Editing Yellowstone National Park (section)

== Geology ==
{{Main|Geothermal areas of Yellowstone|Yellowstone Caldera|Yellowstone hotspot}}

=== Volcanism ===
[[File:Columnar basalt closeup near Tower Fall in Yellowstone.JPG|thumb|[[Basalt#Columnar basalt|Columnar basalt]] near [[Tower Fall]]; large floods of basalt and other lava types preceded mega-eruptions of superheated ash and pumice.]]
[[File:Caldera rim.jpg|thumb|Caldera rim on the horizon south of Yellowstone Lake]]
Yellowstone is at the northeastern end of the [[Snake River Plain]], a great bow-shaped arc through the mountains that extends roughly {{convert|400|mi|km|-1}} from the park to the Idaho-Oregon border.

The volcanism of Yellowstone is believed to be linked to the somewhat older volcanism of the Snake River Plain. Yellowstone is thus the active part of a [[hotspot (geology)|hotspot]] that the [[North American Plate]] has moved over in a southwest direction over time.<ref name="snake">{{cite web |url=http://tapestry.usgs.gov/features/34snakeriver.html |title=The Snake River Plain |publisher=U.S. Geological Survey |date=March 12, 2001 |access-date=March 12, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20130412140625/http://tapestry.usgs.gov/features/34snakeriver.html |archive-date=April 12, 2013 }}</ref> The origin of this hotspot volcanism is disputed.<ref name=James2011/> One theory holds that a [[mantle plume]] has caused the [[Yellowstone hotspot]] to migrate, while another theory explains migrating hotspot volcanism as the result of the fragmentation and dynamics of the [[subduction|subducted]] [[Farallon Plate]] in Earth's interior.<ref name=James2011>{{cite journal |last1=James |first1=David |last2=Fouch |first2=Matthew |last3=Carlson |first3=Richard W. |last4=Roth |first4=Jeffrey |year=2011 |title=Slab Fragmentation, Edge Flow and the Origin of the Yellowstone Hotspot Track |journal=Earth and Planetary Science Letters |volume=311 |issue=1–2 |pages=124–135 |doi=10.1016/j.epsl.2011.09.007 |bibcode=2011E&PSL.311..124J }}</ref><ref name=zhou2018>{{cite journal |last1=Zhou |first1=Ying |year=2018 |title=Anomalous mantle transition zone beneath the Yellowstone hotspot track |journal=Nature Geoscience |volume=11 |issue=6 |pages=449–453 |doi=10.1038/s41561-018-0126-4 |bibcode=2018NatGe..11..449Z |s2cid=134251160 }}</ref>

The [[Yellowstone Caldera]] is the largest volcanic system in North America, and worldwide it is only rivaled by the [[Lake Toba|Lake Toba Caldera]] on [[Sumatra]]. It has been termed a "[[supervolcano]]" because the caldera was formed by exceptionally large explosive eruptions. The [[magma chamber]] that lies under Yellowstone is estimated to be a single connected chamber, about {{convert|37|mi|km}} long, {{convert|18|mi|km}} wide, and {{convert|3|to|7|mi|km}} deep.<ref name=Oskin>{{cite news |last=Oskin |first=Becky |title=Yellowstone's Volcano Bigger Than Thought |url=http://www.livescience.com/28821-yellowstone-supervolcano-bigger-plume.html |access-date=August 11, 2013 |newspaper=[[LiveScience]] |date=April 17, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130702230721/http://www.livescience.com/28821-yellowstone-supervolcano-bigger-plume.html |archive-date=July 2, 2013 }}</ref> The current [[caldera]] was created by a cataclysmic eruption that occurred 640,000&nbsp;years ago, which released more than {{convert|240|mi3|km3|abbr=on}} of ash, rock and [[pyroclast]]ic materials.<ref name="640ka">{{cite web |url=http://pubs.usgs.gov/pp/pp729g |title=The Quaternary and Pliocene Yellowstone Plateau Volcanic Field of Wyoming, Idaho, and Montana |publisher=U.S. Geological Survey |date=August 27, 2001 |access-date=May 11, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130512144946/http://pubs.usgs.gov/pp/pp729g/ |archive-date=May 12, 2013}}/</ref> This eruption was more than 1,000 times larger than the [[1980 eruption of Mount St. Helens]].<ref name="volcanic">{{cite web |url=http://pubs.usgs.gov/fs/fs100-03/ |title=Tracking Changes in Yellowstone's Restless Volcanic System |publisher=U.S. Geological Survey |date=January 19, 2006 |access-date=March 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070206103530/http://pubs.usgs.gov/fs/fs100-03/ |archive-date=February 6, 2007 }}</ref> It produced a caldera nearly {{cvt|5/8|mi}} deep and {{convert|45|by|28|mi|km}} in area and deposited the [[Lava Creek Tuff]], a [[welded tuff]] [[geologic formation]]. The most violent known eruption, which occurred 2.1&nbsp;million years ago, ejected {{convert|588|mi3|km3|abbr=on}} of volcanic material and created the rock formation known as the [[Huckleberry Ridge Tuff]] and the [[Island Park Caldera]].<ref name="volcanic history">{{cite web |url=http://volcanoes.usgs.gov/yvo/history.html |title=Volcanic History of the Yellowstone Plateau Volcanic Field |website=Yellowstone Volcano Observatory |publisher=U.S. Geological Survey |date=February 2, 2007 |access-date=March 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070318093739/http://volcanoes.usgs.gov/yvo/history.html |archive-date=March 18, 2007 }}</ref> A smaller eruption ejected {{convert|67|mi3|km3|abbr=on}} of material 1.3&nbsp;million years ago, forming the [[Henry's Fork Caldera]] and depositing the [[Mesa Falls Tuff]].<ref name="volcanic"/>

Each of the three climactic eruptions released vast amounts of ash that blanketed much of central North America, falling many hundreds of miles away. The amount of ash and gases released into the atmosphere probably caused significant impacts on world weather patterns and led to the [[extinction]] of some species, primarily in North America.<ref name="sciamerican">{{cite journal |last=Bindeman |first=Ilya N. |title=The Secrets of Supervolcanoes |journal=Scientific American |url=http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0006E0BF-BB43-146C-BB4383414B7F0000 |archive-url=https://web.archive.org/web/20071016204122/http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0006E0BF-BB43-146C-BB4383414B7F0000 |archive-date=October 16, 2007 |date=June 2006 |volume=294 |issue=6 |pages=36–43 |doi=10.1038/scientificamerican0606-36 |pmid=16711358 |bibcode=2006SciAm.294f..36B |access-date=August 24, 2011 |url-access=subscription }}</ref>
[[File:Aerial image of Grand Prismatic Spring (view from the south).jpg|left|thumb|Boardwalks allow visitors to safely approach the thermal features, such as [[Grand Prismatic Spring]]]]

A subsequent caldera-forming eruption occurred about 160,000 years ago. It formed the relatively small caldera that contains the [[Yellowstone Lake|West Thumb]] of Yellowstone Lake. Since the last supereruption, a series of smaller eruptive cycles between 640,000 and 70,000&nbsp;years ago, has nearly filled in the Yellowstone Caldera with 80 different eruptions of [[rhyolite|rhyolitic]] lavas such as those that can be seen at [[Obsidian Cliff]]s and [[basalt]]ic lavas which can be viewed at [[Sheepeater Cliff]]. Lava strata are most easily seen at the Grand Canyon of the Yellowstone, where the Yellowstone River continues to carve into the ancient lava flows. The canyon is a classic [[V-shaped valley]], indicative of river-type erosion rather than erosion caused by [[glacier|glaciation]].<ref name="volcanic history"/>

Each eruption is part of an eruptive cycle that climaxes with the partial collapse of the roof of the volcano's partially emptied magma chamber. This creates a collapsed depression, called a caldera, and releases vast amounts of volcanic material, usually through fissures that ring the caldera. The time between the last three cataclysmic eruptions in the Yellowstone area has ranged from 600,000 to 800,000&nbsp;years; however, the small number of such climactic eruptions cannot be used to make an accurate prediction for future volcanic events.<ref name="time">{{cite web |url=http://volcanoes.usgs.gov/yvo/faqsfactivity.html#eruptagain |title=Questions About Future Volcanic Activity |website=Yellowstone Volcano Observatory |publisher=U.S. Geological Survey |date=February 2, 2007 |access-date=April 8, 2007 |url-status=live |archive-url=https://web.archive.org/web/20120118011434/http://volcanoes.usgs.gov/yvo/faqsfactivity.html#eruptagain |archive-date=January 18, 2012 }}</ref>

===Geysers and the hydrothermal system===
{{see also|List of Yellowstone geothermal features}}
{{Multiple image|total_width=330|align=right|direction=horizontal
|image1= Old faithful geyser 2015.jpg|caption1= [[Old Faithful]] erupts approximately every 90 minutes.
|image2= Steamboat Geyser Major Eruption in 2005.jpg|caption2= [[Steamboat Geyser]] is the world's largest active geyser.
}}

The most famous [[geyser]] in the park, and perhaps the world, is [[Old Faithful]] geyser, located in [[Upper Geyser Basin]]. [[Castle Geyser]], [[Lion Geyser]], [[Beehive Geyser]], [[Grand Geyser]] (the world's tallest predictable geyser), [[Giant Geyser]] (the world's most voluminous geyser), [[Riverside Geyser]] and numerous other geysers are in the same basin. The park contains the tallest active geyser in the world—[[Steamboat Geyser]] in the [[Norris Geyser Basin]]. A study that was completed in 2011 found that at least 1,283 geysers have erupted in Yellowstone. Of these, an average of 465 are active in a given year.<ref>{{cite conference |last1=Cross |first1=Jeff |title=How many geysers are found in Yellowstone? |conference=The 11th Biennial Scientific Conference on the Greater Yellowstone Ecosystem |date=October 8–10, 2012 |location=Mammoth Hot Springs Hotel, Yellowstone National Park, Wyoming }}</ref><ref>{{cite news |last=Lundquist |first=Laura |title=Dormant Yellowstone geyser erupts |newspaper=The Bozeman Daily Chronicle |date=August 2, 2013 |url=https://www.bozemandailychronicle.com/news/environment/dormant-yellowstone-geyser-erupts/article_b92f45b8-fb07-11e2-b4ea-0019bb2963f4.html |access-date=August 6, 2018 |archive-date=August 2, 2021 |archive-url=https://web.archive.org/web/20210802222245/https://www.bozemandailychronicle.com/news/environment/dormant-yellowstone-geyser-erupts/article_b92f45b8-fb07-11e2-b4ea-0019bb2963f4.html |url-status=live }}</ref> Yellowstone contains at least 10,000 [[Geothermal activity|geothermal features]] altogether, including [[geyser]]s, [[hot spring]]s, [[mudpot]]s, and [[fumarole]]s.<ref>{{cite web |url=https://pubs.usgs.gov/sir/2014/5137/pdf/sir2014-5137.pdf |title=Provisional Maps of Thermal Areas in Yellowstone National Park, based on Satellite Thermal Infrared Imaging and Field Observations |id=Scientific Investigations Report 2014–5137 |publisher=U.S. Department of the Interior, U.S. Geological Survey |first1=R. Greg |last1=Vaughan |first2=Henry |last2=Heasler |first3=Cheryl |last3=Jaworowski |first4=Jacob B. |last4=Lowenstern |first5=Laszlo P. |last5=Keszthely |year=2014 |page=6 |access-date=August 9, 2018 |archive-date=March 1, 2021 |archive-url=https://web.archive.org/web/20210301024440/https://pubs.usgs.gov/sir/2014/5137/pdf/sir2014-5137.pdf |url-status=live }}</ref> Over half of the world's geysers and hydrothermal features are concentrated in Yellowstone.<ref name="un">{{cite web |url=https://whc.unesco.org/en/list/28 |title=Yellowstone National Park |website=World Heritage Sites |publisher=UNESCO World Heritage Centre |date=April 23, 2007 |access-date=April 23, 2007 |url-status=live |archive-url=https://web.archive.org/web/20170224234321/https://whc.unesco.org/en/list/28 |archive-date=February 24, 2017 }}</ref><ref name=britannica/>

In May 2001, the [[U.S. Geological Survey]], Yellowstone National Park, and the [[University of Utah]] created the Yellowstone Volcano Observatory (YVO), a partnership for long-term monitoring of the geological processes of the Yellowstone Plateau volcanic field, for disseminating information concerning the potential hazards of this geologically active region.<ref name="yvo">{{cite web |url=http://volcanoes.usgs.gov/yvo/yvo.html |title=Information about the Yellowstone Volcano Observatory |website=Yellowstone Volcano Observatory |publisher=U.S. Geological Survey |date=February 2, 2007 |access-date=March 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20080514160440/http://volcanoes.usgs.gov/yvo/yvo.html |archive-date=May 14, 2008 }}</ref>
[[File:Albert_Bierstadt_-_Geysers_in_Yellowstone_(c.1881).jpg|alt=Geysers erupting vertically. Sunlight illuminating the one in the foreground and the breeze is blowing the steam and spray to the left.|thumb|[[Albert Bierstadt]], ''Geysers in Yellowstone'', 1881]]
In 2003, changes at the Norris Geyser Basin resulted in the temporary closure of some trails in the basin. New [[fumarole]]s were observed, and several geysers showed enhanced activity and increasing water temperatures. Several geysers became so hot that they were transformed into purely steaming features; the water had become superheated and they could no longer erupt normally.<ref name="geyserbasin">{{cite web |url=http://volcanoes.usgs.gov/yvo/2003/NorrisTherm03.html |title=Notable Changes in Thermal Activity at Norris Geyser Basin Provide Opportunity to Study Hydrothermal System |website=Yellowstone Volcano Observatory |publisher=U.S. Geological Survey |date=March 16, 2005 |access-date=March 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20120118013707/http://volcanoes.usgs.gov/yvo/2003/NorrisTherm03.html |archive-date=January 18, 2012 }}</ref> This coincided with the release of reports of a multiple year United States Geological Survey research project which mapped the bottom of Yellowstone Lake and identified a structural dome that had uplifted at some time in the past. Research indicated that these uplifts posed no immediate threat of a volcanic eruption, since they may have developed long ago, and there had been no temperature increase found near the uplifts.<ref name="uplift2">{{cite web |title=Frequently asked questions about recent findings at Yellowstone Lake |url=http://volcanoes.usgs.gov/yvo/new.html |url-status=live |archive-url=https://web.archive.org/web/20120204035350/http://volcanoes.usgs.gov/yvo/new.html |archive-date=February 4, 2012 |access-date=March 12, 2007 |website=Yellowstone Volcano Observatory |publisher=U.S. Geological Survey }}</ref> Most recently, in July 2024, a hydrothermal explosion occurred in Biscuit Basin.<ref>{{Cite web |date=July 24, 2024 |title=Surprise Yellowstone geyser eruption highlights little known hazard at popular park |url=https://apnews.com/article/yellowstone-park-hydrothermal-explosion-geyser-basin-17e575de4b9a22823d50f08086478a5b |access-date=September 10, 2024 |website=AP News |language=en |archive-date=September 10, 2024 |archive-url=https://web.archive.org/web/20240910234502/https://apnews.com/article/yellowstone-park-hydrothermal-explosion-geyser-basin-17e575de4b9a22823d50f08086478a5b |url-status=live }}</ref>

On March 10, 2004, a biologist discovered 5 dead bison which apparently had inhaled toxic geothermal gases trapped in the Norris Geyser Basin by a seasonal atmospheric inversion. This was closely followed by an upsurge in earthquake activity in April 2004.<ref name="news">{{cite web |url=http://volcanoes.usgs.gov/yvo/NewsArchive.html |title=Archive of Stories About the Yellowstone Volcanic System |website=Yellowstone Volcano Observatory |publisher=U.S. Geological Survey |date=February 2, 2007 |access-date=March 12, 2007 |archive-url=https://web.archive.org/web/20070210050433/http://volcanoes.usgs.gov/yvo/NewsArchive.html |archive-date=February 10, 2007 }}</ref> In 2006, it was reported that the Mallard Lake Dome and the Sour Creek Dome—areas that have long been known to show significant changes in their ground movement—had risen at a rate of {{convert|1.5|to|2.4|in|cm}} per year from mid–2004 through 2006. As of late 2007, the uplift has continued at a reduced rate.<ref>{{cite news |title=Earthquake Swarms at Yellowstone Continue |publisher=Inland Park News |date=December 19, 2008 |url=http://www.islandparknews.com/atf.php?sid=5600&current_edition=2008-12-19 |access-date=August 24, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20130520181706/http://www.islandparknews.com/atf.php?sid=5600&current_edition=2008-12-19 |archive-date=May 20, 2013 }}</ref><ref>{{cite news |last=Smith |first=Robert B. |author2=Wu-Lung Chang |author3=Lee Siegel |title=Yellowstone rising: Volcano inflating with molten rock at record rate |work=Press release, University of Utah Public Relations |publisher=EurekAlert! (American Association for the Advancement of Science) |date=November 8, 2007 |url=http://www.eurekalert.org/pub_releases/2007-11/uou-yr103007.php |access-date=November 9, 2007 |url-status=live |archive-url=https://web.archive.org/web/20071115095510/http://www.eurekalert.org/pub_releases/2007-11/uou-yr103007.php |archive-date=November 15, 2007 }}</ref> These events inspired a great deal of media attention and speculation about the geologic future of the region. Experts responded to the conjecture by informing the public that there was no increased risk of a volcanic eruption in the near future.<ref>{{cite journal |last=Lowenstern |first=Jake |title=Truth, fiction and everything in between at Yellowstone |journal=Geotimes |date=June 2005 |url=http://www.agiweb.org/geotimes/june05/feature_supervolcano.html |access-date=March 12, 2007 |archive-date=February 3, 2019 |archive-url=https://web.archive.org/web/20190203211435/http://www.agiweb.org/geotimes/june05/feature_supervolcano.html |url-status=live }}</ref> These changes demonstrate the dynamic nature of the Yellowstone hydrothermal system.

=== Earthquakes ===
[[File:State Highway 287 slumped into Hebgen Lake.jpg|thumb|Infrastructure damage at [[Hebgen Lake]] due to the 7.2 magnitude [[1959 Hebgen Lake earthquake|earthquake of 1959]]]]
Yellowstone experiences thousands of small earthquakes every year, virtually all of which are undetectable to people. About 2/3 of the earthquakes occur in an area between Hegben Lake and the Yellowstone Caldera along a buried fracture zone left from the 2.1 mya eruption.<ref name="Lowenstern">{{cite journal |last1=Lowenstern |first1=Jacob B. |last2=Smith |first2=Robert B. |last3=Hill |first3=David P. |title=Monitoring Super-Volcanoes: Geophysical and Geochemical Signals at Yellowstone and Other Large Caldera Systems |journal=Philosophical Transactions: Mathematical, Physical and Engineering Sciences |date=August 15, 2006 |volume=364 |issue=1845 |pages=2055–2072 |doi=10.1098/rsta.2006.1813 |pmid=16844648 |bibcode=2006RSPTA.364.2055L |s2cid=12160214 }}</ref>

There have been six earthquakes with at least [[Moment magnitude scale|magnitude]] 6 or greater in historical times, including the 7.2‑magnitude [[1959 Hebgen Lake earthquake|Hebgen Lake earthquake]] which occurred just outside the northwest boundary of the park in 1959.<ref>[https://earthquake.usgs.gov/earthquakes/eventpage/iscgem882673/executive "M 7.2 – Hebgen Lake, Wyoming Earthquake"] {{Webarchive |url=https://web.archive.org/web/20181128215558/https://earthquake.usgs.gov/earthquakes/eventpage/iscgem882673/executive |date=November 28, 2018 }}. ''earthquake.usgs.gov''. United States Geological Survey via the International Seismological Centre. Retrieved November 28, 2018.</ref> This quake triggered a huge [[landslide]], which caused a partial dam collapse on Hebgen Lake; immediately downstream, the [[sediment]] from the landslide dammed the river and created a new lake, known as [[Quake Lake|Earthquake Lake]]. Twenty-eight people were killed, and property damage was extensive in the immediate region. The earthquake caused some geysers in the northwestern section of the park to erupt, large cracks in the ground formed and emitted steam, and some hot springs that normally have clear water turned muddy.<ref name="earthquake"/> The stress created in the fracture zone by this quake is theorized to be responsible for the current quake activity in the northwestern section of Yellowstone.<ref name="Lowenstern" /> A 6.1‑magnitude earthquake struck inside the park on June 30, 1975, but the damage was minimal.

For three months in 1985, 3,000 minor earthquakes were detected in the northwestern section of the park, during what has been referred to as an [[earthquake swarm]], and has been attributed to minor subsidence of the Yellowstone caldera.<ref name="volcanic"/> Beginning on April 30, 2007, 16 small earthquakes with magnitudes up to 2.7 occurred in the Yellowstone Caldera for several days. These swarms of earthquakes are common, and there have been 70 such swarms between 1983 and 2008.<ref name="swarms">{{cite news |title=More Than A Dozen Earthquakes Shake Yellowstone |publisher=KUTV News |date=May 6, 2007 |url=http://kutv.com/national/local_story_126175405.html |access-date=May 7, 2007 |archive-url=https://web.archive.org/web/20070526111246/http://kutv.com/national/local_story_126175405.html |archive-date=May 26, 2007 }}</ref> In December 2008, over 250 earthquakes were measured over four days under Yellowstone Lake, the largest measuring a magnitude of 3.9.<ref>{{cite web |url=http://volcanoes.usgs.gov/yvo/activity/archive/2008.php |title=Archive of Yellowstone Updates for 2008 |publisher=Yellowstone Volcanic Observatory |access-date=December 31, 2008 |url-status=live |archive-url=https://web.archive.org/web/20090123054301/http://volcanoes.usgs.gov/yvo/activity/archive/2008.php |archive-date=January 23, 2009 }}</ref> In January 2010, more than 250 earthquakes were detected over two days.<ref>{{cite news |url=http://www.denverpost.com/ci_14216212 |title=Yellowstone hit by swarm of earthquakes |work=[[The Denver Post]] |date=January 18, 2010 |url-status=live |archive-url=https://web.archive.org/web/20100121133535/http://www.denverpost.com/ci_14216212#ixzz0d0TCeanj |archive-date=January 21, 2010 }}</ref> Seismic activity in Yellowstone National Park continues and is reported hourly by the Earthquake Hazards Program of the U.S. Geological Survey.<ref>{{cite web |url=https://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/special/Yellowstone.php |publisher=United States Geological Survey |title=Latest Earthquakes – US " Yellowstone Region |url-status=dead |archive-url=https://web.archive.org/web/20081206022248/http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/special/Yellowstone.php |archive-date=December 6, 2008 }}</ref>

On March 30, 2014, a magnitude 4.8 earthquake struck almost the very middle of Yellowstone near the Norris Basin at 6:34&nbsp;am; reports indicated no damage. This was the largest earthquake to hit the park since February 22, 1980.<ref>{{cite web |url=http://guardianlv.com/2014/03/4-8-magnitude-earthquake-hits-yellowstone-national-park/ |title=4.8 Magnitude Earthquake Hits Yellowstone National Park |publisher=Liberty Voice |date=March 30, 2014 |access-date=March 31, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140331011654/http://guardianlv.com/2014/03/4-8-magnitude-earthquake-hits-yellowstone-national-park/ |archive-date=March 31, 2014 }}</ref>