers of lava.{{Sfn|Williams|1944|p=52}}
As Pleistocene glaciers retreated, basaltic cinder cone volcanoes formed south of Todd Lake right as Cayuse Crater was forming.{{sfn|Taylor|1978|p=8}} Cayuse Crater, an unrelated postglacial volcano which formed 11,000 years ago,{{sfn|Hildreth|2007|p=28}} also sits on Broken Top's southern flank.{{sfn|Williams|1944|p=54}} It is made up of basaltic lava and scoria that erupted after Broken Top ceased activity,<ref name=hazard/> suggesting that it formed due to an underlying magma chamber closer to South Sister.{{sfn|Fierstein|Hildreth|Calvert|2011|p=171}} Cayuse Crater also consists partly of yellow lapilli tuff and tuff breccia. It has a double rim, its southern wall having been breached by lava flows, with two additional smaller cones, about {{convert|30|-|40|ft|m}} in elevation, to the northwest.{{sfn|Williams|1944|p=54}} More recent Holocene activity on the volcano's flanks constructed basaltic lava flows, cones, and ash that have become interbedded with moraine and material from outwash plains from the Neoglacial period.{{sfn|Wood|Kienle|1992|p=183}}
Ball Butte refers to an additional cone, {{convert|2466|m|ft|disp=flip}} in elevation, which is considered one of Broken Top's subfeatures.<ref name=GVP>{{cite web|url=http://volcano.si.edu/volcano.cfm?vn=322811|editor=Venzke, E.|title=Broken Top: Synonyms and Subfeatures|date=2013|work=Global Volcanism Program|publisher=Smithsonian Institution|access-date=2017-12-11}}</ref> There are also a number of parasitic cones in the area, which helped build Ball Butte over time. They also produced much red scoria and formed hot springs and fumaroles (openings in the earth that emit steam and gases). The remnants of a large scoria cone near Bend Glacier, for the most part destroyed by ice, include volcanic bombs that extend up to {{convert|8|ft|m}} in length.{{Sfn|Williams|1944|p=45}}
During the late Pleistocene, six cinder cone and auxiliary vents between Broken Top and Tumalo Mountain erupted, yielding glomeroporphyritic basaltic andesite. They all likely derived from the same magma source.{{sfn|Taylor|1978|p=5}}
=== Recent history and potential hazards ===
When the first geological reconnaissance of the surrounding region was published in 1925, its author, Edwin T. Hodge, suggested that the Broken Top, the Three Sisters, and several other mountains in the area constituted the remains of an enormous collapsed volcano that had been active during the Miocene or early Pliocene epochs. Naming this ancient volcano {{nowrap|Mount Multnomah}}, Hodge theorized that it had collapsed to form a caldera just as Mount Mazama collapsed to form Crater Lake.{{sfn|Harris|2005|p=182}} In the 1940s, Howel Williams completed an analysis of the vicinity and concluded that Multnomah had never existed, instead demonstrating that each volcano in the area possessed its own individual eruptive history.{{sfn|Harris|2005|p=182}}{{sfn|Williams|1944|p=37}} Williams' 1944 paper, titled "Volcanoes of the Three Sisters Region, Oregon Cascades",{{sfn|Williams|1944|p=37}} defined the basic outline of the region, though he lacked access to chemical techniques and radiometric dating.{{sfn|Hildreth|Fierstein|Calvert|2012|p=1}} {{nowrap|Oregon State University}} geologist and volcanologist Edward Taylor's analysis in 1978{{sfn|Taylor|1978|p=1}} determined that the current Broken Top cone was constructed on basaltic andesite lavas that built a platform.{{sfn|Harris|2005|p=185}} As dikes and sills invaded the edifice over time, it formed a volcanic cone made of different lavas including basaltic andesite, dacite, and rhyodacite, as well as tephra and pyroclastic materials from more explosive eruptions.{{sfn|Harris|2005|p=185}}
Broken Top poses significant hazards to the surrounding area, especially within the proximal hazard zone with a diameter of {{nowrap|{{convert|12|mi|km}}}} that surrounds Broken Top and the Three Sisters. A landslide at Broken Top, or an eruption from the nearby South Sister, could initiate a lahar (rapid flows of water, rock, and mud) that could cascade down river valleys in the surrounding area.{{sfn|Scott|Iverson|Schilling|Fisher|2000|p=1}} While smaller landslides of less than {{convert|10,000,000|m3|cuft|disp=flip}} are more probable than huge avalanches, they can still cause significant damage and cause lahars. Larger landslide events would most likely be the result of magma intrusion, and thus they would be predicted by seismometers and volcanic surveying devices.{{sfn|Scott|Iverson|Schilling|Fisher|2000|p=8}}
An eruption from South Sister would pose a threat to nearby life, as the proximal danger zone extends {{convert|2|to|10|km|mi|disp=flip}} from the volcano's summits.{{sfn|Scott|Iverson|Schilling|Fisher|2000|p=8}} During an eruption, tephra could accumulate to {{convert|1|to|2|in}} in the city of Bend, and mudflows and pyroclastic flows could run down the sides of the mountain, threatening any life in their paths.{{sfn|Sherrod|Taylor|Ferns|Scott|2004|p=11}}
Over the course of the past century, five or more lahars have occurred at the Three Sisters and Broken Top, either as a result of glacier-outburst flooding or the failure of moraine-dammed lakes. However, these only affected undeveloped areas, as they extended less than roughly {{convert|6|mi|km}} from their original source.{{sfn|Scott|Iverson|Schilling|Fisher|2000|p=6}} Future dam failures leading to similar events would likely still only affect the proximal hazard zone with a diameter of {{convert|12|mi|km}}, but they might reach more distal areas if they originate from certain lakes, such as Carver Lake or the unnamed lake on the eastern side of Broken Top draining to Sparks Lake. Lakes with less threat of reaching the distal hazard zone include small lakes in the headwaters of Whychus Creek and the basin below {{nowrap|Collier Glacier}}.{{sfn|Scott|Iverson|Schilling|Fisher|2000|p=8–9}}
== Recreation == thumb|180px|A hiker on the Tam McArthur Rim Trail to Broken Top in the Three Sisters Wilderness|alt=A woman with a backpack stands on a hiking trail, next to a tree
Broken Top and the nearby Three Sisters represent a popular climbing destination for hikers and mountaineers. The United States Forest Service requires permits (of which a limited number are available) for use during the busier parts of the year, and dogs must be kept on leashes on the Green Lakes, Moraine Lakes, South Sister, Soda Creek, Todd Lake, and Crater Ditch trails from July 15 through September 15. Horses are prohibited, and ice axes are sensible during the winter climbing season for safety reasons.<ref>{{cite web|url=http://www.fs.usda.gov/r06/deschutes/recreation|title=South Sister Climber Trail|publisher=U.S. Forest Service|access-date=2014-08-15}}</ref> Motor vehicles and other mechanical means of transport such as bicycles, wagons, motorboats, and helicopters are generally prohibited within the Three Sisters Wilderness under the rules of the National Wilderness Preservation System.
The hiking trail on Broken Top begins at the Green Lakes Basin at the trailhead east of Bend, running {{convert|12|mi|km}} and gaining {{Convert|3450|ft|m}} in elevation. It can be scrambled, though the route demands Yosemite Decimal System class 4 or lower class 5 climbing and has significant exposure.<ref>{{Cite news|author=Urness, Zach|url=http://www.statesmanjournal.com/story/travel/outdoors/2014/08/07/cascade-mountain-peaks-worth-trek/13725809/|title=Oregon Top 5: Best Cascade climbs that don't require ropes|work=Statesman Journal|publisher=Gannett Company|date=2017-08-07|access-date=2017-12-04}}</ref> The Broken Top trail begins at a junction with the Green Lakes Trail. It runs for {{nowrap|{{convert|0.8|mi|km}}}} to Crater Creek, including {{Convert|0.5|mi|km}} of trail that passes right by the volcano and Crook Glacier. There is also an unofficial trail that runs up the moraine of Crook Glacier.{{Sfn|Bishop|Allen|2004|p=144}} The northern slopes of Broken Top can be accessed by trailheads north of Tam McArthur Rim, while its southern slopes can be reached by trailheads near Crater Creek.{{sfn|Wood|Kienle|1992|p=183}}
== See also ==
* Geology of the Pacific Northwest
== Footnotes == * [a] {{note|art5}} Sources disagree on the number of cirques that carved into Broken Top; Wood and Kienle (1992) say three cirques,{{sfn|Wood| Kienle|1992|p=183}} but Williams (1944) claims that five cirques altered the volcano's core.{{sfn|Williams|1944|p=45}}
== Notes == {{reflist}}
== References == *{{Cite book|last1=Bishop|first1=E. M.|last2=Allen|first2=J. E.|title=Hiking Oregon's Geology|publisher=The Mountaineers Books|year=2004|isbn=978-0898868470}} *{{cite journal |title=Eruptive history of South Sister, Oregon Cascades |last1=Fierstein |first1=J. |author-link=Judy Fierstein |last2=Hildreth |first2=W. |author-link2=Wes Hildreth |last3=Calvert |first3=A. T. |journal=Journal of Volcanology and Geothermal Research |volume=207 |issue=3–4 |pages=145–179 |doi=10.1016/j.jvolgeores.2011.06.003 |year=2011 |bibcode=2011JVGR..207..145F}} * {{cite book|last=Harris|first=S. L.|title=Fire Mountains of the West: The Cascade and Mono Lake Volcanoes|publisher=Mountain Press Publishing Company|location=Missoula, Montana|year=2005|edition=Third|chapter=Chapter 13: The Three Sisters|isbn=978-0-87842-511-2}} * {{cite book |last=Hildreth |first=W. |publisher=United States Geological Survey |title=Quaternary Magmatism in the Cascades, Geologic Perspectives |id=Professional Paper 1744 |year=2007 |url=https://pubs.usgs.gov/pp/pp1744/ |author-link=Wes Hildreth |access-date=2017-11-29}} * {{Cite book |last1=Hildreth |first1=W. |last2=Fierstein |first2=J. |last3=Calvert |first3=A. T. |title=Geologic map of Three Sisters volcanic cluster, Cascade Range, Oregon: U.S. Geological Survey Scientific Investigations Map 3186, pamphlet |url=https://pubs.usgs.gov/sim/3186/ |year=2012 |author-link1=Wes Hildreth |author-link2=Judy Fierstein |access-date=2017-11-29 |publisher=United States Geological Survey}} * {{cite book|last=Joslin|first=L.|title=The Wilderness Concept and the Three Sisters Wilderness: Deschutes and Willamette National Forests, Oregon|year=2005|publisher=Wilderness Associates|location=Bend, Oregon|isbn=978-0-9647167-4-2}} *{{Cite journal|last1=Marcott|first1=S. A.|last2=Fountain|first2=A. G.|last3=O'Connor|first3=J. E.|last4=Sniffen|first4=P. J.|last5=Dethierd|first5=D. P.|title=A latest Pleistocene and Holocene glacial history and paleoclimate reconstruction at Three Sisters and Broken Top Volcanoes, Oregon, U.S.A.|journal=Quaternary Research|volume=71|issue=2|year=2009|doi=10.1016/j.yqres.2008.09.002|pages=181–189|bibcode=2009QuRes..71..181M|s2cid=129150777}} *{{cite journal|last1=Nolf|first1=B.|year=1966|title=Broken Top breaks; flood released by erosion of glacial moraine|journal=Ore Bin|publisher=Oregon Department of Geology and Mineral Industries|volume=28|issue=10|pages=182–188}} *{{cite journal|last1=Riddick|first1= S. N.|last2=Schmidt|first2=D. A.|title=Time-dependent changes in volcanic inflation rate near Three Sisters, Oregon, revealed by InSAR|journal= Geochemistry, Geophysics, Geosystems|date=2011|doi=10.1029/2011GC003826|volume=12|issue=12|pages= n/a|bibcode=2011GGG....1212005R|s2cid= 134308941|doi-access=free}} * {{cite journal|last1 = Scott|first1 = W. E.|first2 = R. M. |last2=Iverson |first3=S. P. |last3=Schilling |first4=B. J. |last4=Fisher|title = Volcano Hazards in the Three Sisters Region, Oregon|journal = Open-File Report 99-437|publisher = U.S. Geological Survey|year = 2000|url = https://geopubs.wr.usgs.gov/open-file/of99-437/|access-date = 2008-05-01}} * {{cite journal|title = Geologic Map of the Bend 30-×60-Minute Quadrangle, Central Oregon|url = https://pubs.usgs.gov/imap/i2683/i2683_bend_pamphlet_tagged.pdf|publisher = U.S. Geological Survey| last1 = Sherrod|first1 = D. R.|last2= Taylor |first2=E. M.|last3=Ferns|first3=M. L.|last4=Scott|first4=W. E.|last5=Conrey|first5=R. M.|last6=Smith|first6=G. A.|journal = Geologic Investigations Series I–2683|year = 2004|access-date=2017-11-29}} *{{Cite journal|title=Field geology of S. W. Broken Top quadrangle, Oregon|last1=Taylor|first1=E. M.|url=http://www.oregongeology.org/pubs/sp/SP-02.pdf|publisher=State of Oregon|journal=Department of Geology and Mineral Industries|date=1978}} *{{cite book| last1 = Wood| first1 = C. A.|last2=Kienle|first2=J.|title = Volcanoes of North America| publisher = Cambridge University Press| year = 1992| isbn = 978-0-521-43811-7}} * {{cite journal |last=Williams |first=H. |title=Volcanoes of the Three Sisters Region, Oregon Cascades |year=1944 |publisher=University of California Press |journal=Bulletin of the Department of Geological Sciences |volume=27 |issue=3 |pages=37–84 |editor-last1=Louderback |editor-first1=G. D. |editor-last2=Anderson |editor-first2=C. A. |editor-last3=Camp |editor-first3=C. L. |editor-last4=Chaney |editor-first4=R. W. |url=http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/11300/Vol_Thr_Sis_Reg_Ore_Cas.pdf?sequence=1 |access-date=2017-11-26}}
== External links ==
{{Commons category|Broken Top}} * {{cite summitpost |id=150574 |name=Broken Top |access-date=2011-05-07}} * {{cite web |url = http://www.skiingthebackcountry.com/ski_guide/UNITED-STATES/OREGON/CASCADES-CENTRAL/BROKEN-TOP |title = Broken Top |publisher = SkiingtheBackcountry.org |access-date = 2009-12-07 |url-status = usurped |archive-url = https://web.archive.org/web/20091212135310/http://www.skiingthebackcountry.com/ski_guide/UNITED-STATES/OREGON/CASCADES-CENTRAL/BROKEN-TOP |archive-date = 2009-12-12 }}
{{Cascade volcanoes}} {{Volcanoes of Oregon}}
Category:Mountains of Oregon Category:Subduction volcanoes Category:Cascade Volcanoes Category:Pleistocene stratovolcanoes Category:Volcanoes of Deschutes County, Oregon Category:Mountains of Deschutes County, Oregon Category:Stratovolcanoes of Oregon Category:Quaternary Oregon